Undersowing wheat with different living mulches in a no-till system. I. Yield analysis

The classical management of no-till wheat has several environmental and economic drawbacks such as the use and cost of herbicides, and the degradation of soil physical quality. Recent investigations suggest that undersowing crops with a living mulch could be a sustainable alternative. Therefore, we studied during three growing seasons the effect of undersowing wheat with living mulches on wheat grain yield. Treatments were wheat grown on a conventionally-tilled soil, on a no-till soil, and on a no-till soil with various living mulches. The living mulches were red fescue, sheep's fescue, alfalfa, bird's-foot-trefoil, black medic and white clover. Our results show that the use of living muches during wheat cropping decreased wheat yield of 19-81% by comparison with wheat cropped alone. This decrease is linked to the biomass of living mulches and weeds at the time of flowering. As a consequence, the control of living mulch and weed biomass is a major issue. Our findings also reveal that the wheat yield decrease is mainly the consequence of a decrease in grain number from 37 to 32 grains per spike on average, and of a decrease in spike number from 0.7 to 0.4 spikes per stem. We thus conclude that stem elongation, flowering and fecundation are the major stages of stress for wheat grown with living mulches. Our findings will help to design innovative crop management systems that take into account the biological interactions in agro-ecosystems better.