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

摘要

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. Field studies were conducted in France, from 2002 to 2005, to evaluate 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, lucerne, bird's-foot-trefoil, black medic and white clover. The results showed that the use of living muches during wheat cropping decreased wheat yield of 19-81% by comparison to wheat cropped alone. This decrease was 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. These findings also revealed that the wheat yield decrease was 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. It was thus concluded that stem elongation, flowering and fecundation are the major stages of stress for wheat grown with living mulches. These findings will help to design innovative crop management systems that take into account the biological interactions in agroecosystems better.