Effects Of Nutrient Management On Nitrogen Absorption And Utilization By Rice And Wheat

The inefficient utilization of nutrient resources,serious losses and the decline of soil nutrient supply capacity as result of disproportionate nutrient input has become common problems in rice-wheat rotation in China.Nitrogen is the first nutrient elements of restricting crop yield.Excessive application of nitrogen fertilizer causes lower nitrogen utilization efficiency(NUE)and a series of environmental problems.It is difficult for NUE to reflect nitrogen utilization of somesystem under different level of agricultural production which needs a variety of measuring indicators including yield,nitrogen utilization,nitrogen residue and nitrogen loss etal..The study of the effects of the residual nitrogen on the subsequent crop has already caused the extensive concern.However,most researches are focusing on the effects of preceding crop's total nitrogen fertilizer on the growth of subsequent crop with little consideration of the different periods of fertilization.Therefore,two trials were conducted with setting three nutrient managements:OF(optimized fertilization),ORF(optimization of reducing fertilization)and CF(conventional fertilizer).Two trials:(1)field and micro plot experiments were conducted in Danyang,Jiangsu Province using rice variety Wuyunjing 23 and wheat variety Yangmai 16.Two micro plots were set in a field plot with fertilizing 15N-labelled base-tillering nitrogen and panical nitrogen in the rice season separately.General fertizer was used in the following wheat season.The fate of rice base-tillering fertilizer and panical fertilizer was studied in rice-wheat rotation.(2)Field and micro plot experiments were conducted in Danyang,Jiangsu Province using rice variety Wuyunjing 23 and wheat variety Yangmai 16.Two micro plots were set in a field plot with fertilizing 15N-labelled base-tillering nitrogen and panical nitrogen in the wheat season separately.General fertizer was used in the following rice season.The fate of wheat base-tillering fertilizer and panical fertilizer was studied in rice-wheat rotation.The results were showed as followings:1 Effects of nutrient managements on yield and nitrogen uptake of rice and wheatCompared to conventional fertilization(CF,N:315kg ha-1,basal fertilizer:tillering fertilizer:spikelets promoting fertilizer:spikelets protecting fertilizer=2:1:1:0),nutrition optimization managements(OF,N:300 kg ha-1;ORF,N:180 kg ha-1;basal fertilizer:tillering fertilizer:spikelets promoting fertilizer:spikelets protecting fertilizer=2:1:1:1)decreased nitrogen application,but didn't decrease rice and wheat yields because of the total number of spikelets of OF treatment and the filled-grain percentage and 1000-grain weight of ORF treatment increasing.Meanwhile,compared OF and ORF with CF,they increased nitrogen uptake efficiency(REN),nitrogen agronomy efficiency(AEN)and partial factor productivity of applied N(PFPN)of rice with having no significant difference among them in wheat season.OF and ORF improved the proportion of rice-wheat nitrogen accumulation and dry matter accumulation from jointing to heading stage.It suggested that nutrition optimization managements can increase nitrogen uptake efficiency and ensure high yield ofrice-wheat on the basis of reducing nitrogen application.2The fate of rice base-tillering and panical nitrogen fertilizer14.4%?14.7%of rice base-tillering nitrogen was absorbed by rice and 2.1%?3.7%was absorbed by following wheat.Rice panical nitrogen uptake by rice was 36.9%-65.4%and uptake by wheat was 0.9%?1.7%.The panical nitrogen uptake efficiency of OF and ORF were higher than that of CF.14.3%-24.5%of rice base-tillering fertilizer nitrogen remained in 0-20cm soil after rice was harvested while 2.3%?8.8%remained after subsequent wheat was harvested.Only 4.6%-10.7%of rice panicle fertilizer nitrogen remained in 0-20cm soil after rice was harvested while 2.4%-5.7%remained after wheat was harvested.Compared rice panical fertilizer with rice base-tillering fertilizer,it loss more during wheat season.Rice panical nitrogen loss rate declined as panical nitrogen uptake efficiency rose.The sum of the proportion of rice base-tillering and panicle fertilizer N uptake by crops(rice and wheat)and residual soil N at wheat harvest was ORF>OF>CF.It suggested that nutrition optimization managements reduced rice base-tilllering and panicle fertilizer N loss from the rice-wheat rotation system by increasing N recovery rate in the plant-soil system.3 The fate of wheat base-tillering and panical nitrogen fertilizer10.0%-18.8%of wheat base-tillering fertilizer nitrogen was absorbed by wheat and 3.2%-5.9%was absorbed by following rice with no significant difference among them.Wheat panical nitrogen uptake by wheat was 23.4%-37.8%and uptake by rice was 3.4%-6.3%.28.2%-41.6%of wheat base-tillering fertilizer nitrogen remained in 0-20cm soil after wheat was harvested and 8.9%-30.8%remained after rice was harvested while 15.4%-31.0%of wheat panical fertilizer nitrogen remained after wheat was harvested and 5.3%-14.6%remained after rice was harvested.Wheat base-tillering fertilizer and panical fertilizer remained more in soil after wheat was harvest and loss more during rice season..Wheat base-tillering fertilizer loss rate of wheat season wasn't higher than wheat panical fertilizer loss rate significantly.The sum of the proportion of wheat base-tillering fertilizer N uptake by crops(rice and wheat)and residual soil N at wheat harvest was OF>ORF>CF.The sum of the proportion of rice panicle fertilizer N uptake by crops(rice and wheat)and residual soil N at wheat harvest was ORF>OF>CF.It suggested that nutrition optimization managements reduced wheat base-tilllering and panicle fertilizer N loss from the rice-wheat rotation system by increasing N recovery rate in the plant-soil system.