Exploring Winter Legume Cover Crop Management Strategies in Irrigated Maize Monoculture Systems

Management of legume cover crops to reduce their cost by using no-tillage and reducing seed rate could increase their adoption. Despite the growing interest in cover crops, no information exists simultaneously regarding the potential of different species and how the sowing method and seed rate affect nitrogen (N) contribution and the yield of the subsequent maize crop. During a four-year field trial, under irrigated conditions in the Ebro valley (NE Spain), three leguminous cover crop species (pea, common vetch and hairy vetch), two cover crop seeding methods (conventional tillage and no-tillage) and two seeding rates (normal and 25% reduced) were tested and compared with a control treatment without a cover crop. The aboveground cover crop biomass and the N derived from biological fixation (BNF); aboveground biomass and total N in weeds; soil mineral nitrogen; and the effect on maize grain yield and N content were evaluated. Pea and common vetch produced more biomass (+76%) and had a higher N uptake (+50 to 60%) compared to hairy vetch. The sowing of the cover crops after no-tillage combined with a reduced sowing rate reduced biomass production by 14%. The percentage of nitrogen derived from the atmosphere (Ndfa) was above 60% for all species and the differences in total N derived from biological fixation (BNF) among treatments were related to the aboveground biomass. The introduction of cover crops reduced weed growth compared to the control especially in the no-tillage treatment. Cover crops increased maize grain yield by 12% and N uptake by 17% compared to the control treatment without a cover crop.