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Foreword

Here we are again for a new survey and monitoring work! Here, we promise to leave Ecophyto and the wine industry alone and to focus on an equally exciting subject: soil conservation agriculture. Why? Well, why not… An uncle who is a fervent advocate of conservation agriculture, a natural curiosity about a domain that is not very well mastered, and an eternal questioning about the responsible and relevant use of digital technology in agriculture. That’s all there is to it, and the subject has been chosen: Is there a place for digital technology in conservation agriculture? What are the bridges and synergies between the two? You can imagine that the answer is not binary…

After field meetings with farmers, each more passionate than the last, telephone surveys with various audiences (farmers, agricultural advisors, technicians, professors, researchers), bibliographic cross-checking with scientific articles, reports, and forums, we present here the synthesis of our survey work. Here, we do not judge. We discuss, we give reading tips, we sometimes ask questions without having answers, and we leave to think. The list of people we met and called is presented at the end of the articles. Once again, I thank all these people for the time they were able to give me and the richness of the exchanges we were able to have together. Once again, I let them have their say in this synthesis.

This work was spread out over time, with the first field meetings in early 2020. During the summer of 2020, I was accompanied in my reflection by Hyrsene Jecolia Guei, an agricultural engineer student, to continue investigating with me and to take a step back on this complicated subject. Hyrsene, thank you for this beautiful collaboration.

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A few words about digital before we get starte

Is there really a definition of digital agriculture or a definition of Agtech? Obviously not… The Agtechcommunity initiative, launched in mid-2020, has made it one of its main missions to propose a definition. If no clear definition exists, perhaps it is not surprising that the digital agriculture ecosystem is so blurred. The maps of the Agtech ecosystem in France, recently published on the blog, certainly show a strong trend in digital innovation in agriculture, but above all they show an extremely complex ecosystem, with a rather impressive quantity of start-ups.

When discussing digital technologies applied to agriculture, it is also hard to miss precision agriculture (PA). Unlike the case of digital technology, some actors have proposed a definition. For example, the recent definition (2019) of a panel of scientists from the International Society for Precision Agriculture (ISPA): “Precision Agriculture is a management strategy that gathers, processes, and analyzes spatial, temporal, and individual data, and combines them with other information to guide modulated management decisions related to the plant or animal to improve resource efficiency, productivity, quality, profitability, and sustainability of agricultural production.” Without giving a clear definition of digital agriculture, we nevertheless distinguish it from precision agriculture. For us, precision agriculture is initially a scientific discipline aimed at studying the spatio-temporal variability of production factors – a discipline from which a number of agronomic services and applications are currently proposed. Digital technology in agriculture is something broader, encompassing both agricultural production as such, and all its ancillary aspects (land management, marketing, etc.).

Generally speaking, digital farming is often considered or discussed for agriculture in the broadest sense, with a dichotomy between crop and animal production, and a separation of tools and solutions by sector. Here we wanted to think about the positioning of digital technology in a slightly different way, by looking at it through the prism of conservation agriculture. Conservation agriculture is a technical subject, linked to agricultural production. In this context, we see digital technology as an ally to help measure and quantify things, to acquire and generate agronomic knowledge, so as to guide thinking towards an improvement, an evolution, or even a complete change of the system in place. Digital technology should be seen as an intelligent layer added to an already intelligent agricultural system, and not as a means to optimize anything and everything.

Before we (finally) get into conservation agriculture, and its potential links with digital tools, perhaps this is also an opportunity to revisit terminologies that I consider increasingly harmful when discussing digital in agriculture:

“Digital Agriculture” does not exist. Digital tools serve agriculture and/or are deployed in the agricultural sector. Agriculture is not digital per se, it is only accompanied by digital tools

Even though this is one of my areas of work, I think that the terminology “Precision Agriculture” is poorly chosen. It suggests that farmers who do not practice it would work poorly or would not be precise. Many technical itineraries, centered on the soil and agronomy, are extremely precise.

“Intelligent Agriculture”: I think that the condescension of this association of terms for farmers who do not practice it speaks for itself

“Agriculture 2.0, 3.0, 4.0” (have we moved on to 5?) gives the impression that farmers using few or no digital tools are behind the curve, while some of them are so advanced agronomically speaking.

Soil conservation agriculture

Introduction to Soil Conservation Agriculture (SCA)

Far be it from me to give you a detailed course in Conservation Agriculture – I would not be able to and I would not have the legitimacy to do so. The objective here is rather to give you a feel for the main concepts and to let you observe what I have seen in the field. In this section, we will go back to the main principles of conservation agriculture to recontextualize this monitoring work: limiting tillage, permanent soil cover, and diversification and lengthening of rotations. We will not dwell on the functioning of the soil, its biological activity or its metabolomic activity; the subject is far too vast to discuss here. We will not mention either all the additional practices implemented by many farmers in conservation agriculture (low volume spraying to be very efficient and therefore lower doses; fermented extracts, decoctions, macerations and essential oils; paramagnetism…), which, although extremely technical, are not at the heart of this work. But what is left then? Enough, don’t worry…

Let’s start at the beginning. Soil Conservation Agriculture (SCA), as its name indicates, places the soil at the heart of its production system. It could be seen as a pure and simple return to soil agronomy. Also called by some “living soil agriculture” or “soil regeneration agriculture”, soil conservation agriculture, as the APAD network (Association for Sustainable Agriculture) points out, is a set of farming techniques that are at the heart of three major pillars:

the maximum limitation of the work of the ground, in particular for the sowing,

the maximum coverage of the soil, made of crop residues or sown cover, and

the diversification of cultivated species with long rotations and associated crops

The previous definition is nevertheless rather theoretical and does not necessarily represent all the diversity of forms of conservation agriculture that can be found in the field. Many farmers have in fact appropriated these broad principles and have more or less converged towards this theoretical definition. If you have ever heard of SCA, you must have come across the terms Simplified cultivation techniques, Direct Seeding, Direct Seeding under Plant Cover, No-till farming techniques. One of our interlocutors explained it to us as follows: “Conservation agriculture is not a dogma, but an orientation to give to one’s system. It is essential to keep in mind economic considerations and to maintain an acceptable level of stress for the entrepreneur. It is therefore necessary to understand the mechanisms, to know how to analyze the risks, and to set realistic stages, acceptable for the soil in the state in which it is. There is therefore no single definition of conservation agriculture. Each approach must be put into context and is specific to the state of the soil at a given time and to the maturity of the farmer. Other contacts had similar reactions: “I don’t want to identify SCA with no-till. Direct seeding is part of the solution. SCA means taking into account the biology of the soil. It’s beyond changing soil practices“. One of our contacts will even try to give us some figures: “There are only 4 to 5% of farmers in France who practice true SCA with 0 disturbances and 20 to 30% who do not plow but work the soil”. Keep in mind that SCA is made up of a range of different practices, among which it is not always easy to find one’s way, but whose common goal is to put the soil back at the center of the farmer’s work.

Soil conservation agriculture would appear to be a real paradigm shift, a new kingdom in which the soil is king. Some farmers perceive this form of agriculture as an evolution or a new direction to give to the agricultural system in place: “SCA is an evolution of production systems, it is a pure and simple return to soil agronomy. I identify SCA as an evolution, not a change, because change has a negative side. The factory that runs the plants is the soil and it must be taken into account. SCA is also about taking into account the biology of the soil, it goes beyond changing soil practices. What steps should be taken to move towards a conservation agriculture system? To this question, a contact will answer soberly: “Know how to modify your system in a measured way, limiting the risk and the investments, and in a progressive way”.

We can understand the interest of those who have turned to SCA. Clearly, the benefits appear to be extremely numerous. Here are a few of them:

Decreased land erosion due to improved soil structural condition

Improved soil bearing capacity to reduce soil compaction and bogging down of farm machinery,

Improved soil fertility and biological activity

Increased sequestration of carbon in the soil

Increased biodiversity through crop diversification

Improvement of water quality

Savings in fuel and active ingredients

Nevertheless, we have to admit that the number of French farms using SCA is not very important. You may indeed retort that it depends on the type of SCA considered, but it is not one of the most common farming techniques in France. Nevertheless, SCA is quite popular, and this farming system is starting to change many people’s minds. In response to a question about the factors that triggered this awareness, our farmer contacts gave us a fairly long list. We could find (1) people who are evolving in a system whose economic results are gradually decreasing, (2) others who feel that they are at the end of their rope with yields that are leveling off or starting to decrease, and varieties with genetics that are not expressing themselves enough (whatever the region), (3) farmers who find themselves in technical impasses with regard to pesticides with problems of resistance to weed killers (vulpine, ray-grass), (4) others who would have difficulty recovering from droughts and/or excess water, or even farmers of 40-50 years old who, having stabilized the economic balance of their farm, are wondering what they will leave to their children… In short, nothing to look forward to: “With last fall’s conditions in many regions, only the no-tillers succeeded in planting cereals. In the southwest, with the storms and erosion, it’s still the no-tillers who are doing the best. This is starting to be known in the countryside”.

In view of what SCA seems to consider, could we not even go so far as to refer to it as Agro-Ecology? Whether it is during our interviews or through our different research, the two terms often seem to be put in the same box. The FAO defines agroecology as an integrated approach that applies ecological and social concepts and principles to the design and management of food and agricultural systems. Centered on the soil and committed to the enhancement of biological processes that ensure good soil health, GBA would seem to find its place in agroecology. In this regard, one of our interlocutors stated that “SCA is a set of techniques in phase with agro-ecology, in the same way that organic farming could be“. And a second added: “For me, in the end, everything converges, agro-ecology, SCA, sustainable development”. The Center for the Development of Agroecology (CDA) will also go so far as to establish a connection between agroecology and soil conservation. According to them, agro-ecology would encompass and even rely on soil conservation techniques in order to promote interactions within agricultural and food systems between plants, animals, humans and the environment. Restoring natural relationships within a farming system (agro-ecological objective) would require, for example, an increase in soil organic matter, which could be achieved through permanent soil cover. This increase in organic matter would result in an increase in biodiversity and thus in natural interactions. One of our contacts, taking a step back, considered that Soil conservation agriculture should be considered from the point of view of agricultural techniques, whereas agro-ecology would be broader and perhaps more complete: “We only work on the agricultural aspect. But agro-ecology encompasses social, environmental, economic, short circuit… it is not just a technique, it is not an agricultural system, it is a societal system. GBA is a technique that is in line with agro-ecology, just as organic farming could be a technique that is part of an agro-ecological system“.

Sidebar: GBA in a few key facts :

Pioneering associations: “APAD” and “BASE”.

Several networks that are being set up: “Verre de terre production”, “Agro’Doc”, “Pour une agriculture du vivant” ….

