Relationship between soil cover rate and biomass of crop residues: A predictive simplification is possible.

Abstract

In a conservation agriculture system, crop residues are no longer mixed in a volume of ploughed soil, but maintained on the surface or partially buried. Their presence contributes to the sustainability of these systems by maintaining the agronomic and environmental balances. In this context, knowledge of the evolution of their quantity on the soil surface, from harvest to sowing of the next crop, becomes an important stake of soil management. Several authors have established a relationship between the soil cover ratio and biomass, specific to each plant species, from an identical formalism developed by Gregory (1982). The objectives of this work are to test its use in the pedoclimatic context of the Grand-Est region (France), after harvesting and during the residue degradation process, on several crops. This work has been carried out on farms practicing conservation agriculture for several years. The residues were ground during the harvest or a subsequent specific operation. Biomass data were collected using 0.5 m × 0.5 m frames, while ground cover were studied using digital photographs. The cover rates were calculated using an image analysis software. This work also compares two measurement periods: at the end of winter, several months after the harvest, and right after the summer harvest. The results show a very good correspondence between the soil cover ratio and the biomass measured on the ground, for all species and measurement periods, by adding a parameter to the Gregory (1982) formalism. The integration of spatial variability on the ground makes it possible to propose the use of a single linear adjustment that simplifies the prediction of soil cover ratio or the amount of biomass.