Co-effects Of Polymer-coated Urea And Irrigation On Growth And Water-nitrogen Productivity Of Winter Wheat

Water and nitrogen are the most important limiting factors of agricultural production in North China Plain.Optimizing irrigation and fertilizer management measures in winter wheat-summer maize rotation system to improve water and nitrogen utilization efficiency is very important to ensure grain production security and farmland ecosystem protection in China.Therefore,this study took"Jimai 22",a winter wheat variety widely planted in North China Plain and sensitive to water and nitrogen,as the research object.Through field experiments for two consecutive years at the Environmental Soil Science Experimental Station of Liaocheng University,this study explored the effects of the coupling of water and controlled-release nitrogen on soil profile water content,nitrate nitrogen transport and winter wheat growth,combined with the analysis of dry matter transport and nitrogen absorption characteristics of winter wheat,the synchronization of nitrogen release from coated urea and nitrogen absorption of winter wheat under different water management measures was studied.At the same time,aiming at the grain yield,water and nitrogen productivity of winter wheat,the water and nitrogen management measures of winter wheat were optimized by fitting the reasonable input range of water and fertilizer.The main research results are as follows:（1）The nitrogen release of PCU in the field was much different from that in 25℃water.Two N release peaks of PCU were observedin the first 60 days and 140～200 days respectively,which crossponding to the N sensentive stage and N accumulation peak stage of winter wheat,respectively.In addition,a significant linear positive correlation between the N release of PCU and the N requirments of winter wheat was observed during the whole growth periods（R²=0.93,0.98 and 0.90 with 100%,85%and 70%irrigation,respectively）,indicating that the successive release rate of N from PCU corresponded well tothe N requirements of winter wheat plants.（2）With the same application fertilization,higher irrigation,increased the biomass and N accumulation,prolonged the filling time,increased the biomass transshipment volume and N accumulation volume of winter wheat before anthesis.With the same irrigation amounts,the contents of soil available N（NO₃^--N and NH₄⁺-N）were significantly increased from the jointing stage to the anthesis stage by using PCU compared with urea.In addition,the NO₃^--N contents in the 0～40 cm soil layer were enhanced,while the leaching of soil NO₃^--N was mitigated by using PCU.Furthermore,the net photosynthetic rate（P_n）of the flag leaves were signifcantly higher at booting stage and filling stage by using PCU,thus promoted the biomass and N accumulation after anthesis,ultimiately achieved higher grain yield and advanced N and water productivity.（3）The yield,water and N use efficiency of winter wheat were affected by N fertilizer type,irrigation amount and their interaction.The spike numbers and grains per spike were improved with the fertilization of PCU and higher irrigation.Under the same irrigation,PCU treatments produced 7.5%～9.3%more grain yield in 2020 and9.7%～20.9%in 2021 compared with U treatments.Under the same N fertilizer,the grain yield of 70%I treatments was 11.2%～13.6%and 3.4%～9.7%,respectively,lower than that in 85%I and 100%I treatments.The grain yield of PCU×100%I treatment was 3.4%～14.5%higher than other N fertilization treatments in 2020 and 4.2%～30.0%higher in 2021.There was no significant difference in grain yields observed among PCU×100%I,U×100%I and PCU×85%I in both years.In summary,to save the irrigation water and mitigate the NO₃^--N moving down through the soil with percolating water,the fertilization of PCU with 15%reduced irrigation could improve wheat growth and development,maintaining the absorption of N and water,enhancing the physiological characteristics,and thereby promoting the N and water utilization as well as the yield formation.