Effects Of Nitrogen Application And Irrigation On Water And Nitrogen Migration In Soil And Yield Of Winter Wheat

Water and nitrogen are two very important factors in the agriculturalproduction. Under the field experiment, soil water content, water consumption characteristic,nitrate nitrogen content and accumulation amount, dry matter accumulation, nitrogenaccumulation and distribution and yield and quality were systematically studied with threewater treatments (W0-no irrigation, W1-once only irrigation at jointing stage, and W2-twiceirrigation at the jointing stage and filling stage) and with four nitrogen levels (0,180,240,300kg N/hm2) using a wheat cultivar named Ping’An8as the experimental material. Theseresults helped to provide basis and guidance for attaining high yield and high efficiency inwinter wheat. The main results are as follows.1. Effects of nitrogen fertilizer and irrigation on soil water content, water consumptioncharacteristics and water use efficiency in winter wheatThe experimental results showed that water content at the40-60cm soil layer was lowerduring sowing to wintering period, and water content at the20-40cm soil layer wasrelatively higher in reviving period, but the water content of each layer were lower than thewinter period. At jointing stage, water content in soil increased with the increase of soli layerdepth, and the irrigation treatments slightly higher than no irrigation treatments. Atflowering stage, water content of no irrigation treatment at0-60cm soil layer was lower, andonce irrigation at0-40cm soil layer relatively low, but were higher than that of no irrigationtreatments. Water content of once irrigation treatment at each layer in soil was higher thanthat of no irrigation at grain filling stage, while water content of twice irrigation treatment at0-60cm layer in soil was significantly higher than that of once irrigation treatments. Duringgain filling to mature stage of winter wheat, water content at each layer increased with theincrease of soil depth, and irrigation treatment was higher than that of no irrigation.With the increase of nitrogen application rate, water consumption and soil water storageconsumption amount increased first and then decreased, and amount of rainfall andirrigation percentage of the total water consumption decreased. With the increase ofirrigation, water consumption and irrigation percentage could be increased, rainfallprecipitation and soil water storage consumption amount could be decreased gradually. Atsowing to jointing stage, water consumption was increased with the increase of nitrogenapplication, but decreased with increase of irrigation times, and there were no significantdifferences in water consumption per day and water consumption percentage betweentreatments. From jointing to grain filling stage, total water consumption and waterconsumption per day in W0treatment was decreased with the increase of nitrogen application rate, but W1treatment with first increased and then decreased, and N1washigher in W2treatment. From filling to maturity, water consumption, water consumption perday, water consumption percentage was increased first and then decreased with the increaseof the amount of nitrogen application, and increased with the increase of irrigation times.2. Effects of nitrogen application and irrigation on soil nitrate content andaccumulationThe results showed that each treatment of nitrogen application significantly increasedthe accumulation of soil nitrate nitrogen. And the accumulation of nitrogen content indifferent growth period of nitrate increased with nitrogen application, showed the highestaccumulation at N3treatment (W0treatment under the blossom period N treatments werenot obvious). In wintering, nitrate nitrogen content at40cm layer in soil was higher, andmainly accumulated in40cm soil. During reviving period, nitrate content of20-40cm and100-120cm at soil layer with higher levels of nitrate lead to be accumulated mainly in the20-40cm and100-120cm soil. At jointing stage, flowing stage, grain filling stage, maturestage nitrate in no irrigation treatment was mainly accumulated in0-60cm soil layer, but forthe irrigation treatments, it had the high accumulation of soil nitrate nitrogen in0-60cm and120-160cm soil layer, and the surface accumulation slightly higher. During the floweringperiod and at the filling stage, nitrate nitrogen in the surface soil in twice irrigation treatmentwas slightly higher than that of once irrigation, and significantly higher than once irrigationin deeper soil. Nitrate accumulation in once irrigation treatment was increased with theincrease of soil depth, and80-100cm was significantly higher than that of no irrigationtreatment. At the mature period, nitrate accumulation in irrigation treatment in80-100cmsoil was significantly higher than that of no irrigation, and twice irrigation treatments in0-40cm and100-160cm soil significantly higher than that of once irrigation.3. Effects of nitrogen application and irrigation on water and nitrogen use efficiencyAt the same irrigation treatments, water use efficiency (WUE), rainfall use efficiency,irrigation use efficiency increased gradually with the increase of nitrogen applicationamount but nitrogen agronomic efficiency and nitrogen partial productivity decreased. Atthe same amount of nitrogen levels, water use efficiency(WUE), rainfall use efficiency,nitrogen partial productivity gradually increased with the increasing of irrigation amount,but irrigation use efficiency decreased.4. Effects of nitrogen application and irrigation on dry matter and nitrogenaccumulation and distribution in winter wheatThe results showed that leaf area index (LAI) was increased with the increase ofnitrogen application rate and times of irrigation water. Dry matter accumulation wasincreased gradually with the development process of winter wheat, and reached themaximum value at grain filling stage, and increased with increasing nitrogen application and irrigation. There were no significant differences between the N2and N3level in the samewater treatment, and dry matter accumulation was the highest among nitrogen applicationlevels in twice irrigation treatment. Results also showed that the transportation rate ofstorages on the vegetative organs of wheat plant at pre-anthesis was increased with increaseof nitrogen application rate and irrigation times, and storages before anthesis decreased withthe increase of irrigation times, and also increased at post-anthesis, moreover, dry matterinput grain was also increased with irrigation times. The accumulation and distribution ofdry matter in different organs presented the trend of the maximum grain, stem and leaffollowed by, rachis and glume minimum.At maturity, nitrogen accumulation above ground in no irrigation treatment wasincreased with the increase of nitrogen fertilization and irrigation. Nitrogen accumulation ingrain was increased with the increase of nitrogen fertilizer and irrigation, and nitrogentransportation rate in grain was also increased with nitrogen application rate, buttransportation ratios were decreased with the increase of nitrogen fertilizer and irrigation.Moreover, results also showed that the ratios of contribution to seed nitrogen stored atpre-anthesis were decreased with the increase of irrigation times, but the ratios ofcontribution to seed nitrogen stored at post-anthesis w increased gradually. Distribution ofnitrogen in different organs presented the trend of grain> stem> leaf> rachis and glume.5. Effects of nitrogen application and irrigation on yield and grain starch content ofwinter wheatThe results showed that biomass, grain yield and spike number was increased with theincrease of nitrogen application rate in certain range of nitrogen application, but number ofgrains per spike decreased, and N0with the higher1000-grain weight. With the increase ofirrigation times, grain yield, spike number,1000-grain weight and biomass was increasedgradually. Results also showed that the grain filling rate in rainfall treatment (no irrigation)appeared quickly at earlier filling stage and early in end, and peak value appeared in15dafter anthesis, and once irrigation in20d, twice irrigation in15-20d and the higher fillingrate maintained.Results showed that it was not obvious effect of nitrogen on grain starch content, and theamylose content was decreased with the increase of irrigation times, but starch content ofgrain amylopectin and starch content was increased with the increase of irrigation.