What is water-flush fertilization, and how effective is it really?
What is water-flush fertilization? How effective is it? Please explain. "Water-flush fertilization," also called water-carried fertilizer, is a method of topdressing. It is widely used in applied horticulture, and the method is to dissolve solid quick-acting chemical fertilizer in water and apply the fertilizer with the water. Water-flush fertilization usually uses water-soluble chemical fertilizers, mainly nitrogen fertilizer and potassium...
What is water-flush fertilization? How effective is it? Please explain.
"Water-flush fertilization," also called water-carried fertilizer, is a method of topdressing. It is widely used in applied horticulture, and the method is to dissolve solid quick-acting chemical fertilizer in water and apply the fertilizer with the water. Water-flush fertilization usually uses water-soluble chemical fertilizers, mainly nitrogen fertilizer and potassium fertilizer; both are highly water-soluble, and by combining fertilizer with water, the soluble nitrogen and potassium nutrients seep into the soil and are then absorbed by the crop roots. Water-flush fertilization is fertigation, and the irrigation methods can be divided into well irrigation and border irrigation, also including drip irrigation and sprinkler irrigation. But in some places, rough management uses flood irrigation to flush chemical fertilizer. This flood-irrigation fertilization method highlights the word "flush," easily causing large losses of nitrogen and also causing the problem of low water use efficiency.
At present, water-flush fertilization is widely used on greenhouse plantings and open-field vegetables. Because the fertilizer effect of water-flush fertilization comes quickly, it fits the mentality of some growers who are eager for quick results; therefore, water-flush fertilization has developed very quickly in recent years, and besides vegetables there are also other cash crops. This has also stimulated the market launch of a large number of small-package water-soluble fertilizers such as "ammonium nitrate" and "potassium nitrate." These small-package fertilizers are all relatively expensive.
When evaluating the application prospects of water-flush fertilization, one must first understand the purpose of fertilization in modern agriculture. It is not only for high crop yields, but also, from the comprehensive benefits of economic returns and environmental ecology, water-flush fertilization should be applied appropriately. For this reason, one must grasp the technical essentials of "water-flush fertilization" and should pay attention to the following points:
First, correctly choose the type of fertilizer for water-flush fertilization. Only water-soluble fertilizers may be applied with water. Among nitrogen fertilizers, urea, ammonia water, ammonium sulfate and ammonium nitrate are commonly used; among potassium fertilizers, there are potassium chloride and potassium sulfate, and potassium nitrate can also be used. But among phosphorus fertilizers, even water-soluble monoammonium phosphate and diammonium phosphate should not be applied by flushing, because after dissolving, phosphorus fertilizer has very poor mobility and is easily fixed, and cannot seep into the root layer with water. For this reason, the best application method for phosphorus fertilizer is to bury it in the soil in layers, so as to improve its use efficiency.
The nutrient amount of a single water-flush fertilization must be standardized. In high-yield vegetable cultivation, the pure nitrogen amount per application should be controlled at 2-4 kg/mu, especially nitrate nitrogen should be controlled below 2-3 kg/mu, and the potassium fertilizer amount (potassium oxide) for a limited number of applications is generally 2-4 kg/mu; otherwise, the waste and loss of nutrients will be large, which not only reduces nitrogen fertilizer use efficiency but may also cause water pollution. For the whole growth period, water-flush fertilization is generally suitable 2 times.
The period for water-flush fertilization of crops is during the crop's period of vigorous growth. For example, fruit vegetables are flushed during the full fruiting period and after picking the melons and fruits; another example is the hearting period of Chinese cabbage. In autumn vegetable planting, it is suitable to choose a time when the temperature drops and soil mineralization decreases, while the vegetable crops are still in a period of vigorous growth.
Control of irrigation volume. Under border irrigation, prevent flood irrigation; under canal irrigation, the ditch depth and water volume should be appropriate, to prevent the fertilizer nutrients dissolved in the water from being lost with the water.
Although the fertilizer effect of water-flush fertilization comes quickly, if in pursuit of apparent results one ignores cost and one-sidedly uses large amounts of nitrogen fertilizer and abuses water-flush fertilization, it will lead to excessive vegetative growth of vegetables, reduced quality, lower fertilizer use efficiency, large nitrogen losses, and intensified salinization of soil properties. Some people flush with undecomposed, insoluble solid organic fertilizer or microbial preparations; these are all inappropriate.
In short, the method of water-flush fertilization should be used at the right time and in the right amount, mainly for topdressing in intensive vegetable cultivation, topdressing nitrogen and potassium. Several fertilizers should not be applied by flushing: first, do not flush phosphorus; second, do not flush granular compound fertilizer; third, do not flush solid organic fertilizer; fourth, do not flush microbial preparations.
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