A label that is beginning to make a name for itself: “Au cœur des sols” (At the heart of the soil)

Specialized magazines and websites: “TCS”, “A2C

Discussion forums, including a group with over 50,000 subscribers on Facebook

And a recent film on the subject: “Welcome earthworms”.

Limiting tillage

“Ploughing and grazing are the two breasts of which France is fed…”. If the Duke of Sully, appointed at the time by Henri IV to reorganize the finances of an extremely agricultural country like France, liked to speak in this way of the territory’s agriculture, the same cannot be said of the advocates of SCA. You probably sensed it in the previous section, but conservation agriculture advocates minimal tillage – perhaps none at all in a perfect world. And when you think of tillage, you think of plowing pretty quickly. Tillage is that tilling technique that involves turning the soil with a plow to loosen it. Often done at a depth of more than 15-20 cm, it is seen by conservation farmers as the source of all evils.

First victim: soil fertility. The crumbling of soils by the repeated passage of rotary tools would artificially increase the fertility of soils by excess mineralization: “plowing deeper and deeper is decapitalization. During these years, there is a lot of mineralization, but we only realize it at the end. We need both humus creation and mineralization! If we don’t do that, the organic matter level melts and the soil doesn’t respond at all. By switching to SCA, we capitalize on the soil, and the soil is enriched and nourished. The microbial engine is stronger. The benchmark is 0 nitrogen and 0 phosphorus controls [i.e., no fertilizer input by the farmer] and to see how the plants grow in those places”; “For years, we have lived on the pile of gold that previous generations had accumulated with subsistence farming, meadows, livestock, small potential. We stored in the soils. We were part of the generation that destocked the soil. Second victim: the physical structure and the bearing capacity of the soil. The porosity created by the mechanical working of the soil would in fact be artificial since the soil would recompact extremely quickly. The soil would be more compacted than we think: “With the beet harvesting machines, we crush everything. And by ploughing at 20cm, we actually plough at 25cm because the soil is compacted“. The soil aggregates would also be much less stable and would no longer hold together (glomalin, the sticky excretion produced by fungi and used to stabilize the soil, would no longer be present). The result is a compacted soil in which the roots sink with greater difficulty and have more difficulty meeting their food needs, and in which tractors get stuck as soon as it rains. The following figures are rather telling…

Figure 1: Soil compaction due to a tractor pass. Left: Plot in SCA. Right: Plot plowed. The two photos are taken on the same day, at the same time, and the plots are joined. It had been raining heavily for a few days when the photos were taken. There is still water on the surface of the ploughed plot, which is not good for the young wheat (one could think it was a rice field, but no!), nor for the tractor wheels which are clearly visible. On the contrary, the water has infiltrated (and will be better stored, which will make the wheat more resistant to hot weather) in the soil of the SCA plot, hence the wet but not waterlogged aspect of the soil, and the tire tracks are much less marked. Seeding was later on the plowed plot. This may be surprising, as it appears that the plants are more numerous and developed on the plowed plot. The wheat on the SCA plot grew slower, but its roots are more developed and full.

Figure 2: Structural state and bearing capacity of the soil after a rain. On both pictures, the red dotted line separates on the left, a plot in SCA, from a neighbouring ploughed plot on the right (And yes, the sky is grey, we were in the North anyway)

The structural stability of the soil is largely supported by the presence of earthworms. Epigeous, endogeous, and anecic (earthworms!) present respectively in the soil horizons 5-10 cm, 10-20 cm, and 0 to 3m, participate to stabilize the soil thanks to their dejections, and homogenize the contents in mineral elements by moving and seeding the soil. And these earthworms, especially the anecdotes, have a life span of at least 7-8 years! The galleries they create in the soil can even last for more than thirty years. In a no-till soil, the litter – deposited on the ground – is eaten by earthworms. When plowed, the litter is under the soil – the epigeous and endogeous are gone. As one farmer explained to me, “With a warm and humid climate in the fall, there is a strong development of fungi and earthworms, so this is the time when you should not work your soil too much. The big bullshit is stubble plowing and early plowing for rapeseed. You don’t need many elements in autumn before winter. In the spring, bacteria mineralize the soil so it’s less embarrassing to touch the soil at that time“. Add to that the fact that with plowing, the mycelium of the fungi, which favored the production of humus, is cut out, leaving only mineral horizons. The agriculture of our grandparents, less powerful, degraded the soils less and left them favorable to mycorrhization. Farmers also worked more with mycorrhized plants, which limited the development of diseases.

As one expert explained, it is not so much the tillage as the depth at which it is done that is problematic. Technically controlled plowing, at a shallow depth, in a horizon of up to 15 cm, and under good moisture conditions would not affect the biological processes of the soil. Another farmer confirmed this to me: “In very clayey soils, by not working more than 10 cm of soil, we recover the soil’s bearing capacity”. It is indeed the deep ploughing between 20 and 30 cm that would generate important imbalances. Let’s not even talk about the cumulative effect of deep plowing and the repeated use of tools that encourage soil crumbling. One farmer told me about his father’s past experiences with intensive tillage: “My father was a member of the 100-quart club. He practiced intensive tillage, with stubble plowing during the summer (he put the dust back) and systematic plowing every other year. As a result, we got to the end of the nematodes [earthworms], a decrease in organic matter, soil compaction – my father cultivated between a driving crust and a plow sole, and aphanomyces [pathogenic fungi] in the peas because of residue management.”

So would there only be benefits to limiting tillage? What about weeds? Without going into too much detail on the subject, a farmer will go into some technical details: “There is nothing easier on perennials, you have to stop deep tillage. There is a 5% chance that they will germinate in 80 years. Weeding with a spade allows you to see how it works. What bothers me are the plants that go to seed a lot. Black nightshades contain alkaloids – the same size as a pea. Black nightshade breaks just above the crown so it comes back quickly.” Another farmer will talk to me about another problem, the lack of soil warming: “In our system, there is a problem with soil warming because we have little tillage. There is no problem in South America because it is warmer. We would have to open the soil with shallow tillage. To counteract this in the spring, we would also have to plant later, but that would limit the yield“. With climate change, however, perhaps this problem will disappear fairly quickly…

For some farmers, seen from the outside, ploughing would seem to be a way of not asking too many questions about their soil, of avoiding turns in the plain, of not really trying to understand what is going on. A farmer will tell me that “when you don’t know the behavior of a soil, you don’t look at it“. This farmer will make me dig, touch, and feel his soil to make me aware of it, before comparing it with the soil of his neighbor in conventional agriculture. It is amusing to realize that in France, most soil analyses are interested in what is missing in the soil, as if it was necessary to correct deficiencies or shortcomings by adding things. And if understanding your soil also meant looking for what is too much, to correct the imbalances and get back on the right track ?

The reality is terrible: it would take 50 years to empty a soil and 150 years to recharge it. Nevertheless, it would seem that even soils that have been subjected to repeated tillage for many years are just waiting to regain their balance: “It is a false idea to describe a soil as dead. We should talk about a degraded soil, with less fertility, unbalanced. All of the microbial and mycorrhizal diversity remains present, regardless of the state of the soil, but at insignificant levels. A change of practice allows us to correct and regain a certain balance over relatively short periods of time“. Isn’t this encouraging for a farmer who is committed to conservation agriculture?

Here is a small photo of a soil profile, taken from a farmer’s plot visited at the beginning of 2020.

Figure 3. Soil profile photographed in February 2020 with a canopy of about 10 species, including oats, white clover, and radish. The soil is lumpy to the touch. You can walk on it without getting mud sticking to your boots despite the heavy rains of the previous days. We can distinguish some earthworm galleries. The roots penetrate without difficulty. This cover will be destroyed to make way for a direct spring seeding

Box Agro-equipment – 1 :

Some examples of machines used for relatively superficial tillage without inversion of horizons: The Rotovator for soil aeration on a horizon of 2 to 3 cm or the rotovator with 90° tines for scalping; The Rotator for leveling and crumbling the soil; The Fissurator for surface cracking of the soil

Figure 4: Examples of shallow tillage tools.

Permanent soil cover

In SCA, you don’t want to see bare soil. The soil must be covered almost permanently by what is simply called plant cover. One farmer will tell us that the cover crop should even come before the cash crop, which is an understatement. According to experts, the benefits of using cover crops are extremely numerous. Here are some of them:

Nitrogen storage by the leguminous present in the cover crop

Biomass contribution to the soil for future cash crops

Erosion control through improved soil structural condition

Improvement of water infiltration,

Decrease in pH of agricultural land

Production of biomass to feed animals in the framework of a mixed farming/livestock breeding or working near livestock breeders

And there are a lot of cover crops! Phacelia, radish, vetch, Alexandrian clover, mustard, sunflower, fava beans… In the field, it is quite rare to see cover crops made of only one species (even if some will do it to respect the regulation by planting for example only mustard, notably because of its rather low price per hectare). These are often mixtures, more or less complicated, each species bringing its own advantages. As for the composition of the cover crops, some farmers will give us telling examples: “cover crop mixtures are at least 50% legumes”; “we put 40% legumes, 40% grasses, and 20% other species“. What some farmers are looking for in plant cover is to return to a notion of soil verticality, in the sense that it would counterbalance the mechanical soil horizons created by years of repeated tillage. Others will look for biomass contributions to the soil.

The management of plant cover is extremely complex. Some approaches are obviously more simplistic than others, but in all cases, it is necessary to think about the type of cover crop to put in place, its integration into a rotation, the time and conditions of its establishment, and the way it is planted. You may have already heard about the whole range of seeding methods in use: direct seeding, direct seeding under plant cover, sub-seeding, relay-cropping…. As one farmer will testify: “You can leave strips to resow beets or sensitive plants, you can have strips without cover, you can organize the cover in strips, you can do relay-cropping like in the USA where their cover consists of winter cereals. Instead of destroying them, farmers will come and sow soybeans instead“. Seeding is so important that the seeder is often the gateway to conservation agriculture. In short, just thinking about it makes you dizzy, but the subject is no less exciting.

There are roughly two main ways of looking at plant cover. It can be :

dead cover, for example residues of previous crops (canes, cereal straws…),

living cover crops, harvested or not, with a particular interest for a future cash crop or for the soil, or simply to avoid leaving the soil bare and limit its erosion.

From a terminology point of view, when you hear about “CIPAN (intermediate crop nitrate trap)”, “plant cover”, or “green manure”, you are starting to get closer to the subject. The CIPAN is still a regulation. These are cover crops that were made mandatory in certain regions of France following the Nitrates Directive in order to fight against the risks of water pollution by nitrates. As one farmer confided to us, “CIPANs are not a great green manure. Often, it is mustard. The root system is quite incredible, but it gives off sulphur compounds that are not very good for the soil. Mustard is often used because it’s cheap“. The notion of green manure, on the other hand, goes much further in the sense that there is a real reflection on the effect that plant cover can have on cash crops, the environment, or on the soil. The use of green manure is the consequence of a voluntary effort by the farmer, and requires a high level of technicality.

