Effect Of Incorporation Of February Orchid(Orychophragmus Violaceus L.) On Nitrogen Uptake And Utilization Of Spring Maize

February Orchid-Spring maize production system is an innovative eco-agricultural practice,developed to suppress the increasing winter fallow area in North China, in which February Orchid iscultured as winter green manure. For this system, it is still indistinct that how maize takes up andutilizes the different sources of nitrogen and that how the green manure affects soil nitrogen pools afterFebruary Orchid application. In this study, the capability of soil nutrient supply after green manureapplication was investigated and the absorption and utilization characteristics of different nitrogensources during maize growing season were evaluated by using the15N isotope method. Moreover, aposition field experiment was analyzed to explore the effects of green manure and its combinationapplications with various amounts of chemical fertilizer on soil nitrogen pools during the maize growthperiod. The main results were as follows:1. Sole green manure application could sustain the normal growth of maize before jointing, thecombined application of green manure and chemical fertilizer improved the soil nutrient statusobviously. The biomass and nutrient uptake of maize before jointing stage in the sole green manuretreatments (50%G, G) were similar to or higher than those of the2treatments of chemicalfertilization (F) and the combined fertilization (G+F). Not only the sole green manure application butalso the combined application with green manure stimulated the growth of maize root by increasingthe root biomass and root/shoot DW ratio. Compared with the F treatment, the G+F treatmentsignificantly improved the soil nutrient status by increasing soil Nmin, Olsen-P and NH4OAc-K by29.2-116.4%,9.5-28.8%and24.3-50.3%, respectively.2. The15N study results showed that both the2green manure application rates could meet the Ndemand of maize before jointing, while the G+F treatment could synchronize better the N uptakewith the growth rate of maize. For the50%G and G treatments, the maximum green manure N(G-source N) uptake rate by maize was appeared during the period from seedling to jointing, and theG-source N accumulated up to the jointing stage accounted for96.7%and84.1%, respectively, ofthe total G-source N absorbed by maize at maturity. As for the G+F treatment, most of the G-sourceN was accumulated during the period from jointing to silking, which completed57.5%of theG-source N absorbed by maize at maturity and kept pace better with the growth of maize.3. G-source N use efficiency (NUE) was little affected by the green manure application rates, but wassubstantially improved after the combined application. The50%G and G treatments shared similarG-source NUE of about30%, while it was raised to about43%in the G+F treatment.4. Green manure application enhanced the soil nitrogen pools capacity effectively. Compared with theF treatment, the G+F treatment significantly increased soil total N, SON, POMN, NO-3-N, DON andSMBN content. Moreover, the contents of the main nitrogen forms mentioned above were highlycorrelated with soil total N at0.05or0.01probability levels.