Effects Of Soil Water Content Before Sowing And Nitrogen Fertilizer On Water And Nitrogen Utilization,yield And Quality Of Dryland Wheat

In order to clarify the high-efficiency utilization mechanism of dryland wheat water and nutrients,field trials were carried out at the Wenxi County Experimental Base in Yuncheng City in 2018-2020.The experiment adopted a two-factor split zone design,with different soil moisture as the main zone,set up two treatments of no supplemental irrigation and supplemental irrigation before sowing,with nitrogen application as the sub zone,set 0 kg·hm^-2 120 kg·hm^-2,150 kg·hm^-2 and 180 kg·hm^-2 to study the effects of soil moisture and nitrogen fertilizer on the growth characteristics,yield and quality of dryland wheat and their relationship with water consumption and nitrogen absorption and utilization.The main findings are as follows:（1）Supplementary irrigation before sowing significantly increased the plant height and leaf area of wheat in each growth period,slowed the decrease of SPAD value after flowering;significantly increased the total water consumption during the growth period and the water consumption before flowering,and increased the yield.In the drought year 2018-2019,supplementary irrigation before planting increased the water consumption during the growth period of the soil and increased the thousand-grain weight at the mature stage,thereby significantly increasing the yield;in the wet year 2019-2020,the number of grains per spike was significantly increased under the supplemental irrigation before planting.,And under the nitrogen application rates of 120 kg·hm^-2 and 180 kg·hm^-2,the thousand-grain weight was significantly increased,and finally the yield and dry matter quality were improved.（2）When the nitrogen application rate is 120 kg·hm^-2,the photosynthesis of wheat plants at the flowering stage is significantly improved,and the specific performance is that compared with other nitrogen application treatments,the intercellular carbon dioxide concentration,stomatal conductance and transpiration rate are increased and reach the maximum value..The appropriate amount of nitrogen application is different under different soil moisture levels,because soil moisture fertilization plays an important role in increasing yield.Under supplemental irrigation before sowing,when the nitrogen application rate was 150 kg·hm^-2,the yield reached the maximum,and the yield increased by 1%-14%;without supplemental irrigation,when the nitrogen application rate was 120 kg·hm^-2 The output reached the maximum,and the output increased by 4%-8%.Scanning electron microscopy observation results of starch grains in post-flowering grains showed that with the advancement of growth,the density of starch grains in post-flowering wheat grains increased,and starch grains changed from small to large.Irrigation before sowing can increase the compactness of amyloid,and with the increase of nitrogen application,the density and viscosity of amylum increase.（3）Precipitation during the growth period affects the interactive effect of soil moisture and nitrogen application rate on nitrogen efficiency.Under different supplementary irrigation treatments,the nitrogen efficiency showed a decreasing trend with the increase of nitrogen application rate,and the decrease of nitrogen efficiency was mainly manifested in the decrease of nitrogen use efficiency.By analyzing the two components of nitrogen use efficiency,the grain nitrogen productivity and the nitrogen harvest index showed that the grain nitrogen productivity of the 2018-2019 growing season showed a downward trend with the increase of nitrogen application rate without supplementary irrigation treatment,and the overall nitrogen harvest index showed that The maximum nitrogen content was 150 kg·hm^-2;the grain nitrogen productivity under the 2019-2020 growing season without supplemental irrigation treatment increased with the increase of nitrogen application rate,and under the supplementary irrigation treatment before sowing,it showed a decreasing trend.In short,the interaction of soil moisture and nitrogen fertilizer has an important influence on the formation of water and nitrogen utilization,yield and quality of dryland wheat.In dry years,by supplementing irrigation before planting to increase the soil moisture by 40 mm,increasing the soil moisture in dryland wheat will help plants to absorb nitrogen and increase soil water consumption before anthesis.At the same time,because moisture fertilization is beneficial to the increase of winter wheat yield in dry land,in dry years with little precipitation during the growth period,the yield of irrigation before planting is highest when the nitrogen application rate is 120 kg·hm^-2;in wet years with higher precipitation during the growth period,the amount of nitrogen is higher.When it is 150 kg·hm^-2,the yield is the highest.