Effects Of Water And Nitrogen Regulation On Nitrogen Absorption Of Spring Wheat And Soil Stoichiometry Of Carbon,Nitrogen And Phosphorus

Water and nitrogen are the main limiting factors affecting spring wheat production in arid areas,blindly increasing the amount of irrigation and nitrogen fertilizer not only waste resources,but also cause environmental pollution,the promotion of water-saving irrigation and scientific nitrogen production methods are of great significance for the sustainable development of arid areas such as Dingxi.To this end,the field experiment of different water and nitrogen treatment is carried out,we use completely random split plot design,we set W0(0mm),W1(50mm),W2(100mm),W3(150mm),W4(200mm)as the main treatment,and set N0(0kg/hm~2),N1(62.5kg/hm~2),N2(102.5kg/hm~2),N3(152.5kg/hm~2)as secondary treatments,we study the changes of nitrogen accumulation,transportion and utilization,yield and water use efficiency of spring wheat,soil stoichiometry of carbon,nitrogen and phosphorus under different water and nitrogen treatments,in order to improve water use efficiency,nitrogen recovery efficiency and yield of spring wheat,to explore high-yield and high-standard water-nitrogen management model of spring wheat in the region.The main findings are as follows:(1)Irrigation,nitrogen application and the interaction between the two significantly affect nitrogen accumulation,transportion and utilization of wheat.With the increase of irrigation amount and nitrogen application rate,nitrogen accumulation in wheat plants,vegetative organs,grain increase gradually and the growth rate gradually decrease,nitrogen transportion in the vegetative organs,nitrogen transport rate in the vegetative organs,contribution rate of vegetative organs nitrogen to grain,nitrogen harvest index,nitrogen recovery efficiency increase first and then decrease,and reach the maximum under the conditions of 150 mm irrigation and 102.5 kg/hm~2 nitrogen application.(2)With the progress of growth process,nitrogen accumulation of wheat plants increase gradually,nitrogen accumulation of wheat vegetative organs(leaf,stem sheath,cob and glume)increase first and then decrease,nitrogen accumulation of grain increase gradually;the proportion of nitrogen accumulation in various organs of wheat at maturity is:grain>stem sheath>leaf>cob and glume,the contribution rate of vegetative organs to grain nitrogen accumulation is:leaf>stem sheath>cob and glume.(3)Irrigation,nitrogen application and the interaction of the two significantly affect grain yield and water use efficiency.With the increase of irrigation amount and nitrogen application rate,spike number,grain number per spike and biomass of wheat increase gradually,1000-grain weight and grain yield increase first and then decrease,and reach the maximum under the conditions of 150 mm irrigation and 102.5 kg/hm~2 nitrogen application;with the increase of irrigation amount and nitrogen application rate,water consumption of wheat increase gradually,water use efficiency of wheat increase first and then decrease;there is a linear relationship between water consumption and biomass,and there is a quadratic curve relationship between water consumption and yield,and there is a quadratic curve relationship between water consumption and water use efficiency.(4)Irrigation and nitrogen application affect soil stoichiometry of carbon,nitrogen and phosphorus in the study area.With the increase of irrigation amount and nitrogen application rate,soil organic carbon content decrease gradually;with the increase of irrigation amount,soil total nitrogen content decrease gradually,with the increase of nitrogen application rate,soil total nitrogen content increase gradually;with the increase of irrigation amount,soil total phosphorus content remain unchanged,with the increase of nitrogen application rate,soil total phosphorus content decrease gradually;the content of soil organic carbon,total nitrogen and total phosphorus decrease layer by layer with the increase of soil depth.With the increase of irrigation amount,the soil C:N show a trend of“rise-lower-rise”,N:P and C:P show a decreasing trend;with the increase of nitrogen application rate,the soil C:N show a decreasing trend,N:P and C:P show a increasing trend.Considering the factors of water use efficiency,nitrogen recovery efficiency,yield,under the N2(102.5kg/hm~2)and W3(150mm)levels,the nitrogen application rate and irrigation amount balance the relationship between vegetative growth and reproductive growth of spring wheat,and promote the accumulation and transportion of nitrogen in wheat,and obtain higher water use efficiency,nitrogen recovery efficiency,grain yield,it is superior water and nitrogen combination that meet local production conditions.