Introduction To Foliar Fertilization

Foliar fertilizers are applied to plant leaves and absorbed for use, serving primarily to supplement essential nutrients. As a supplement to soil fertilization, foliar application offers rapid absorption, targeted action, and high utilization efficiency; while it provides nutrients directly to the plant, it cannot entirely replace root-zone fertilization.

Foliar application should adhere to the principles of timeliness, suitability, and cost-effectiveness: applying fertilizers during critical growth stages (such as for correcting nutrient deficiencies or preserving flowers and fruit), selecting the right product based on crop needs, and prioritizing economic returns.

Fertilizers used for foliar application include macronutrients (nitrogen, phosphorus, potassium), secondary nutrients (calcium, magnesium, sulfur), and micronutrients (iron, zinc, manganese, etc.). Selection requires attention to nutrient forms and compatibility; for instance, nitrogen sources should primarily be nitrate-based, while micronutrients are best applied in chelated forms to enhance availability and minimize antagonistic interactions. Iron, zinc, manganese, and copper should ideally be chelated so they can be applied alongside phosphorus without causing antagonistic effects. Calcium and magnesium should not be sprayed with phosphorus to avoid the formation of insoluble precipitates. It is best to apply as many required nutrient types as possible in a single spraying session to ensure comprehensive nutrition while saving labor.

Foliar spraying should be performed in the early morning, late afternoon, or on overcast days to prevent high-temperature leaf scorch; re-application is necessary if rain occurs shortly after spraying.

Foliar fertilizers can be mixed with pesticides to improve efficiency, though compatibility must be considered; small-scale tests should be conducted before initial mixed application. Nutrients-particularly potassium nitrate-can be sprayed alongside pesticides; mixing potassium nitrate with most pesticides can actually enhance their efficacy. However, when mixing products for the first time and lacking experience, you should first prepare the mixture in a small container according to the specified ratio and spray it on a few crop plants; large-scale application should only proceed if no phytotoxicity is observed after 1–2 days.