Pollution-free vegetables have principles of fertilization
Grasping the principles of fertilization for the production of pollution-free vegetables can ensure that the contents of nitrates and other harmful substances in vegetables that are highly carcinogenic are not excessive. The principle of fertilization for the production of pollution-free vegetables is: mainly organic fertilizer, supplemented by other fertilizers; mainly by multiple compound fertilizers, supplemented by single element fertilizers; mainly by base fertilizers, supplemented by top dressing. The following principles must be applied to the application of chemical fertilizers: The use of nitrate nitrogen fertilizers is prohibited. If application is required, the amount of fertilizer per acre should be controlled under 25 kg; the fertilizer must be applied in conjunction with organic fertilizer, and the ratio is 2:1. The last time fertilizer is applied The time should be 30 days before harvest. In the fertilization should pay attention to the following questions: Human fecal urine should be thoroughly fermented and decomposed, and after flushing, it should be poured with clean water. 2. Fertilizers should be deepened and applied early. Deep application can avoid the volatilization of fertilizers and increase the utilization rate of nitrogen. Early application will help the plants to grow quickly and prolong the efficiency of the fertilizer. When fertilizing, ammonium nitrogen is applied to soil below 6 cm, and urea should be applied to soil below 10 cm. 3. Should apply biological nitrogen fertilizer, increase phosphorus, potassium fertilizer. The application of biological nitrogen fertilizer can effectively solve the phenomenon of soil compaction caused by the use of chemical fertilizers; phosphorus and potassium fertilizers have a very significant effect on enhancing the stress resistance of vegetables. 4. According to the type of vegetables and cultivation conditions, flexible fertilization. Different types of vegetables, there is a great difference in the degree of nitrate accumulation, leaf vegetables are generally higher than fruit vegetables. Nitrate content of the same vegetable under different climatic conditions is also different. Generally, nitrate accumulation is less under high temperature and strong light, and nitrate is easy to accumulate under low temperature and low light. In the process of fertilization, the types of vegetables, cultivation season and climatic conditions should be taken into consideration. A reasonable amount of fertilizer should be mastered to ensure that the nitrate content is within the stipulated range of pollution-free vegetables.