Do you know where the biggest biodiversity reservoir on Earth lies? Right under your feet – well, maybe not if you are sitting in an office or standing on a pavement. But if you are lucky enough to be in the countryside, talking a walk in a forest or through fields, you are actually standing on the biggest biodiversity reservoir on Earth: the soil. After decades of careless ploughing and use of chemical fertilisers, architectural techniques are being developped which recognise the importance of the soil’s microbiology in maintaining yield while protecting the environment. And scientists are playing their part in raising awareness, as it is one of the most promising research fields for sustainable agriculture.
Intensive agriculture and soil fertility
The Laboratory of Microbiological Analysis of the Soil and INRA’s GenoSol (Dijon, France), for instance, work to increase knowledge of subterranean life and its importance. In the video below, made by LeMonde.fr and Universcience.tv, Lydia and Claude Bourguignon, the French “stars” of soil microbiology and researchers at GenoSol, explain the crucial role played by the fauna and the microbes present in the soil.
Micro-arthropods, acaridae, worms, bacteria and mushrooms all play complementary parts in a global process: they destroy organic matter while helping ventilate the soil. They transform organic matter into mineral matter, which plants need to grow. Plants feed only on mineral elements: if organic matter accumulates in the soil, the system loses its biological fertility, asphyxiates and eventually dies. Worms even “make” the soil, by combining clays they find in the deep layers of the soil and organic matter they find on the surface, and digesting them into what we call soil.
Now, intensive agricultural practices (which involve ploughing and the use of artificial fertilisers) can be harmful to this fauna and to the microbial population of the soil. Aggressive work on the ground decreases its biological richness and can sometimes favour the implantation of pathogenic elements. As the video explains, “a soil that is poor in fauna and microbes accelerates drought, can favour erosion and demands the use of fertilisers.”It creates a sort of a vicious circle, where the products that caused the soil to lose its fertility in the first place are used to “remedy” the phenomenon.
Develop innovative systems
The challenge for farmers is then to change their practices in order to develop innovative systems that preserve the microbiological life of the soil while maintaining yield. A technique that has proven an effective substitute for ploughing, in certain contexts, is that of “direct seeding.” The idea is to plant an intermediary crop between the harvest and the next seeding. Instead of leaving the soil bare, which favours leaching and thus the loss of soil fertility, planting these crops has several advantages. Claude Bourguignon explains that these plants “pump” the elements that were not used by the previous crop from the soil; the system feeds the fauna; and it ensures that nothing is lost. “We fight the physical and chemical degradation of the soil and we revive the biological systems.” On top of that, it makes for “entirely non-polluting agriculture.”
Is direct seeding a miracle solution for sustainable agriculture? There are obstacles, of course. The most significant one is that this model requires more knowledge than the use of ploughing and chemical fertilisers. It demands an accurate understanding of the microbiological processes in the soil, and of the plants that should be used for direct seeding. There are also technical obstacles: for instance, the management of weeds, that can counter the beneficial effects of direct seeding. But as research progresses and farmers’ awareness increases, a growing number of producers will hopefully adopt and invent these new practices, at the frontier between science ansd agriculture.
Photo © HTU