Regenerating soil fertility through cover crops and soil conservation approach: experiences in adoption and evaluation of these innovative techniques

Global agriculture is at the centre of a new revolution which requires on one hand to produce more and more, and with good quality, as the International Year of Plant Health 2020 reminds us, for a growing population and on the other to use less and less inputs impacting the environment – fertilizers, plant protection products, fuel. However, agriculture as a productive activity must be economically sustainable - therefore obtaining satisfactory yields at low cost is an objective for each farmer - but it must also be environmentally sustainable: first of all for the survival of the agricultural activity itself, and secondly because can be a key player in the fight against climate change. In fact, agriculture deals with the management of the territory of vast areas on the planet, and the soil is the main tool for agricultural production and the most important asset of every farmer. Fertile soil allows you to produce a lot and well with few inputs, allows you to make a profit that makes its cultivation sustainable and constitutes one of the most important carbon stocks globally. An agronomic approach has existed for almost a century which aims to conserve fertile soil, and which in recent years has also learned to regenerate its fertility where necessary: it is conservative agriculture. One of the fundamental principles of this technique is the continuous coverage of the soil, together with the minimization of tillage, which may be absent, and the maximization of biodiversity. Continuous coverage is achieved by maintaining crop residues on the surface but in particular by cultivating intercrops, or plant covers. Usually mixtures of species are used which are devitalized before the next sowing. A particular case is represented by “indefinite duration covers”, i.e. multi-year plant covers (typically legumes) in which cash crops (typically cereals) are sown without devitalizing the cover crops. These approaches open up innovative agronomic systems such as intercropping rapeseed with multiple cover crops (some annual and some perennial) that offer ecosystem services such as the regulation of phytophagous insects, nitrogen nutrition and weed management. Weed management and nitrogen nutrition are also the keys to direct sowing of cereals with straw under indefinite duration cover. The reduction of inputs with a stabilization of yields and an increase in the quality of cereals, which can have increases of 1-1.5% in protein, can bring an improvement in agricultural profitability with a decrease in costs and an increase in the economic margin. Soil management techniques without tillage and the constant presence of crops, both for cash and for cover or other ecosystem services, present at least two challenges. The first is that of increasing organic matter in the soil, with the notable benefits on soil fertility and the environment, summarized in the 4p1000 initiative launched at COP21 to relaunch carbon sequestration in soils to be removed from the atmosphere. This profound improvement can also respond to the need to improve the health of multi-year crops such as vines and fruit trees, which experience widespread phenomena of death and decay which could find a solution in more vital and fertile soil. The second challenge is to understand the dynamics of fertility in a new context, with different needs from conventional agronomic management. Agricultural soils managed with these innovative practices are one of the best opportunities to validate new methods both to study and describe the biological, chemical and physical fertility of a soil, and to monitor it, giving farmers new tools to manage fertility and control nutrition. of crops in a more effective, sustainable and economical way.