Written by Matthieu Archambeaud - TCS n ° 62; March/April/May 2011
Conservation agriculture is commonly presented as the combination of reduced tillage, maintaining permanent coverage of the soil and the setting up of suitable rotations. It is often forgotten, that this is often only possible with the help of total herbicides that allow the farmer to get rid of weeds without the help of ploughing and weeding. It was the appearance of molecules such as paraquat, 2-4 D, then glyphosate, that simplified the work of tillage and direct seeding. At this time when the active and it most common trade name Roundup and its counterparts are being put on the spot, a recent review by TCS Magazine wished to make some very important observations on the subject.
Remove weeds without tilling
Since the beginning of agriculture, cultivation has been used primarily to fertilize crops by oxygenation of the organic matter. It also lets you control the weeds by burial of vegetation (ploughing) or a simple removal (weeding) of above ground material. In recent decades, the depth and the speed of ploughing strongly increased, with the massive development of industrial style mechanization. Mineral fertilization, is itself, is very effective along with the selection of suitable crop varieties that were developed at the same time. The result was a huge leap in productivity. In this system, the concept of nurturing the ground gradually faded in favour of intensive cultivation, and artificial fertilization of crops.
This system has given very good results so far, allowing France, weakened and hungry in the late 1940s, to become one of the world’s major agricultural exporters. The context changed however with the emergence of environmental problems induced by inappropriate treatment of agricultural soils, reflecting their degradation: erosion, reduction of organic matter content, nutrient losses, reduction in biological activity, etc. Becoming less and less, alive and fertile, agricultural soils are no longer able to tolerate mechanical damage, fertilization organic or mineral, or even irrigation.
Too effective a weed killer Glyphosate can effectively remove unwanted vegetation without touching the ground, in a way that is fast, easy to apply, very economic and with extremely low energy consumption. It also has a significant agronomic asset in that it is destroying weeds while leaving the soil undisturbed without fresh weed germination, unlike mechanical destruction. This explains no doubt its popularity and its use as well by (conventional, conservation agriculture and direct seeding) farmers, gardeners, alongside roadways, and even by the military.
Of course, this product ‘miracle’ raises complex problems. The first question is the popularity of glyphosate which makes it the best-selling and most widely used herbicide molecule in the world, far beyond the circle of conservation agriculture. It follows that the product is used by all, not always in good conditions, at any dose, not always for the right reasons, and therefore one finds it or it’s degradation products (including AMPA) in analysis of water quality.
The second phenomenon is a consequence of the first and becomes more worrying at the agricultural level: nature works more easily around an obstacle if it is repeated and widespread. The systematic use of glyphosate inevitably results in resistance phenomena. These resistances are not related to glyphosate itself but its mode and intensity of use. For example, there is in France more resistance from populations of ryegrass and fescues. The first French case of glyphosate resistance was in a population of vetch in vineyards where this product is used extensively alone.
These phenomena of resistance also appear much more quickly when the product is used alone, since the use of several active ingredients to eliminate cross-resistant individuals (a plant resistant to the active substance) with glyphosate is unlikely to be more resistant to a different active. The Australians did so to reintroduce paraquat in combination with glyphosate, to achieve what they call a “double knock”. The same phenomenon is observed in North and South America where genetically modified soy and corn RR (Roundup Ready) are widely used and require a number of passes pre-emergence and post emergence. The third and final point is the designation of glyphosate as a symbol of an intensive, destruction of the environment and that it may affect human health.
This challenge is of three orders:
• the massive international use of the product
• its obvious link with GMOs grown today
• the involvement of Monsanto in military operations with the Government of the United States of America, whether it’s Agent Orange in the Vietnam war or concentrated spray of glyphosate on plantations of coca in Latin America.
Impacts on the soil and living organisms
The purpose of glyphosate is to suppress plant organisms: the molecule is an amino acid analogue onto which a different chemical group is grafted: glycine-phosphonate whose contraction gives its name to the molecule. This compound disrupts the synthesis of some essential amino acids and plant compounds, resulting in the death of the plant that absorbed the herbicide. Since glyphosate is poorly absorbed in its pure state, additives intended to facilitate its absorption (surfactant, surfactants,) are attached to it. Glyphosate acting specifically in a plant biochemical pathway has long been considered harmless to animals and the environment.
