含DMPP缓释氮肥与尿素配施对坡耕地青贮玉米生长及土壤养分的影响OA

The effects of the combined application of controlled-release nitrogen fertilizer and urea on red soil nutrient content,nitrogen release characteristics,and the growth of silage maize were investigated,aiming to provide a theoretical basis for green and efficient fertilization of silage maize on sloping farmland.Runoff flumes were used to simulate the sloping farmland environment,with silage maize as the test crop.Three treatments were conducted under equal nitrogen conditions:conventional urea alone(CK),25％slow-release nitrogen fertilizer+75％conventional urea(P1),and 50％slow-release nitrogen fertilizer+50％conventional urea(P2).Based on the fertilization treatments,a synchronous laboratory incubation experiment was implemented to monitor nitrogen release dynamics and soil enzyme activities.These data were integrated with the growth indicators of silage maize at the milk and wax stages from the runoff flume experiment to evaluate the effects of controlled-release nitrogen fertilizer application.(1)At the milk stage of silage maize,compared with CK,treatments P1 and P2 significantly increased soil alkali-hydrolyzable nitrogen content by 13.67％and 27.09％,and ammonium nitrogen content by 3.54％and 4.28％(P＜0.05),respectively,while decreasing nitrate nitrogen content by 13.22％and 17.01％,and available phosphorus content by 19.72％and 31.89％,respectively.Soil incubation experiments demonstrated that the combined application treatments slowed the nitrogen release rate,thereby increasing the contents of alkali-hydrolyzable nitrogen and ammonium nitrogen in the mid to late incubation stages,while simultaneously suppressing nitrate nitrogen accumulation,resulting in a more stable nitrogen supply system.Furthermore,the combined application of slow-release nitrogen fertilizer enhanced the activities of soil urease and nitrate reductase,with their peak activities delayed as the proportion of slow-release fertilizer increased.The maximum urease activities for the CK,P1,and P2 treatments occurred at 2 d(0.72 mg·d-1·g-1),4 d(0.70 mg·d-1·g-1)and 8 d(0.68 mg·d-1·g-1)of incubation,respectively.Similarly,the peak nitrate reductase activities were observed at 4 d(2.68 μg·d-1·g-1),8 d(2.52 μg·d-1·g-1)and 8 d(2.18μg·d-1·g-1),respectively.These results indicated that the nitrification inhibitor(DMPP)contained in the slow-release fertilizer effectively delayed the nitrification process.(2)Compared to CK,P1 and P2 treatments increased plant height by 8.50％and 6.01％,stem diameter by 10.80％and 13.68％,and leaf area index by 13.22％and 8.36％,respectively,at the milk-ripening stage.Root morphology parameters(root length,surface area,and volume)improved by 27.53％-50.33％.P1 achieved the highest dry matter yield(24.26 t·hm-2).In addition,compared with CK,P1 and P2 treatments significantly increased the content of crude protein(9.10％and 18.18％),ether extract(43.32％and 57.33％)and starch content(13.46％and 21.04％)in silage corn(P＜0.05),respectively,while the fiber content was significantly reduced,effectively improving the palatability and energy density of the silage.Under equal nitrogen fertilization conditions,the combined application of controlled-release nitrogen fertilizer(CRNF)with conventional fertilizer effectively slowed nitrogen release rates in soil,maintained higher soil nitrogen availability during mid-to-late crop growth stages,and promoted silage maize growth,root development,and nitrogen uptake.This synergistic effect ultimately enhanced both yield and quality while achieving fertilizer reduction and efficiency improvement.Among the treatments,the combination of 25％controlled-release nitrogen fertilizer with 75％urea(P1)was identified as the optimal treatment.