What are the precautions for foliar feeding of crops?
What should be noted when doing foliar feeding of crops? Please give an introduction. There are many types of fertilizers used for foliar feeding of crops, but some are suitable for foliar spraying and some are not. For example, urea, potassium dihydrogen phosphate, borax, ammonium molybdate, zinc sulfate, etc. can all be sprayed on the leaves. Some fertilizers containing chloride ions, volatile fertilizers and poorly...
What should be noted when doing foliar feeding of crops? Please give an introduction.
There are many types of fertilizers used for foliar feeding of crops, but some are suitable for foliar spraying and some are not. For example, urea, potassium dihydrogen phosphate, borax, ammonium molybdate, zinc sulfate, etc. can all be sprayed on the leaves. Some fertilizers containing chloride ions, volatile fertilizers and poorly soluble fertilizers cannot be used for foliar spraying, such as ammonium chloride, ammonium bicarbonate, calcium magnesium phosphate, etc.
The spraying concentration must be appropriate. For foliar feeding, the corresponding concentration should be used for spraying according to the 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%-0.05%, superphosphate extract 2%-4%, ammonium sulfate 0.2%-0.3%.
It must be targeted. According to the fertilizer deficiency situation of the crop and soil, spraying should be carried out on the principle of supplementing whatever is lacking. If the seedlings are thin and yellow, it indicates nitrogen deficiency, so nitrogen fertilizer should mainly be sprayed; if the seedlings look average, a mixed solution of nitrogen and phosphorus should mainly be sprayed; if the seedlings look tender green, a mixed solution of phosphorus and potassium should mainly be sprayed.
Spraying should be done during the key fertilizer-demand period of the crop. Different crops have different fertilizer-demand periods for various fertilizers, so this must be handled flexibly. For example, rice and wheat should be sprayed after full heading; soybean, peanut and rapeseed should be sprayed at the initial flowering stage and full flowering stage respectively; corn and sorghum should be sprayed during the grain-filling stage; sweet potato and potato should be sprayed during the fruit enlargement stage.
The spraying site must be appropriate. The absorption capacity of leaves is stronger in new leaves than in old leaves. For monocot crops such as rice and wheat, the stomata on the leaf surface and leaf underside are about the same, and the leaf surface easily retains the fertilizer solution, so the front side of the leaf should mainly be sprayed. For dicot plants such as soybean and cotton, there are more stomata on the leaf underside than on the leaf surface, and the spongy tissue on the leaf underside has a stronger ability to absorb fertilizer, so both the front and back sides of the leaves should be sprayed.
The fertilizer spraying time should be chosen well. Foliar feeding is best done in relatively humid weather. On sunny days, spray before 10 a.m. and after 4 p.m.; on cloudy and windless days, spraying can be done all day.
An active agent should be added. Adding a small amount of active agent (such as neutral soap or washing powder) to the fertilizer can reduce the surface tension of the fertilizer solution, help the fertilizer solution spread and penetrate, and improve the spraying effect.
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