Due to the large amount of fertilizer in greenhouses, the winter and spring seasons are tightly closed, and the temperature is low and the light is weak. The activity of nitrate reductase in vegetables is low, and nitrates are easily accumulated. How to reduce the accumulation of nitrate in vegetables by top-dressing is a problem that should be paid attention to when fertilizing vegetables without pollution.
First, the prohibition of the application of nitrate nitrogen fertilizer. Such as ammonium nitrate, ammonium sulfate, potassium phosphorus nitrate, phosphorus nitrate, potassium nitrate and compound fertilizer containing nitrate nitrogen. After application, it is easy to accumulate nitrate in vegetables and seriously endanger human health. In addition, it is not suitable to apply chlorinated fertilizers such as potassium chloride, ammonium chloride, etc., chloride ions can reduce the starch and sugar content of vegetables, so that the quality is deteriorating and the yield is reduced.
Second, control the amount of nitrogen fertilizer. Nitrogen fertilizer in vegetable fields should not be excessive. To make vegetables meet the national pollution-free standards, the nitrate content in vegetables must be reduced. According to the amount of fertilizer required for different vegetables, generally 10 to 12 kilograms of pure nitrogen per acre is appropriate. The nitrogen fertilizer should be applied deeply, and should be combined with the application of phosphorus and potassium fertilizers or application of ternary compound, and the soil should be timely covered before application. Days stop chasing.
Third, the application of ecological organic fertilizer. Eco-organic fertilizer produced by fermentation using livestock manure. The organic matter content of ecological organic fertilizer can reach 45%, and it can play a role in fixing nitrogen and potassium, phosphorus, and potassium in vegetables, and can also classify pesticides and chemical fertilizer residues. Create a good environment for the development of pollution-free vegetables.
Fourth, the implementation of formula fertilization. The maximum period of demand for nitrogen, phosphorus and potassium in greenhouse vegetables was: cucumbers ranged from 75 to 140 days after planting, tomatoes ranged from 30 to 52 days, and sweet peppers ranged from 30 to 60 days. The best fertilizer (nitrogen, phosphorus, potassium application ratio of cucumber 1:0.67:1.83, tomato 1:0.38:1.75, sweet pepper 1:0.38:1). Although micronutrients are rarely needed for vegetables, they are indispensable. For use of micro-fertilizer foliar sprays, good dosage standards should be used. Note that foliar vegetables should not be sprayed with foliar to avoid increasing the nitrate content and it is not appropriate to apply more diammonium phosphate.
Fifth, limit the use of hormones. Some vegetable farmers do not talk about the quality of vegetables. In order to pursue high yields, early-morning morning markets, the use of gibberellin, ethizol, paclobutrazol and other hormones to promote long, ripening, greatly reducing the quality of vegetables, people long-term consumption is extremely unfavorable to health.
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