Nitrogen Uptake And Utility Characters Of Paddy Soil In Cold Area

By using15N tracing field micro-plot experiments, setting up different nutrient management modes (integrated nutrient management and farmer’s fertilization practice) and experiments in different nitrogen application stage (base fertilizer, tillering fertilizer and panicle fertilizer) to research the characteristics of uptake, utilization and distribution of fertilizer N in paddy fields. The main results are:Overall, rice absorbs nitrogen mainly in soil, accounting for60%-70%of the nitrogen absorption in rice life; nutrient management can change the proportion of soil nitrogen and fertilizer nitrogen, large amounts of nitrogen fertilizer can make the rice uptake most of its nitrogen from fertilizer. If the nutrient management is appropriate, the proportion of nitrogen that rice absorbed in a life from soil and fertilizer wouldn’t change so much. Of all the fertilizers that rice will absorb, basal fertilizer nitrogen has a much higher proportion than tillering fertilizer in all periods, but after heading, rice absorbs more panicle fertilizer nitrogen.Integrated nutrient management can promote nitrogen uptake of rice from soil and fertilizer, and improve the utilization rate of fertilizer. The fastest period of dry matter accumulation of the rice is3days after jointing stage, in this period rice also accumulated nitrogen at the fastest rate. Therefore, among basal fertilizer, tillering fertilizer and panicle fertilizer, panicle fertilizer has the highest utilization percent, up to50%or so, and with the tiniest apparent loss. The tillering fertilizer has the lowest utilization percent of20%or so. Because of FFP, all the nitrogen fertilization is used as tillering fertilizer. Although nitrogen uptake is higher before heading stage, nitrogen efficiency is low, around20%only. But in INM, panicle fertilizer accounted for35%and the use of it improved the root activity of the rice in later stage, increases the nitrogen absorption from soil and fertilizer, nitrogen efficiency increased by10%, and the rice production is markedly improved.Nitrogen that fertilized into the soil of rice fields was mainly residue at0cm to20cm soil layer; it is less in20cm to40cm soil layer, and there’s no nitrogen residue below40cm soil layer. INM and FFP leaves nitrogen fertilizer in0cm-40cm soil layer are11.77kg·hm-2and14.14kg·hm-2respectively, and retention rates are10.70%and9.42%respectively, which are not far from each other. INM has higher crops recovery ratio than FFP, INM’s apparent loss is12.09%lower than FFP, only56.05%. Nitrogen that fertilized in the soil during different periods have different residues, and the performance is basal fertilizer> tillering fertilizer> panicle fertilizer.In short, maintain appropriate proportion of tillering fertilizer and panicle fertilizer can promote the coordination of the soil nitrogen supply and rice nitrogen uptake, increase rice root activity, promote the nitrogen absorption of rice from soil and fertilizer in later stage, improve nitrogen efficiency and reduce nitrogen losses.