The Mechanism Of Effect Of Reduction And Combination Of Slow-release Nitrogen Fertilizer And Conventional Nitrogen Fertilizer On The Rice Growth

To understand the effect of slow release nitrogen fertilizer(SRF)combined with conventional nitrogen fertilizer(CRF)and its nitrogen(N)fertilizer reduction under one-time applications on soil properties,rice yield and nitrogen absorption and utilization efficiency,two years paddy field experiments with randomized block design were conducted in 2018 and 2019.The rice variety of Nanjing 9108 and Nanjing 46 were adopted in Gaoyou and Kunshan of Jiangsu Province,respectively.There were three main N application amount treatments,i.e.(1)no N fertilizer treatment(NO-F);(2)convention N fertilizer application amount(300kg/ha N,NN),on basis of this N fertilizer amount,five treatments were conducted,i.e.CRF:SRF 0:10,3:7,5:5,7:3,10:0;(3)N fertilizer application amount 15%reduction(255 kg/ha N,NR),at basis of this N fertilizer amount,five treatments were also conducted,i.e.CRF:SRF 0:10,3:7,5:5,7:3,10:0.The single application of CRF(CRF:SRF 10:0)was applied three times as basal fertilizer,tillering fertilizer and panicle fertilizer,N fertilizer of the other treatments were applied one time as basal fertilizer before sowing.The main research results are as followsN fertilizer application was easy to cause soil acidification.N fertilizer application increased soil organic matter(OM),total nitrogen(TN)and available N(AN)and improved rice biomass production,gain yield,N absorption amount(NAA)at heading and maturity,while decreased N use efficiency for grain yield(IEN)and N use efficiency for biomass production(NUEb)Compared with single application of CRF,SRF combined with CRF reduced soil acidification,increased soil OM,TN,AN contents as well as improved rice biomass production,grain yield,NAA at heading and maturity stages,FRN,AEN,PFPN.While,there was no obvious advantage of SRF combined with CRF in the improvement of IEN and NUEb.On the basis of SRF combined with CRF,compared with conventioan N fertilizer application amount,Reduction15%N fertilizer amount showed no significant advantage in relieving soil acidity,decreased soil OM,TN contents and had no significant influence on soil AN,didn't cause a significant decline in rice biological yield.Although reduction 15%N fertilizer amount decreased panicle number ha-1,didn't significantly decrease spikies numbers per panicle,1000-grain weight and filled grain percentage,therefore didn't cause a significant decline in rice grain yield.And,reduction 15%N fertilizer amount didn't significantly decreased NAA at heading and maturity stages and IEN,while improved FRN,NUEb,AEN,PFPN.In Gaoyou area,on the basis of reduction15%N fertilizer amount,compared with other ratios of SRF combined with CRF,CRF:SRF3:7 showed highest the soil TN and AN.Rice biomass production,panicle number ha-1 of CRF:SRF 0:10,3:7and 5:5 were higher than CRF:SRF 7:3,there was no significant difference on rice biomass production and panicle number ha-1 among CRF:SRF 0:10,3:7and 5:5.Single application of SRF had higher grain yield,while,didn't significantly decreased spikelets per panicle,1000-filled grain weight and filled grain percentage.Compared with CRF:SRF 5:5 and7:3,CRF:SRF0:10 and CRF:SRF 3:7 had higher NAA at maturity and FRN.Single application of SRF had higher AEN,PFPN The IEN and NUEb of CRF:SRF 0:10 and 3:7 were lower than CRF:SRF 5:5 and7:3.In Kunshan area,compared with other ratios of SRF combined with CRF,single application of SRF showed highest soil OM,AN,rice grain yield,spikelets per panicle,AEN and PFPN and lowest filled grain percentage,while,CRF:SRF 3:7 showed highest soil TN.Rice biomass production,panicle number ha-1 of CRF:SRF 0:10,3:7and5:5 were higher than CRF:SRF 7:3,there was no significant difference on rice biomass production and panicle number ha-1 among CRF:SRF 0:10,3:7and5:5.CRF:SRF 0:10 and3:7 showed higher NAA at maturity and FRN as well as lower IEN and NUEb.In summary,SRF combined with CRF was superior to single application of CRF in soil properties,biomass and grain yield and N absorption and utilization efficiency.On the basis of SRF combined with CRF,N reduction by 15%can maintain the soil AN,not reduce NAA,ensure the stable yield of rice,and significantly improve the FRN,NUEb,AEN and PFPN.On the basis of N reduction by 15%,the single application of SRF and CRF:SRF 3:7 were optimum.