Successive alternation of annual cash crops and cover crops, so that the soil is always occupied by controlled plants.
The choice of species to plant during the intercrop period is essential. It depends on the succession of crops and the material available for sowing, as well as on the objectives and constraints of the intercrop period (improvement of nitrogen fertility thanks to legumes, management of bio-aggressors). This choice will also be made with regards to the type of soil, the mode of destruction of the cover crop (i.e. physical or chemical) and the price of seeds.
The direct effects of permanent plant cover of soils are:
- An increase in organic matter, provided that crop residues and the cover crop are left behind and decompose on the plot.
- An improved soil structure and fertility thanks to the different root systems and nitrogen fixation through the legumes.
- The establishment of biological regulations against weeds through hydromineral and light competition and granivorous predators enhancement, and against pests by favouring entomophagous predators.
- The introduction of new species in the rotation, therefore decreasing parasite pressure.
- A reduction in the use of plant protection / phytopharmaceuticals products, on the one hand, and a reduction of nitrate leaching, on the other hand, thus reducing pollution of rivers and groundwater.
Permanent plant cover of soil induces indirect effects. Indeed, it increases biological activity in the soil and thereby improves its physico-chemical properties (buffered temperature, chemical fertility, circulation and retention of water, aeration of the soil …). The roots of the plants used also contribute. This cover also acts as a wind and rain shield, thus limiting wind and water erosion and improving cultivation conditions.