Study On The Effects Of Nitrogen,Phosphorus,and Potassium Fertilization And Nitrogen Fertilizer Management In Rice-oilseed Rape Rotation System In Jianghan Plain,China

Arable farming has historically been dominated by attempts to achieve higher levels of production;however,new and diverse objectives now need to be considered.The environmental impact of crops and production systems,the quality of crop products,reduced costs of production and improved nutrients use efficiencies are among the main objectives of modern agriculture.Rice-upland rotations are important in south Asian countries and cover an estimated area of 26.7 million ha.In China,these rotations contribute 72% of total cereal production and occupy an area of about 13 million ha.The Yangtze River basin in China is a major planting area for rice-oilseed rape rotation system,contributing 70% of the total rice and 91% of the total oilseed rape production in China.In this area,oilseed rape is usually cultivated under either the single rice-oilseed rape system or the double rice-oilseed rape system,both of which limits the crop duration and soil nutrient supply accessible for increasing yield.Furthermore,the yield of rice-upland rotations faces significant decline or stagnation as their sustainability is threatened by imbalance applications of fertilizers,lower nutrients use efficiencies and deterioration in soil fertility.Consequently,which causes a series of economic and environmental problems.Therefore,a series of field experiments were conducted to address the concerned issues.Incredible accomplishments have been achieved in agricultural production of China,while there are still numerous challenges ahead that demands to ensure food security and environmental security.Analyzing balanced fertilization and indigenous nutrients supply capacity will help to increase grain yield and environmental sustainability.Rice-upland rotations are important agricultural production systems in the study region.Considerable attention has already been paid to increase the yield of rice(Oryza sativa L.)and oilseed rape(Brassica napus L.)by applying mineral fertilizers.However,the accumulation and appropriate utilization of nitrogen(N),phosphorus(P)and potassium(K)of rice-oilseed rape rotation with high yield and nutrient supplying capacity is still obscure.Therefore,field experiments were conducted during 2011-2013 at three different sites,including Honghu(HH),Shayang(SY)and Jingzhou(JZ)in Hubei province,central China to find out the fertilization responses for enhancing crop productivity and indigenous nutrients supplying capacity for rice-oilseed rape rotation.Four mineral fertilizer treatments(NPK,NP,NK and PK)were laid out in the randomized complete block design with three replicates.Crops yield were significantly increased by 19-41%(rice)and 61-76%(oilseed rape)during two years of rice-oilseed rape rotation(2011-2013)under NPK fertilization as compared to PK across study sites.Yield responses to fertilization were ranked as NPK>NP>NK>PK,illustrating that N was the most limiting nutrient in rice-oilseed rape rotation following P and K.Highest N,P and K accumulation was observed under NPK fertilization and least uptake was marked under PK treatment.Moreover,the responses of P and K accumulation were high when these were applied with N.The indigenous nitrogen supplying capacity(INS),indigenous phosphorus supplying capacity(IPS)and indigenous potassium supplying capacity(IKS)of soil decreases to a significant level and affects the rice-oilseed rape rotation productivity at each site when these were compared with NPK fertilization.The results of INS,IPS and IKS reveal that balanced fertilization on these soils is requisite to evade further deterioration of soil fertility status.Based on crops yield,nutrient's accumulation and nutrients supplying capacity of soil,it was concluded that balanced nutrient application under NPK fertilization is a key management strategy for enhancing rice-oilseed rape productivity and environment safety.The use of efficient rates of nitrogen(N)fertilizer application is important with regard to increasing crop productivity and maintaining environmental sustainability.Rice-oilseed rape rotations are a mainstay of the economy and food security of central China.Hence,a field experiment was carried out during 2011–2013 in Honghu to identify the most appropriate N application rates for enhancing crop productivity and N use efficiency for rice(Oryza sativa L.)-oilseed rape(Brassica napus L.)rotations.Six N fertilizer treatments(RO1,RO2,RO3,RO4,RO5,and RO6)were laid out in a randomized complete block design with three replicates.ROx represented the N fertilizer application rates(kg ha–1)for rice and oilseed rape,respectively.Grain yields from plots receiving N fertilizer were significantly increased by 59–71%(rice)and 109–160%(oilseed rape)during the total rotation(2011–2013),as compared to RO1(control;no N application).Furthermore,a similar trend was observed for N accumulation,ranging from 88–125% and 134–200% in aerial parts of rice and oilseed rape,respectively.Nitrogen use efficiency(NUE)was significantly higher(38.5%)under RO2 and lower(34.2%)under RO6 while apparent N balance(ANB)was positively lowest under R05(183.4 kg ha–1)followed by R02(234.2 kg ha–1)and highest under R06(344.5 kg ha–1)during the total rotation.The results of grain yield,NUE,and ANB indicated that the R02 rate of N application was superior.This information should help to develop a cost-effective and environment-friendly N management strategy for rice-oilseed rape rotation systems of central China.Winter rapeseed(Brassica napus L.)is a dominant oilseed crop and has become an alternate crop both for edible oil production and energy agriculture.This study was conducted to find out the response of nitrogen(N),phosphorus(P)and potassium(K)fertilizer combinations on yield,oil and protein contents in oilseed rape crop.Four fertilizer treatments of N,P and K fertilizers(NPK,NP,NK,and PK)were applied according to the local recommendations at three different sites in Hubei province,during the year 2012-2013.Rapeseed yield was significantly increased by 61-72% under NPK fertilization as compared to PK across study sites.Yield responses to fertilization were ranked as NPK>NP>NK>PK,illustrating that N was the most limiting nutrient in rapeseed productivity following P and K.Oil and protein yields were significantly affected to applied N,P,and K fertilizers.Among all combinations,NPK combination performed best.Oil and protein contents along with other fatty acids(palmitic acid,stearic acid,oleic acid,linoleic acid and linolenic acid)were not influenced significantly by the application of P and K fertilizer.By increasing the amounts of N fertilizer application,oil contents of rapeseed reduced and protein contents increased consistently.These results suggest that NPK combination is more productive as compared to the other combinations.