Through a few examples, I wanted to introduce you to the diversity of possible uses of cover crops:

Figure 5: Case study 1: Winter barley planted in wheat straw residue. Here, the wheat straw is used as a cover and to conserve soil moisture. The barley is sown directly into the wheat straw. Barley is planted after wheat to limit the transmission of diseases from wheat crop residues

Figure 6. Case study 2: Winter wheat planted in a dwarf clover cover sown 1.5 years earlier and not destroyed until then. The clover is used as a permanent cover (more than one year) to store atmospheric nitrogen. The remains of corn stalks are left to bring food to the soil, and are also used as cover. Translation: Couvert de trèfle nain en inter-rang (Dwarf clover cover in inter-row), Ligne de semis de blé d’hiver (Winter wheat seeding line), Canne de maïs (Corn stover)

Figure 7a. Case Study 3 (See Figure 7b) Translation : Féverole (Beans), Radis (Radishes), Phacélie (Phacelia), Paille de blé (Wheat straw), Avoine (Oats)

Figure 7b. Case study 3: On this plot, oilseed rape was harvested in 2018, winter wheat in 2019, and a green manure was sown in 2019 after harvest. The cover crop will be destroyed in 2020 prior to the installation of a barley crop. For the cover crop: faba beans, clover, and vetch store atmospheric nitrogen; radish structures the soil; phacelia provides food for bees and repels aphids; wheat straws conserve soil moisture; oats cover the soil and stimulate soil fungi. Translation : Radis (Radishes), Paille de blé (Wheat straw), Avoine (Oats), Phacélie (Phacelia), Vesce (Vetch), Cannes de colza (Rapeseed canes)

Figure 8. Study case 4: Direct seeding of nyger, clover, and faba bean in summer 2019 into cereal straw. Direct seeding of rapeseed in fall 2019. Here, the faba beans and clover are there to store atmospheric nitrogen, the faba bean acts as a lure for the rapeseed flea beetles, the nyger is there to attract slugs and leave the rapeseed alone, the cereal straws conserve moisture. This cover, in its composition, ensures that the pests are disoriented. No insecticide was applied in autumn, which is very unusual for rapeseed, which is subject to pest attacks during almost its entire development cycle, generating numerous insecticide interventions. Translation : Féverole (Beans), Colza (Rapeseed), Paille (Straw), Trèfle (clover)

Isn’t this diversity fascinating? Once again, the use of plant cover is not always obvious and is often subject to debate. This is especially true of chemical inputs – particularly glyphosate – used to calm a canopy when establishing a cash crop (more on glyphosate at the end of this article). To give you an idea of the complexity of establishing some cover crops, I’ll let farmers testify: “In our climate, establishing cover crops is increasingly complicated. Even if we sow within 3 days after harvest, we can’t get the cover crop to grow. We have repeated heat waves and the soil has no water reserves. We are in the fourth year of a complicated situation. We did a crop profile, we couldn’t find any moisture. Not all farms are irrigated. I like the idea of annual cover crops and it bothers me that I can no longer sow them… We would like to develop broadcast seeding in cereals at the end of May so that the cover crop benefits from the last rains of May/June. We are working on it, we have done trials, it is not always conclusive but we will get there little by little”; “the frost cover? There are always three ryegrass plants lying around, it’s always more complex than that. The gel covers work on certain crops but it doesn’t work all the time”; “the harvests are earlier and earlier so we can sow the covers earlier and earlier too. We dream of planting it in wheat but it’s very random. We only plant small seeds in this case. It depends on the moisture at the time of seeding. It has to be moist in the wheat. Maybe we should replant with wider rows?“

In the end, if we push this concept of permanent cover to the end, one of the major advances of the ACS should be the success of a living mulch, that is to say: the realization of an annual crop in a perennial cover. As an expert confided to us: “It is the superposition, at each moment, of a perennial cover in which we succeed in producing annual crops of interest. Some farmers are already doing this! For example, with dwarf alfalfa cover that they calm with glyphosate, combining it with a strip-till of crops of interest that benefit from a localized fertilizer application to ensure their start – with perhaps a localized irrigation – the time that the crop of interest passes over the present cover. The alfalfa cover takes over after harvest. There are no problems with weed infestations or weeds. However, there can be strong competition for resources at times“.

Box Agro-equipment

Some examples of machines used to destroy plant cover: Disc harrow, Tine harrow, FACA roller, Simple roller, Rotovator, Shredder, Row weeder, Rotary hoe, Currycomb harrow, Roto Étrille….

Figure 9. Examples of tools used to destroy plant cover. Translation : Déchaumeur à disques (Disc harrow), herse étrille (weed whacker)

Some examples of drills used in conservation agriculture: the Strip-till drill that only works the seed rows, with the possibility of adding water and inputs at the time the seed is sown; the disc drill on living cover (does not destroy the cover but folds it into the furrow); the tine drill on destroyed plant cover (sows under the straw obtained from the destroyed plant cover); the front hopper with boom….

Figure 10. Two examples of seeders used in conservation agriculture. Translation : Strip-till, Semoir direct (direct seeder)

Extending rotations and diversifying crops

The extension and diversification of crop successions is the last pillar of conservation agriculture. And here again, there is a lot to say. Breaking disease cycles through different sowing dates and development times, structuring the soil with varied root systems, providing organic matter by leaving crop residues or cover crops on the soil, storing nitrogen in the soil for subsequent crops… Most of these effects are completely in line with soil conservation agriculture. We will discuss this further on the digital part, but the choice of crop successions and crop rotation can be extremely complex, especially when one starts juggling with agronomic rules of crop succession, technical and economic constraints (particular soil and climatic conditions, existing production channels, need for fodder…), or production objectives on the farm… Crop successions are only limited by the imagination (I agree that this is a bit naive, there are quite a few constraints), but when you look at the diversity of existing rotations, between for example simple rotations, simple rotations with perennial crops, simple rotations added together, or 2+2 rotations, you can see that there is something to think about.

In short, rather than going into extremely technical details – that would be particularly long and difficult to follow – I have preferred to present here a few examples of crop successions that I have seen during my travels:

First example: Alfalfa (2 years) – corn – triticale – green beans/red beet (on the same field) – triticale/wheat – corn – barley “

“This is a rotation resulting from 5 years of work with economic constraints, and the dirtiness of the plots taken into account… With the drought, all the legumes, especially faba beans, it is complicated. Short-cycle crops – pulses, canning peas, beans – with a drought in the middle, it’s hell. 25 quintals in good years (compared to 80 quintals)“

Second example: A current 7-year rotation with :
- 5 winter crops: peas, wheat, rapeseed associated with clover/alfalfa, bread wheat, alfalfa or clover alone for regenerative fallow over 2 years (not harvested), spelt or winter oats
- 1 spring crop: soybean or sunflower (or both together). This may seem low, but the farmer explained that many spring weeds (thistles, ragweed, vulpine, etc.) develop with spring crops

“The rotation allows for 5 to 6 crops over 7 years. There is only one spring crop because of the weeds present (thistles, ambrosia, vulpine…). The alfalfa is not valorized, it is left on the ground. The crop after alfalfa fallow is in very good shape. The fallow increases very strongly the content of assimilable phosphorus“.

Third example: peas in double-cropping, wheat + soybeans in relay-cropping, sunflower sown with strip-till in white clover, oats in double-cropping with white clover, and alfalfa underseeding, wheat in direct seeding in white clover + alfalfa

This rotation is not yet in place but is being considered. The rotation allows 7 harvests in 5 years. The objective is to intensify the number of crops in the same time.

Reconciling Conservation agriculture and digital tools

A first general observation

Now that you’re starting to get familiar with conservation tillage, let’s move on a bit and look at the digital tools that could accompany it. We’re going to take it easy at first with some general observations and feedback from our contacts, before placing digital tools within the main pillars of soil conservation agriculture that we’ve already discussed: tillage, cover crops, and crop diversification. As you will have understood, this blog is mainly oriented towards conservation agriculture, so we will try to present digital tools as much as possible in this sense. We will therefore put aside transversal digital tools – applicable to all forms of agriculture – such as farm management information systems (FMIS) to monitor one’s plot of land and track cultivation practices, social networks and sharing platforms to decompartmentalize exchanges and knowledge, digital tools for marketing production… (even if some of them have been mentioned by our interviewees). Precision farming practices will also be set aside, in particular within-field rate (modulated fertilization, seeding density modulation…). These subjects are widely described elsewhere.

Digital, digital, precision agriculture, it more or less speaks to everyone, or at least it always evoked something in our interviewees. Several of them quickly made the distinction between these tools, considered as “high-tech”, and knowledge of agronomy, seen rather as “low-tech”. Without particularly positive or negative connotations, the high-tech/low-tech distinction was presented to us as follows: “Low tech is agronomy, that is, how it works basically. It’s something that requires no expense, only knowledge. Once you know what you want to do, you can ask yourself how you want to go further. High tech is cameras, GPS on tractors, sensors, irrigation triggering … It’s something the farmer can’t make himself“; “I’m pretty low tech but I look at a lot of what’s going on in digital. There are things that appeal to me“; “There is no more precision in conservation agriculture. In SCA, there is less precision. There is a whole fringe that remains in low tech“. In these interviews, we could feel the importance given to the return to the land, to agronomy, or to the understanding of the functioning of the system – which comes before the use of these digital tools. Nevertheless, from an external point of view, the high-tech/low-tech dichotomy that was sometimes discussed at length during our exchanges is amusing in the sense that several interlocutors who consider themselves low tech are actually quite well equipped compared to the vast majority of farmers. A small example that might appear dissonant to some: the farmer who considers himself low tech and watches “what’s happening in the digital world” is equipped with RTK guidance on all his tractors and camera guidance for his hoe. Some tools, particularly those for guidance and geo-positioning, are now largely commonplace and would therefore no longer appear as high-tech to some farmers in the field. This was all the more surprising for me because these geo-positioning technologies had allowed some SCA routes to flourish, especially those where the precision of the machine applications is extremely interesting. To this last assertion, a farmer – also a dealer in agricultural equipment – argued that geo-positioning tools had not made it possible to create new cultivation itineraries, but above all to gain a great deal of comfort in setting up these itineraries: “GPS is a comfort in use, but that is not what determines whether or not we go with SCA. This comfort is even more present in the conventional sector. The digital equipment we sell around the machines is first and foremost about ease of use. The objective is to be more efficient than fast. European agriculture is facing a cruel lack of manpower. We have the impression that this is accelerating. There are fewer and fewer people in agriculture. We don’t have robotic machines yet, even though everyone is talking about them. It’s the same thing in industry. Agriculture is no exception to this rule. The market is shifting towards highly equipped machines (bigger and bigger) where more and more hectares have to be worked“.

