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. So, what are the harms of excessive application of phosphate fertilizer? How much is phosphate fertilizer per mu? Let’s take a look.
What are the hazards of excessive application of phosphate fertilizer
1. Excessive application of phosphate fertilizer will make crops absorb too much phosphorus nutrients from the soil.
Excessive application of phosphate fertilizer will make crops absorb too much phosphorus nutrients from the soil. Excessive phosphorus nutrition will greatly enhance the respiration of crops, thereby consuming the sugar and energy stored in the crops.
2. Inducing soil zinc deficiency.
Excessive application of calcium phosphate will cause zinc in the soil to interact with excess phosphorus, resulting in precipitation of zinc phosphate, which cannot be absorbed by crops, causing obvious symptoms of zinc deficiency in crops; excessive application of calcium magnesium phosphate and other alkaline phosphate fertilizers will make the soil alkaline It reduces the effectiveness of zinc and affects the absorption of zinc by crops.
3. Excessive application of phosphorus will make crops gain phosphorus and lose silicon.
According to research, excessive application of phosphate fertilizer will also cause silicon in the soil to be fixed and unable to be absorbed, causing silicon deficiency in crops, especially for silicon-loving grass crops. For example, silicon-loving crops rice, if more silicon cannot be absorbed from the soil, silicon deficiency symptoms such as slender stalks, lodging and poor disease resistance will occur.
4. Excessive application of phosphorus will make crops lack of molybdenum and phosphorus.
Appropriate application of phosphate fertilizer will promote the absorption of molybdenum by crops, but excessive application of phosphate fertilizer will cause phosphorus and molybdenum to lose the nutritional balance and affect the absorption of molybdenum by crops, showing a "molybdenum deficiency syndrome".
5. Accumulation of harmful elements in the soil.
Phosphate fertilizer is mainly derived from phosphate rock, which contains many impurities. These include harmful elements such as cadmium, lead, and fluorine. Moreover, the application of phosphate fertilizer will cause the increase of cadmium in the soil, the annual increase is 0.15% and 0.08%, and this cadmium is highly effective, easy to be absorbed by crops, and cause harm to humans and animals.
6. Excessive application of phosphate fertilizer will cause deterioration of soil physical and chemical properties.
Superphosphate contains a large amount of free acid, and continuous application in large amounts will cause soil acidification. Calcium magnesium phosphate contains 25%-30% lime. Extensive application will aggravate soil alkalinity and deteriorate physical and chemical properties.
How much is appropriate per mu
Generally speaking, even on phosphorus-deficient soil, the application rate per mu should not exceed 40 kg, and 30-35 kg is appropriate.