Fertilization Effect And Fertilizer Recommendation Of Nitrogen,phosphorus And Potassium On The Winter Oilseed Rape Of China

Winter oilseed rape is a major oil crop in China,which accounted 90%of planting area and total production of oilseed rape in China.Meanwhile,mineral element is the basis for the growth and development of winter oilseed rape.Fertilizations of nitrogen（N）,phosphorus（P）and potassium（K）provide nutrients for the growth of winter oilseed rape.Therefore,increasing rapeseed yield by application of N,P,and K fertilizers is crucial to edible oil supply security of China.Many studies has been focus on fertilization effects and fertilizer recommendation on winter oilseed rape using single or small sample numbers of experiments.However,fertilization effects would be various across different regions and cultivation methods..And regional fertilization effects could not be found in the field experiment with small sample.In this study,we conducted 1787 site-year on-farm winter oilseed rape experiments during the period of 2005 to 2010.We divided the planting area into four regions,i.e.,（i）region with upland-upland rotation（RUU）,（ii）region with paddy-upland rotation in the upper Yangtze river（RPUU）,（iii）region with paddy-upland rotation in the middle and lower Yangtze river（RPUML）and（iv）region with paddy-paddy-upland rotation（RPPU）,according to the climate,soil chemical properties and cropping systems.We calculated the economic optimum fertilizer rate for each site and regions using fertilizer effect function and regional average fertilizer amount methods.And different groups of soil indigenous nutrient supply（INS,IPS and IKS）were graded according to the relationship between yield of nutrient omission treatment and relative yield.Our objectives were（i）to analyze the fertilization effects of N,P and K in different regions,（ii）to compare the difference between the recommended fertilizer rate in experiment and economic optimum fertilizer rate in different indigenous nutrient supply level,（iii）to determine the economic optimum fertilizer rate（EONR,EOPR and EOKR）for the different regions.The main results are summarized below.（1）Fertilization of N,P and K made a significant increased effect on the yield and profit of winter oilseed rape.The yield of winter oilseed rape could be 2562（±591）kg/hm² under the balanced application of N,P and K fertilizer.Application of N,P and K fertilier could significantly increase yield,nutrient uptake and profit of rapeseed.The averaged yield increment by N,P and K fertilizer were 1084（±522）,629（±425）and 408（±319）kg/hm²,with the agronomic efficiency of 6.3（±3.0）kg/kg N,8.2（±5.8）kg/kg P₂O₅ and 4.8（±4.1）kg/kg K₂O,respectively.The net profit by N,P and K fertilization were 3252（±1915）,1927（±1579）and 1014（±1200）yuan/hm²,respectively.The nutrient absorptions of 100 kg rapeseed were 5.27（±0.83）kg N,1.0（±0.17）kg P and 5.02（±1.39）kg K in the NPK treatment,respectively.The apparent recovery efficiency of N,P and K fertilizer were 39.2%（±17.6%）,25.3%（±14.7%）and 39.9%（±29.7%）,respectively.（2）Affected by cropping systems,climate and soil chemical properties,fertilization effect of N,P and K fertilizer were different among different regions.Sound soil physical and chemical properties and sufficient sunshine duration would be benefit for rapeseed yield.Fertilization effect of RUU was better than the regions with paddy-upland rotation.Comparing with other regions,the RPUML region had lower rapeseed yield in the nutrient omission treatments due to the poor soil chemical properties.As a result,the fertilization effects were greater on the RPUML region than other regions.The soil chemical properties and the rapeseed yield of the nutrient omission treatment in RPUU were higher than RPUML.However,the fertilization effect of RPUU was lower than RPUML.Affected by the short growth period,more precipitation and low sunshine duration in spring,the RPPU region had the lowest rapeseed yield under NPK treatment and fertilization effect.（3）Current N applicaton rate should be optimized in different planting area.Comparing with EONR,nearly 45.0%of the sites applied suitable rate of N fertilizer in the planting area of winter oilseed rape.However,N rates of N2 treatment were excessive in 28.0%of the experiments and insufficient in 27.0%of the experiments.The EONR could increase rapeseed yield with efficient N fertilizers input under different INS levels.The averaged EONR were 166,201,170 and 159 kg N/hm² in the RUU,RPUU,RPUML and RPPU regions,respectively.（4）Current P application rate was suggested reduced to improve rapeseed yield and P fertilizer efficency.Comparing with EOPR,nearly 40.9%of the sites applied suitable rate of P fertilizer in the planting area of winter oilseed rape.However,P rates of P2treatment were excessive in 38.1%of the experiments and insufficient in 21.0%of the experiments.The EOPR could improve rapeseed yield with decreased P fertilizers input under different IPS levels.The averaged EOPR were 73,75,72 and 69 kg P₂O₅/hm² in the RUU,RPUU,RPUML and RPPU regions,respectively.（5）Current K application rate could be decreased to improve rapeseed yield and K fertilizer efficiency.Comparing with EOKR,nearly 47.5%of the sites applied suitable rate of K fertilizer in the planting area of winter oilseed rape.However,K rates of K2treatment were excessive in 37.6%of the experiments and insufficient in 14.9%of the experiments.EOKR could increase rapeseed yield with decreased K fertilizers input under different IKS levels.The averaged EOKR were 64,73,90 and 107 kg K₂O/hm² in the RUU,RPUU,RPUML and RPPU regions,respectively.The averaged decrements were 8-13 kg K₂O per hectare in different regions.