Pollution-free vegetables refer to vegetables whose harmful substances (such as pesticide residues, heavy metals, nitrites, etc.) are controlled within the allowable scope of the state and people do not cause harm to human health after eating.
However, vegetables are a kind of crop that is prone to enrichment and residual pollutants such as nitrates, heavy metals and pesticides. The blind and excessive use of chemical fertilizers, pesticides, and the presence of various pollution sources by vegetable farmers in pursuit of yield are the main causes of vegetable contamination. Therefore, in the vegetable production, reasonable fertilization should be done so that the content of harmful substances in vegetables can be controlled within the standards set by the state to achieve high yield, high quality, and no pollution.
First, the rational application of nitrogen fertilizer
1. Controlling the amount of nitrogenous fertilizer with a reasonable amount of nitrogen fertilizer can not only improve the yield of vegetables, but also improve the quality of vegetables. Therefore, reasonable application of nitrogen fertilizer is one of the main problems in the production of pollution-free vegetables. The application amount of nitrogen fertilizer should be properly controlled, and low nitrate nitrogen fertilizer ammonium sulfate should be used to reduce the nitrate content in vegetables. In the application of nitrogen fertilizer, the ratio of inorganic nitrogen to organic nitrogen is 1:1.
2. Nitrogen fertilizer technology with â€œsplit head and tail controlâ€ did not apply fast-acting nitrogen fertilizer at the later stage of growth; short-term vegetables used 70% of nitrogen fertilizer as basic fertilizer; long-term vegetables used 40% of the total amount of nitrogen fertilizer as basic fertilizer, and applied base fertilizer deep application and seed fertilizer application. , Dressing ditch or acupuncture methods.
Second, increase phosphorus and potassium fertilizer application of phosphate fertilizer, can provide phosphorus nutrients for vegetables, but also inhibit the activity of heavy metals cadmium, lead, zinc, arsenic, reduce toxicity, reduce hazards; increase potassium fertilizer can reduce the accumulation of nitrate in vegetables, Improve the quality of vegetables.
Potassium is also called â€œquality elementâ€. After potassium fertilizer is applied to vegetables, the content of vitamin C and sugar in fruits is obviously improved, and the durability of storage is also improved. research shows. The application of potash fertilizer on the basis of nitrogen fertilizer and phosphorus fertilizer can reduce the nitrate content of spinach, and the nitrate content of lettuce and celery also decreases with the increase of potassium application rate. The proportions of nitrogen, phosphorus and potassium are: 1:0.2:0.5 for short-term vegetables and 1:0.5:0.6 for long-term vegetables.
Third, increasing organic manure by increasing the maturity of the organic fertilizer can increase soil organic matter content, enhance soil adsorption capacity and complexing ability of pollutants, effectively curb the toxicity of cadmium, lead to vegetable crops; at the same time, the application of organic fertilizer ratio Fertilizer can reduce the nitrate content and reduce the nitrate content by about 45%. Experiments have shown that: the application of organic fertilizer celery, nitrate content of 744mg/kg, and chemical fertilizer, nitrate content as high as 1480mg/kg. Therefore, the organic fertilizer has little pollution to the soil environment in the vegetable field.
4. Interplanting green manures, such as manure and manure, is an effective way to maintain and increase soil fertility. Through nitrogen fixation of legume green manure, more abundant nitrogen resources can be obtained to increase soil organic matter content. At the same time, the granule structure of soil can be improved through microbial activity and decomposition.
5. To promote balanced fertilization According to the soil fertility and vegetable yield, as well as the characteristics of different fertilizers for different vegetables, apply chemical fertilizers scientifically and rationally, develop special fertilizers, and promote techniques for extra-root fertilizer application. For example, the application of molybdenum fertilizer can reduce the nitrate content in lettuce, Chinese cabbage and spinach.
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