Pay attention when irrigating and fertilizing farmland: these four types of fertilizer are not suitable for application with water
The application method of fertilizing with water is also called "fertilizing with irrigation water". It is generally a topdressing method that provides supplementary nutrients during the period of rapid crop growth. Since it is supplementary fertilization, it cannot replace main fertilization methods such as base fertilizer. However, because this method is both convenient and quick-acting, it is widely used on vegetable land and on irrigated land where cash crops and special edible crops are grown...
The application method of fertilizing with water is also called "fertilizing with irrigation water". It is generally a topdressing method that provides supplementary nutrients during the period of rapid crop growth. Since it is supplementary fertilization, it cannot replace main fertilization methods such as base fertilizer. However, because this method is both convenient and quick-acting, it is widely used on vegetable land and on irrigated land where cash crops and special edible crops are grown.
At present, fertilizing with irrigation water is mainly used for topdressing during the vigorous growing season of vegetable crops, and is widely used in greenhouse cultivation and open-field vegetables. Because fertilizing with irrigation water has a fast fertilizer effect, it usually shows results from 2-3 days to 3-5 days after application, reflected in obvious changes in leaf color and plant height, which fits the mentality of some growers who are eager for quick success. Therefore, fertilizing with irrigation water has been widely used for many years.
Considering the agricultural production goals of high yield, high quality and high efficiency of crops while also taking environmental protection into account, and the current situation of rural labor shortage, in order to give play to the strengths of "fertilizing with irrigation water" and avoid its shortcomings, the technical essentials of "fertilizing with irrigation water" are briefly described as follows:
1. Correctly choose the fertilizer type for fertilizing with irrigation water
Only water-soluble fertilizers can be applied with water. Among nitrogen fertilizers, urea, ammonia water, ammonium sulfate and ammonium nitrate are commonly used; among potassium fertilizers, potassium chloride and potassium sulfate are available, and potassium nitrate can also be used. But among phosphate fertilizers, even water-soluble monoammonium phosphate and diammonium phosphate should not be applied with water, because phosphate fertilizer has very poor mobility after dissolving and is easily fixed, and cannot infiltrate into the root layer with water. The best application method for phosphate fertilizer is only to bury it in the soil in layers, so as to improve its utilization rate.
2. Nutrient amount per single application of fertilizing with irrigation water
It must be kept minimal. In high-yield vegetable cultivation, the amount of pure nitrogen per application should be controlled at 2-3 kg/mu, especially nitrate nitrogen should be controlled at 2-3 kg/mu or less, and the amount of potassium fertilizer (potassium oxide) for a limited number of applications is generally 2-4 kg/mu; otherwise, the waste and loss of nutrients will be large. This not only reduces nitrogen fertilizer utilization rate, but may also cause pollution of water quality. Fertilizing with irrigation water during the whole growth period is generally suitable 2 times.
3. Timing of fertilizing with irrigation water
During the period of massive crop growth, for example, fruit vegetables are applied with irrigation water during the full fruit stage and after picking melons and fruits; another example is the hearting stage of Chinese cabbage. In autumn vegetable cultivation, it is suitable to choose when the temperature drops, soil mineralization decreases, and vegetable crops are in the period of massive growth.
4. Control of irrigation volume
Under border irrigation, avoid flooding irrigation; when using canal irrigation, the ditch depth and water volume should be appropriate to prevent nutrients dissolved in water from being lost with the water.
Many farmers like to use this topdressing method, and when used well it is effective. But if, in pursuit of superficial effects, costs are ignored, large amounts of nitrogen fertilizer are one-sidedly used, and fertilizing with irrigation water is abused, it will lead to excessive vegetative growth of vegetables, decreased quality, reduced fertilizer utilization rate, large nitrogen loss, and intensified salinization of soil properties.
Some people crush granular high-concentration compound fertilizer and apply it with irrigation water; some people use undecomposed, insoluble solid organic fertilizer or microbial preparations as fertilizer to apply with irrigation water. These are all inappropriate.
In short, in principle the following points should be mastered:
The method of fertilizing with irrigation water should be used at the right time and in the right amount, mainly for topdressing in intensive vegetable cultivation, mainly topdressing nitrogen and potassium.
Four types of fertilizer should not be applied with irrigation water: first, do not apply phosphate with irrigation water; second, do not apply granular compound fertilizer with irrigation water; third, do not apply solid organic fertilizer with irrigation water; fourth, do not apply microbial preparations or fertilizers with irrigation water.