However, because of its popularity and its strong link with the GMO problem, a multitude of scientific studies have been carried out around the world relating to the safety of the active substance. In the first place glyphosate, being relatively immobile, would tend to concentrate in soils that receive applications regularly. This concentration would disrupt the absorption of some mineral elements by crops, such as for example manganese, iron, calcium or magnesium.
This lack of absorption could be caused by several mechanisms according to D. Huber of Purdue University: it would physically block a part of trace elements available in the root environment by the phenomenon of chelation. Second, it would hurt populations of rhizosphere microorganisms that facilitate the absorption of minerals. Finally, these phenomena are amplified on a RR crop that radiates into the ground by its roots glyphosate that the plant absorbed and cannot metabolize (Digest). This researcher goes further and considers that it is not the glyphosate which is responsible for the death of the plants, it is the molecule that would that suppress the immune system the plant would then be the victim of fungi and pathogenic bacteria. Direct seeding, focusing the organic material on the surface, could amplify the phenomenon by focusing the glyphosate near the rhizosphere.
This type of result was also confirmed by Professor Römheld of the University of Stuttgart, who showed the negative impact of glyphosate on root growth of RR crops in the presence of glyphosate even at a low dose compared to other herbicides. Other studies have also shown the harmfulness of glyphosate, admixtures and their products of degradation, on the flora and fauna, and even on human health. As such, there is little doubt that molecules that are intended to remove organisms may have negative effects on animal and human health.
It reinforces the idea that users must imperatively protect themselves, take the necessary measures to avoid the derivatives in the atmosphere and in water, and finally that it is essential to implement technical and agronomic solutions that maximally reduce the use of pesticides.
Direct seeding with conservation agriculture
With the “dust bowl” American 1930s, and serious erosion problems in Brazil in the 1970s, farmers and scientists are finding that the reduction of cultivation can reduce or even remove the problems of land degradation.
In pursuing this non-cultivation on an ongoing basis, they realize that soils are a framework comparable to that of a meadow, which allows it to produce as in a conventional system or even more, with a very low of cost of production in mechanization and labour. It is enough to weed a soil, sow a crop, protect and fertilize it to make good returns: American farmers are past mechanical tillage moving on to “chemical ploughing.” With the introduction of resistance to glyphosate in crops, the system becomes even more simple and profitable, if not sustainable over time.
From the 1992 CAP reform, reduction of cultivation has also been sought by French farmers to reduce production workloads. However, unlike the systems pioneers of South America, Europe and Eastern Australia, European agriculture has evolved in a social, regulatory and environmental framework, forcing growers to go further than their direct seeding “GM and glyphosate” and leading them to increase exchanges with organic farmers themselves, in pursuit of agronomic and technical solutions. Conservation agriculture systems (or even agroecological, on living soils, environmentally intensive, etc.), in which we redefine principles as farmers who rely on the natural organization of the soil (no-till and always covered), looking to produce a maximum plant biomass on a permanent basis in order to increase the physical, chemical and biological fertility of the soil.
In this context, glyphosate, or other existing or future active materials allows a control of this biomass without damaging the soil. Based on the principle that control of the soil is related to control of the plants in the system (choking, competition, allelopathy, mulching, local fertilizing, rotation...), herbicides are a way to push the systems further without excessive risk taking. Finally, it must be recognized that it is thanks to glyphosate that pioneer farmers and technicians are developing efficient, effective and innovative agroecological systems based on living soils. And the more we develop and validate alternatives, the less it will become necessary. To continue the development of conservation agriculture, without undue risk, the strategy is to find new methods of action, even if we restrict the uses of the product without the need to remove its approval. Glyphosate was the mainstay of direct drilling, it has become the safety net of conservation agriculture.
Read the article in the digital version - https://issuu.com/directdriller/docs/direct_driller_issue_2/60