Appropriate application of phosphate fertilizer in phosphorus-deficient soil has a good effect on improving the yield and quality of crops. Some farmers mistakenly believe that the more phosphate fertilizer is applied, the better. In fact, excessive application of phosphate fertilizer is not only useless, but also harmful.

1. excessive application of phosphorus fertilizer, crops from the soil to absorb too much phosphorus nutrients.

Excessive phosphorus nutrition will promote crop respiration is too strong, the consumption of dry matter is greater than the accumulation of dry matter, resulting in the early development of reproductive organs, causing premature maturity of crops, small grain, low yield.

2. induced zinc deficiency in soil.

Excessive application of calcium phosphate will cause zinc in the soil to interact with excessive phosphorus, resulting in zinc phosphate precipitation, which can not be absorbed by crops, making crops appear obvious symptoms of zinc deficiency. Excessive application of alkaline phosphate fertilizers such as calcium magnesium phosphate fertilizer will make the soil alkaline, reduce the effectiveness of zinc, and affect the absorption of zinc by crops.

3. excessive application of phosphorus will make crops lose phosphorus and silicon.

According to the study, excessive application of phosphorus fertilizer, will also cause the silicon in the soil is fixed, can not be absorbed, causing crops lack of silicon, especially the impact of silicon-loving grass crops is greater. Such as rice, a silicon-loving crop, if it cannot absorb more silicon from the soil, silicon deficiency symptoms such as slender stems, lodging and poor disease resistance will occur.

4. excessive application of phosphorus will cause crops to be deficient in phosphorus and molybdenum.

Appropriate application of phosphate fertilizer will promote the absorption of molybdenum by crops, but excessive application of phosphate fertilizer will make phosphorus and molybdenum lose their nutritional balance, affect the absorption of molybdenum by crops, and show "molybdenum deficiency".

5. cause the accumulation of harmful elements in the soil.

Phosphate fertilizer mainly comes from phosphate rock, which contains many impurities. These include cadmium, lead, fluorine and other harmful elements. And the application of phosphate fertilizer will cause the increase of cadmium in the soil, the annual growth rate of 0.15 and 0.08, respectively, and this cadmium is highly effective, easy to be absorbed by crops, causing harm to humans and animals.

6. excessive application of phosphate fertilizer will cause the deterioration of soil physical and chemical properties.

Superphosphate contains a large amount of free acid, and continuous application of large amounts will cause soil acidification. Calcium magnesium phosphate fertilizer contains 25%-30% lime. A large amount of application will aggravate the soil alkalinity and deteriorate the physical and chemical properties.

So how much is the appropriate amount of phosphate fertilizer? Generally speaking, even on phosphorus-deficient soil, the application amount per mu should not exceed 40kg, and 30-35kg is appropriate.