How long after spraying foliar fertilizer before it is safe from rain

It depends on the instructions for the foliar fertilizer. If there is no special note, then after it rains there is no need to re-spray. If the precautions state that re-spraying is required when rain occurs 4-6 hours after spraying, then you need to re-spray. Generally, it is only safe from rain 4-5 hours after application.

Precautions for spraying foliar fertilizer

1. Choose an appropriate spraying concentration. The concentration of the foliar fertilizer solution is directly related to the spraying effect. If the solution concentration is too high, it is easy to burn the crop leaves after spraying; if the solution concentration is too low, it not only increases the workload but also fails to meet the requirement of supplementing crop nutrition. Therefore, in application, the solution should be prepared according to the fertilizer, the crop, and local conditions to suit the symptoms.

2. Choose an appropriate spraying method. The solution should be prepared evenly, the spray droplets should be uniform and fine, and the number of sprays should depend on need.

3. Master the spraying period well. The period for foliar fertilization should be based on the demand for nutrient elements at different growth and development stages of various crops, and spraying should be carried out when the crop's demand for nutrient elements is greatest and most urgent, so as to achieve the best effect.

4. Choose an appropriate spraying time. The effect of foliar fertilization is directly related to temperature, humidity, wind, and so on. For foliar spraying, it is best to choose a windless cloudy day or a time before 9 a.m. when humidity is relatively high and evaporation is low. The most suitable time is after 4 p.m. If it rains 3-4 hours after spraying, then re-spraying is needed.

5. Choose appropriate spraying parts. Because the leaves and stems in the upper, middle, and lower parts of the plant differ in metabolic activity, their ability to absorb nutrients from the outside differs greatly, so appropriate spraying parts should be selected.

6. Add adjuvants. When spraying fertilizer liquid on the leaves, appropriately add adjuvants to improve the adhesion of the fertilizer liquid on the plant leaves and promote the absorption of the fertilizer.

7. Combine with soil fertilization. Because the roots have a larger and more complete absorption system than the leaves, for nutrient elements needed in large amounts such as nitrogen, phosphorus, and potassium, it is determined that more than 10 foliar applications are needed to reach the total amount of nutrients absorbed by the roots. Therefore, foliar fertilization cannot completely replace root fertilization of crops and must be combined with root fertilization.

8. Soaking and extraction. From the perspective of agricultural production costs, the use effect is more cost-effective than soil fertilization. Move the dried fermented material into a container and soak it with 5% brown sugar water to extract amino acid water. The soaking ratio is 1 kg of soybean powder plus 5 kg of 5% brown sugar water. The soaking time is 5-15 days. After soaking is complete (no odor, the liquid is dark brown), the amino acid water should be extracted in time with a vacuum pump, packaged well, and stored in a cool place.