Enhancement of nitrogen uptake in oat by cutting hairy vetch grown as an associated crop

Legume-grass mixed cropping has significant advantages that affect crop yield and soil resources. Generally, grasses grown with legumes take up more nitrogen than those grown under sole cropping. We focused on the effect of cutting hairy vetch during a vigorous growth stage on N uptake in oat under mixed cropping. We evaluated the amounts of N transferred from hairy vetch to oat by using a 15 N dilution method. Cutting hairy vetch increased the number of tillers and dry weight of oat, but total N content was not significantly higher than that under mixed cropping without cutting. In contrast, the amount of N transferred to oat was increased by cutting. Estimated amounts of N transferred to oat were 2.7 g m -2 with cutting of hairy vetch and 0.8 g m -2 without cutting. Cutting half of the oats under sole cropping did not indicate the transfer of rhizodeposited N in oat to the residual plants. In addition, cutting hairy vetch increased the amounts of accumulated solar radiation in the middle canopy of the mixed cropping plots. Therefore, in a hairy vetch and oat mixed cropping system, cutting of the hairy vetch might enhance growth of oat due to the transfer of N from hairy vetch and the reduction of light interception to the oat canopy. N fertility enhancement of the soil by cutting of the legume would be valuable for low-input crop production.