The effect of phosphorus level on nitrogen uptake of different soybean varieties

Three soybean varieties,which were widely planted in Heilongjiang province,were planted in pots with the same amount of N and K fertilizer,but four different levels of phosphorus.The nitrogen amounts in different organs were determined with the classical method of Kai's Fixed Nitrogen.The results suggested that there were relatively large effects of phosphorus on the nitrogen accumulation in total plants and each organ.In all three soybean varieties with different phosphorus treatments,the nitrogen amounts in total plants were gradually increased from branching stage and reached peak values at ripening stage.Suitable phosphorus level showed beneficial for the accumulation of nitrogen.The highest accumulation of nitrogen in total plants were obtained with P_5 treatment after flowering stage,indicating that suitable phosphorus application can help nitrogen reaching optimum balance,acquiring higher accumulation level.Nitrogen accumulation was higher in the variety with high protein than that in the variety with medium level of protein and high level of oil content,suggesting the nitrogen requirements was higher in high protein content variety.The higher nitrogen amounts in plants was followed by higher yield of single plant and higher content of protein,whereas fat content was lower.The nitrogen had little effect on fat formation.