There are two main ways that fertilization can contaminate vegetables: First, through the direct use of harmful substances contained in fertilizers, such as heavy metals, pathogenic microorganisms, and poisonous gases, to contaminate vegetables or soil; and secondly, to infuse vegetables with large amounts of nitrogen fertilizers. Over-accumulation of nitrate. In order to reduce the pollution of vegetables caused by fertilization, the following points should be noted in fertilization:
Re-applying organic manure organic fertilizer will not lead to the accumulation of nitrate in vegetables, but also improve the quality of vegetables. The organic fertilizer is preferably applied after high-temperature stacking or biogas fermentation and decomposing, which can kill bacteria and eggs, reduce the amount of pesticides, and increase the yield and quality of vegetables. The use of biogas fertilizer to grow vegetables is the best pollution-free vegetables.
The use of nitrate nitrogen fertilizers and compound fertilizers containing nitrate nitrogen in the absence of or minimal application of nitrate fertilizers tends to accumulate nitrates in vegetables, so they should not be used on vegetables. The use of ammonium nitrogen fertilizers and ammonium ammonium fertilizers such as ammonium sulfate and carbonic acid can be used. Hydrogen ammonium, urea and so on.
Controlling the amount of nitrogen fertilizer The accumulation of nitrate in vegetables increased with the increase of nitrogen fertilizer application amount. The amount of nitrogen applied per acre should be controlled within 30 kilograms, of which 70% to 80% should be applied as a deep-rooted basal application, and 20% to 30% should be used as a deep application to seedlings.
Nitrogen fertilizer should be applied early as deep-rooted nitrogen fertilizer as base fertilizer or top-dressing fertilizer application, which is conducive to early growth of vegetables and will help reduce the accumulation of nitrate in soil and vegetables. Deep application of nitrogen fertilizer to the soil layer of 10-15 cm can reduce the loss of nitrogen and increase the nitrogen fertilizer utilization rate. In deep soils, soil air is in an off-gassing condition, and nitrification is slow, which can reduce the accumulation of nitrates in vegetables.
Due to the high fertility of fertilization due to the seasons and seasons, soils rich in organic matter, and vegetables tend to accumulate nitrates, the use of nitrogen fertilizers should be prohibited or less. In low-fertilizer vegetable fields, nitrate accumulated in vegetables is lighter, and nitrogen fertilizer and organic fertilizer can be applied to fertility. In general vegetable fields, such as adopting balanced fertilization for soil testing, it is not only beneficial to high quality and high yield, but also makes it difficult for vegetables to accumulate nitrate, and is also conducive to fertility. High temperatures in summer and autumn are not conducive to the accumulation of nitrates, and appropriate nitrogen fertilizers may be used. 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.
Because vegetables use different types of vegetables to absorb different levels of accumulated nitrates, cabbage and green leafy vegetables can easily accumulate nitrates, and nitrate-type fertilizers cannot be used. Solanum, fruit vegetables, and root vegetables accumulate nitrate. If it is less, it can be applied properly, but the application of nitrate nitrogen fertilizer should be stopped 15-30 days before harvesting.
Leafy vegetables should not be foliar spray nitrogen fertilizer nitrogen fertilizer for direct contact with the air, ammonium ions can easily become nitrate ions absorbed by the leaves, increased nitrate accumulation. Therefore, foliar spraying of nitrogen fertilizers should be forbidden in the production of non-polluted leafy vegetables. In particular, it is not possible to spray nitrogenous fertilizer on foliar one month before harvest.
It is easy to be polluted without watering the sewage to water the vegetables. Wastewater discharged from factories and mines contains more toxic substances such as chlorine, arsenic, tin and lead, and should not be used for watering vegetables. Urban sewage should be treated in a harmless manner. After killing germs and eggs, it is mixed with clear water.
Syndromes of deficiency of Qi and blood (shortness of breath, laziness, white face, light tongue, or even deficiency of fat, weak pulse, etc.) can be used with Codonopsis Pilosula combined with Atractylodes macrocephala, Poria cocos, licorice, angelica, Radix Angelicae sinensis, Radix Paeoniae alba, and Ligusticum chuanxiong (such as Bazhen Decoction), in order to achieve the effect of both qi and blood Moreover, the previous experience believes that tonifying Qi can promote blood, strengthening spleen can help blood, so in the treatment of blood deficiency syndrome, Codonopsis pilosula is often used to tonify Qi and spleen to help blood. According to recent experiments, this product can increase hemoglobin and erythrocyte through spleen stimulation. In recent years, it has been used to treat various anemia with Angelica sinensis, Paeonia lactiflora, raw land and cooked land.
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