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Experts: Crops mainly rely on roots to absorb the nutrients needed from the soil. At the same time, non-root organs such as stems, leaves and seed coats of crops can also absorb and utilize nutrients. However, foliar fertilization outside the roots is only an auxiliary method of crop fertilization and cannot replace root fertilization. Under normal circumstances, on the basis of soil fertilization, foliar fertilization helps crops to supplement some medium and micro nutrients or growth regulators, which is necessary to improve crop yield and improve quality, especially for fruit trees and Many cash crops. In some special cases, such as the reproductive growth stage in the late growth stage, the carbohydrates needed for development are used in a large number of fruits and Other parts, resulting in a decrease in the vitality of the root system and a decrease in nutrient absorption, which requires the application of leaf fertilization; When the topsoil is dry and there is no irrigation condition, the effective nutrient transport of the rhizosphere soil is not smooth; or the conditions of the flood water accumulation, the roots of the crops are hypoxia, and the nutrients cannot be absorbed normally, the role of foliar nutrition and fertilization should be exerted. . Therefore, crop leaf fertilization is often used to solve two problems: one is the nutrient supply of medium and trace elements, and the other is the supply of nutrients when the root system is temporarily unable to absorb.
Q: Why is foliar spray fertilizer the main method to correct trace element deficiency?
Experts: Plants require less trace elements. If the soil application method is mainly used, the application rate is small, the application is uneven, the application cost is high, and the soil is fixed, which cannot be effectively absorbed and utilized by plants. The nutritional characteristics of trace elements are different from those of a large number of elements. For example, the tree of fruit trees is tall, the transport of trace elements from the roots to the leaves is long, and the redistribution of the leaves into the leaves is difficult. Therefore, trace elements are only supplied from the roots. , can not meet the needs of plants. The application of trace elements on the surface of the fruit leaves is highly targeted and fast in supply, and can solve the problem of trace element deficiency directly, effectively and quickly.
Q: What are the characteristics of leaf nutrition? What are the advantages and disadvantages of foliar fertilization?
Expert: The main feature is that the leaf nutrients provide nutrients faster than the roots, but the application rate is limited and the effect is relatively short. The efficiency of leaf nutrition is related to leaf structure. The leaves have low permeability to mineral nutrients, especially those with thick horny leaves, such as olives, citrus and coffee. The fertilizer drops are not easy to infiltrate the leaves, and the liquid fertilizer drops from the leaves, causing loss. If it is raining soon after spraying, the rain will lose liquid fertilizer, and the windy days and high temperature days will cause the fertilizer to dry quickly on the leaves. These conditions may reduce the effect of foliar fertilization. In short, the advantages of foliar fertilization are: direct supply of nutrients, avoiding the fixation and degradation of nutrients in the soil, and the efficiency of nutrient use is higher than that of soil fertilization. However, the technique of spraying fertilizer is more complicated and must be strictly controlled.
Q: What technical tips should be mastered in foliar fertilization?
Expert: 1. First of all, we must choose the right fertilizer. Foliar fertilization is mainly for the supply of trace elements, but a large amount of combination with trace elements is beneficial to the absorption and utilization of nutrients. Specific determination of which fertilizer type depends on the demand of the crop, the soil's restricted nutrient types, etc., in order to improve the pertinence of foliar fertilization. Do not choose the kind of full-fledged rehydration, which is expensive and non-targeting, but it is not effective. For example, to solve the problem of chlorosis in new leaves of northern peanuts, it is necessary to spray iron; to solve the problem of increasing 1000-grain weight during the grain filling period of winter wheat, spray urea and potassium dihydrogen phosphate.
2. The concentration of leaf fertilizer should be well mastered. If the concentration is too high, it will damage the leaves, but it will reduce the fertilizer efficiency; if the concentration is too low, it will not work. Suitable concentrations vary by element and crop type.
3. The time and climatic conditions for spraying fertilizer should be selected. It is generally necessary to avoid noon, before 10 o'clock in the morning and after 4 o'clock in the evening. Also avoid the rain.
4. Pay attention to the spraying area. Leaves, stems, flowers, and fruits can be sprayed, but the concentration should not be too high when spraying flowers and buds; spray the leaves, spray both sides, and the number of vents on the back is more.
(The author is a senior consultant of Sinofert, Professor of China Agricultural University Cao Yiping) Source: Farmer Daily
How to use good foliar fertilizer for crops
Q: Generally, fertilizing crops is to apply fertilizer to the soil and absorb it by the roots of the crop. What is the use of foliar fertilizer for crops? What problem can I solve?
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