Before crossing digital tools and SCA pillars, I wanted to introduce here two general questions that were raised during our interviews (these aspects will be taken up in the discussion part of this post). These elements are not specific to SCA but continue – from a personal point of view – to question me a lot. The first has to do with the need for precision that is regularly raised by actors in the Agtech ecosystem. The question, quite soberly, could be summarized as follows: Is the main objective of digital technology to bring precision? I was given an insight during an interview: “Precision agriculture can provide a large block that does not concern the precision of practices, but rather the measurement of these different components, with the objective of certification to support labeling processes. This is where everything is expected. It’s more digital than precise“. The second questioning, supported by some of the people we spoke to, comes back to the capacity of digital tools to help understand the functioning of plots that are considered to be extremely complex: “Given the complexity of cropping and production systems, how can precision agriculture know everything about the soil, the precedents, the history…“; “Well, in precision agriculture, trying to modulate and put in a precise way what is necessary for the plants, is a good idea. When we talk about fertility, some of the yield variation is more due to soil factors (water management, structure management) than fertility problems per se. Using PA to make diagnoses and then being more precise in those diagnoses can be useful, but you have to be smarter than stopping at the idea that it’s growing less, I’m putting less in. Sometimes it can grow less because there is less fertility“. Are these questions at the heart of your concerns? We’ll come back to that later!

Improve your knowledge of your soil

The soil being the leitmotiv of all the SCA defenders, we are somewhat obliged to start there if we don’t want to be slapped on the wrist. Measuring what’s going on in the soil, we agree, is time consuming, relatively expensive, we don’t always know what we’re looking for and it’s not easy to be exhaustive. What is happening in the soil can be accessed directly – we are putting our foot down in a big way (this is what we will see here) – or in a slightly more subtle way (we will come back to this with plant cover and indicator plants). Some examples put forward by our interlocutors:

For the SCA aficionados, the farmer must go around his plots and it is with regret that some of the interviewees will tell us that farmers are rare in the field. In SCA, not much is needed, at least a spade to go and look at the soil. So why not imagine a connected spade or a connected penetrometer that would give an indication of the state of the soil structure?

“We need to monitor the soil temperature. In some crops, we won’t go to plant a seed if it’s too cold. If we had the temperature of the plots with 2-3 sensors per plot, it could provide information“.

“When do I intervene in SCA? The main thing to watch is the structural state and the biological activity of the soil. If it’s not the time to go out or to work the soil at the risk of compacting it, it’s better to stay at home and go out when the soil is dry again, but you still need to have the information. The Swiss have networks of tensiometers where they follow the state of soil re-wetting. They have set up red/orange/green lights to know if it’s worth getting out the shallow tillage tools“.

One farmer will suggest using imagery to track soil moisture status, before qualifying his statement, “As long as the growth is there and the soil is responding, there may not be much need to do“.

The most comprehensive way to measure soil condition is to make electrical conductivity or resistivity maps, combined with field expertise and soil analysis. Conductivity/resistivity, although exhaustive, is difficult to interpret alone because of its cross-relationship with soil water content, stoniness level, soil texture, soil depth, or the level of chemical elements present.

Little is known about the development and functioning of the underground organs of plants and their interactions with the rest of the soil ecosystem. The company Mycéa is currently developing and testing an underground imaging tool – Scanorhize – to study the development of roots, mycelia and mycorrhizae. The objective is also to understand to what extent cultural practices impact the installation of mycorrhizal systems.

Farmers advanced in SCA need to know what is happening in their soil, and to know it precisely. Some criticize the current physico-chemical analyses for their lack of exhaustiveness in the sense that they should go much further on texture (granulometric analysis), microbiology (counting micro-organisms, characterization of biological activity levels), metabolomics (analysis of metabolites – is the function ensured? has there been mineralization/depollution by micro-organisms?) Others also advocate being more specific about the different forms of nitrogen in the soil, especially about potentially mineralizable nitrogen (PMN), or the different types of soil organic matter (fast OM, slow OM). During the interviews, the names of laboratories such as Celestalab or Auréa came up regularly. One interviewee said that other laboratories “have the will to change; they would like to but they do not necessarily have the skills“. Could digital tools and sensors help to move in this direction?

To continue in this same vein and make the link with the energy/climate issues discussed later in the document, a field operator explained to me that “there is not much in the way of tools to determine the carbon in the soil. It is complicated and we have nothing“. Nevertheless, there is a lot of research work in the field of spectroscopy (near infrared, mid infrared…) to measure the organic carbon content of soils. Some portable spectrometers, to be used directly in the fields, are being developed. However, this work is complicated by the fact that the spectral signature of soils depends on many things, including soil moisture and soil type. So we will not see carbon spectrometers for use in the field just yet.

Rethinking tillage

Non-tillage in the strict sense, i.e. with shallow tillage (without ploughing), is still little practiced by farmers. Certain agricultural soils (stony soils, compacted soils, etc.), certain environmental or climatic conditions (drought, desiccation, etc.) do not easily lend themselves to no-tillage practices and lead some farmers in SCA to work the soil more or less deeply, at the risk, for example, of not having a fruitful harvest. These pedo-climatic variabilities could be an entry point for digital technology: “It is necessary to be able to control the depths according to the types of soil, to control the depths of sowing and tillage. If we move towards SCA, in the long term, we will work the soil less and less. There is an interest in determining notions of compaction in areas that are more compacted than others. SCA means coming back with a decompactor in a zone of silts (which would have been delimited beforehand)“. Another interviewee added: “The future of precision can be found in everything that has to do with soil compaction. Knowing how to preserve the active life of the soil without bludgeoning it. What could be interesting for the SCA is the precision that revolves around control farming, i.e., recording the trajectory of tools that have entered the plot. From this information, the farmer can opt for one of two strategies: Either, always bludgeon the same passage and do everything in offset from these areas, we speak then of ‘land staring’, or bludgeon the whole surface of the plot in a homogeneous way, in this case, it is about ‘land sharing’ “. Precision would then have its place in this journey towards no-till and non-disturbance of agricultural soils, particularly in terms of detecting areas compacted naturally or by the action of agricultural machinery.

Limiting the work and disturbance of the soil means limiting the passage of agricultural machinery in the plots as much as possible. So why not get some fresh air? One farmer noted that “there is a future in the drone. We could sow 400 ha for example with a drone and the sowing could be done on 3 to 9m wide. This would allow us to reduce the use of the seeder attached to the tractor, which is too heavy and forces us to wait until we have harvested before seeding. In addition, the drone could make it possible to share tools. It is easy to find several farmers who will buy a drone“. We haven’t talked much about robotics so far, but it would be possible to imagine fleets of small robots weighing a few tens of kilos, working in swarms, and taking care of the seeding with precision. These very light robots would make it possible to limit soil compaction to a minimum.

Focus on permanent soil cover

Characterize the quantity and quality of plant cover. This is perhaps the service one might first think of given the plethora of agricultural imaging providers – whether by drone, aircraft or satellite. In ACS, however, we don’t just think in terms of vegetative expression or biomass: “Digital technology could provide us with global information on the cover and its mass. This could be interesting. Depending on the mass produced, we could capitalize on this or that. The difficulty is that all of the information is made up of the underground and aerial parts of the canopy. It is not easy to have relevant information on the roots. So how do you assess the diversification of the root system and the condition of the rootlets? There are conductivity measurements but conductivity is a resultant. We must be able to explain it. What explains it? Is it the fact that the soil is fine? Is it the hydromorphy? Is there a limestone slab underneath? Is it pebbles? It could be all of these things at the same time“. You won’t be surprised by the reference to the roots of these cover crops – and not only to their aerial part – for SCA enthusiasts, as soil is an important element for them. This aspect will be raised in another interview: “I can see a camera above the ground to characterize the cover. However, just because I have a lot of above-ground biomass doesn’t mean I’ll have a lot of below-ground biomass. For myself, I sometimes prefer to see roots that have made structure than to see a lot of aboveground biomass.”

Having an observation of the canopy, using an image for example, is good, it already gives information. This information is direct: we follow the state of the canopy. But if we go a little further, we realize that the state of the plant cover, by the development of certain species rather than others or by the speed of its development, could provide indirect information on the soil. And this is where things start to get interesting: “Plant cover is an excellent indicator of soil condition and much better than a yield map. Being able to map the vegetative state of cover crops tells you much more than other things. As for a cultivated plant, there are many biases, especially concerning fertilization, which attenuates a lot of variability in the plot. When you sow your cover crops, you always find yourself in more complicated climatic conditions, there is no fertilization, and everything comes out”; “In plant cover crops, we have mixtures, and in certain areas we will see different things develop. Could we map it tomorrow? Mapping plant cover crops to be able to bring down this mineralization – which varies from one area to another – in the manure forecast plans. Cover crops are revealing plants and what we need is to be able to quantify the development of cover crops before destruction in order to determine these heterogeneous zones and adapt to them. Why not modulate the cover crops, taking into account the complexity that they can have. To be able to say to myself that on soils where historically I have a high potential mineralization, I could observe the presence of crucifers and grasses or even on soils limited in nitrogen, to be able to observe leguminous“. Getting information about the soil indirectly from revealing or indicator plants, in a non-invasive way, may give some people ideas: “What could be the cause of the heterogeneity observed? To compaction? To a lack of phosphorus? We replace the eye and the feeling of agriculture. Digital technology is an aid, that’s for sure. Seeing differences in coverage makes you put on your boots to go and see the middle of the field where you don’t often go, and possibly take a sample. Digital can be a trigger for reflection. It won’t be the reflection but it will help to find the solution“.

To be able to characterize the state of the soil, it would be necessary to be able to identify precisely the plants in the canopy, and not only if they grow or not. And this is true that it is not yet won. Some players are starting to offer solutions for detecting and even identifying plants. For example, we could mention Carbon Bee Agtech and certain perennials or Telespazio and Datura plants in cash crops. This detection/identification could then go even further, to discriminate them within plant cover. And there, we could begin to open new doors: “If tomorrow we know how to do this, we will change the regulations. We will no longer say that SCA has the right to a glyphosate exemption but that glyphosate only has the right to be used to kill perennials in a very localized way by localized drenching or spraying or whatever“.

Let’s also go back to seeding for a moment. We had discussed above about drone seeding with regard to the limitation of tillage. Drone seeding of plant cover could also be totally feasible. For example, trials have been set up for the seeding of cover crops in wheat without damaging the wheat plants, and the seeding of double cover crops on farmers’ plots in SCA in order to reduce the use of weedkillers. One of the interviewees is more interested in planting cover crops in plots that are difficult to access: “In viticulture, the use of drones to plant cover crops in sloping areas where the tractor cannot reach. It’s still in development, but it’s already making it possible to introduce biodiversity into the vineyard in places that are difficult to access“.

