Effect of phosphorus Nutrition on double-low rape and its Application period

First, the effect of phosphorus deficiency: phosphorus is an indispensable nutrient for the production and development of rapeseed. Phosphorus deficiency will lead to poor root development, smaller leaves and thicker mesophyll. Moderate phosphorus deficiency, branches and pods decreased, the grain was not full, and the yield decreased significantly; in severe phosphorus deficiency, the leaves turned dark purple and gradually withered, so that bolting and flowering could not be allowed. During the growing period of rape, the content of available phosphorus in soil is required to be kept at 10 mg / kg. If it is less than 5 mg / kg, the soil is prone to phosphorus deficiency, so phosphate fertilizer must be applied in time. Second, correct application of phosphorus nutrition: although rape needs less phosphorus fertilizer than nitrogen and potassium, rapeseed is very sensitive to phosphorus. In the whole life of rape, the absorption of phosphorus takes bolting stage as the peak, but from the point of view of the utilization of phosphate fertilizer and the effect of increasing yield, the effect of applying phosphate fertilizer before 2-leaf stage is the best. The utilization rate of applying phosphorus before 2-leaf stage is 17.3%, while it is 8.5% 20 days before bolting, and the yield of rape is only 27.4% of that of applying phosphorus at 2-leaf stage. It can be seen that the earlier the lack of phosphorus in rape, the greater the effect on the yield, even if phosphorus is supplemented in the later stage, it is difficult to increase the yield. Therefore, phosphate fertilizer should be used as seed fertilizer and base fertilizer or with root fertilizer, such as topdressing, it should also be applied before the 5-leaf stage.