Study Of Water And Fertilizer Efficient Utilization And Coupling On Winter Wheat Of The Loess Plateau

Reasonable application, increasi ng the utilization efficiency, and to explicit the role oftwo-way drive function between water and fertilizer is one important issue for continuingto improve the economic and ecological benefits of the agriculture development insemi-arid regions. In this paper, the2-years field experiment on winter wheat wasconducted with different water and fertilizer treatments, which aimed to evaluate the yieldeffect of water and fertilizer coupling on plant growth, yield, soil moisture profile andnitrate-N transport. Targeting high yield and water use efficiency （WUE）, we estimated theoptimal coupled interval of water and nutrients supplies for high yield and water useefficiency. The mainly results as follow:1. Water and N-fertilizer coupling could significantly impact crop growth, yield, andthe yield components. There was a sharp positive interaction between irrigation （W） andnitrogen application （N）, which contributed to the higher plant height and grain yield. Thegrain yields were increased significantly with the increase in irrigation under applicationthe N fertilizer from N0to N3treatments, while it were showed a downward trend slightlyafter the first rise under N4and N5treatment. Meanwhile, grain yield was improved byirrigation amount increased from W0to W3, and then decrease slightly. The highest yieldwas9.97t·ha^-1occurred in W5N3treatment during2008-2009, and was8.62t·ha^-1inW3N4treatment during2009-2010. The similarly results occurred in biomass and leafareas response to different water and N-fertilizer coupling. Notably, the irrigation wasconsistently produced higher LAI and the longer physiologically functional period ofwinter wheat.2. The variations soil moisture profile response to the different water and N-fertilizer coupling in the harvest period. The soil moisture content was decreased with the increasein N-fertilizer under rain-fed condition, but increased with the increase in irrigation. Baseon the interaction between irrigation and N-fertilizer application, the depth of the soilinfiltration supplement was achieved200cm in the W0N0treatment and more than300cmin W3N0or W3N0treatments. In the lower （W0）, middle （W3）, and higher （W5） irrigationtreatments, the depth of the soil infiltration supplement decreased from200cm to140cmwith the increase in N-fertilizer application. During2008-2009, the highest WUE was18.43kg·（ha mm）^-1occurred in W2N2treatment, and the least WUE was4.29kg·（ha mm）^-1. Similarly, the highest WUE was16.71kg·（ha mm）^-1occurred in W2N5during2009-2010.3. The soil nitrate-N accumulation was clearly improved by N-fertilizer than byirrigation. During both growing season, crop growth needs to be consumed part of soil Nwhen the n application rate is less than225kg·ha^-1, conversely, cause of nitrate-N residualin soil when the N application rate is greater than225kg·ha^-1. In application of noN-fertilizer treatment, the soil nitrate-N have not changed much in0-300cm soil layer dueto the lower soil N content. In the other N-fertilizer treatments, the nitrate-N results inwaveform with the rising of soil depth from0to300cm, and the least nitrate-N occurred at60cm. We also found that the large number of nitrate-N residues in soil profile led tonitrate-N leaching when the N application of300and375kg·ha^-1. Hence, blindly pursuinghigh crop grain yield with higher water and N-fertilizer input will cause greater nitrate-Nresidues lead to fertilizer waste and environmental pollution.4. irrigation and/or nitrogen input can increase the finalyield significantly and therewasa positive interactive term between water and nitrogen fertilizer on final yield.However, the overuse of water and/or nitrogen led to the low yield, and met the law ofdiminishing return. During2008-2009, when the irrigation amount is331mm and thenitrogen fertilizer is290kg·ha^-1, there is the maximum yield (10.34t·ha^-1), and the input ofnitrogen fertilizer is243.6kg·ha^-1plus the irrigation138mm, which can get the maximumvalue on WUE [18.96kg·（ha·mm）^-1], While in2009-2010, application of283kg·ha^-1nitrogen and309mm irrigation can get the highest wheat yield (9.168t·ha^-1); and85.9mmirrigation amount and242.8kg·ha^-1nitrogen input can reach the maximum WUE [16.73kg·（ha·mm）^-1]. Yield and ET responses to water and nitrogen inputs followed a quadratic and a line function, respectively. The optimal-coupling domains are determined byelasticity index （EI） and its expression in the water-nitrogen dimensions, which are theellipse forms with the global maximum WUE and Y corresponding to the left and right endpoints on its long axis. Considering of local maximum yields, the optimal-coupling domainwas the lower half-ellipse form with the two end points of the global maximum yield andWUE on its long axis. Total irrigation amount to winter wheat should not exceed331mm.The optimal-coupling domain reflects visually range of water and nitrogen inputs. It canprovide reference for the water and nitrogen inputs in agricultural applications.