In addition to facilitating the planting of cover crops, digital tools could also be used to provide advice and recommendations on these cover crops: “Should we plant cover crops if nothing will grow? Digital tools will help the farmer to decide whether or not to act“. We are also witnessing relevant initiatives in this sense within the framework of the GBA. This is the case, for example, with the Acacia decision and calculation sheet, developed by the Magellan GIEE and available free of charge, or the cover crop quantification tool, MERCI, developed by the Charentes Chamber of Agriculture. These local initiatives are very interesting, as one of our contacts pointed out: “Locally, the chambers of agriculture try to personalize advice on plant cover. Cover crops are regulated region by region“.

Digital and crop diversification

Let’s end this overview with the last pillar that SCA emphasizes: diversification and extension of rotations. Managing rotations is particularly complex for a farmer. It can be reasoned out :

in space (crop rotation) and time (crop succession),

in the form of short or long rotations,

according to the constraints and/or objectives of the farm,

according to predefined agronomic rules or past experience,

according to the farmer’s profile,

….

Some farmers will reason in the very short term while others will imagine it in the long term. Some will have fixed rotation strategies no matter what, while their neighbors will have very adaptive strategies. Some will not even think in terms of rotations, but will put the right crop in the right plot at the right time, depending on how dirty the plot is or on the development of the canopy.

In short, “When it comes to designing rotations, it’s a headache. For the longer term management of a farm, there is only digital technology that allows us to do this,” confided one of our interlocutors. And to continue: “Digital technology is capable of modeling many things: crop successions, disease risks, agronomic rules. If it is a limiting factor, it will take it into account. The objective is to collect this data from Arvalis and others, and to compile it all. There are a lot of people who have interesting things, but it all stays with each other. It is not capitalized. We need to bring in tools to provide diverse and varied things. Everyone should share their experimental results in a large national library. The tool must take into account all these elements, but we could also imagine taking into account priorities for crop rotation management – which actions should be undertaken first? We won’t be able to track everything, we’ll have to prioritize things. What is the most important issue? Fertility? A lack of organic matter? All of this will determine the type of rotations that we will implement“. What is perhaps already lacking in France is a clear picture of the current state of crop successions and crop rotation, and to follow these rotations over time. It is a pity because one of the most useful data sources for working on this subject exists and is available in open-source. It is the graphical parcel register (RPG) which is used as a reference for the instruction of the CAP aids. The RPG has evolved a lot since its creation in 2006, with a major change in 2015 (the availability of crops grown at the scale of the crop block with more than 300 different crop classes), but it remains that there is only to enhance it. INRAE has worked hard to develop a tool that takes advantage of the RPG to monitor the dynamics of agricultural land use: RPG Explorer.

Even if the tools available in the field are more a collection of expertise and experience than modeling as such, let us salute once again the initiative of the GIEE Magellan, which has made the “Acacia” tool available free of charge, and that of Arvalis, which has developed the “Choix des Couverts” tool.

A little nod here to the yield maps (this was the subject of my PhD thesis). They are generally presented as a result of everything that happened during the year, and can be used to evaluate the production potential of a plot of land, and why not rework the itineraries carried out there. As one participant explained: “the yield map, provided that it is reliable (in 99% of cases, it is not reliable because the machine is not calibrated), will allow us to adapt. If I have a small potential, there is no point in investing. The yield map is a report at the moment ‘t’ of what happened during the campaign. It is an indicator, a tool that will allow us to determine if the action is positive or not. If I see that in a zone the cursor does not move, it means that the potential part was perhaps not of interest. The fertility may be the cause of a major imbalance that may cause it to not produce. If I stop at the yield map, I could have been wrong. It needs to become more reliable. It’s a great tool because you can go down to the very fine points and you can explain things. The most important thing is the yield maps to quantify the work we do on the plot“. I’d like to take this opportunity to also share a scientific article – not particularly difficult to read – that suggests using yield maps to discriminate between profitable and unprofitable production areas, and implementing conservation strategies in the latter (wildflowers, red clover, white clover, alfalfa, phacelia, peas and oats…). The title of the article is quite evocative – and I have taken part of it for the title of this synthesis – ‘when conservation agriculture meets precision agriculture

Figure 11. Spatial distribution of benefits in identified potentially fallow lands. Source: Capmourteres et al. 2018. Precision conservation meets precision agriculture: A case study from southern Ontario. Agricultural Systems. 167, 176-185

Yield maps are also used in a number of other scientific studies to implement systems that are close to SCA (Kitchen et al., 2005; Yost et al., 2017, 2019). For readers interested in yield mappings, I invite you to find the blog posts on Aspexit that discuss them, there are quite a few.

At the convergence of digital and agri-equipment, let’s ramble on about the extreme cultural diversity we might see in the fields. We have just seen that some unprofitable areas could be reoriented towards something other than cash crops. Let’s think about the variation of seedling density according to soil characteristics (this is already starting to be done): “They have quite precise soil resistivity maps that they correlate with plant behavior, they know that in the shallows, lentils do not do as well but flax does better, and they also manage the fertilizer inputs that go with it“. But let’s also think about multi-cropping, or mixing varieties with multi-hopper drills, and geo-positioning systems to place seeds so that these multi-crops or varieties develop and interact as well as possible. Let’s think about placing annual crops in perennial cover. “We can leave strips to reseed beets or sensitive plants, we can have strips without cover, we can organize the cover in strips, we can do relay-cropping.” All these cropping itineraries are complex, much more so than those currently used. The implementation of these itineraries would also require a huge revision of the digital solutions currently developed which, although already technically advanced, often only consider one crop at a time.

Let’s try to take a step back

Does the constant search for precision make sense

Soil conservation agriculture is an agriculture that seems to be returning more and more to the valorization of agronomic knowledge that some of our interlocutors describe as “low tech”. The current orientation of agricultural systems towards this soil-centered agriculture would require actors in the world of SCA to constantly learn about the realities of their agricultural environments, researching, experimenting, and discovering several scenarios that would allow them to fulfill the promises of this agriculture (we will talk about experimentation a little later). Soil conservation agriculture as we have observed it during this monitoring work is an agriculture that is still building its knowledge base. It necessarily requires a transition period, and that takes time. It takes time to revitalize your soils. It takes time to build up organic matter levels. It takes time, simply because we work with living things: “the transition must be well thought out. It is essential to consider the state of the soil in order to modify one’s practices, especially the battance index. The reduction of intensive tillage must be done in a soil whose biology is capable of compensating for the reduction of tillage. The weaker the biology is at the initial stage, the more gradual the transition must be“.

With this reading prism, in a transitional agriculture, should the notion of precision be preponderant? “We work with living levers, crop varieties, permanent cover. I have never asked myself what tool is missing to implement this or that technique. I talk a lot with a group of 15 to 20 French farmers who do some organic farming but who mostly practice direct seeding or are close to it. Nobody talks to me about within-field variable rate. Yet these are people who are very careful about what they do. At worst, these farmers will redo a few small tasks that they would have missed, but they don’t do modulation”; “I do soil tests and I zone inputs, but it’s by the big ladle. I am located in a rather specific area. I reason according to the limiting factors. Precision in the plots is not my first challenge. My first challenge is rather to increase the level of productivity. I prefer to put material than precision. I mainly use cereals and corn; I’m on somewhat complicated land with reduced potential and I don’t make it a limiting factor. I preferred to reintroduce livestock into my system and manage game damage… today, precision is not my limiting factor. Today, precision is not my limiting factor. The day when precision comes to the top of the list, it will become topical again“. A final contact, after having accompanied many farmers in this transition to SCA will say to me: “I advise the farmer to work with live rather than digital. Some players tend to focus on digital technology, but I’m more in favor of agriculture that tries to simplify and reduce our dependence on technology. If we continue on this path, we risk ending up in a dead end. Then it’s contradictory: we are developing the strip till technique. Without GPS, we couldn’t do it. I am a bit of an idealist, but is the debate in the right place? We need to go much further and not only focus on the technique. We are not solving the real problems and issues. It’s a bit like the electric car. We move too much in fact “.

Precision Agriculture, in its terminology, implies that we try to reason out the cultivation itineraries as precisely as possible, taking into account the spatio-temporal variability of the production factors in the fields. In principle, there is nothing wrong with being precise, it is even highly recommended. But as we have just seen, precision is not necessarily the number one factor to consider, especially in the context of agriculture in transition (in SCA, for example), simply because we have many other things to worry about. Precision comes at the end, once you are well established in your system and you are very clear on your itineraries and practices. Nevertheless, I think it is relevant to question the legitimacy of this precision in the sense that so many behaviors, flows, relationships, interactions or even cycles are still unknown to us, starting with the soil. Does precision make sense when the range of uncertainty in which it is integrated is absolutely gigantic?

Farmers, technicians and advisors who are very interested in SCA are, in general, very humble about the fact that the interactions between soil, plant and climate are incredibly complex and that they do not always understand them. The feedback from these respondents is particularly edifying and should be taken much more deeply into consideration by the digital and precision agriculture players. One of the people I spoke to spoke at length on the subject: “When we look at nitrogen fertilization, the UAC (apparent use coefficient) is close to 60% and it drops to 50% with direct seeding, I’m sure. That means that only 50% of the nitrogen applied will actually be taken up by the crop. It doesn’t mean that the rest is lost but that it is captured by a set of other elements (biological activity, residues, mycorrhizae…) because the rest is covered with mulch. A large part of the nitrogen is already consumed by all the biological activity. In return, this nitrogen will be given in a diffuse way by the degradation and the consumption or the evolution of activity of the organic matter. When you see that the UAC is 50% (in SCA), that the impact of climate can make mineralization vary from 30 to 50%, then what do we do, try to be precise at 10-20 units of nitrogen? While the climate will make it vary to 50-80 units? If only 50% of the nitrogen is absorbed, where is the precision? We set up an experiment at the agricultural high school not far from us. They measured the autonomous annual mineralization of a plot. The extremes ranged from 70 to 120 units of nitrogen. What do we do with that?“

And this interviewee reiterates, “The more self-fertility we have, the less we’ll be able to predict how much fertility the soil will spit out in terms of nitrogen. There are several ways to deal with this, notably through crop associations. Because if we are in a period where there is favorable photosynthesis, it is the legumes that will fix the nitrogen and do precision agriculture. If we are in a period where the soil has a lot of nitrogen, it is the grasses and crucifers that will take their place. The use of plants is a much simpler and more precise way of integrating the variability and unpredictability of the climate“. Still on the subject of fertility, one speaker returned to the method of nitrogenous residues: “The problem with the residue method is that it is not dynamic. 4% OM means nothing. What is the mineralization rate of my soil? What will my soil release?” On these aspects of fertilization, one of the interlocutors was a little more moderate on this precision: “Yes, it makes sense to modulate. The real sense in modulating is when you have at least 20-30 units to modulate. When you have differences of 10 units and plant cover, it is difficult to consider the dynamics of nitrogen within the soil. On the whole, however, the difference is expressed more or less, but at some point it is there. The dynamics of nitrogen in relation to the potential generates a need for nitrogen“.

