Effect Of Reduced And Simplified Nitrogen Fertilizer On Comprehensive Productivity And Economic Benefit Of Mechanical Transplanting Rice

The experiments were conducted out in Diaoyu Town,Xinghua City,Jiangsu Province in 2019 and 2020.The experiments used Nanjing 9108 as the material,no nitrogen fertilizer（ON）,conventional nitrogen fertilization（CK,nitrogen application rate was 300 kg·ha-1）,nitrogen reduction（RNF,nitrogen application rate was 240 kg·ha-1）,nitrogen reduction and increasing density（RNF+ID）,nitrogen reduction and thickening organic fertilizer（RNF+OF）and nitrogen reduction and thickening rapeseed cake fertilizer（RNF+RCF）,on the basis of four nitrogen reduction treatments（RNF,RNF+ID,RNF+OF and RNF+RCF）,replacing tillering fertilizer and panicle fertilizer with 40-day and 100-day controlled release fertilizer,four controlled release fertilizers for one-time base application（CRF,CRF+ID,CRF+OF and CRF+RCF）were set to explore the effects of reduced and simplified nitrogen fertilizer application on the yield and its composition,dry matter production,nitrogen absorption and utilization,rice quality and economic benefits of mechanical transplanting rice.The study is to provide theoretical basis and technical support for high quality,high yield and high efficiency of mechanical transplanting rice.The main research results are as follows:1.Yield and its formation:Compared with CK,the panicle number and spikelet number per panicle of RNF treatment decreased,the yield of RNF treatment decreased significantly.On the basis of RNF,increasing density,increasing organic fertilizer and increasing rapeseed cake fertilizer significantly increased the number of panicles and spikelet number per panicle,which production has rebounded.Under the same nitrogen fertilizer level,the panicle number and seed setting rate increased,and the spikelet number per panicle and 1000-grain weight decreased,the yield of one-time basal application of controlled-release fertilizer was equivalent to that of nitrogen-reduction fractional application.Therefore,reducing the application rate of nitrogen fertilizer is not conducive to the formation of panicle number and grain number per panicle,thereby reducing the yield.On the basis of reducing nitrogen,increasing density,increasing organic fertilizer and increasing rapeseed cake fertilizer can compensate for the yield loss caused by the decrease of nitrogen fertilizer.Replacing tillering fertilizer with controlled-release fertilizer and one-time basal application of panicle fertilizer can achieve the goal of stable yield of mechanical transplanting rice and reducing the number of fertilizations.2.Dry matter production:（1）In terms of tiller dynamics,compared with CK,the number of tillers in RNF treatment decreased at tillering stage,jointing stage,heading stage and maturity stage,and increased density,organic fertilizer and rapeseed cake fertilizer could effectively promote the formation of tillers on the basis of nitrogen reduction;compared with the treatment of nitrogen reduction and graded fertilization,the tiller numbers at tillering stage,jointing stage,heading stage and maturity stage and maturity stage of the one-time basal application of controlled-release fertilizer showed an increasing trend,and the tiller numbers at tillering stage,jointing stage,heading stage and maturity stage of CRF+RCF treatment were higher than those of CK.（2）In terms of dry matter accumulation,compared with CK,the dry matter accumulation of RNF treatment was significantly reduced at jointing stage,heading stage and mature stage,and the dry matter accumulation was increased by increasing density,applying organic fertilizer and rapeseed cake fertilizer on the basis of nitrogen reduction;compared with the treatment of reducing nitrogen fertilizer,the dry matter accumulation at jointing stage,heading stage and maturity stage of one-time base application of controlled release fertilizer treatment,the dry matter accumulation at jointing stage,heading stage and maturity stage of CRF+RCF treatment was higher than that of CK.（3）In photosynthetic production compared with CK,the leaf area index and photosynthetic potential of RNF treatment decreased significantly at the main growth stages.On the basis of RNF,increasing density,applying organic fertilizer and rapeseed cake fertilizer could improve leaf area index and photosynthetic potential;one-time basal application of controlled-release fertilizer could improve leaf area index and photosynthetic potential,especially after heading,compared with the treatment of nitrogen reduction and fractional fertilization.3.Nitrogen uptake and utilization:（1）Compared with CK,the nitrogen content in the main growth stages of RNF treatment decreased significantly,the nitrogen content in the main growth stages of mechanical transplanting rice decreased further after increasing density,while the nitrogen content in the main growth stages increased with the application of organic fertilizer and rapeseed cake fertilizer.The nitrogen content in the aboveground part of RNF+RCF treatment was similar to that of CK.Under the same nitrogen application level,the nitrogen content of aboveground parts in the one-time basal application of controlled-release fertilizer increased compared with that in the fractional application of nitrogen reduction at the main growth stages.