Three Major Misconceptions About Foliar Fertilizer Application
(1) Thinking that anything that "dissolves" can be sprayed—Wrong!
When applying foliar fertilizers to crops and vegetables, some farmers like to mix several types together, believing that a wider variety yields better results. Many also assume that any fertilizer can be used as a foliar spray as long as it dissolves in water; however, this is not the case.
For instance, highly volatile fertilizers like aqueous ammonia or ammonium bicarbonate should not be used as foliar sprays. If applied in high temperatures, they can damage crops by scorching the leaves.
Furthermore, many micronutrient fertilizers cannot be mixed with pesticides, and acidic fertilizers should not be mixed with alkaline ones. Mixing fertilizers with other fertilizers or pesticides requires a targeted approach to achieve "multiple effects from a single application"; otherwise, the results may be counterproductive.
(2) Thinking that higher concentration is better—Wrong!
Some farmers believe that a higher concentration of foliar fertilizer solution is always better, but this is incorrect. For example, the concentration of high-nitrogen water-soluble fertilizers and potassium dihydrogen phosphate should generally be kept below 1%. For many secondary and micronutrient fertilizers—such as sugar-alcohol calcium, sugar-alcohol calcium-boron, sugar-alcohol zinc, chelated iron, and chelated copper—the concentration should be kept below 0.2%.
Excessive concentration not only fails to provide the intended benefits but can actually cause leaf dehydration and wilting, leading to "fertilizer burn"—a condition similar to pesticide or chemical toxicity. The ideal application involves spraying until the solution coats both the upper and lower leaf surfaces and just begins to drip. Excessive solution leads to higher costs and fertilizer waste.
(3) Thinking it can be applied at any time—Wrong!
Some farmers fail to identify the critical stages for foliar application, preventing them from achieving the desired results. Some believe foliar fertilizer can be applied at any stage of plant growth and development, but this is also incorrect.
Foliar fertilizer is best applied during key transitional growth stages. Applications should be spaced at least 20 days apart, with a general recommendation of 2 to 3 applications per crop season. The optimal timing for foliar fertilization varies depending on the plant species and the type of fertilizer used. For cereal crops such as rice, corn, and wheat, it is best to apply fertilizer during the booting, flowering, and grain-filling stages.
For legume crops—such as soybeans, peanuts, broad beans, and kidney beans—fertilizer application is most effective during the flowering and pod-setting stages. Cotton should be fertilized during the flowering and boll- formation stage. Molybdenum fertilizers are best applied before flowering, whereas boron and zinc fertilizers yield the best results when applied at the onset of flowering.
Regarding the time of day, application should take place on calm, overcast days or on sunny mornings after the dew has evaporated; spraying in the early morning or evening is most effective, while periods of intense midday heat and sunlight should be avoided.
When applying foliar fertilizers to crops and vegetables, some farmers like to mix several types together, believing that a wider variety yields better results. Many also assume that any fertilizer can be used as a foliar spray as long as it dissolves in water; however, this is not the case.
For instance, highly volatile fertilizers like aqueous ammonia or ammonium bicarbonate should not be used as foliar sprays. If applied in high temperatures, they can damage crops by scorching the leaves.
Furthermore, many micronutrient fertilizers cannot be mixed with pesticides, and acidic fertilizers should not be mixed with alkaline ones. Mixing fertilizers with other fertilizers or pesticides requires a targeted approach to achieve "multiple effects from a single application"; otherwise, the results may be counterproductive.
(2) Thinking that higher concentration is better—Wrong!
Some farmers believe that a higher concentration of foliar fertilizer solution is always better, but this is incorrect. For example, the concentration of high-nitrogen water-soluble fertilizers and potassium dihydrogen phosphate should generally be kept below 1%. For many secondary and micronutrient fertilizers—such as sugar-alcohol calcium, sugar-alcohol calcium-boron, sugar-alcohol zinc, chelated iron, and chelated copper—the concentration should be kept below 0.2%.
Excessive concentration not only fails to provide the intended benefits but can actually cause leaf dehydration and wilting, leading to "fertilizer burn"—a condition similar to pesticide or chemical toxicity. The ideal application involves spraying until the solution coats both the upper and lower leaf surfaces and just begins to drip. Excessive solution leads to higher costs and fertilizer waste.
(3) Thinking it can be applied at any time—Wrong!
Some farmers fail to identify the critical stages for foliar application, preventing them from achieving the desired results. Some believe foliar fertilizer can be applied at any stage of plant growth and development, but this is also incorrect.
Foliar fertilizer is best applied during key transitional growth stages. Applications should be spaced at least 20 days apart, with a general recommendation of 2 to 3 applications per crop season. The optimal timing for foliar fertilization varies depending on the plant species and the type of fertilizer used. For cereal crops such as rice, corn, and wheat, it is best to apply fertilizer during the booting, flowering, and grain-filling stages.
For legume crops—such as soybeans, peanuts, broad beans, and kidney beans—fertilizer application is most effective during the flowering and pod-setting stages. Cotton should be fertilized during the flowering and boll- formation stage. Molybdenum fertilizers are best applied before flowering, whereas boron and zinc fertilizers yield the best results when applied at the onset of flowering.
Regarding the time of day, application should take place on calm, overcast days or on sunny mornings after the dew has evaporated; spraying in the early morning or evening is most effective, while periods of intense midday heat and sunlight should be avoided.