Let’s also take a detour into soil electrical conductivity/resistivity, currently one of the only methods to map soil units at high resolution. Once again, the spatial precision is important, but the mapped data remains objective. As one respondent confirmed to me by telephone: “Electrical conductivity is important, but you also need redox potential and pH, the depth of the soil, the useful reserve to qualify a soil. Maybe one day we will have tools to obtain the redox potential, but for the moment we are not there. Because the electrical conductivity depends on the soil moisture content and the number of ions able to transmit electrons. It also depends on the farmer’s practices. The measurement of electrical conductivity will give the speed at which organic matter is mineralized but will not give the quantity of organic matter in the soil, even if there is a weak correlation between the two“.

You will have seen from these examples that precision, even if it can be reassuring at the time of a recommendation or an application in the field, is perhaps not as precise as all that when you take a step back. And we have only explored a small part of it. I haven’t even talked about all the nitrogen cycles in the soil, or how mycorrhization was created and how their interactions were managed…

Conservation Agriculture, Precision Agriculture, and within-field variability

You should have understood my position on Precision Agriculture by now. For me, it remains above all a scientific discipline that aims to study and exploit the spatio-temporal variability of production factors in plots (the soil, the plant, the climate, or the farmers’ practices). At the basis of precision agriculture, there is therefore heterogeneity – be it spatial and/or temporal. But what is the final objective of all the applications deployed in Precision Agriculture? To erase this heterogeneity, i.e. to homogenize the plots, or on the contrary to accentuate it? The answers are often in the direction of homogenization, even if some contexts prefer to maintain heterogeneity. But does precision agriculture really achieve its goals? During an interview, a farmer put it this way: “We are accentuating the heterogeneity of the plots when I should be trying to homogenize the fertility of my plots, and that is my role as a farmer. Tillage is a great way to make a plot more heterogeneous! If you have a little relief, you pull the soil from the top to the bottom. Over the years, we will limit the thickness of the soil in one place, we will look for a little bit of subsoil (and thus dilute the organic matter in some places and increase it in others…). Under the pretext that it produces less on a dry area, we put less fertilizer, less seed, and we increase again this process. It is logical in the short term from an economic point of view but it is illogical in the medium term. I tend to load the less productive areas with organic matter. I’ll load a little more because it’s maybe sandier and shallower. Since the organic matter is low, the ability to store water is even lower. I’m correcting from the bottom up by encouraging better productivity by encouraging better soil. If PA could be used to re-homogenize the plots from above, that would be really interesting“. In the same vein, a second expert added: “The enemy of soil is mechanization. If we work on the structure, we improve things from the start. Those who work well on a regular basis, the year is certainly less good but they are much less affected than the others“. A final contact explained it to me as follows: “The AP wants to erase heterogeneities. The objective in SCA is to homogenize the plot”. Do you feel this difference, which at first seems subtle, but is in fact strangely powerful?

Once again, Precision Farming is based on heterogeneity; these are really two notions that are intertwined. And if we want to find heterogeneity, we will always find it… Many tools exist to measure and quantify the heterogeneity of production factors in agriculture (I refer you to the various infographics on this subject on the blog). Measuring heterogeneity is not as complicated as all that. The complexity lies in taking it into account. “With variable rate applications, when we map and they tell me that it grows less well, what do I do with it? Mapping tools are for financiers and not for agronomists,” said one of the interviewees scathingly. The question is always the same: What to do with these observed heterogeneities? To this question, one of the interviewees answered as follows: “What is not clear in the literature – grey or scientific – is what to do with the heterogeneities. I see two possible paths. The first is homogeneity at the time of market entry. Identifying heterogeneities is a way to increase standardization at field exit. The dry spots will be where there is less grain, and we can provide some sort of compensation with targeted irrigation. In this first case, the measurement of heterogeneity is seen as a first step of characterization, to make up for the causes of the differences. The second path is more oriented towards an agro-ecological vision of the matter, with an ambition to amplify heterogeneities in order to increase diversification and improve the overall performance of the system, but by relaxing the assumption that we end up with a single product or a single ambition for a plot. We can not only amplify but drive heterogeneities made desirable. There are many things about the effect of heterogeneity that can make tasks less attractive for a pest, that can allow us to increase the genotype-environment relationship at each point and to do at each point what it is good at. And this same expert concludes: “There is a major ambition, and we have sensors to measure heterogeneity. And this ambition is not the same for SCA or organic farming“.

What if it were possible to homogenize the plots in a different way than by making modulated or differentiated applications? Within the framework of the SCA, could we not let the plots homogenize themselves with the help of plant cover? This observation struck me after my field visits and the discussions I had. As one of the farmers interviewed summed it up: “The less the soils are worked, the more homogeneous they become“. Another farmer spoke at greater length on the subject: “We take a plot of cereals that is fertilized flat throughout the season. At harvest, we will have quite variable levels of residues. We put a multi-species cover crop in this plot. We can be sure that we will have very little risk of leaching with this cover. The risk of having too much nitrogen is zero since we have a cover crop and we don’t work the soil. It’s a multi-species cover, so in places where there is an oversupply (or if the wild boars have eaten the cereals), there is a lot of nitrogen left and the crucifers and grasses will explode. And where there is less [nitrogen], the legumes will grow. At the end of the season, I’ll have a canopy with a biomass between 3 and 5 tons of dry matter with heterogeneous aspects of the canopy. If we do a nitrogen residue analysis, we will have between 35 and 45 units. And if we analyze the biomass of the canopy, I would have around 100 units of nitrogen in the canopy with +/- 20 units of nitrogen in the system. Thanks to this conservation agriculture strategy, the environmental risk and all the arguments of precision have been evacuated and, in addition, we have worked to restore homogeneity in the overall quantity of nitrogen and organic matter. And that on the whole plot, it is almost impossible to do with an algo! And there, we don’t need this technology. An additional heterogeneous element: manure is spread in the cover crop. We make beautiful analyses but between the manure under the trough, under the scraping of the platform, the one that was in stock, there is nothing homogeneous. When it’s spread, it’s not homogeneous either; all that will be settled“. To tie in with the section on the notion of precision in transitional agriculture, do we really understand everything that is going on here? “What is the effect of a crop canopy on mobilizing and making elements available to the plant? Is it related to biological activity? To mycorrhizal activity? Is the heterogeneity not due to a soil dysfunction? We will move the cursors but we will have some heterogeneity. Sometimes, there are things that are unblocked at the structural level with cover crops“. The heterogeneity can come from structural problems”, said one of the interviewees.

Nevertheless, as an expert in the field confided to me, we will never be able to homogenize everything: “The more we advance in time, the more we will erase the heterogeneity. But if we have structural heterogeneity, we will not erase it. There is no such thing as a homogeneous plot of land in France in terms of soil texture. In the same plot of land, we can have silts, alluviums, silty-clayey soils… And this will not be erased. We will make the soil evolve in 10 years with a real difference“.

Field experimentation and feedback in conservation agriculture

Soil conservation agriculture is starting to be talked about, and is gradually becoming popular. Many farmers are interested in it, groups and structures are being formed, the subject is taking place in the current debates for many reasons (carbon agriculture, soil agriculture…). From an external point of view, one could have the impression that SCA is a new way of farming, but is it really the case? Some of the techniques developed in SCA today would have complemented the ancestral techniques practiced in different parts of the world; these techniques were especially practiced in arid environments where the conservation of resources used to produce water in particular, was paramount. Our exchanges will have allowed us to discuss some of these techniques: “There are “ancestral” practices such as the zaï, the half-moon or the stone cordon, and also practices of cultural association that have been broken with the new technical itineraries of the green revolution. Fortunately, there was strong resistance and these practices were able to persist. Today, there is a large proportion of farmers who have acquired a good deal of technical knowledge that has evolved over time. Current techniques such as direct seeding have been added for the physical protection of the soil against erosion. These innovations were added to the first palette of these early practices such as zaï“.

The world of SCA, but also the world of agriculture in general, is a world that evolves very quickly. As mentioned above, SCA allows for a lot of experimentation on the part of farmers. But have you ever wondered how to envisage experimentation in an agriculture that necessarily requires a transition period and that takes time? If we assume that SCA is one of the interesting technical itineraries to implement on a farm, how can we ensure that the benefits of these approaches can be put forward on the farm? This is a line of work of one of the interviewees that I found particularly relevant to share in this article. Here are a few excerpts: “We start from the principle that when you talk to a farmer who is going into SCA, there is a more or less long transition period. Based on this principle, how can we set up experiments without taking this transition into account? It is very complicated. When you want to set up a control, what do you set up? Do you put a ploughing control in a no-till field? If you plow a land that has been in no-till for 10 years, it is sure that your plow control will have the best yields because you will have the bonuses of plowing and no-till for 10 years! In SCA, there is a different rotation aspect. It’s complicated to compare things. Less and less, we focus on the controls because thinking about the controls is complicated“. My interlocutor will give the following examples in the rest of the interview:

“For an experiment with associated versus non-associated rapeseed, there it’s easy, you don’t work your soil.”

“As soon as we set up experiments on tillage (no-till, Simplified Cultivation Techniques and others), the question of the control becomes complex. More and more, the control is the farmer’s technique. It is already a control that is advanced.

“We no longer compare the modalities in terms of yield but in terms of margin!”

“It is complicated to follow complete systems because of the lack of human and financial resources. More and more, we work on an associated rapeseed in year ‘n’ but also on the wheat of the associated rapeseed and we realize that we have an effect on the following wheat. When we make calculations, we try to go as far as possible. For the beets with companion plants, yes, we lost a little bit in beets, but we follow the yield on the wheat after the beets. On the scale of the mini-rotation, you can do some pretty good things. We managed to do it in rapeseed and we are trying to do the same thing elsewhere. It’s complicated for very profitable plants like potatoes. We have cropping patterns that are very good from an environmental point of view but that cause yield losses on profitable crops. There is this notion of a complete system. Until you get better at marketing these potatoes in these new itineraries, there’s no way around it.”

