Technical measures to reduce nitrate accumulation in vegetables
2018-08-06 22:01:20
With the continuous improvement of people's living standards and the awareness of health care, consumers are paying more and more attention to the quality of vegetables. Modern medicine has proven that nitrate is reduced to nitrite in the human body. If it accumulates too much, it can cause methemoglobinemia, and it can also react with amines in the human body to form a strong carcinogen and induce cancer in the digestive system. Vegetables are crops that are easily enriched in nitrates, and 81.2% of the nitrates ingested by the human body are derived from vegetables. Therefore, nitrate content is one of the important indicators for evaluating the quality of vegetables. There are many factors affecting the accumulation of nitrate in vegetables, which are related to the variety of vegetables, related to water, temperature and light. They are also related to nitrogen application rate, nitrogen fertilizer type and nitrogen application method, but fertilization is one of the most important factors.
To reduce the nitrate content of vegetables, first, we must carry out reasonable fertilization, control the type and quantity of fertilization, and master the fertilization methods. The second is to adjust the environmental conditions such as water, temperature, light, etc., so as to control the absorption rate of the root system of the plant, reduce the absorption, and accelerate the metabolism of nitrate in the plant.
First, rational fertilization
1. Choose the right nitrogen fertilizer variety. The nitrate nitrogen absorbed by the vegetable plants from the soil is reduced to ammonia and participates in the synthesis of amino acids to form proteins. If the nitrate nitrogen is too late to convert, it will cause the accumulation of nitrate. It can be seen that the nitrate nitrogen fertilizer has a great influence on the vegetable content. Ammonium nitrogen fertilizer can also be converted to nitrate nitrogen by nitrification in dryland soil with good aeration and other suitable conditions. In addition, the improper use of urea and organic matter is also likely to cause the accumulation of nitrate. Different types and forms of nitrogen fertilizer have great influence on the nitrate content of vegetables (ammonium nitrate > urea > ammonium bicarbonate > ammonium sulfate > ammonium chloride). Generally, when applying nitrogen fertilizer, it should be applied with urea, ammonium chloride or ammonium nitrate (ammonium nitrate) ammonium nitrogen fertilizer (ammonium chloride) (a ratio of about 3:7), which can reduce the nitrate concentration. To make the vegetables grow well, the nitrate fertilizer should be applied as little as possible.
2. Properly control the amount of nitrogen fertilizer. The application rate of nitrogen fertilizer was significantly correlated with nitrate accumulation in vegetables. To this end, to ensure the quality of vegetables, it is necessary to properly control the amount of nitrogen fertilizer applied to the vegetable fields. In the soil, organic fertilizer, humic acid fertilizer, microbial fertilizer should be applied, and nitrogen fertilizer should be applied less. Reasonable organic and inorganic ratios can promote a balanced supply of nutrients, improve the nutrient environment of vegetables, and reduce nitrate accumulation. For example, the nitrate content of edible parts such as cabbage and spinach after application of organic fertilizer is reduced from 1000 mg/kg to about 600 mg/kg of single fertilizer. However, the organic fertilizer should be applied after high temperature stacking and decomposing to kill the bacteria and eggs. The ability of different types of vegetables to absorb and accumulate nitrate is also different, generally leafy vegetables> melons> cane fruits.
3. Nitrogen fertilizer should be used together with phosphorus and potassium. Phosphorus and potassium can promote the synthesis of proteins and important nitrogen-containing compounds and reduce the accumulation of nitrate. When phosphorus is sufficient, it can promote the reduction and assimilation of nitrate, and also enhance the absorption of nitrate by vegetables. Potassium is beneficial to the reduction and utilization of nitrate nitrogen, which can minimize the nitrate content in vegetables. Therefore, the balanced application of nitrogen, phosphorus and potassium has an important role in controlling the nitrate content of vegetables. The appropriate ratio of the three elements of NPK can not only increase the yield of vegetables, but also minimize the nitrate content in vegetables.
4. Strictly master the application method of nitrogen fertilizer. Nitrogen fertilizer should be applied deep and early. Deep application can reduce nitrogen volatilization, prolong fertilizer supply time and increase nitrogen fertilizer utilization rate. Early application is beneficial to the early growth of vegetable plants, prolonging fertilizer efficiency and reducing nitrate accumulation. It should also be applied flexibly according to vegetable types, cultivation conditions and climatic conditions.
The nitrate content of nuisance-free vegetables is constantly changing. According to research, with the time of nitrogen fertilizer topdressing, the nitrate content in vegetables has gradually decreased. For vegetables, the time for topdressing should be arranged 30 days before harvesting. The principle of topdressing is "a small number of times".
5. Add nitrogen fertilizer synergist. Nitrogen fertilizer can inhibit the activity of nitrifying bacteria in soil, slow down the reaction rate of ammonium nitrogen in soil to nitrate nitrogen, and reduce the accumulation of nitrate in vegetables. Commonly used: the amount of nitrogen pyridinium (CP) and dicyandiamide (DCD) generally accounts for 0.5-3% of pure nitrogen in nitrogen fertilizer.
