What do you need to pay attention to after topdressing crops?

What do you need to pay attention to after topdressing crops? Please give us a wide variety of fertilizers for topdressing crops outside the roots, but some are suitable for foliar spraying and some are not suitable for foliar spraying. Such as urea, potassium dihydrogen phosphate, borax, ammonium molybdate, zinc sulfate and so on can be foliar spraying. Some chloride ions, volatile and insoluble fertilizers can not be foliar sprayed, such as ammonium chloride, ammonium bicarbonate, calcium magnesium phosphorus and so on. Spraying concentration should be appropriate extra-root topdressing should be sprayed according to different fertilizers. Urea 1%-3%, potassium dihydrogen phosphate 0.3%-0.5%, borax 0.1%-0.2%, zinc sulfate 0.2%-0.4%, ammonium molybdate 0.03%-0.5%, calcium superphosphate leaching solution 2%-4%, ammonium sulfate 0.2%-0.3%. Should be targeted according to the lack of fertilizer in crops and soil, in line with the principle of what is missing to make up for what to spray. If the seedlings are thin and yellowing, it shows that nitrogen deficiency should be dominated by spraying nitrogen fertilizer; if the appearance of the seedlings is average, the mixture of nitrogen and phosphorus should be sprayed mainly; if the seedlings grow tender green, the mixture of phosphorus and potassium should be sprayed mainly. In order to spray different crops in the critical period of fertilizer demand, different crops have different fertilizer requirements, so it is necessary to master them flexibly. For example, rice and wheat should be sprayed after heading, soybean, peanut and rape should be sprayed at the beginning and full flowering stage, corn and sorghum should be sprayed at filling stage, and sweet potato and potato should be sprayed at fruit expansion stage. The absorptive capacity of the new leaf is stronger than that of the old leaf. For Monocotyledon crops such as rice and wheat, the stomata on the back of the leaves are almost the same, and the leaves are easy to attach fertilizer, so they should be mainly sprayed on the front of the leaves, while the stomata on the back of dicotyledons such as soybean and cotton are more than those on the leaf surface. and the sponge tissue on the back of the leaf has a strong ability to absorb fertilizer, and both sides of the leaves should be sprayed. To choose a good time to spray fertilizer outside the root topdressing in relatively humid weather is the best. Spray before 10:00 and after 4pm on sunny days and all day on cloudy days when there is no wind. Adding a small amount of surfactant (such as neutral soap and washing powder) to the fertilizer can reduce the surface tension of the fertilizer liquid, facilitate the spread and deepening of the fertilizer liquid, and improve the spraying effect. Click to get more compound fertilizer application techniques