Evaluation of relay intercropping hairy vetch (Vicia villosa Roth) as a green manure to reduce chemical fertilizer input in the cultivation of root crops

Producing cash and green manure crops during the same growing season is a promising strategy for sustainable crop production. The present study evaluated the relay intercropping of a legume green manure crop (Vicia villosa Roth, hairy vetch) and root crops (radish and carrot). The hairy vetch was interseeded approximately 40 d after root crop seeding. Competitive effects were not observed in the production of either root crop, even when relay intercropped with hairy vetch. The biomass production of hairy vetch ranged from 376–990 kg DW 10a−1, and the biomass and nutrient (nitrogen, phosphorus, and potassium) accumulation of hairy vetch relay intercropped with carrot were significantly higher than those of radish. The fertilizer effects of hairy vetch incorporation obtained by relay intercropping were compared with those of conventional chemical fertilizer input in subsequent crop production (vegetable soybean and sweet corn). The yield of vegetable soybean was maintained at the same level as that of chemical fertilizer, even when cultivated with hairy vetch alone. In the sweet corn, although hairy vetch alone could not provide sufficient nutrients and growth was inferior compared to chemical fertilizers, the incorporation of hairy vetch relay intercropped with carrot showed relatively higher fertilizer effects and significant difference in ear weight was not observed with chemical fertilizer. Our results show the possibility of reducing chemical fertilizer input in succeeding crop production by hairy vetch relay intercropped with root crops.