With the rising standard of living, people's awareness of health and the environment has significantly increased. As a result, there is a growing demand for vegetables that are free from pollution. Non-polluted vegetables are those that meet national health and safety standards in terms of harmful substance residues. First, pesticide residues must not exceed the legal limits. These vegetables should not contain banned, highly toxic, or high-residue pesticides, and other pesticides must remain within the maximum allowable levels set by the state. Second, the levels of nitrates and nitrites must also be within acceptable limits. Third, the presence of "three wastes" (waste gas, waste water, and solid waste), heavy metals, and pathogenic microorganisms must not exceed safe thresholds. Among these, the content of heavy metals, nitrates, and nitrites is closely related to the proper use of fertilizers. There are many factors that affect the production of pollution-free vegetables, and selecting and applying fertilizers correctly is one of the most important measures in achieving this goal.
When it comes to choosing fertilizers, it is essential to select those that do not harm the environment or negatively impact the nutritional value and quality of the vegetables. The following types of fertilizers can be used in the production of pollution-free vegetables:
(1) Organic manure includes farmyard manure and commercial organic fertilizers. This category encompasses compost, slurry manure, cake manure, animal manure, biogas slurry, green manure, and crop straw. Compost should meet the requirements of NY/T 394-2000, the "High Temperature Composting Hygienic Standards." Commercial organic fertilizers must comply with the "Standards for Permissible Content of Contaminants in Organic Fertilizers" (NY/T 5018).
(b) Microbial fertilizers include humic acid-based, rhizobium, potassium bacteria, phosphate bacteria, and composite microbial fertilizers. The number of viable microorganisms must meet the requirements outlined in section 4.1 of the "Microbial Fertilizer" standard (NY227), and the hygiene indicators must conform to the "Integrated Product Harm Index" specified in the same standard.
(3) Inorganic mineral fertilizers include nitrogen, phosphorus, and potassium fertilizers. For nitrogen, it is recommended to use iron ammonium sulfate or urea. Phosphorus and potassium fertilizers should meet the health standards outlined in NY/T 394-2000. For phosphate fertilizer, calcined phosphate is encouraged, with impurity control limits such as 1% P₂O₅, As ≤ 0.004%, Cd ≤ 0.01%, Pb ≤ 0.002%. Potassium fertilizer should preferably be potassium sulfate, with impurity limits of 1% K₂O, As ≤ 0.004%, Cl ≤ 3%, and sulfuric acid ≤ 0.5%.
(d) Trace elements such as calcium, magnesium, copper, iron, boron, zinc, molybdenum, and manganese may also be included in fertilizers to support plant growth and enhance nutrient uptake. Using these fertilizers appropriately ensures both environmental protection and the production of high-quality, safe vegetables for consumers.
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