Relay intercropping of hairy vetch green manure into broccoli–sweet corn cropping system: Fertilizer effects on sweet corn growth

Abstract Relay intercropping legume cover crops with cash crops can protect soil while enhancing nutrient cycling. This study aimed to evaluate the feasibility of relay‐intercropping hairy vetch (HV; Vicia villosa Roth) with broccoli ( Brassica oleracea L. var. italica ) and its subsequent fertilizer effect on sweet corn ( Zea mays L.) production. A 2‐year field experiment was conducted in a Gleysol field in Osaka, Japan. Three HV varieties (Namoi, Savane, and Massa) were interseeded into broccoli 1 month after planting. Upon broccoli harvest, the HV biomass was incorporated into the soil. Subsequent sweet corn growth and yield were compared between the HV‐incorporated treatments and a conventional chemical fertilizer treatment. HV was successfully established without reducing broccoli yields. The average aboveground biomass of HV was 3400 kg dry weight ha −1 , providing nutrient inputs of 125 kg N, 27 kg P 2 O 5 , and 88 kg K 2 O ha −1 . Significant varietal differences were observed in the C:N ratio; Massa and Namoi exhibited higher ratios, while Savane consistently showed the lowest ratio. In the first year, sweet corn ear weights in all HV treatments were comparable to the conventional treatment. In the second year, however, the conventional treatment significantly outperformed the Massa treatment. Namoi and Savane showed superior fertilizer effects compared to Massa, likely due to their lower C:N ratios. Although the fertilizer effect of HV was slightly inferior to chemical fertilizers in the long term, relay intercropping HV can significantly reduce chemical fertilizer requirements in broccoli–sweet corn cropping systems without compromising the primary crop yield.