Chemical fertilizers and pesticides are indispensable means of production for modern agriculture. In order to improve the yield and quality, the number and types of chemical fertilizers applied by farmers are increasing day by day, among which foliar spraying fertilizer has become a technical measure often adopted by farmers, especially fruit farmers and vegetable farmers, due to its small amount of fertilizer and quick effect; On the other hand, farmers should also spray pesticides regularly to control diseases and pests. Many people try to mix medicine and fertilizer and spray them together with the purpose of saving labor and improving work efficiency. For example, the "one spray and three prevention" technology widely promoted in the northern wheat ear stage is to mix ketone (or diniconazole), piramifos (or acetamiprid) and potassium dihydrogen phosphate for a single spray. It can not only control wheat rust, powdery mildew and wheat aphid, but also reduce the damage of lodging and dry hot wind, achieving the good effect of saving labor, increasing production and income. The first reason why the "one spray and three prevention" technology is worthy of recognition and promotion is that the timing is appropriate. Because the spike stage of wheat is just the key period to control "two diseases and one insect" and to supplement the spike fertilizer and increase the 1000-grain weight, it needs to be mixed with medicine and fertilizer. In other periods, it may become a waste without targeted mixing. As far as the scientific use of pesticides is concerned, the preparation of liquid medicine with clear water can ensure the efficacy.

The key of mixed use is that chemical reactions between fungicides and pesticides, and between drugs and fertilizers cannot occur, which does not affect the physical properties of drugs and fertilizers, such as solubility, suspension, emulsification, etc., nor affect their respective efficacy. Of course, if there is no chemical reaction, it will not increase the toxicity of drugs to humans, animals and plants and the decomposition of drugs and fertilizers. From the point of view of maintaining efficacy, we already know that some pesticides cannot be mixed with basic pesticides (sulfur mixture, Bordeaux liquid), such as fipronil, chlorfenuron, acetamiprid, tin and other insecticides and fungicides such as mancozeb, aluminum triethylphosphate, oxazolin, metalaxyl, ketone, diniconazole, isocarburide, chrysromycin, polyantimycin, and nanningmycin. It is reasoned that they cannot be mixed with basic or weakly basic fertilizers such as ammonium carbonate, plant ash, calcium magnesium phosphate, diammonium phosphate, borax and ammonium molybdate.

Some plant growth regulators, such as gibberellin, chlormequat and ethephon, cannot be mixed with alkaline pesticides or fertilizers, otherwise they will decompose and fail. If herbicides are used for soil treatment, they are safe in most cases, especially when they are mixed with fine soil (or water) before use. However, if it is used for the treatment of stems and leaves, it should be very careful. When it is used alone, a slightly larger dose or uneven spraying may cause drug damage, so it should not be mixed with fertilizer generally. If mixed, the herbicide should also be prepared into the mother liquor first, and the fertilizer should also be dissolved with water before mixing with the mother liquor, and should be sprayed and prepared immediately.

Biological pesticides cannot be mixed with chemical fertilizers or fungicides, because chemical fertilizers and fungicides may kill beneficial microorganisms and reduce the control effect. In addition, we should also pay attention to the special provisions of some chemicals on mixed use, such as a bactericide called chlorobromoisocyanuric acid, which can cure fungal, bacterial and viral diseases simultaneously, and is a rare good medicine. However, there are also provisions on "not to be mixed with other pesticides", which is not to be mixed with chemical fertilizers.