What are the key points of efficient chemical fertilizer application techniques
When applying chemical fertilizers to crops, to achieve efficient application of chemical fertilizers, attention must be paid to the acidity and alkalinity of the fertilizers. Chemical fertilizers can be divided by acidity and alkalinity into two types: chemical acidity-alkalinity and physiological acidity-alkalinity.
Chemical fertilizers can be divided by acidity and alkalinity into two types: chemical acidity-alkalinity and physiological acidity-alkalinity. Chemical acidity-alkalinity refers to the acidity or alkalinity shown when the fertilizer dissolves in water. On this basis, fertilizers can be divided into chemically acidic fertilizers, chemically alkaline fertilizers, and chemically neutral fertilizers. Fertilizers such as ammonium sulfate and superphosphate that show acidity or weak acidity when dissolved in water are chemically acidic fertilizers; ammonia water, potassium carbonate and others that show alkalinity or weak alkalinity when dissolved in water are chemically alkaline fertilizers; urea, potassium sulfate, calcium nitrate and others that are neutral or nearly neutral when dissolved in water are chemically neutral fertilizers.
Physiological acidity-alkalinity refers to the acidity or alkalinity shown by the soil after the fertilizer is applied to the soil and absorbed by crops. On this basis, fertilizers can be divided into physiologically acidic fertilizers, alkaline fertilizers, and neutral fertilizers. Ammonium sulfate is a commonly used nitrogen fertilizer. After application, it generates ammonium ions and sulfate ions in the soil. Although both ions can be absorbed by plants, the amount of ammonium ions absorbed by plants is far greater than that of sulfate, so most of the sulfate remains in the soil. While absorbing ammonium ions, plants release hydrogen ions, making the soil acidic, so it is called a physiologically acidic fertilizer. Sodium nitrate, calcium nitrate and others cause the soil to become alkaline after being absorbed by plants, so they are called physiologically alkaline fertilizers. After ammonium bicarbonate and urea are absorbed by plants, the soil appears neutral or nearly neutral, so they are called physiologically neutral fertilizers.
When purchasing and using chemical fertilizers, first understand the acidity and alkalinity of the fertilizer so as to apply it rationally and improve fertilizer efficiency. Soil pH can not only directly affect the dissolution and precipitation of nutrients in the soil, but also affect the activity of microorganisms, thereby indirectly affecting the availability of soil nutrients. In acidic soil, soluble phosphorus easily combines with iron and aluminum to form iron phosphate and aluminum phosphate, thereby reducing availability. Acidic soil is also often deficient in sulfur and molybdenum. Therefore, for acidic soil, alkaline or physiologically alkaline fertilizers should be selected, such as calcium nitrate, ammonia water, ammonium bicarbonate, calcium magnesium phosphate, etc. In this way, the soil will not continue to acidify, and the activity of nutrients such as sulfur and molybdenum can also be improved; otherwise, the effectiveness of phosphate fertilizer will be reduced, causing leaching loss of nutrients such as potassium, calcium, and magnesium. In alkaline soil, especially calcareous soil, soluble phosphorus easily combines with calcium to form sparingly soluble calcium phosphate salts, which reduces the effectiveness of phosphorus. The effectiveness of many trace elements such as boron, manganese, molybdenum, zinc, and iron will also be greatly reduced, leading to deficiencies of these nutrient elements, and crops will suffer various physiological diseases. Therefore, in calcareous or alkaline soil, acidic and physiologically acidic fertilizers such as superphosphate, ammonium sulfate, and ammonium chloride should preferably be applied to increase soil acidity, so that phosphorus is less likely to combine with calcium to form sparingly soluble calcium phosphate salts and reduce phosphorus effectiveness, and the effectiveness of boron, manganese, molybdenum, zinc, iron, and copper can also be improved. Conversely, if acidic fertilizers are applied to acidic soil for a long time, the soil will become acidified, compacted, and impoverished; while in calcareous or alkaline soil, excessive application of alkaline or physiologically alkaline fertilizers will cause secondary salinization of the soil, deterioration of structure, and degradation of fertility.