（2）Compared with CK,nitrogen accumulation of RNF treatment decreased significantly at jointing,heading and maturity stages.Increasing density,organic fertilizer and rapeseed cake fertilizer on the basis of nitrogen reduction could increase nitrogen accumulation in main growth stages.Under the same nitrogen application level,the nitrogen accumulation in the jointing stage,heading stage and maturity stage of controlled-release fertilizer with one-time basal application was higher than that with nitrogen reduction and fractional application,and the total nitrogen accumulation was significantly increased.At jointing stage and heading stage,the nitrogen accumulation in CK treatment was the highest;at maturity stage,the nitrogen accumulation of CRF+RCF treatment was higher than that of CK in the 2019 test,and the nitrogen accumulation of CRF+OF and CRF+RCF treatments was higher than that of CK in the 2020 test.（3）Nitrogen uptake efficiency,nitrogen agronomic efficiency and nitrogen physiological efficiency of machine-transplanted rice decreased and nitrogen partial productivity increased after reducing nitrogen fertilizer application rate;nitrogen uptake efficiency,nitrogen agronomy efficiency,nitrogen partial productivity and nitrogen physiological efficiency were improved by increasing density and applying organic fertilizer on the basis of nitrogen reduction.Nitrogen uptake efficiency and nitrogen agronomy efficiency were improved by applying rapeseed cake fertilizer.Under the same nitrogen level,the nitrogen absorption and utilization rate,nitrogen agronomy utilization rate and nitrogen physiological utilization rate of controlled release fertilizer treatment were improved,and the nitrogen physiological utilization rate was decreased.4.Rice quality:（1）Processing quality,compared with CK,the brown rice rate,milled rice rate and head rice rate of RNF treatment decreased,and the increase of density on the basis of RNF decreased the brown rice rate,milled rice rate and head rice rate.After the application of organic fertilizer and rapeseed cake fertilizer,the brown rice rate,milled rice rate and head rice rate increased significantly.Under the same nitrogen fertilizer level,the brown rice rate,milled rice rate and head rice rate of one-time basal application of controlled release fertilizer were higher than those of fractional application.（2）Appearance quality,with the decrease of nitrogen fertilizer,chalky grain rate,chalky area and chalkiness decreased.Increasing density will increase chalky grain rate,chalky area and chalkiness.Adding organic fertilizer and rapeseed cake fertilizer on the basis of nitrogen reduction will reduce chalky grain rate,chalky area and chalkiness;under the same nitrogen fertilizer level,the chalky grain rate,chalkiness area and chalkiness degree of single basal application of controlled release fertilizer were lower than those of fractional application of nitrogen reduction.（3）Nutrition and cooking and eating quality,after nitrogen reduction,amylose content and gel consistency increased,protein content decreased,and the related indexes of eating value increased;after thickening on the basis of nitrogen reduction,organic fertilizer and rapeseed cake fertilizer increased,amylose content and gel consistency decreased,protein content increased,and the related indexes of eating value decreased;at the same nitrogen level,the application of controlled release fertilizer decreased amylose content and gel consistency,increased protein content,and decreased the related indexes of taste value.In the 2019 experiment,the taste values of RNF+OF and CRF+OF treatments decreased compared with CK.In the 2020 experiment,the taste values of RNF+OF,CRF+OF and CRF+RCF treatments decreased compared with those of CK.5.Economic benefits:（1）Cost,after reducing the amount of nitrogen fertilizer,fertilizer costs decreased significantly compared with CK.Densification treatment increased seed cost and machine transplanting cost.After adding organic fertilizer and rapeseed cake fertilizer,the fertilizer cost increased significantly,and the fertilizer cost of RNF+RCF increased compared with CK.Application of controlled release fertilizers also increases fertilizer costs.In terms of labor costs,the densification treatment increased the labor costs of seedling raising and mechanical transplanting,and the labor costs of one-time base application of controlled release fertilizer were significantly lower than those of other treatments.In terms of total cost,RNF was lower than CK.RNF+RCF and CRF+RCF treatments increased significantly compared with CK.The total cost of one-time basal application of controlled-release fertilizer was equivalent to that of nitrogen reduction and fractional fertilization（2）Benefits,after nitrogen fertilizer reduction,the yield decreased significantly,and the rice output decreased accordingly;increasing density and applying rapeseed cake fertilizer and organic fertilizer on the basis of nitrogen reduction can increase output value;under the same nitrogen level,the output value of one-time basal application of controlled-release fertilizer was equivalent to that of nitrogen reduction and fractional application;on net income,net income decreased significantly after nitrogen reduction,density,organic fertilizer and rapeseed cake fertilizer increased,compared with CK still decreased.The net income of one-time base application of controlled-release fertilizer was equivalent to that of nitrogen reduction and fractional application,and there was no significant difference.In summary,under the condition of carpet seedling transplanting,RNF+RCF treatment not only ensured high yield,but also reduced the use of conventional fertilizers and fertilization times.It could also improve nitrogen use efficiency,processing quality,appearance quality and nutritional quality,which could be used as a fertilization method for high yield and high quality of late-maturing medium japonica rice under the condition of carpet seedling transplanting.