Understanding the role of grain legumes in the N cycling of agroecosystems

Summary

Grain legumes have three major functions in cropping systems: 1) to produce feed and food protein, 2) to contribute N to the cropping system via symbiotic N2 fixation, and 3) to serve as a break-crop in cereal-rich rotations. Depending on specific farming system principles these functions have different priorities. Some conventional systems may focus on protein production whereas organic farming systems try to integrate them all.
Symbiotic N2 fixation (SNF) is a unique biological process influenced by several environmental factors; optimising SNF is not an easy task. Integrated management of crop rotation should be considered to combine and exploit better the specific characteristics of each crop (self-sufficient or not in N, different C/N ratio, more or less rapid residue mineralisation, etc.).