Les cultures intermédiaires pièges à nitrate (CIPAN) et engrais verts : protection de l'environnement et intérêt agronomique

Abstract

Autumn cover crops and green manures: environment protection and agronomic interest. Due to the evolution of the environmental policy, practice of green manure cropping has been replaced by autumn cover crops in order to take up nitrate residues of the soil. These crops (mustard, phacelia, rye-grass, rye) show a high ability to take up N (sometimes more than 100 kg N.ha-1), leading to a decreasing threat for nitrate leaching. Such an ability is however related to species, but also to cropping practices mainly sowing date. Subsequent mineralization (measured with labeling 15N technic) of this organic-green manure-N, influenced by physical and chemical characteristics of the ploughed biomass, seems however limited (less than 45% of N ploughed in the soil) and does not lead obviously to a reduction of the N advice for the following crop. Nevertheless, stocking of organic N and C in the soil is expected to have a beneficial long-term effect on both mineralization (providing more N) and soil humus content leading to improve structural properties of soil.

Keywords

• N
• autumn cover crops
• mineralization
• humus
• N losses