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How to Reduce Fertilizer Pollution on Vegetables
There are two main ways that fertilization can cause pollution to vegetables. One is through the direct use of toxic and hazardous substances contained in fertilizers, such as heavy metals, pathogenic microorganisms, and poisonous gases, to directly contaminate vegetables or soil; the second is through the application of large amounts of nitrogen fertilizers. Causes excessive accumulation of nitrate in vegetables. Therefore, the principle of using fertilizer in the production of green vegetables is to return enough organic matter to the soil in order to maintain the increase of soil fertility and soil biological activity without adversely affecting the environment and crops (nutrition, taste and plant resistance). . For the two ways of fertilizing vegetables, the following points should be noted in the fertilization: (1) The green manure fertilizer should be used on manure fertilizers. Commercial fertilizers should firstly use commodity organic fertilizers, humic acid fertilizers, microbial fertilizers, and semi-organic fertilizers. Fertilizers and inorganic fertilizers containing phosphorus, potassium, calcium, and sulfur. (B) should pay attention to the following points in the fertilization 1. Re-applied organic fertilizer: Organic fertilizer will not cause nitrate pollution of vegetables, resistant to storage, good quality. However, organic fertilizers used in vegetables should be fully cooked. 2. Do not apply nitrate fertilizer: improper use of nitrogen fertilizer, it is easy to cause vegetables to accumulate nitrogen, the formation of nitrate. In particular, nitrates such as ammonium nitrate and potassium nitrate are more likely to accumulate nitrates. Nitrogen fertilizers such as ammonium bicarbonate, ammonium sulfate and urea should be used to control the amount, and deep application of soil can reduce the accumulation of nitrate in vegetables. Nitrate accumulation in vegetables increases with the amount of fertilizer applied. Therefore, the amount of nitrogen applied per 667m2 should be controlled within 15kg of pure nitrogen, 2/3 of basal fertilizer and 1/3 of deep application of seedling fertilizer. 3. Indigenous fertilization: nitrates with high fertility, rich in organic matter, and vegetables that are easy to accumulate should be banned from applying nitrogen fertilizers. In low-fertilizer vegetable fields, nitrate accumulated in vegetables is lighter, and nitrogen fertilizer and organic fertilizer can be applied to fertility. General vegetable plots, such as the use of soil testing and formula fertilization, are both beneficial to high yields and make it less prone to nitrate accumulation. It is also conducive to fertility. 4. Because of seedling fertilization: vegetable nitrogen fertilizer is better at seedling stage, is conducive to early-onset vegetables, fast and long, reducing nitrate content. 5. Because of seasonal fertilization: high temperatures in summer and autumn are not conducive to weaving with nitrates, and nitrogen may be applied in an appropriate amount. In winter and spring, the temperature is low, the light is weak, the activity of nitrate reductase is decreased, and nitrate is easy to accumulate. No nitrogen fertilizer should be applied or reduced. 6. Leaf vegetables do not use urea as foliar fertilizer, nitrogen fertilizer as leaf fertilizer directly in contact with air, ammonium ions can easily become nitrate ions absorbed by the leaves, and the accumulation of nitrate increases.