Several incorrect practices in applying chemical fertilizers

Thread Content

1. Application of urea and ammonium bicarbonate on the soil surface: Although urea has a high nitrogen content, it must be converted into ammonium nitrogen before it can be absorbed and utilized by crops. At the same time, urea exists in a molecular state during conversion, is not adsorbed by the soil, and can easily be lost through soil erosion, making it difficult for crops to utilize it. When using urea as a top dressing, it should be applied in trenches and covered with soil. When using it as a foliar fertilizer, it is important to control the application concentration properly. For wheat, rice, cotton, and corn, a concentration of 0.8%–1.0% is suitable, while for vegetables, 0.3%–0.5% is appropriate. When applied to the soil surface, ammonium bicarbonate tends to volatilize, and the ammonia gas released can burn the stems and leaves of crops, causing fertilizer damage. The correct method is to apply it at a depth of about 10 centimeters, covering it with soil immediately after application. 2. Topdressing with calcium-magnesium-phosphorus fertilizer: This type of fertilizer has a slow rate of release and a short period during which it is available for use. When applied as a topdressing, especially in the later stages of crop growth, its utilization efficiency is low and its effectiveness is poor. Therefore, calcium-magnesium-phosphorus fertilizer should be used as a base fertilizer and mixed with organic fertilizers, or applied as a seed fertilizer. In this way, nutrients are gradually released for use by crops, providing long-lasting fertility that supports steady growth and prevents premature aging of the plants. 3. Seed treatment with superphosphate: Superphosphate contains 3.5%–5.0% free acid, and using it for seed treatment reduces the seed germination rate and emergence rate. If superphosphate is used as top dressing, it should be applied deeply by digging furrows ； For seed fertilizer, it should be applied 8–10 cm below or beside the seeds, to ensure separation between the seeds and the fertilizer. 4. When potassium-containing fertilizers such as potassium sulfate and potassium chloride are applied alone, they exhibit a weakly acidic physiological property; once applied to the soil, the potassium ions are easily absorbed and fixed by the cations in the soil colloids, making it difficult for crops to utilize them. Therefore, potassium fertilizer should be applied in combination with nitrogen and phosphorus fertilizers; especially in areas lacking phosphorus such as mountainous regions, infertile lands, and newly reclaimed land, it is necessary to use it together with phosphorus fertilizer in order to fully utilize the effects of both potassium and phosphorus fertilizers.