| The Guanzhong area in Shaanxi is a semi-arid area in the northwest.There is a shortage of water resources,and agricultural production is relatively extensive.Basically,the whole production period is uniform irrigation and excessive application of fertilizers for agricultural production.The pursuit of high yields and the serious application of excessive fertilizers not only increase production costs,but also waste water and nutrients.Therefore,improving the efficiency of water and nutrient utilization is an urgent problem that needs to be solved.Nitrogen fertilizer and soil moisture conditions are important factors affecting the yield of winter wheat,only a reasonable combination of water and nitrogen can effectively increase winter wheat yield and water and fertilizer use efficiency.The field experiment was performed in 2017-2018 at the Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas of Ministry of Education.And?Xiaoyan 22?was used as the research variety.The experiment consisted of three levels of nitrogen(75,150 and 300 kg/hm~2,marked as F1,F2 and F3)and five levels of irrigation(I0:no irrigation;I1:irrigation at jointing stage;I2:irrigation at heading stage;I3:irrigation at jointing and heading stage;I4:irrigation at jointing,heading and mature stage).In order to provide theoretical and scientific basis for high grain yield and efficient use of water and nitrogen,our research mainly focus on the effects of different water and nitrogen coupling on dry matter accumulation,leaf area index(LAI),yield and water use efficiency(WUE).The main findings are as follows:1:Soil water consumption increased with the increase of irrigation water amount(P<0.01)and nitrogen application rate(P>0.05).Soil water content and soil water storage increased with the increase of irrigation amount.The soil water storage of irrigation was increased by 4.06%?28.09%compared with that of rain-fed wheat during harvest period.Under the same nitrogen fertilization,the nitrate content residue decreased with the increase of irrigation amount.Under the same water level,the content of nitrate nitrogen in the soil increased with the increase of nitrogen rate.The residual nitrate content of F2I4 was 78.85%lower than that of F3I4.Increasing the amount of irrigation and nitrogen can greatly reduce the content of residual nitrate nitrogen in soil.2:The dynamic variation of biomass was similar during the whole growth period under different irrigation and nitrogen treatment,namely increased with the growth period.Under the same nitrogen application and different irrigation rates,The maximum biomass was obtained under the treatment of F3I4,which was 24.02%higher than that under the treatment of F3I0.Under the same irrigation volume and different nitrogen application rates,F3I0 treatment was 11.60%higher than F1I0 treatment,and combined water and nitrogen coupling effects,F3I4 treatment was 24.03%higher than F1I0 treatment.The leaf area index of winter wheat has significant difference under different water and nitrogen coupling treatments.The leaf area index first increased and then decreased with the growth period.The leaf area index increased with the increase of nitrogen rate and reached the maximum value at the filling stage.The leaf area index of F3I3 reached 5.79 cm3/cm-3at the filling stage,which was 88.60%higher than that of F1I0.3:The yield of winter wheat was significantly affected by irrigation and nitrogen,and there was a significant positive interaction between the yield and the amount of nitrogen and irrigation(P<0.05).The nitrogen rate has a positive correlation with the water use efficiency(P<0.01).Appropriate increase of nitrogen and irrigation can improve winter wheat yield and water use efficiency.At different irrigation levels,F3I4 obtained the highest grain yield(5905.90kg/hm~2),which was 22.61%higher than that of F3I0 treatment.F2I1 obtained the maximum water use efficiency(1.88kg/hm~3),which was 27.03%higher than that of F2I0treatment.Under different nitrogen application rates,the yield of F3I0 treatment was 38.80%higher than that of F1I0 treatment,and the WUE was 30.95%higher than that of F1I0treatment.Considering the coupling effect of water and nitrogen,the grain yield of F3I4 was58.42%higher than that of F1I0.The WUE of F2I1 was 49.21%higher than that of F1I0.Taking the input amount of water and nitrogen as the independent variable,and the yield and WUE as the dependent variables,we constructed binary quadratic regression equation.Based on the regression equation,we conclude that irrigation at jointing stage and applying150kg/hm~2nitrogen was beneficial to improving of yield and WUE.In conclusion,irrigation at jointing stage and applying 150 kg/hm~2 nitrogen not only guarantee the yield but also significantly save the irrigation water and nitrogen fertilizer.Therefore,F2I1 treatment is recommended as a scientific and reasonable water and nitrogen management strategy in Guanzhong Plain. |
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