Foliar fertilization, also known as top dressing, is a fertilization method in which the fertilizer is dissolved in water, and then the liquid fertilizer is sprayed on the crop leaves with a sprayer. After the general fertilization, the amount of the fertilizer attached to the leaf surface of the plant is 30% to 60% of the total amount of spraying, and the amount of the crop absorbed is 40% to 80% of the amount of the deposition. The following points should be noted when applying foliar fertilizers:
1. It is best to do it from 3pm to late afternoon (as the case may be). At this time, the temperature is low and the humidity is high, which is beneficial to the absorption of the leaves.
2, both sides of the blade should be sprayed on both sides, especially the leaves of more vegetable leaves, the back should be sprayed, because the back of the leaf than the front of the absorption rate is more than 1 times.
3. Adding urea when spraying trace elements can increase the absorption rate of crops and prevent the occurrence of temporary yellowing of crops.
4, can be sprayed with pesticides. This can not only prevent and treat diseases and insect pests, but also achieve the purpose of fertilization, but it should be noted that phosphorus-containing fertilizers generally cannot be mixed with lime-containing pesticides.
5, spray concentration should be appropriate. Poor concentration results in poor results and high yields of fertilizer. The quality of fertilizer applied is better. For example, when the biuret content in urea exceeds 2%, foliar spray fertilizer tends to produce poisoning.
6. The nitrogenous fertilizer demand of leafy vegetables in each growth stage is high, and the nitrogen fertilizer is the main fertilizer for foliar fertilizer; the nitrogen, phosphorus and potassium need to be balanced in fruit and vegetable, and the mixture of nitrogen, phosphorus and potassium should be used for foliar fertilizer; Vegetables and bulb vegetables have a good response to phosphorus and potassium fertilizers, and phosphorus and potassium are the main fertilizers for foliar application.
7. Fertilizer should be fully dissolved and mixed with water before spraying. For example, when superphosphate is used, calcium superphosphate should be soaked in hot water, and after 24 hours, the supernatant should be diluted to 3% and sprayed again.