The Risks of Overapplying DAP Fertilizer and Practical Solutions

Diammonium Phosphate (DAP) is widely valued in agriculture for its high phosphorus and nitrogen content, which effectively promotes root development and early crop growth. However, like any fertilizer, excessive application of DAP can lead to a series of adverse consequences, ranging from direct crop damage to long-term soil degradation and environmental pollution. Understanding these risks and mastering corresponding mitigation and prevention measures is essential for scientific fertilization and sustainable agricultural production. The most immediate and obvious harm of overapplying DAP is fertilizer burn, also known as salt stress, which severely impairs crop health. DAP contains high levels of soluble salts, and an excessive amount in the soil disrupts the osmotic balance around plant roots. This causes water to be drawn out of the root cells, resulting in dehydration of the root system—a condition known as osmotic stress. Damaged roots lose their ability to absorb water and nutrients, leading to a range of above-ground symptoms: leaves turn yellow or brown, especially at the tips and margins, and may curl, wilt, or appear scorched. In severe cases, crop growth is stunted, plants become weak and leggy, and roots may turn brown or black and become mushy, eventually leading to plant death. Overapplication of DAP also poses significant threats to soil health and seedling survival. DAP releases ammonia during decomposition, and excessive amounts can form toxic ammonia pockets in the soil, particularly in alkaline (high pH) soils. These ammonia pockets are highly harmful to seeds and young seedlings, often causing seed rot or seedling death, drastically reducing germination rates. Additionally, excess salts from DAP can accumulate on the soil surface, forming a visible white salt crust that further inhibits water infiltration and root respiration. High salt concentrations also kill beneficial soil microorganisms, which play a crucial role in nutrient cycling and soil structure improvement, disrupting the soil's ecological balance and reducing long-term soil fertility.

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