Green manure is a cover crop sown on an agricultural plot in order to fertilize the soil for the following crop mainly through the intake of nitrogen. This cover crop is sown between two sales crops (usually between two highly demanding nitrogen crops) or in combination with the previous crop. Green manure provides improvement in soil structure with their root system and a relatively little supply of stable organic matter. Stable organic matter as well as nitrogen intake for the following crop are obtained after degradation of the plant by the soil’s microorganisms (microbial or enzymatic activity)… Green manure consists of legume-based cover crops. The green manure cover crops can be destructed through:
- A mechanical cultivation (grinding, cutting, landfill, etc).
- A chemical application (herbicides – mainly glyphosate based)
Green manure constitute a full-fledged agronomic lever since it mobilizes various other ecosystem services (loss of nitrates during intercropping, soil erosion reduction, production of organic matter…).
The use of green manure in agroecology makes possible to address various agronomic challenges. It provides with the opportunity to limit the supply of mineral fertilizer products from the petrochemical industry. However, if their destruction is done with herbicide, the use of green manure can increase the Treatment Frequency Index (TFI). Green manure allows for better sustainability of the systems because of a long-term effect due to residues incorporation that can convert into stable organic matter which remains in the soil for a longer term. Specifically, it is possible to substitute – at least partially – conventional inputs of synthetic nitrogen fertilizer with legume seeding during an intercrop. Indeed, the use of green manure can be a first step in building a coherent and sustainable agro-ecological approach.
References to explore
Ecological Agriculture Projects (EAP). 1980. The Basics of Green Manuring. EAP Publication – 51
Miguel Angel Florentín; Marcos Peñalva; Ademir Calegari; Rolf Derpsch; Melissa J. McDonald (trad.). 2011. Green manure/cover crops and crop rotation in conservation agriculture on small farms. Integrated Crop Management, Vol.12-2010. Plant Production and Protection division Food and agriculture organization of the united nations Rome, 2011. 109p. ISBN 978-92-5-106856-4