| In view of the excessive nitrogen application in some areas of the Loess Plateau,the effect of nitrogen reduction and irrigation on water and nitrogen utilization and yield of winter wheat was studied based on the requirements of water saving and nitrogen reduction.In this study,the field test method was used to set up four nitrogen levels.The nitrogen application is 0 kg/hm~2(N0),60 kg/hm~2(N60),120 kg/hm~2(N120)and 180 kg/hm~2(N180)significantly.Two water treatments were set up: the whole growth period was not filled with irrigation(N0,N60,N120,N180),and 30 mm water(N0W,N60 W,N120W,N180W)at the jointing stage.It is to study the winter wheat yield,water and nitrogen use efficiency under different nitrogen treatments,and analyzing the regulation of population dynamics,grain quality,root characteristics and soil water and nitrogen distribution in the growth period of winter wheat.The main results are as follows:1.Effects of deficient irrigation on winter wheat yield and its components under different nitrogen levels.The results showed that the yield of wheat increased with the increase of nitrogen application rate.When the amount of nitrogen was reduced from 180 kg/hm~2 to 120 kg/hm~2,the grain yield of wheat decreased when the amount of nitrogen was reduced to 120 kg/hm~2,and there was no significant difference between the yield of wheat grain and the treatment of nitrogen 180 kg/hm~2 when the amount of nitrogen was reduced to 120 kg/hm~2.From the analysis of yield components,supplementary irrigation increased the number of ears per spike and grain number per spike.2.Effects of deficient irrigation on water and nitrogen use efficiency under different nitrogen levels.From the aspect of water use efficiency,the water consumption of wheat increased significantly with the increase of nitrogen application rate.When the amount of nitrogen was greater than 120 kg/hm ~2,water consumption did not increase significantly.Under the condition of plenty of water in the year of abundant water,there was no difference in water consumption between different nitrogen treatments,but water use efficiency decreased significantly.The results of two years showed that water use efficiency was significantly correlated with nitrogen level,and it increased first and then decreased with the increase of nitrogen level.The results showed that the water use efficiency of the 180 kg/hm~2 was the highest when the nitrogen was not irrigated,and the highest water efficiency was 120 kg/hm~2.From the aspect of nitrogen use efficiency,the nitrogen content of wheat grain increased significantly with the increase of nitrogen level.After irrigation,nitrogen content in grains treated with nitrogen 0 kg/hm~2 treatment decreased,but there was no difference in other treatments.The amount of nitrogen decreased from 180 kg/hm~2 to 120 kg/hm~2,and the amount of nitrogen absorbed increased after 30 mm irrigation.At the same time,the partial productivity of nitrogen increased when the nitrogen was reduced to 120 kg/hm~2.Upplementary irrigation further increased the partial productivity of nitrogen.However,there was no significant effect of supplemental irrigation on nitrogen partial productivity in wet season.3.Effects of deficient irrigation on the above-ground organs of winter wheat under different nitrogen levels.The number of tillers and aboveground biomass of winter wheat increased with the increase of nitrogen level.There was no significant difference in the number of stems and tillers when nitrogen application was 180 kg/hm~2 nitrogen reduction to 120 kg/hm~2,but the number of stems and tillers of 120 kg/hm~2 treatments at mature stage were increased after irrigation of 30 mm water.The aboveground biomass of each growth period was the maximum treatment of nitrogen application 180 kg/hm~2,supplementing irrigation treatment,nitrogen treatment with nitrogen 120 kg/hm~2 treatment and nitrogen treatment 180 kg/hm~2 treatment no significant difference,even higher than nitrogen application 180 kg/hm ~2treatment.By comparing the dry matter transport rate and the spike rate of wheat before and after flowering,it was found that the amount of nitrogen fertilizer decreased from 180 kg/hm~2 to 120 kg/hm ~2,which promoted the transport of dry matter to grain and increased the percentage of spikes,and laid a high yield basis.4.Effects of deficient irrigation on root growth and soil water and nitrogen content under different nitrogen levels.The increase of nitrogen application was beneficial to the growth of wheat root system.By analyzing the distribution of root system at flowering stage,it has the maximum root density under 180 kg/hm~2 nitrogen level,and the maximum density of root was 120 kg/hm~2treatment(N120W)after nitrogen reduction and irrigation.Supplemental irrigation increased the root amount of 0-1 m treated by N120 W,and had no effect on the root volume of 1-2 m.However,the amount of 0-1 m and 1-2 m of N180 W treatment decreased.Further analysis of root surface area,root volume,root weight and other indicators,combined with various indicators,the study showed that nitrogen application of 120 kg/hm~2 was most conducive to root growth.From the analysis of soil moisture content during the growth period,the increase of nitrogen application promoted the utilization of deep water by roots.The depth of soil moisture decreased by 120 kg/hm~2 and 180 kg/hm~2.Deficient supplementary irrigation had no significant effect on soil water content.On the other hand,soil nitrate nitrogen increased significantly with the increase of nitrogen level,especially in 0-60 cm soillayer.The effect of deficient irrigation on the content of nitrate nitrogen in soil was not significant.Therefore,under the conditions of this study,the nitrogen application was reduced to120 kg/hm~2,supplemented by 30 mm water for irrigation,that is,under the condition of N120 W,the parameters of winter wheat were optimal,and water and nitrogen use efficiency could be improved on the premise of ensuring the stability of wheat yield,and the purpose of water saving and reducing nitrogen was realized. |
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