Experimentation is therefore particularly complex. So much so that some of the people we spoke to highlighted the delay of certain support or experimentation structures on these subjects: “At the level of the technicians, we are not all there. The institutes are far from the reality of things. I did a training course that was developed in cover crops, the trainer gave us examples of grasses from the 70s and 80s…“. Several interlocutors, most of them farmers, urged to really look at what is happening in the field, on the farmer’s plot: “The technical institutes are useful, but those who pay them tell them which way to go. These institutes are behind the times. Agriculture is changing at a great speed but the farmers don’t know it. Today, agriculture is going in all directions and at full speed. Some are going too fast and others are lagging behind. Arvalis is doing direct seeding, yes, but not in the right conditions”. Some farmers will nevertheless be more nuanced: “Originally, our technician was a chamber technician. He found a place at Terres Inovia and we wondered how to do it. In the end, we didn’t find an answer with the local chamber of agriculture and we worked with Terres Inovia, which agreed to give us 25 days a year of our technician’s time. Today, at the chamber, there is nothing… But there are chambers that have the people in front of them“.

In reality, without trying to pit one against the other, it is perhaps more collaboration and co-construction that the SCA could use: “There is a need for collective and collaborative intelligence“; “There needs to be a co-construction of researchers, decision makers and farmers for the regeneration and maintenance of soil fertility.” And this co-construction could already be done between farmers: “For a farmer who would like to start conservation agriculture, he must get closer to a local group because there are important differences between regions. He can find farmers who have been practicing it for years or even decades”. Let’s think about forums, social networks, and exchange platforms to exchange and share knowledge, date/attach photos to a plot, set up discussion groups… A few examples: Twitter, Whatsapp, Landfiles, Neayi… Be careful not to be overwhelmed by tools, and not to have too much redundant information This co-construction could also take place between many different structures (well, I may be a bit naive…) – a collaboration between farmers and technical and research institutes for the choice of research tracks, for the choice of experiments and in the popularization of information. On the educational side, collaboration between teachers and farmers would promote the training of engineers, technicians and doctors, in line with advances in SCA. Finally, a broader collaboration between farmers, institutes, and decision makers would feed the decision making process with a positive impact on soil conservation agriculture.

And digital technology could play an important role in supporting these experiments, in order to set up experimental plans, to avoid making mistakes, to have objective data, to have a spatial and temporal follow-up…: “maybe we should do large-scale phenotyping, on a farm scale. Couldn’t farmers in the future work on accumulating data on the mixed crops they have set up on their farms? In terms of digital technology, you have to discriminate between crops, measure a lot of parameters, it’s not an insignificant job. It’s something I’ve taken up quite a bit, it gives farmers a more interesting place in the creation of knowledge. It is more in line with agro-ecology in the sense that lay and traditional knowledge would be much more integrated“. However, it is still necessary to have sensors that measure indicators of interest to farmers in soil conservation, including more detailed information on soil elements.

Conservation and Precision Agriculture : Efficiency, Substitution, or Redesign

In 1996, Hill and MacRae proposed a classification of three strategies to accompany the transition to a more sustainable agriculture, moving away from the current conventional model. We had already talked about them in a previous blog post ‘Precision agriculture in all its intimacy’. It was about the strategies:

“Efficiency”: the objective of this strategy is to optimize the existing production system by limiting the consumption and waste of inputs and resources but without changing the functioning of the existing system (e.g., reasoning the application of chemical weed killer in the plot in space, time or dose for example)

“Substitution”: the objective of this strategy is to replace the use of non-renewable resources and/or resources with a strong impact on the environment by resources with a much more limited impact (e.g. replacing a chemical weeding method by mechanized agricultural robots)

“Re-design”: the objective of this strategy is to attack the intrinsic causes of the problem and to rethink the production system in order to avoid the need for external inputs (e.g., to use associated crops to limit the appearance of weeds).

These three strategies were recontextualized for us within the framework of the SCA by one of our interlocutors: “The ESR theory – Efficiency, Substitution, Reconception – these are the three steps of the agroecological transition. Let’s take the example of a farmer who is not in GBA but who reasons his inputs as well as possible, he is in the E. Then, let’s look at the case of some Brazilian farmers in GBA who use treatments based on microorganisms. They are in the S of Substitution because they replace chemical treatments with treatments based on natural products. Finally, a farmer in the R of Redesign is the one who will say: “I don’t want to treat anymore or I want to treat as little as possible”. As a result, he will start to transform his system. This farmer may, for example, reintroduce cows into his system in order to put his soils in good condition. The plants in such a system will most certainly be healthy“.

So how do digital tools and precision agriculture fit into this framework? Two interviewees will give us an overview: “For me, precision agriculture is used 9 times out of 10 in E systems. It is also used in S systems, but much less than in E systems“; “Digital tools allow for input optimization. Before, we used to apply the same treatment everywhere on the plot, but now this is no longer the case thanks to digital technology, which allows us to better understand the specificities of each plot“. Precision, as it is currently presented, seems to be at the service of any system that tends to optimize the use of its inputs. But is the problem well posed? Shouldn’t we question the use of these inputs rather than trying to optimize them? This observation was also discussed during one of our interviews: “precision spraying? It’s a good idea with the recuperator panels and others, we have the possibility of reducing the quantity of pesticides… What we see at the same time is that, having put the emphasis on these sprayers, we continue to remain in an agriculture where we spray… What do you call a sick situation? Precision has embedded in it the fact that this is where we’re going to make the advances. It is the way for some to change nothing and to push a step further in its industrialization“.

However, one could qualify this statement by arguing that the optimization of inputs in agriculture has also allowed us to reflect on the agriculture we want for tomorrow. However, it may be necessary for precision to rethink its intervention in a different way, at the risk of not keeping up with the evolution of agricultural and agri-food systems.

The thorny issue of glyphosate

Come on, admit it, you’re happy… I can feel you rubbing your hands together! You would have been so disappointed to hear about SCA and not read a single line about glyphosate. A good French-style debate, everything we like! We’ll try to outline the debate before pointing out where digital technology could help.

For the non-aficionados, glyphosate is often used in direct seeding under cover, essentially to calm down or help destroy the cover so as to let the cash crop develop at its best. And that’s what people are talking about! Let’s not wait any longer and put our foot down, what do the people interviewed say? “We can’t do without glyphosate. The very first weed killer is fire. The state of Australia today? We burn the organic matter. It’s a desert now. The second weed killer is tillage, which is used in Iran, Iraq and Syria. What is the long-term impact? These are also deserts… The third weed killer is chemical. It is thanks to glyphosate that we have been able to limit erosion. It is the first time that we have managed to regenerate the soil”; “we have one of the oldest SCA farms in France; we have been doing this for 40 years. If there was a problem, I would have to see it”; “Glyphosate is the sword of Damocles that SCA has over its head“.

The detractors of glyphosate will blame it for its harmful effects on human health, soil health, earthworms, or the sanitary state of waterways: “It is true that we do not find residues in seeds and therefore we do not find them in human consumption. But in SCA, we talk about soil conservation, we can’t say that glyphosate has no impact on soil life. There is a study that shows that glyphosate has an impact on earthworms. Glyphosate is not water, I think that the discourse is not well put. Glyphosate is found in water even if agriculture is not the only cause of the presence of glyphosate in water, there is also household water from homes”. To which the defenders of ACS will reply: “Glyphosate does not have an aromatic nucleus. It has a half-life of 21 days in a well-functioning soil. In water, it is those who do tillage that make the soil take the glyphosate away. We don’t have erosion, so there’s no [glyphosate] in the water. The problem comes more from the adjuvants (fatty acids) than from glyphosate“; “What is missing in organic field crops is the use of glyphosate. If the crop gets dirty, if the weed seeds mature, it will take 20 years“; “If we had an AB label with an authorization to use 1L of glyphosate per hectare per year, we would be doing super virtuous agriculture with energy savings, a return of biodiversity… Glyphosate is one of the least dangerous pesticides if it is used under these conditions. A tiny drop, it’s incredible what it can do”; “Glyphosate is a false problem! It is not applied to crops. We don’t have GMOs, we have rotations – natural agriculture is an oxymoron”; “For me, precisely because there are virtuous practices with glyphosate, it is a huge mistake. It is unfortunate for this form of agriculture. The big laboratories are very clear, there will be no other molecules, we are not looking for anything. And their competitors, it’s the same. I think we have to be aware of this. I think it’s a pity that this molecule has been stigmatized“. To have seen soils worked in SCA, the earthworms seem to be doing quite well…

Glyphosate remains a pesticide, no farmer is happy to spray his fields (no, really, I assure you…). Are there alternatives? Do they make sense? One farmer summed it up for me this way: “It will take more effort and it will be more expensive. Either you stay in conventional and mix herbicides – and it’s much more expensive than glyphosate – or we will have to use mechanical tillage again. It will have an impact on the soil, so it will have to be counterbalanced by something, maybe a lot more cover?“; “Glypho is crap but it’s no worse than the others. With 2L of glyphosate per hectare, my soil is getting better and better. We produce spring barley for brewing; we test for glyphosate and the barley does not contain it. If we don’t use glyphosate, we’ll go back to intensive tillage, which means a lot of mineralization and therefore less carbon storage and more erosion. We don’t touch the soil and therefore we have to weed“. In the first case, the problem of pesticides is not solved (except by producing elements with an effect similar to glyphosate – a cyanobacteria from algae?) and one can wonder in any case if we will really stay with glyphosate: “Glyphosate is the first on the list, after that it will be the rest. Civil society does not want it anymore. Will it change? I am unable to say,” replied one of the interviewees. In the second case, we would return to tillage, but we would be attacking one of the pillars of the SCA. In reality, it is a little more complicated than that because the definition of SCA is not crystal clear. Some people do light tillage, others do no-till but with little cover, and still others will do no-till under plant cover. Could we have found the solution? It would be enough to do SCA but with a little more flexibility on the tillage! To be more precise, it is mainly direct seeding under green cover that is threatened by a stop of glyphosate – this itinerary does not rely on tillage.

There would therefore be several forms of SCA, and this does not help matters, especially from a legal point of view: “If it turns out that glyphosate is exempt from SCA, we will have to define who is entitled to it, who is not, and according to what criteria”; “We may be moving towards an exception for SCA, but I still have questions: how will this exception be justified and who will be legal on it? Who has the right, who does not? A no-till drill is a disc that goes into the soil. What’s the difference? The conventional farmer with his chisel is a tooth that goes into the soil. How can we legally make the difference? What is the message that is going to get through…?“; “Either people have the right to chemistry and they have to be in SCA; or they don’t have the right to chemistry and they work the soil”. But perhaps it is in these prevarications that the digital could come in. If we consider that SCA brings many positive benefits – reduction of fossil energy emissions, carbon storage, biodiversity, better water efficiency … – we will have to set up metrics to qualify and then quantify in a performance score what farmers are doing in relation to the objectives set. Digital tools could be used here to objectify the measurements and to monitor them over time. As you can see, if SCA expands, it will certainly be necessary in the coming years to monitor the practices of farmers engaged in SCA. Remote sensing could, for example, be a territorial monitoring tool to highlight the plots actually worked in SCA. This is what a Spanish team from the company Agrosat has been working on in the Albacete region. Using Sentinel-2 images, they have shown that it would be possible to discriminate between plots of land used for direct seeding under cover: “If there is permanent cover, we can see it. With any image, you can see it. The problem is when it’s too dry and there’s nothing living in the soil. I don’t know if this is being worked on by other research centers, but I have the impression that it is not because other people have contacted us about this. There are still some plots where we can have doubts, but the majority of the plots are clear. For what we call “secanos”, we realize that the curve of no-tillage is still above those that are tilled“.

