Legacy effects of cover crops on weed biomass and yield of the subsequent corn crop

Cover crops (CC) can exert legacy effects on subsequent crops and weeds by modulating nutrient dynamics and weed pressure. These effects can influence crop performance and weed–crop competition, yet their combined impacts remain poorly understood. We investigated CC legacy effects over six seasons in Pennsylvania (USA), where silage (2012–2015) and grain (2015–2018) corn (Zea mays) followed either no CC or 11 CC treatments, including legumes, grasses, brassicas, and mixtures. Each year, CC biomass, C:N ratio, weed biomass and community composition, peak soil N, and corn yield were measured. Path analysis revealed that weed biomass in the preceding CC increased weed biomass in corn and reduced yield. High soil N and C:N ratio also promoted weed biomass in grain corn, while high CC C:N ratio reduced yields in both periods. Legacy effects varied among CC functional groups: in the silage corn period, yields after legumes were 43 % higher than after grasses, while weed biomass was twice as high after legumes compared to grasses. Mixtures containing multiple functional groups achieved both effective weed suppression and high yields. These findings highlight the role of CC functional group selection in shaping cascading effects from cover crops to weeds and crop yield, offering opportunities to improve weed management while maintaining productivity.