Optimum application rates and influence of nitrogen,phosphorus and potassium on yield of high density and direct seeding oilseed rape

To improve the fertilizer efficiency in oilseed rape under direct seeding and high density planting(as 375 000 plant per hectare),a 3414 design were used to study the optimum rates of nitrogen(N),phosphorus(P) and potassium(K) fertilizers in oilseed rape(Brassica napus L.) in field.Experiments were carried out in three sites in Guilin of Guangxi Province,Zhijiang of Hubei Province and Yulong of Yunnan Province.Results showed that rates of NPK fertilizers significantly affected rapeseed yield.By establishing the fertilizer response equations,the optimum fertilizer rates in oilseed rape were as following,N 118.5kg per hectare,P2O5 36.5kg per hectare,K2O 60.6kg per hectare for the yield of 2 416.3kg per hectare at Guilin;N 176.3kg per hectare,P2O5 73.0kg per hectare,K2O 100.6kg per hectare for the yield of 3 095.1kg per hectare at Zhijiang;N 256.7 kg per hectare,P2O5 88.1kg per hectare,K2O 137.7kg per hectare for the yield of 4 474.3kg/hm2 at Yulong.It could be concluded that the most important influence factors on optimum rates of fertilizer applied to rapeseed included agro ecology condition,genotype of cultivar,marginal profit ratio,prices of seeds and fertilizers.It was inaccurate to get the optimum fertilizer rates if they were only based on basic available nutrients of soil.