| Focus on the problem of low yield of crops caused by heavy soil texture and nutrient deficiency in Ningxia Tongxin county pumps up the Yellow River irrigation area,through a two-year field positioning experiment of straw returning combined with nitrogen fertilizer in 2017 and 2018.Four kinds of pure nitrogen application levels(0,150,300 and 450 kg/hm2)were set under the condition of total maize straw crushing returning(12000 kg/hm2),and conventional nitrogen application of 225 kg/hm2 without straw returning as the control(CK),to study the effects of straw returning combined with different amounts of nitrogen fertilizer on soil physical properties,nutrient status and maize yield in drip irrigation maize field.The results of two-year experiment as follows:1st,compared with no-straw returning treatment,the straw returning treatment combined nitrogen fertilizer with 300 kg/hm2 and 450 kg/hm2 could reduce the average soil bulk density of 0-20 cm layer by 3.32%and 5.40%,but increase the soil porosity by 3.69%and 7.10%respectively.The soil water storage of straw returning combined with nitrogen fertilizer increased significantly,which increased by 13.64%and 22.07%respectively in the year of 2017and 2018 on the treatment of straw returning combined with nitrogen fertilizer 300 kg/hm2.2nd,compared with no-straw returning treatment,the straw returning treatments combined nitrogen fertilizer could improve chemical properties of the soil.The soil organic matter increased by 36.91%to 102%,at the same times,increased soil total N by 17.59-51.11%,he content of available phosphorus,available potassium and alkaline nitrogen in soil increased greatly in two years,among which the content of available phosphorus in soil increased by 47.21%-129.11%in the annual average,the content of available potassium decreased by 16.41%-103.31%,and the content of soil alkaline nitrogen increased 26.53%-141.39%compared with that of control treatment.With straw returning to field with nitrogen fertilizer,the treatment of 300 kg/hm2 performed best.3rd,straw returning combined with nitrogen fertilizer treatments could promote the growth of maize,for example,the treatment of straw returning combined nitrogen fertilizer with 300 kg/hm2 and 450 kg/hm2 could increase the plant height of maize by 4.84%to 31.68%,it also increased the stem dimeter by 11.91%to 22.24%,and those treatments still had a strong influence on LAI(leaf area index),leave SPAD value,leave PI value and etc.,the average LAI in two years increase was 17.12%-29.32%compared with the control,the increase of leaf SPAD value was 6.8%-38.36%,and the fluorescence PI value increased by 23.28%compared with the control.4th,compared with no-straw returning treatment,the straw returning treatments combined nitrogen fertilizer with 300 kg/hm2 could improve the yield of maize for 31.09%and 46.02%respectively in the year of 2017 and 2018.The analysis of yield components showed that the high yield of maize could be achieved mainly by increasing the number of grains and the weight of 100 grains.Curve fitting showed that the optimum amount of nitrogen fertilizer was 260 kg/hm2.To sum up,the application of nitrogen fertilizer to straw returning to the field can improve the physical and chemical properties of the soil,promote the growth of maize,and then increase the yield of maize,in which the treatment of straw returning combined with nitrogen fertilizer 300kg/hm2 performed the best,through correlation analysis and principal component analysis of the impact of soil physicochemical characters and maize growth indicators,It 1s concluded that the application of nitrogen fertilizer to straw returning to the field mainly affects the physical properties of soil by affecting soil organic matter,total nitrogen,available potassium,alkaline nitrogen and agglomerates,and the agronomic traits measured in this experiment all promote the growth of maize. |
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