Study On Nitrogen Use Efficiency Of Multiple Cropping Different Types Of Vegetables After Wheat

Multiple cropping after spring wheat is one of the main multiple cropping types in the Yellow River Irrigation Area of Ningxia Previous studies have clarified the types and varieties of vegetables suitable for multiple cropping after wheat in the irrigation area,but the effects of multiple cropping of different vegetables on soil characteristics and nitrogen use efficiency under different nitrogen application rates are not deep enough.Therefore,a single factor randomized block design was used in this experiment,and four nitrogen application levels were set:0 kg·hm-2(N1),180 kg·hm-2(N2),225 kg·hm-2(N3),270 kg·hm-2(N4),and the types of replanted vegetables were baby cabbage(Xiaoyiheqiu),pepper(Jiaolong 7),and radish(Xinlimei).The effects of different nitrogen application rates on soil characteristics,vegetable yield and nitrogen use efficiency under different types of vegetables after wheat were studied by measuring the field growth and soil related indexes of three different types of vegetables.In order to provide theoretical basis and scientific support for rational and efficient utilization of nitrogen fertilizer and high-quality ecological development after wheat in Ningxia Yellow River irrigation area.The results show that:1、The yield of each multiple cropping vegetable changed differently with the increase of nitrogen application rate.The yield of baby cabbage increased continuously with the increase of nitrogen application rate.The highest value under N4 treatment was 4860.84 kg/666.7m2,and the overall performance was N4>N3>N2>N1,and N4 was 239.91%,108.78%and 28.92%higher than N1,N2 and N3,respectively.The yield of pepper and radish changed parabolically with the increase of nitrogen application rate.The highest values under N3 treatment were 1103.47 kg/666.7m2 and 6034.07 kg/666.7m2,respectively.The overall performance was N3>N4>N2>N1,which was significantly higher than other treatments by 70.73%～199.45%and 13.13%～184.57%,respectively.2、The physical and chemical properties of topsoil under different types of vegetables varied with the amount of nitrogen application.During the growth period of each vegetable,the contents of soil organic matter,total nitrogen,alkali-hydrolyzable nitrogen,nitrate nitrogen and ammonium nitrogen increased gradually with the increase of nitrogen application rate within a certain nitrogen application level.The content was the highest under N3 treatment and significantly different from other treatments.The overall performance under various types of vegetables was N3>N4>N2>N1.The soil water content and bulk density decreased with the increase of nitrogen application rate,and the content value was higher than that of other treatments under low nitrogen treatment N2 level.Nitrogen application rate had no significant effect on soil conductivity and pH,and soil inorganic nitrogen residue increased significantly with the increase of nitrogen application rate.3、Different nitrogen application treatments had significant effects on soil enzyme activities under different types of vegetables.During the whole growth period,soil urease,sucrase and alkaline phosphatase activities under different types of vegetables increased with the increase of nitrogen application rate,reaching the maximum value under N3 treatment,which was significantly different from that of control treatment N1.The catalase activity decreased with the increase of nitrogen application rate,and its activity was slightly higher at low nitrogen level than at high nitrogen level.The overall performance was:N2≥N1>N3>N4.4、Under different types of multiple cropping vegetables,with the gradual increase of nitrogen application rate,the agronomic efficiency,partial productivity,absorption efficiency and nitrogen fertilizer contribution rate of nitrogen fertilizer were improved to varying degrees.Under multiple cropping baby vegetables,the utilization rate was the highest under N4 treatment Under multiple cropping pepper and radish,the utilization rate reached the maximum under N3 treatment,while the physiological utilization rate decreased slightly under multiple cropping baby vegetables,and also reached the maximum under multiple cropping pepper and radish under N3 treatment Through comprehensive analysis of yield benefit and nitrogen use efficiency,it was concluded that among the three vegetable types suitable for multiple cropping after wheat,The benefit of multiple cropping baby cabbage was the best under the nitrogen application rate of 270 kg·hk-2,and the benefit of multiple cropping pepper and radish was the best under the nitrogen application rate of 225 kg·hm-2.