Precautions for Using Chemical Fertilizers

First, avoid watering immediately after applying urea. Farmers know that urea must decompose into ammonium carbonate before crops can absorb and utilize it. However, ammonium carbonate is highly unstable and readily decomposes into ammonia gas, making it unsuitable for surface application. Before converting to ammonium carbonate, urea cannot adsorb to soil particles. If heavy rain or excessive watering occurs after application, it dissolves into water, either leaching 20 centimeters deep into the soil or being carried away by runoff, making it difficult for crop roots to absorb.

Secondly, ammonium carbonate should be avoided in greenhouses and plastic tunnels. While stable below 20°C, it decomposes into ammonia and carbon dioxide gases when temperatures exceed 20°C or moisture content surpasses certain thresholds, volatilizing into the air and reducing fertilizer efficiency. Ammonium nitrogen should not be mixed with alkaline fertilizers, as this accelerates its release and reduces utilization efficiency. Nitrate nitrogen should not be used in paddy fields, as it tends to settle below the root zone. Under irrigation or rainfall conditions, it is easily leached into deeper soil layers, reducing utilization and causing losses. Ammonium sulfate should not be applied long-term. As we know, ammonium sulfate is an acidic fertilizer. Prolonged use increases soil acidity, disrupting soil aggregate structure and causing soil compaction.

Additionally, phosphorus fertilizers should not be applied in scattered applications. As farmers know, phosphorus has low mobility and is easily absorbed and fixed by soil, reducing fertilizer efficiency and causing soil compaction with prolonged use. Potassium fertilizers should not be applied during the late crop stage. Due to the plant's characteristic of transporting nutrients from roots to stems and leaves before utilizing them in the tender upper parts, potassium deficiency in earlier stages may go undetected. Therefore, potassium should be applied in advance. Avoid prolonged use of chlorine-containing fertilizers, as chloride ions disrupt soil nutrient structure and cause acidification. Never apply chlorine-based fertilizers to chlorine-sensitive crops like vegetables, melons, fruits, or tobacco. Nitrogen fertilizers should not be applied in large quantities to leguminous crops. The rhizobia bacteria in legumes possess nitrogen-fixing capabilities. Excessive nitrogen fertilizer application wastes nutrients, inhibits rhizobia activity, and reduces the crop's natural nitrogen-fixing capacity.