6533b7dafe1ef96bd126f370

RESEARCH PRODUCT

Carry over effects of cover crop mixtures and management practices on subsequent crops and weeds in no-till systems

subject

description

Cover crop (CC) mixtures appear as a promising agroecological tool to suppress weeds andmaintain crop productivity while reducing chemical inputs such as herbicides and nitrogenfertilizers. The weed suppressive effect of CC and CC nitrogen release have been related to CCcomposition, soil resource availability and CC termination methods but the relative effect ofthese factors and their interactions remain poorly documented, especially in the case of CCmixtures. Most studies have focused on the subsequent spring crop, and hence, lacked toinvestigate long-term carry over effects of CC. A two field: year experiment was conducted toinvestigate the effect of CC mixture (2 or 8 species including or not legume species, comparedto a bare soil control), resource availability (water and nitrogen) at CC sowing and CCtermination method (rolling and glyphosate, compared to a winterkill control) on weedbiomass and productivity of two subsequent unweeded, unfertilized and direct seeded crops(spring barley and winter linseed in year 1 and 2, respectively). In the context of reduction ofherbicide use, our experiments showed that the use of CC to reduce weed biomass in thesubsequent crop was not relevant when CC were terminated by winter or rolling since CCprobably protected weeds from winter instead of creating a physical barrier for weedemergence, weed community composition in crop being mainly represented by weedvolunteers. Weed biomass was the main driver of the subsequent crop productivity but thelatter was enhanced after fertilised or legume-based CC, probably because of a highernitrogen release. No relevant long-term effect of CC on the subsequent crop was observed inour experiment, probably because nitrogen was used by the previous crop and weedcommunity composition changed by year. Our results highlight the importance CCcomposition and management for weed suppression and crop productivity in low-intensitybiodiversity-based cropping systems.