Effects of Water and Root Separation on Nitrogen Uptake,Utilization and Transfer in a Gramineae-Legume Intercropping System
[Objective]Gramineae-legume intercropping can give consideration to production and ecological benefits,improve nitrogen use efficiency and reduce nitrogen pollution.At present,the process of nitrogen utilization,absorption and transfer distribution in gramineae-legume intercropping systems under different water conditions is not clear.[Methods]The above ground biomass,nitrogen absorption and utilization,nitrogen fixation rate,and nitrogen transfer rate of gramineae-legume intercropping were studied by using water treatment with the same total water amount in 2 periods but with an interval of 3 or 5 days,combined with root separation(non-separation,nylon mesh separation and plastic plate separation)and nitrogen isotope labeling methods.[Results]The aboveground biomass,nitrogen content and nitrogen accumulation of E.dahuricus intercropped with alfalfa were significantly increased compared with monoculture E.dahuricus,while,for alfalfa,the intercropping with E.dahuricus resulted in a decrease compared to monoculture alfalfa.Under the condition of the same total water amount,the above-ground biomass of the herbage increased by 6.28％and 17.32％,respectively,by high-frequency water treatment compared with medium and low frequency water treatments,and the nitrogen fixation rate of alfalfa was increased by 39.82％and 44.81％,respectively,under high-frequency water treatment compared with medium and low frequency water treatments.However,the nitrogen concentration and nitrogen accumulation under some middle and low frequency water treatments were significantly higher than those under high frequency water treatment(p＜0.05),and promoted nitrogen transfer.Root separation weakened the interaction between grass and bean,and showed that as root separation increased the aboveground biomass,nitrogen concent and aboveground nitrogen accumulation of intercropping alfalfa,and decreased the corresponding indexes of intercropping E.dahuricus.The nitrogen fixation and nitrogen transfer rate of alfalfa intercropping were in the order of no separation＞nylon mesh separation＞plastic plate separation.[Conclusion]Moderate water regulation can improve the advantages of gramineae-legume intercropping,and root interaction is the key to promote the biological nitrogen fixation and nitrogen transfer of legume herbage.
gramineae-legume intercroppingroot separationwater treatmentnitrogen utilizationnitrogen transfer efficiency
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