When Is the Best Time to Spray Foliar Fertilizer? Types and Precautions

Foliar feeding is a supplement to the nutrients plants absorb, making up for the shortfall in nutrient uptake by the roots; foliar feeding cannot replace soil fertilization.So when is the best time to apply foliar fertilizer? What types are there? What are the precautions for spraying?

When is the best time to apply foliar fertilizer?

1. During each of the spring, summer and autumn flushes of tea plants, when the new shoots grow out to the stage of one bud and one initially unfurled leaf, choose a windless sunny morning, evening or an overcast day to spray, once a week for 2 to 3 consecutive sprays. Spray until the leaves drip.

2. Base it mainly on nitrogen, phosphorus and potassium, with trace elements as a supplement, in a ratio of 4:1:1; the trace elements are proportioned according to the principle of supplementing whatever the tea plants lack.

3. Fertilizer concentration. The fertilizer concentration is related to the fertilizer variety and weather conditions. According to tests, urea is 0.5%, superphosphate 1%, potassium sulfate 0.5%, zinc sulfate 50 to 100 ppm, and ammonium molybdate 20 to 50 ppm. If the concentration is too high it easily causes fertilizer burn; otherwise it has no effect.

4. Combine multiple operations. It can be combined with pest control, sprinkler irrigation and plant growth regulators, saving labor and making mechanized operation easier. Pay attention to the chemical properties of fertilizers and pesticides. Acidic fertilizers should be paired with acidic pesticides, and alkaline fertilizers with alkaline pesticides, so that no chemical reaction or precipitation occurs, preventing the fertilizer and pesticide effects from canceling each other out.

5. Use biological pesticides to control pests and diseases. Using biological pesticides to control tea plant pests and diseases is safe, reliable, pollution-free and hazard-free, and is the best choice with low cost and high control efficiency, such as Bt emulsion, Bacillus thuringiensis, Beauveria bassiana, agricultural antibiotics and plant antibiotics, etc.

What types of foliar fertilizer are there?

Foliar fertilizer is a type of fertilizer in which nutrient elements are applied to the leaf surface of crops and perform their basic function through absorption by the leaves. There are many kinds of foliar fertilizers; according to their action and function they can be summarized into four major categories: nutritional, regulatory, biological and compound. In production, you can choose and buy according to your needs.

1. Nutritional foliar fertilizer: this type of foliar fertilizer has relatively high contents of nutrients such as nitrogen, phosphorus, potassium and trace elements. Its main function is to provide crops with various nutrient elements and improve the nutritional status of the crops, and it is especially suitable for supplementing various nutrients in the later stages of crop growth.

2. Regulatory foliar fertilizer: this type of foliar fertilizer contains substances that regulate plant growth, such as auxins and hormones. Its main function is to regulate the growth and development of crops. It is suitable for use in the early and middle stages of plant growth.

3. Biological foliar fertilizer: this type of fertilizer contains microorganisms and their metabolites, such as amino acids, nucleotides and nucleic acid substances. Its main function is to stimulate crop growth, promote crop metabolism, and reduce and prevent the occurrence of pests and diseases.

4. Compound foliar fertilizer: this type of foliar fertilizer comes in many varieties and diverse composite and mixed forms. It has multiple functions; a single foliar fertilizer can both provide nutrition and stimulate growth and regulate development.

What are the usual precautions for spraying foliar fertilizer?

1. Note that the spray concentration must be appropriate. Since foliar fertilizer is sprayed directly on the upper surface of crops, you must master the spray concentration of the foliar fertilizer. Different foliar fertilizers have different use concentrations, different crop types have different spray concentrations, and the concentration sprayed also differs at different growth stages of the same crop. Therefore, when carrying out foliar spraying, grasp it flexibly according to the specific situation and prepare a suitable concentration; if the concentration is too low the effect is not great, and if the concentration is too high it will damage the stems and leaves.

2. Note that the spraying area must be comprehensive. Many farmers only spray the fertilizer solution on the front of the leaves while neglecting the back, so the results are less than ideal. This is because foliar fertilizer is mainly absorbed by the leaves through stomatal diffusion, and the distribution of stomata on the leaves is generally greater on the back than on the front. Here, when spraying foliar fertilizer, note that both the front and back of the leaves should be sprayed, to expand the absorption area; especially for dicotyledonous plants, more attention should be paid to spraying the back of the leaves.

3. Note that it must be reasonable. In mixed spraying, phosphorus and zinc have an “antagonistic effect”, so zinc fertilizer cannot be mixed with phosphorus fertilizer; mixing zinc fertilizer with phosphorus fertilizer easily forms zinc phosphate precipitate, thereby reducing the availability of zinc. Phosphorus and molybdenum promote each other in crops; for leguminous crops, mixed spraying can be used. Copper fertilizer cannot be mixed with potassium dihydrogen phosphate; zinc fertilizer and copper fertilizer cannot be mixed with superphosphate. Generally, various trace element fertilizers cannot be mixed with alkaline fertilizers. Note that alkaline and acidic fertilizers cannot be mixed; the solution is best prepared just before use and should not be stored for long. The number of foliar applications should be no fewer than 2 to 3 times, with an interval of at least one week or more, with a water volume of 50 to 60 kg/mu.

4. Note the spraying time. Great attention must be paid to the suitable spraying time, as this affects the spraying effect. The effect of foliar fertilizer spraying is affected by factors such as high temperature, light, intensity and rain; spraying should be chosen on a windless sunny day, carried out in the morning and evening, with evening being best. Dry, rainy, windy and hot weather is not suitable, and it should not be sprayed before rain, to prevent the fertilizer from being leached away by rainwater and reducing the fertilizer effect. After spraying, 3 to 4 days without rain, wind speed below 4 m/s, and temperature of 8°C to 25°C are required, with uniform spraying and good atomization. If it rains 3 hours after spraying, spray once more when the weather clears, but the concentration should be appropriately reduced. Note that spraying equipment should be cleaned frequently, to avoid pesticide residues affecting the fertilizer spraying effect.