Effects Of Crop Rotation And Nitrogen Reduction On Soil Quality,Rice Yield And Nitrogen Use Efficiency

In order to actively and quickly promote the pilot work of crop rotation and fallow and zero growth action of chemical fertilizer use in Jiangsu Province,protect cultivated land resources and promote the improvement of ecological environment,this experiment carried out the field research of crop rotation and fallow and nitrogen reduction from 2018 to 2020.There are two main rotation modes:rice wheat rotation and rice fallow rotation;Different nitrogen treatments were set up under the two rotation patterns:(1)no nitrogen application(NO),(2)local large-area conventional fertilization(N1,300kg/ha),and four nitrogen reduction strategies:(3)nitrogen reduction of 10%basal tiller:panicle fertilizer=5:5(N2),(4)nitrogen reduction of 10%basal tiller:panicle fertilizer=6:4(N3),(5)nitrogen reduction of 10%basal tiller:panicle fertilizer=7:3(N4),(6)nitrogen reduction of 10%basal tiller:panicle fertilizer=8:2(N5).There were 12 treatments with 3 repetitions.The amount of P and K fertilizer in each treatment area was equal,P2O5:75kg/Ha and K2O:150kg/ha,respectively.Based on the analysis of soil physical and chemical properties,rice nitrogen absorption and utilization,rice growth and yield change characteristics,the interaction technology of rotation fallow and nitrogen fertilizer was explored,in order to provide a theoretical basis for the selection of rotation fallow and nitrogen fertilizer reduction and efficiency increasing technology mode in Jiangsu Province.The results show that:11.Soil physical and chemical properties:(1)compared with rice wheat rotation,rice fallow rotation increased soil available phosphorus and available potassium by 12.99%～16.87%,9.2%～10.48%,18.65%～33.75%,11.87%～21.40%,respeltively,butreduced soil NH4++NO3-content(3)Under the two rotation patterns,the content of NH4++NO3-was higher in 6:4 or 7:3 of basal tiller:Panicle Fertilizer on the basis of 10%nitrogen reduction.2.Rice growth and development:(1)Compared with rice wheat rotation,SPAD value of rice fallow rotation increased by 11.78%～21.16%,and dry matter weight of rice at maturity increased by 16.9%～19.4%(2)There was no significant effect of 10%nitrogen reduction on dry matter weight of rice at maturity;3.Rice yield and yield components:(1)compared with rice wheat rotation,rice fallow rotation was more conducive to improve rice grain yield,panicles per hectare,grains per panicle,increased by 26.06%～28.71%,15.87%～21.18%,7.96%～18.80%respectively,but it could not significantly improve rice seed setting rate and 1000 grain weight;(2)Compared with the conventional nitrogen application rate,the panicle number per hectare.grain number per panicle,seed setting rate and 1000 grain weight were not significantly reduced by 10%nitrogen reduction;(3)Under the two rotation systems,the ratio of basal tiller:panicle fertilizer 6:4 was more favorable to increase rice yield and panicle number per hectare,which increased by 5.17%～48.81%and 2.12%～48.42%respectively,compared with other nitrogen management ratios;The effect of different N application ratio on grain number per panicle was not regular in different years;There was no significant difference in 1000 grain weight among different N application ratios4.Nitrogen uptake and utilization of rice(1)compared with rice wheat rotation,rice fallow rotation was more conducive to improving nitrogen accumulation,apparent nitrogen use efficiency and partial Nitrogen productivity of rice at maturity,increased by 28.6%～48.9%,4.9%～10.9%and 24.6%～27.1%,respectively;There was no significant difference in nitrogen use efficiency between the two rotation systems;The effects of two rotation patterns on grain nitrogen production efficiency of rice were not consistent among different years;(2)Compared with the conventional nitrogen application rate,the 10%nitrogen reduction treatment did not significantly reduce the nitrogen accumulation and apparent nitrogen use efficiency of rice at maturity;It also increased grain productivity,nitrogen physiological use efficiency,Nitrogen Agronomic use efficiency and nitrogen partial productivity;(3)Under the two rotation systems,the ratio of basal tiller fertilizer to panicle fertilizer was 6:4.which was more beneficial to increase nitrogen accumulation,rice nitrogen apparent use efficiency,rice nitrogen grain production efficiency,nitrogen physiological use efficiency,Nitrogen Agronomic use efficiency and nitrogen partial productivity,which increased by 2.37%～12.05%,6.01%～33.67%,0.15%～31.99%,respectively 6.64%～111.7%、12.08%～155.76%、5.12%～48.76%。In conclusion,the promotion of rice fallow rotation in Jiangsu Province is conducive to soil fertility,rice yield and nitrogen uptake and utilization efficiency.Based on the conventional nitrogen application rate,reducing nitrogen by 10%will not significantly reduce soil nutrient content,nitrogen accumulation and nitrogen utilization efficiency,but improve rice grain,physiological and agronomic efficiency and nitrogen partial productivity,thus will not lead to rice yield reduction.In the interaction of rotation mode and nitrogen reduction operation,rice fallow+10%nitrogen reduction+basal tiller:panicle fertilizer 6:4 is a technical mode that can be popularized in Jiangsu Province.