Second, reasonable adjustment of water, temperature and light conditions. The same vegetable has different nitrate content under different environmental conditions. Generally, nitrate accumulation is low in soil with sufficient water content and high temperature and strong light. Conversely, in the case of low soil water content and low temperature and low light, nitrate is accumulated in large amounts. The use of reasonable irrigation, reasonable close planting, intercropping and other measures can improve the growth environment of vegetables and reduce their nitrate content. For greenhouses, greenhouses and other facilities, effective measures such as auxiliary light source or timely update of the shed film can be adopted.
To reduce the nitrate content of vegetables, first, we must carry out reasonable fertilization, control the type and quantity of fertilization, and master the fertilization methods. The second is to adjust the environmental conditions such as water, temperature, light, etc., so as to control the absorption rate of the root system of the plant, reduce the absorption, and accelerate the metabolism of nitrate in the plant.
First, rational fertilization
1. Choose the right nitrogen fertilizer variety. The nitrate nitrogen absorbed by the vegetable plants from the soil is reduced to ammonia and participates in the synthesis of amino acids to form proteins. If the nitrate nitrogen is too late to convert, it will cause the accumulation of nitrate. It can be seen that the nitrate nitrogen fertilizer has a great influence on the vegetable content. Ammonium nitrogen fertilizer can also be converted to nitrate nitrogen by nitrification in dryland soil with good aeration and other suitable conditions. In addition, the improper use of urea and organic matter is also likely to cause the accumulation of nitrate. Different types and forms of nitrogen fertilizer have great influence on the nitrate content of vegetables (ammonium nitrate > urea > ammonium bicarbonate > ammonium sulfate > ammonium chloride). Generally, when applying nitrogen fertilizer, it should be applied with urea, ammonium chloride or ammonium nitrate (ammonium nitrate) ammonium nitrogen fertilizer (ammonium chloride) (a ratio of about 3:7), which can reduce the nitrate concentration. To make the vegetables grow well, the nitrate fertilizer should be applied as little as possible.
2. Properly control the amount of nitrogen fertilizer. The application rate of nitrogen fertilizer was significantly correlated with nitrate accumulation in vegetables. To this end, to ensure the quality of vegetables, it is necessary to properly control the amount of nitrogen fertilizer applied to the vegetable fields. In the soil, organic fertilizer, humic acid fertilizer, microbial fertilizer should be applied, and nitrogen fertilizer should be applied less. Reasonable organic and inorganic ratios can promote a balanced supply of nutrients, improve the nutrient environment of vegetables, and reduce nitrate accumulation. For example, the nitrate content of edible parts such as cabbage and spinach after application of organic fertilizer is reduced from 1000 mg/kg to about 600 mg/kg of single fertilizer. However, the organic fertilizer should be applied after high temperature stacking and decomposing to kill the bacteria and eggs. The ability of different types of vegetables to absorb and accumulate nitrate is also different, generally leafy vegetables> melons> cane fruits.
3. Nitrogen fertilizer should be used together with phosphorus and potassium. Phosphorus and potassium can promote the synthesis of proteins and important nitrogen-containing compounds and reduce the accumulation of nitrate. When phosphorus is sufficient, it can promote the reduction and assimilation of nitrate, and also enhance the absorption of nitrate by vegetables. Potassium is beneficial to the reduction and utilization of nitrate nitrogen, which can minimize the nitrate content in vegetables. Therefore, the balanced application of nitrogen, phosphorus and potassium has an important role in controlling the nitrate content of vegetables. The appropriate ratio of the three elements of NPK can not only increase the yield of vegetables, but also minimize the nitrate content in vegetables.
4. Strictly master the application method of nitrogen fertilizer. Nitrogen fertilizer should be applied deep and early. Deep application can reduce nitrogen volatilization, prolong fertilizer supply time and increase nitrogen fertilizer utilization rate. Early application is beneficial to the early growth of vegetable plants, prolonging fertilizer efficiency and reducing nitrate accumulation. It should also be applied flexibly according to vegetable types, cultivation conditions and climatic conditions.
The nitrate content of nuisance-free vegetables is constantly changing. According to research, with the time of nitrogen fertilizer topdressing, the nitrate content in vegetables has gradually decreased. For vegetables, the time for topdressing should be arranged 30 days before harvesting. The principle of topdressing is "a small number of times".
5. Add nitrogen fertilizer synergist. Nitrogen fertilizer can inhibit the activity of nitrifying bacteria in soil, slow down the reaction rate of ammonium nitrogen in soil to nitrate nitrogen, and reduce the accumulation of nitrate in vegetables. Commonly used: the amount of nitrogen pyridinium (CP) and dicyandiamide (DCD) generally accounts for 0.5-3% of pure nitrogen in nitrogen fertilizer.
Second, reasonable adjustment of water, temperature and light conditions. The same vegetable has different nitrate content under different environmental conditions. Generally, nitrate accumulation is low in soil with sufficient water content and high temperature and strong light. Conversely, in the case of low soil water content and low temperature and low light, nitrate is accumulated in large amounts. The use of reasonable irrigation, reasonable close planting, intercropping and other measures can improve the growth environment of vegetables and reduce their nitrate content. For greenhouses, greenhouses and other facilities, effective measures such as auxiliary light source or timely update of the shed film can be adopted.
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