Effects Of Controlled Release Nitrogen Fertilizer Reduction On Growth Of Broomcorn Millet And Soil Nitrogen Nutrient

In order to solve the problems of single type of nitrogen fertilizer and low Nitrogen use efficiency of broomcorn millet in the hilly area of the Loess Plateau,and to determine the appropriate local controlled-release nitrogen fertilizer application amount,this experiment took broomcorn millet as the research object and set up different controlled-release nitrogen fertilizer reduction treatments.Through field experiments for two consecutive years,the changes in the morphological indexes,physiological characteristics,soil nutrients,soil biological properties,fertilizer utilization rate,yield and quality and economic benefits of broomcorn millet under reduced controlled-release nitrogen fertilizer were studied.The effects of reduced controlled-release nitrogen fertilizer on the growth of broomcorn millet and soil properties were revealed.The main conclusions are as follows:（1）Compared with the urea,the full application of controlled-release nitrogen fertilizer significantly increased the plant height of broomcorn millet later growth period by 6.16%-8.82%,stem thickness by 4.39%-8.00%and leaf area per plant by7.10%-8.47%.The plant height,stem diameter and leaf area per plant were reduced by20-40%nitrogen reduction by 0.71%-16.58%,0.91%-15.36%and 2.28%-12.17%.（2）Compared with the urea,the full application of controlled-release nitrogen fertilizer and the reduction of nitrogen by 10%can increase the dry matter accumulation of broomcorn millet by 1.37%-8.77%,SPAD value of 1.03%-5.05%,nitrogen balance index of 2.66%-8.34%,and root activity of 1.22%-6.26%.The dry matter accumulation,SPAD value,nitrogen balance index and root vitality of broomcorn millet were lower than that of urea when the nitrogen was reduced by more than 20%.（3）Compared with the application of urea,the full application of controlled-release nitrogen fertilizer significantly increased the total nitrogen,nitrogen and ammonium nitrogen in the 0-40cm soil layer in the middle and late stages of broomcorn millet growth,Among them,the increase of soil nitrate nitrogen can reach 11.80%.Nitrogen reduction by 20%-40%reduced the total nitrogen,nitrate nitrogen and ammonium nitrogen content of the soil by 0.40%-12.29%,1.87%-32.51%and 0.59%-17.07%.Application of controlled-release nitrogen fertilizer and nitrogen reduction0%-30%did not significantly reduce soil catalase,urease,sucrase and microbial carbon and nitrogen content.（4）Compared with the urea,the full application of controlled-release nitrogen fertilizer and the reduction of nitrogen by 10%can increase the crude protein content of broomcorn millet grain by 0.80%-2.60%and reduce the crude fat content by 0.80%-3.00%.Full application of controlled-release nitrogen fertilizer can reduce the starch content of broomcorn millet grain by 1.5%,and increase the nitrogen accumulation of broomcorn millet,the apparent utilization rate of nitrogen fertilizer,the agronomic utilization rate of nitrogen fertilizer,and the partial productivity of nitrogen fertilizer.（5）Compared with urea,the full application of controlled-release nitrogen fertilizer significantly increased the yield of broomcorn millet by 4.96%.When the nitrogen was reduced by 10%,the yield could still be increased by 2.84%.When the controlled-release nitrogen fertilizer was reduced by 20%-40%,the yield decreased by0.84-5.00%The application of controlled-release nitrogen fertilizer mainly affects the yield by changing the ear number and ear weight.Full application of controlled-release nitrogen fertilizer and a 10%reduction in nitrogen increase economic benefits by 1.66%to 2.60%.When the controlled-release nitrogen fertilizer is reduced by 20%-40%,the economic benefit will be reduced by 1.90%-6.74%.In conclusion,compared with urea,controlled release nitrogen fertilizer can improve the soil nitrogen supply capacity and biological activity,promote the growth and development of broomcorn millet,and significantly improve the yield and economic benefit of broomcorn millet.However,when controlled release nitrogen fertilizer decreased by more than 10%,soil inorganic nitrogen content decreased,fertilizer efficiency became worse,and economic benefit decreased compared with urea application.Therefore,120 kg·hm^-2 of pure nitrogen is the best controlled release nitrogen fertilizer for broomcorn millet cultivation in this area.In order to reduce the environmental risk,the amount can be reduced by 10%.