The excessive use of chemical fertilizers in vegetable farming has numerous negative consequences that impact both the quality of vegetables and the health of the soil. As a result, it is essential to reduce the application of chemical fertilizers and combine them with organic alternatives to maintain sustainable agricultural practices.
One major issue is the contamination of vegetables by fertilizers. Prolonged use of chemical fertilizers, particularly those high in nitrogen, can lead to the accumulation of nitrates in the edible parts of plants such as stems and leaves. These nitrates can be converted into nitrites in the human body, which are toxic and can cause oxygen deprivation in cells. Long-term consumption of such vegetables may lead to developmental issues in children and increase the risk of cancer. In response, many developed countries have banned the sale of vegetables grown with excessive nitrogen fertilizer to protect public health.
Another concern is the reduced shelf life of vegetables produced using chemical fertilizers. Although these vegetables may appear fresh and tender, they often contain high levels of nitrates, making them more prone to spoilage during storage. Studies show that cabbages grown with nitrogen-based fertilizers tend to rot more quickly—over 20% more than those grown with manure—leading to increased levels of harmful substances.
Soil structure is also significantly affected by long-term use of chemical fertilizers. The repeated application of ammonium sulfate, potassium sulfate, and nitrogen-rich fertilizers can damage soil structure, leading to compaction, loss of elasticity, and reduced water infiltration. Over time, calcium ions on soil colloids are replaced, and leaching from rain or irrigation washes out essential nutrients, causing calcium deficiency in the topsoil. This weakens the soil structure, reduces fertility, and negatively affects vegetable growth and yield.
In addition, chemical fertilizers contribute to soil acidification. Fertilizers like ammonium sulfate, ammonium chloride, and superphosphate release acidic compounds that gradually lower the soil’s pH. This not only disrupts the balance of microorganisms in the soil but also hinders the growth of most vegetables. Continuous use of chemical fertilizers increases the concentration of harmful ions such as sulfates and chlorides, which can lead to secondary salinization, further damaging the soil and reducing its ability to support healthy plant growth.
Excessive chemical fertilizer use can also create nutrient imbalances in vegetables. For example, too much nitrogen can lead to calcium deficiency, while excess nitrate nitrogen may reduce molybdenum availability. High potassium levels can interfere with the uptake of calcium, magnesium, and boron, and excessive phosphorus can limit the absorption of calcium, zinc, and boron. These imbalances ultimately affect the nutritional quality of the vegetables.
To mitigate these problems, it is recommended to maximize the use of organic fertilizers such as compost, chicken manure, and various cake fertilizers like cottonseed meal, rapeseed meal, and bean cake. Biological bacterial fertilizers can also serve as effective alternatives to chemical nitrogen fertilizers. By reducing reliance on chemical inputs, farmers can help prevent vegetable contamination, minimize chemical residues, and protect the long-term health of the soil.
(Li Cuiying, Rural Office of Lujiang City, Hunan Province)
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