On the subject of glyphosate, some interviewees, even if they agree that digital technology could help to have a more targeted monitoring and a better traceability, find it hard to believe that glyphosate could be used by some but not by others: “Traceability systems yes, but the problem is that if glyphosate continues to be sold, what you won’t see is the guy who hides to put it on. That’s not a solution. If all sprayers were equipped with a traceability system, we could ask the question: “What did you do with the sprayer? But socially, that would not work. On the control of the sprayer, we don’t have all the sprayers in France that have been controlled, even though it is mandatory. If you keep glyphosate just for conservation agriculture, it will be very complicated to check that there are not others who use it for something else. You can ban the sale, but you could always get it on the internet. I find it even more complicated to manage for the public authorities if some molecules are used by some people and are traced. The circulation of this molecule will continue“; “You can’t authorize it for them, it seems difficult to me. What justification do you have? The problem is that politicians will make decisions, there are lobbies that are against glyphosate. Some lobbies focus on this molecule, in my opinion, there were others that were more serious. The politician will take a quick decision, and he will not necessarily ask himself questions about when to use it (when it rains etc…). If it is banned, it will be for everyone“. The debate is far from over! The paradox is however quite terrible: farmers are the first victims of pesticides and yet they are the ones who defend their use the most. Farmers are therefore either all completely stupid, or have good reasons to do so…

Carbon farming, energy transition and climate change

Agriculture is one of the first sectors to influence greenhouse gas (GHG) emissions. A rather long article was shared on the blog on this subject. Although the agricultural sector cannot of course be summed up by its greenhouse gas emissions alone, this article was an opportunity to recall that the sources of emissions in crop production were mainly due to the application of mineral nitrogen fertilizers and the use of fuel to run agricultural machinery. As SCA is often put forward as one of the itineraries in favor of a reduction of GHG emissions – reduction of tillage and therefore of the fossil energy used to operate the machines, plant cover based on leguminous plants storing nitrogen from the air and therefore reducing the need for nitrogen input, better carbon storage in the soil… – it would have been a shame not to add a small layer of energy/climate in this work!

Let’s quickly recall that the soil contains large quantities of carbon. This was detailed by two other long posts on carbon storage in agriculture and carbon markets (First article and Second Article).This carbon comes mainly from the decomposition of plants on the ground, the plants having stored this carbon during their growth thanks to photosynthesis. This carbon will then be stored in the organic matter of the soil. It is important to understand that the evolution of carbon stocks in the soil is dynamic; it is a complex balance between the input of carbon via the decomposing plant biomass and the release of carbon when the micro-organisms mineralize the soil organic matter (to do this mineralization work, the micro-organisms breathe and therefore emit carbon dioxide). Keep in mind that there is almost no permanent storage of carbon in soils. The organic matter will be mineralized one day or another. The whole objective is therefore to promote agricultural practices that limit or delay the mineralization of organic matter, or increase the contribution of plant biomass that will be decomposed. All this is very nice, but we still need to be able to measure this carbon in the soil. We could avoid emissions by counting the reduction in mineral nitrogen and fuel consumption. Stored carbon, on the other hand, is another matter: “We don’t know enough about the soil. How can we measure this carbon? Is it the carbon in the first centimeters of the soil, in the depths? The analyses just target total carbon. Some labs abroad do other analyses where they target oxidizable carbon, the most easily accessible and degradable. Does the soil keep its reactivity and is it able to feed the plants?” We also realize that in addition to not knowing and understanding how soils work, there are still many unknowns. “The challenge of carbon storage is that you have to bring it back into the soil, but it’s not just about bringing it back, you also have to make the soil work! My observation, in the approaches I was putting forward, was that I had significant organic inputs over 10 years. I had 20 tons of compost per hectare, plus 5 years at 10 tons per hectare. I ended up with intact compost that had hardly changed”; “I am convinced that direct seeding under plant cover is a means, but we will not be able to do better than that in terms of carbon balance. Nevertheless, I have followed studies in Switzerland that have shown that some farmers do no-till and store carbon, others do plow and store carbon. Some farmers plow, but as soon as they plow, they put in a multi-species super cover, they put in compost and in the end, they sometimes have better results than guys in SCA. What’s the best solution to store carbon?“

You may have seen them coming, carbon labels have appeared. The “4 for 1000” initiative launched by the former Minister of Agriculture Stéphane le Foll and the “Label Bas Carbone” are two examples. What do we think of these labels? The feedback from the respondents is rather positive: “It’s a bit of communication, but it’s very good to grasp this communication“; “The more it comes, the more I talk about carbon agriculture than about SCA. The glyphosate battle is lost (more on glyphosate later). By the time you have to start justifying yourself, it’s already too late. I think we need to talk about carbon and climate change instead. Agriculture is part of the solution. The key factor is CO2. The more plants you put in, the more you cover your soil, the more carbon you store. Let’s put that forward! If you need half a liter of glyphosate to store 1 ton of carbon in the soil, that becomes a great solution. It would also help incentivize farmers to go for results and not means. If you want to store carbon, you can’t do just anything, you have to invest in the crop rotation, it won’t happen like that. If you make great cover crops, you don’t need much glyphosate. It would be a great idea to say to the farmers: “do what you want“.

Some actors see – behind these carbon labels and the growing interest in energy/climate issues – a good way to push for the development of SCA by paying for the carbon stored, and why not by generating carbon credits: “Tomorrow, in my opinion, the CAP will no longer exist. Europe is falling apart. On the other hand, there are many sectors that are ready to invest millions of euros to compensate for their CO2 emissions“. An initiative on this subject has been launched in Switzerland by Pascal Boivin, in conjunction with the government. Farmers are paid on the amount of carbon stored at the end: “Several hundred farms are monitored. You take a soil sample at the beginning, and see you in 5 years. What he has put in place is that a farmer who is unable to do so is supported in setting up a successful crop rotation”. Other initiatives are appearing in France, such as the low-carbon label, which already exists for forestry and is being created by Arvalis for field crops, the Carbon’Agri label for livestock, and the ‘Naturellement Carbone’ project, set up by Agro’Doc in collaboration with Nataïs and CESBIO, which relies on satellite imagery and kinetic monitoring of crops to establish a carbon footprint in the field.

Some additional information (following exchanges with Sylvain Hypolyte, from Agro’Doc):

Leguminous store nitrogen, thanks to their nodules, this is a reality. However, keep in mind that this storage is not free of charge energetically. One unit of symbiotic nitrogen fixed by the leguminous costs it the energy equivalent of 1/2 liter of fuel oil, consumed in the form of sugars by the bacteria in the nodules. This is as much energy less to make seeds, which partly explains the lower yield of legumes…

The nitrogen stored by the leguminous cannot counterbalance the needs of some following cash crops. Compare here the few tens of units of nitrogen stored by a legume to the few hundreds of units of nitrogen required by wheat for its growth.

The C/N ratio of soil organic matter is close to 10. This means that there is about 10 times more carbon than nitrogen in soil organic matter. Since this ratio is constant, it is important to understand that increasing the carbon stock in the soil also requires increasing the organic nitrogen stock in the soil. Storing 1 ton of carbon per hectare per year means immobilizing 100 kg of nitrogen per hectare per year in organic form. This is as much nitrogen that is temporarily unavailable for crops. The introduction of leguminous plants, which store nitrogen, is therefore essential to store carbon in a sustainable way without increasing mineral fertilization – and therefore the CO2 emissions linked to its production.

The fact of working the soil or not would not have a significant effect on its carbon stock, contrary to other practices such as permanent cover, the contribution of exogenous OM, or the restitution of residues. Compared to SCA, which is the subject of this monitoring work, the change from tillage to no-till would have little effect on the total C stock in the soil. It could simply be seen as a reallocation to the surface, with a consequent depletion at depth.

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Interviewees

Nom et Prénom	Fonction
Eric BOISLEUX	Farmer, CEO of APAD 62
Valentin FIGEAC	Farmer, former from Nataïs
Rémy HEIM	Farmer
Jean-François LANGLET	Farmer
Nicolas LEFEBVRE	Farmer
Sébastien LEMOINE	Farmer
Sarah SINGLA	Farmer
François et Kévin TAMBOISE	Farmers
Jean TAZIO	Farmer
Frédéric THOMAS	Farmer and editor-in-chief of TCS magazine
David GUY	Farmer and director of SKY agriculture
Jérôme SEGUINIER	CEO of GIEE Magellan
Vicente BODAS	Farm advisor – AgroSAT
Bruno ESTANGUET	Agricultural technician Val de Gascogne – ACS
Christophe BARBOT	Farm advisor – Agricultural chamber of Alsace
Sylvain HYPOLITE	R&D manager – Agro d’Oc
Maxime MERCHIER	Agronomist- Green O Tec
Sébastien DIETTE	Forest engineer- MYCEA
Véronique BELLON MAUREL	Director of the Ecotechnologies Department of Irstea (recently merged with INRA) and Director of the #DigitAg Institute of Convergences
Christophe LESUEUR	Pedagogical engineer – Institut Agro Montpellier – Agricultural and food systems from the South to the Institut Agro
Léo GARCIA	Enseignant-chercheur – Institut Agro Montpellier – Département Milieux, Productions, Ressources et Systèmes
Jean-Pierre SARTHOU	Professor – ENSAT – Agronomy and Environment
Xavier REBOUD	Project Manager – Agroecology Unit in Dijon
Bruno TISSEYRE	Professeur Agriculture de Précision – Institut Agro de Montpellier

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When soil conservation agriculture meets digital and precision agriculture

Foreword

A few words about digital before we get starte

Soil conservation agriculture

Introduction to Soil Conservation Agriculture (SCA)

Limiting tillage

Permanent soil cover

Extending rotations and diversifying crops

Reconciling Conservation agriculture and digital tools

A first general observation

Improve your knowledge of your soil

Rethinking tillage

Focus on permanent soil cover

Digital and crop diversification

Let’s try to take a step back

Does the constant search for precision make sense

Conservation Agriculture, Precision Agriculture, and within-field variability

Field experimentation and feedback in conservation agriculture

Conservation and Precision Agriculture : Efficiency, Substitution, or Redesign

The thorny issue of glyphosate

Carbon farming, energy transition and climate change

Interviewees

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