Nitrate is the most easily overlooked vegetable pollutant, and it is also a type of pollution that growers and consumers are not well aware of.
Nitrate contamination of vegetables is mainly through the application of large amounts of chemical fertilizers. What harm does nitrate have for people? First, nitrates are easily reduced to nitrites. Nitrite enters the human body and can oxidize oxygen-carrying methemoglobin in cells to oxygen-poor ferritin and cause tissue hypoxia. Not only that, it is oxidized. High ferritin also reduces the ability of oxygenated oxyhemoglobin to release oxygen to body tissues, causing hypoxia and severe death. Even more frightening is the fact that nitrite and dimethylamine and trimethylamine act to generate nitrosamines. Nitrosamine is a compound with strong carcinogenicity. Among the 120 nitrosamines found, 75% Carcinogenicity has been confirmed, and nitrosamines also pose potential risks of genetic variation and freak. Once the substance enters the vegetables, the impact on people is very terrible. According to statistics, 80% of the human body's intake of nitrate comes from vegetables, so the nitrate pollution of vegetable products is quite serious and widespread.
The following methods can be used to prevent or reduce nitrate pollution:
Appropriate nitrate nitrogen fertilizer
Vegetables like nitrate-nitrogen. However, in order to produce high-quality pollution-free vegetables, and for the health of consumers, nitrate-nitrogen fertilizers such as calcium nitrate, ammonium nitrate, or potassium nitrate cannot be applied, and they all easily accumulate nitrates and nitrites in vegetables. Usually can use ammonium sulfate and urea instead, after all, organic fertilizer plus fertilizer is the most efficient way of fertilization, but pay attention to fertilizer must cover soil is not easy to salinize. Organic fertilizers do not have nitrate-nitrogen fertilizers, and they have a “vegetable†taste, good quality, and resistance to storage. This has become a must for the production of high-grade healthy vegetables. If you want to apply nitrogen fertilizer, you should pay attention to the following tips: The amount of nitrogen fertilizer is best applied according to the amount of available nitrogen in the vegetable field soil to prevent excessive application of nitrogen fertilizer, deeper application, shallow application of chemical fertilizers can easily contact with air, bacteria in the air Oxidation to nitrates under the effect of deep nitrogen fertilizer can not only reduce the loss of fertilizer volatilization, extend fertilizer supply time, but also reduce nitrate accumulation.
Seasonal fertilization
When the same variety of vegetables are cultivated in different seasonal climate conditions, the nitrate content in the products varies greatly. The contents of nitrate in summer and autumn vegetables growing in high temperature and multiple sunshine season were lower, and the nitrate content in winter and spring vegetables growing in low temperature and less sunshine season was higher. Although the use of plastic greenhouses and mulch film coverage in the low-temperature season is beneficial to ensure market supply, it also brings about the accumulation of soil salt and increases the risk of nitrate pollution. Therefore, in production, the intensity and time of light in the greenhouse should be increased. , The number and time of uncovering the shelter should be increased appropriately so as to achieve the purpose of reducing the nitrate content in vegetable products.
Fertilizer type
According to the research, nitrogen fertilizer has less effect on the nitrate accumulation of vegetable products during the early and mid-fertility of vegetable production. Applying nitrogen fertilizer during harvesting can cause a large accumulation of nitrate in vegetable products. Do not apply nitrogen fertilizer. In addition, the application of calcium-containing fertilizers such as quicklime and calcium nitrate in vegetable fields can also reduce the nitrate content in vegetable products.
Fertilization on the ground
The most scientific is the implementation of soil testing and fertilization, which is also a large work being done by the Ministry of Agriculture. It measures the nutrient content of cultivated soil throughout the country, and uses the measured results to guide the growers to formulate fertilization in order to achieve accurate fertilization. aims. After the determination of soil elements, high fertility, rich organic matter without fertilizer, low fertilizer (lighter nitrate accumulation) can be applied in an appropriate amount of fertilizer, but still dominated by organic fertilizer, but also fertility.
Vegetable washing
Vegetables purchased by consumers should be properly washed and salted or cooked. Wash the treated vegetables correctly, and the nitrate content can be reduced by 45% to 70%. In addition, because vitamins A, C can prevent nitrite from forming nitrosamines, eating more fresh fruits and vegetables containing these two types of vitamins is also an effective way to ensure good health. Also worth mentioning is that Sichuanese people love to eat pickles: research shows that pickles in the half month to a month, the content of nitrite is high, more than two weeks to one month, nitrous acid The salt content drastically decreased. Therefore, kimchi either eats “bath†kimchi or eats old kimchi for more than 1 month.
Chengdu Agricultural Quality Monitoring Center Agronomist Liu Jian
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