| In the actual production of silage maize,people have increased the input of chemical fertilizers in order to pursue high yield.However,it also caused negative effects such as soil fertility decline,low fertilizer utilization rate,quality decline and environmental pollution.Not only to ensure crop yield,but also to reduce fertilizer application and improve fertilizer nutrient use efficiency is a key issue that needs to be solved urgently in agricultural production.Therefore,the field experiments were conducted for 2 years from2021 to 2022 with "Q iaodan 6" as the experimental material.There were two cropping patterns,silage maize mixed with white clover(MC)and silage maize monoculture(MM).The two nitrogen application levels were reduced(N1,total nitrogen application amount of240 kg/ha)and Normal nitrogen rate(N2,total nitrogen application amount of 300 kg/ha).Under each nitrogen rate,three phosphate fertilizer managements were set: P1(applying all P fertilizer to basal fertilizer),P2(applying 50% P fertilizer to basal fertilizer and 50%at trumpet stage),and P3(applying 50% at jointing stage and 50% at t rumpet stage).The effects of cropping patterns,N application rates and P managements on the yield and quality,nitrogen and phosphorus nutrient absorption and utilization,soil nutrient and enzyme activity of silage maize were studied.The aim was to achieve the purpose of reducing N without reducing yield by adjusting cropping pattern and P managements.To provide theoretical basis for high yield and high quality cultivation of silage maize.The main results were as follows:(1)Reducing N by 20% generally reduced soil enzyme activity.Compared to conventional N application,under basal application of P,20% N reduction significantly reduced urease and acid phosphatase activities compared to conventional N application(P<0.05).However,the difference in reduction was not significant(P>0.05)under P supplementation.P topdressing can increase urease activity and acid phosphatase activity.The overall average performance of P2 was significantly higher than that of P1 treatment(P< 0.05),and P3 was highe r than P1 treatment.Mixed white clover generally increased soil enzyme activity.However,under conventional N application,the urease activity and phosphatase activity in mixed cropping were not significantly higher than those in monoculture,but significantly different under 20 %N reduction(P<0.05).(2)Reducing N by 20% generally reduced the absorption of N and N,but increased N partial productivity(NPFP)and agronomic efficiency(NAE).Under the basal application of P,compared with conventional N application,the available N and N uptake decreased significantly(P<0.05).NPFP and NAE under P base application,20% N reduction was13.21% and 10.62% higher than conventional N application.Under topdressing of P,the overall average increase in two years was 26.26% and 26.53%(P< 0.05).Compared with conventional N application,soil available P and P uptake decreased significantly(P< 0.05)under basal application of P and 100 % topdressing of P,while the decrease was not obvious under 50 % topdressing of P.P topdressing can improve the absorption and utilization of N and P.Under 20% N reduction,the available N and available P,nitrogen and phosphorus absorption and utilization rate in mixed cropping and monoculture showed that P2 was significantly higher than P1 treatment(P<0.05),and P3 was slightly higher than P1 treatment.Under conventional N application,P3 and P2 in monoculture were significantly higher than P1 treatment(P<0.05).In mixed cropping,it showed P2>P3>P1treatment.Mixed white clover will generally reduce the absorption and utilization of soil N and P under any fertilization conditions.But under the conditions of 20% N reduction in2022 and P1 and P2,mixed cropping increased the N uptake of maize by 5.62 % and1.30 % compared to monoculture.(3)N reduction will generally cause silage maize yield reduction.In monoculture,compared to conventional N application,the yield reduction effect of 20% N reduction was not significant(P>0.05).In the mixed cropping,the difference was significant(P<0.05).Under the base application of P,the average yield reduction of 20% was 6.93 % compared to the conventional N application.Under the topdressing of P,the overall average yield decreased by 0.95% in two years.P topdressing can increase the fresh grass yield of silage corn.Under 20 % N reduction,the fresh grass yield of P2 treatment was the highest in monoculture and mixed cropping,which was significantly higher than that of P3 and P1treatments(P<0.05).Under conventional N application,P3 treatment was the highest in monoculture,followed by P2 and P1 treatments,and P2>P3>P1 treatment in the mixed cropping.In general,mixed cropping will reduce the fresh grass yield of silage maize,which will be weakened in 2022.In 2021,regardless of the fertilization,the mixed cropping was significantly lower than the monoculture(P<0.05).In 2022,the overall decrease was 4.46%,and the difference was not significant under the same nitrogen application and P2 treatment(P > 0.05).(4)Reducing N by 20% generally reduced crude protein(CP)content and increased acid detergent fiber(ADF)and neutral detergent fiber(NDF)content.Compared to conventional N application,the overall average CP content decreased by 20.36 % and8.88 % respectively under P basal application and 100 % topdressing.Under the application of 50 % P,the overall increase was 2.99 %.The content of ADF and NDF increased by 2.04 % and 3.41% respectively under 20% N reduction compared to conventional N application.Under the topdressing of P,the overall average decrease was4.55 % and 4.99 %.From the perspective of the average effect of phosphorus application methods,50% topdressing of P can significantly improve the nutritional quality of silage maize.Under the condition of reducing N by 20 %,mixed white clover can increase CP content and reduce ADF content,and improve the nutritional quality of silage maize.In summary,in the production of silage maize,N f reduction of 20 % + topdressing50 % P can increase soil urease and phosphatase activity,increase available N and available P content,promote nutrient absorption,improve fertilizer utilization rate,thereby increasing yield and improving nutritional quality.Therefore,reducing N application by20 % + topdressing 50% P in silage maize production can reduce N under the condition of ensuring stable yield and yield increase of silage maize.The 20% N reduction + mixed white clover may have the potential to increase production. |
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