The fertilizer is applied properly, and the crops have fewer diseases and insect pests.

Research and practice have proved that the use of chemical fertilizer or organic fertilizer to control crop diseases and insect pests is not only economical, safe and effective, but also can save pesticides, but also has the characteristics of fertilization, no harm to natural enemies and no pollution to the environment. It is worth popularizing in production. Ammonium nitrogen fertilizers such as ① ammonium bicarbonate and ammonia have strong volatility and have certain stimulation, corrosion and fumigation to pests, especially for small and weak pests such as red spiders, aphids and thrips. Application method: spray evenly with 1% ammonium bicarbonate or 0.5% ammonia solution, once every 5-7 days, for 2-3 times. ② urea has the function of destroying insect chitin. The "urine washing mixture", which is mixed with urea, washing powder and water in the ratio of 4 to 1, 400, has a good control effect on aphids, cabbage insects, red spider beads and other pests that harm vegetables and flowers. ③ sprays 50% fresh urine or 3% ammonium sulfate aqueous solution when wheat rust occurs sporadically, and the effect is good. Phosphate fertilizer ① phosphate fertilizer has a seductive effect on cotton bollworm moth; during the occurrence period of cotton bollworm adults, 1%-2% superphosphate leaching solution as foliar spraying fertilizer can turn oxalic acid into calcium oxalate and lose its attraction to cotton bollworm. In this way, the number of eggs can be reduced by 33.3% to 73.4%, with an average of 55%. The duration of each phosphorus spray is generally 2-3 days. ② tomato navel rot is a physiological disease caused by calcium deficiency. From the early flowering stage of tomato, 1% superphosphate extract was sprayed every half month for 2 or 3 times, and the disease control effect was obvious. Potassium fertilizer can enhance the stress resistance of crops, and the application of potassium fertilizer can inhibit a variety of crop diseases and insect pests. It is reported that among 740 kinds of fungal diseases and 68 kinds of bacterial diseases, 71% and 75% of them are reduced by potassium respectively, and 59% of 230 kinds of pests (mites) have the effect of reducing damage. In production, the most potash fertilizer directly used to control crop diseases and insect pests is plant ash. Plant ash is a kind of high quality potash fertilizer, which also contains phosphorus, calcium, magnesium, sulfur, boron, manganese, copper, zinc, molybdenum and other nutrients. It can effectively kill aphids on crops with 10kg of plant ash, 50kg of water, filtration after soaking for 24 hours, and spraying of filtrate. In the seedling stage, 20 kg of plant ash per mu can be spread along the ridge, which can increase the soil temperature and reduce the occurrence of blight, anthracnose and red rot; before the planting of onion, garlic or leek, 20 kg of plant ash per mu is applied to the bottom of the ditch, or 15 kg of plant ash per mu is applied at the seedling stage of onion, garlic, leek and other vegetables, followed by hoeing, which can obviously reduce the harm of root maggots and increase the yield of vegetables by 15% and 20%. At the beginning of the occurrence of wheat sheath blight, 30 kg of plant ash per mu was scattered along the ridge on the base of wheat plants when the dew was not dry in the morning, which had a certain effect on controlling the spread of the disease; for fruit trees with root rot, first dig up the root soil, scrape off the diseased root skin, and hang it slightly, then each plant is buried in 2.5 kg of plant ash, and after about 1 or 2 months, the diseased tree can send out new roots. After the application of silicon-calcium fertilizer to silicon-calcium fertilizer crops, most of the silicon accumulates in the epidermal cells of the crops, forming a very hard epidermis, thus enhancing their ability to resist bacteria and pests. Some data show that the harm of corn borer and bean pod borer can be obviously reduced by applying 30,40kg silicon calcium fertilizer per mu in corn (2343 ~ 3.00 ~ 0.13%) and soybean (4548 ~ 40 kg silicon calcium fertilizer per mu). The application of silicon-calcium fertilizer to rice can increase the degree of silicification of epidermal cells, so the ability of resistance to diseases and insect pests is obviously enhanced, the grain weight is increased, the yield is increased by 10%-50%, the incidence of rice blast is reduced by 0.3%-19%, and the disease index is reduced by 0.5%-13.9%. In the rice area, the rice straw with high silicon content was returned to the field, the panicle neck blast was reduced by 2.63% and 7.23%, and the rice leaf roller was also significantly reduced. After planting slow seedling and fruiting period of sweet pepper, zinc fertilizer was sprayed with 0.05%-0.1% zinc sulfate solution once respectively, which could reduce the occurrence of virus disease, significantly increase the fruit setting rate and single fruit weight, and increase the yield by 15% and 37%. When manganese fertilizer is used to sow Chinese cabbage, mix seeds with trace element manganese, or spray 0.1%-0.2% manganese sulfate solution once at seedling stage, rosette stage and heart-wrapped stage of Chinese cabbage, which has a significant control effect on burning heart disease of Chinese cabbage. After prevention and control, the yield can be increased by 10% to 18%, and the quality has been improved.