BACKGROUND: Mixed cropping of hairy vetch and Barley is widely used as a green manure for reducing chemical fertilizers while maintaining soil fertility in paddy soil. We investigated the effect of Molybdenum (Mo) fertilizer on vetch N2 fixation, biomass production and transfer N from vetch to barley under a hairy vetch-barley mixed cropping system.
METHODS AND RESULTS: The barley and hairy vetch were sowed at a rate of 135 and 23 kg/ha, respectively, without chemical fertilizer application but with Mo fertilizer at 0, 0.5, 1.0, 2.0, and 4.0 kg/ha as a treatment. The percentage of hairy vetch N derived from air N2 fixation (%Ndfa) and N transfer from hairy vetch to barley (%Ndfv) was determined by the 15N natural abundance method. Although application of Mo at 2.0 kg/ha significantly increased biomass of both barley and hairy vetch, the biomass was decreased at application of Mo 4.0 kg/ha. At the application of Mo 2.0 kg/ha, the percentage of Ndfa and Ndfv was 81.7 and 53.9, respectively, which are significantly higher than that of the treatments without Mo.
CONCLUSION: These results highlight that application of Mo fertilizer can be an effective measures to improve N fixation in hairy vetch and biomass production in both barley and hairy vetch.