Foliar fertilizer spraying can not be "bathed" at will.

Foliar fertilizer spraying has many advantages such as low dosage, quick response, high fertilizer efficiency and good effect. It has been widely popularized and applied in recent years. However, some farmers mistakenly believe that foliar fertilizer is like supplementing nutrition for people,"beneficial and harmless, the more the better", so there are problems in actual application such as random selection of fertilizer types, random increase of fertilizer dosage, random determination of fertilizer spraying time, random increase of fertilizer spraying times, etc., which not only affect the effect of foliar fertilizer spraying, but sometimes even cause different degrees of damage to plants. A large number of surveys show that foliar fertilizer should be applied to plants, at least paying attention to the following points: Many farmers believe that no matter what fertilizer, as long as it is "opened", it can be sprayed as foliar fertilizer, but it is not. For example, some highly volatile fertilizers (such as ammonia and ammonium bicarbonate) cannot be used as foliar fertilizers because they will cause damage to crops at high temperatures after spraying. In addition, some crops (such as tea, tobacco, potato, citrus) are chlorine-free plants, potassium chloride, calcium chloride and other chlorine-containing fertilizers can not be sprayed on such crops. In addition, it is also necessary to see the seedling fertilizer: if the crop grows slowly, thin, short, yellow leaf color, belonging to nitrogen deficiency, foliar fertilizer should be nitrogen-based, with a small amount of phosphorus, potassium fertilizer; on the contrary, if the plant leaves are large, tender green, internode long, nitrogen nutrition is sufficient, foliar fertilizer should be changed to phosphorus, potassium-based, can not be unchanged. Fertilizer concentration Some farmers believe that the fertilizer concentration is a little higher, and the effect of spraying fertilizer is better. However, different crops have different tolerance to different fertilizers at different stages. High concentration of fertilizer solution often causes fertilizer damage and leaf burning. Especially when the temperature is higher, spray fertilizer on plant leaves. In the appropriate concentration range, in principle, we should grasp the principle of "low is not high". Different foliar fertilizers, spraying concentration is generally: urea 0.5%~2.0%, calcium superphosphate 1%~5%, potassium dihydrogen phosphate 0.2%~0.5%, boric acid 0.1%~0.5%, ammonium molybdate 0.02%~0.05%, zinc sulfate 0.05%~0.2%. Some farmers believe that foliar fertilizer can be applied at any time during plant growth and development, but it is not. From the fertilizer spraying period, generally should be in the plant growth and development, late leaf area is larger when spraying fertilizer, the best effect. Spraying fertilizer when the plant leaf area is small not only wastes more fertilizer, but also has less ideal effect. In addition, different plants, different fertilizer foliar fertilizer spraying appropriate period also has certain differences. Rice, wheat, corn and other cereal crops, should be in the booting, flowering, filling stage spray fertilizer. Soybean, peanut, broad bean, kidney bean and other bean crops, appropriate in flowering, pod stage spray fertilizer. Cotton should be sprayed with fertilizer at the flowering and boll stage. Molybdenum fertilizer should be sprayed before flowering. Boron and zinc fertilizers should be sprayed at the early flowering stage of plants. In terms of spraying time, it should be sprayed in the morning and evening after the dew dries in the windless cloudy day or sunny morning, avoiding the hot sun and high temperature period. If the fertilizer is sprayed at high temperature in the sun, the air humidity is small, not only the fertilizer is volatilized and wasted, but also the fertilizer is dried quickly after spraying, and the leaves are difficult to absorb, which will reduce the fertilizer utilization rate. Sometimes, the fertilizer water on the leaves evaporates too fast and the concentration increases rapidly, causing "burning leaves". Many farmers believe that the more times foliar fertilizer is sprayed, the better. In fact, plants with short growth periods can be sprayed 1 to 2 times. Plants with long growth periods can be sprayed 2 to 3 times. And each spraying time, generally should be more than 7~10 days apart. For trace element fertilizer, the spraying frequency should not be too much, and the concentration should not be too large, otherwise it will not only not increase the yield, but will cause plant trace element poisoning.