The principle of fertilizing the production of pollution-free vegetables can ensure that the contents of nitrates and other harmful substances that are highly carcinogenic in vegetables do not exceed the standards. 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 the application of compost, supplemented by top dressing. Try to limit the trials of chemical fertilizers. If it is really necessary to use chemical fertilizers, there should be limited and selective application. When applying chemical fertilizers, you must master the principle of prohibiting the use of nitrate fertilizers; the amount should be controlled at 25 kg per mu; chemical fertilizers must be combined with organic fertilizers. With the application, the organic nitrogen ratio is 2:1, and the last topdressing should be 30 days before harvesting. The following problems should be paid attention to in fertilization: Human fecal urine and toilet fertilizer should be thoroughly fermented and decomposed, and after flushing, water should be poured and flushed. Fertilizers should be applied deeply and early, and physical application can reduce nitrogen volatilization, extend fertilizer supply time, and increase nitrogen utilization rate. Early application will help the plant grow faster and longer, prolong the effect of fertilizer and reduce the accumulation of nitrate. Half of the ammonium nitrogen is applied to the soil below 6 cm, and urea is applied to the soil below 10 cm. Should apply biological nitrogen fertilizer, increase phosphorus, potassium fertilizer. The application of biological nitrogen fertilizer can effectively solve the problem of limited use of chemical fertilizers. Phosphorus and potassium fertilizers have a significant effect on increasing the stress resistance of vegetables. Uses flexible fertilization according to the type of rubbing and cultivation conditions. Different types of vegetables, there is a great difference in the degree of nitrate accumulation, leaf vegetables are generally higher than fruit vegetables. The nitrate content of the same vegetable under different climatic conditions also differs. Generally, under high temperature and strong light, nitrate accumulation is less, whereas, under low temperature and weak light, nitrate is accumulated in large quantities. During the fertilization process, the types of vegetables, cultivation seasons, and climatic conditions should be taken into consideration. A reasonable amount of chemical fertilizer should be used to ensure that the nitrate content is within the regulated range of nuisance-free vegetables. China Agricultural Network Editor