After crop planting and planting, in order to meet the needs of its growth and development, it often needs more topdressing, and the amount of topdressing generally accounts for 1/3 or more of the total fertilization amount of the crop during the whole growth period . Several commonly used topdressing methods are introduced, and their advantages and disadvantages are listed for farmers' reference.
　　 1  Direct application
After the crops are watered or after the rain, the fields are suitable for squatting, and when they are able to go down, the fertilizer is directly applied to the crops. This method is simple compared, but some will evaporate fertilizer losses, especially highly volatile ammonium bicarbonate, can not be used; ammonium sulfate, potassium sulfate and urea Although applicator, but inconvenient to operate only in the field, crop Use when you need fertilizer and more urgent .
　　 2  Watering
When the crop is watered, the fertilizer is applied with water to the soil surrounding the roots of the crop. The disadvantage of this method is that it is wasteful and easy to lose, and it can not reach the deep layer of the crop roots; the advantage is that it is simple to use, saves labor and time, and has a small amount of labor. This method can be used when the fertilizer source is sufficient, the planting area is large, and the labor force is contradictory. When symptoms appear severe lack of fertilizer in a large area of crops, fertilizer can be used as the preferred method.
　　 3  Deep fertilization
Ditching and digging between crops and between rows, applying fertilizer and covering the soil. This approach to waste less fertilizer, the most economical, but a large amount of labor, and labor, and the operation is not easy. When applying, pay attention to the ditch and pit of the embedding should be more than 10cm from the base of the crop and the base of the stem . If it is too close to the root, it will easily damage the root system. Due to the concentration of fertilizer and the high concentration, the method is not suitable for use in summers where crops are vigorously growing and water is needed, and it cannot be used in the critical period of crop water demand. Generally, in the winter leisure season, when the labor force is sufficient, and the amount of crop growth is not large, this method can be adopted, so that the fertilizer buried in the soil is gradually decomposed and continuously supplied to the crop. However, in actual production, the peak of crop growth is often the peak of fertilizer demand. Therefore, the method of burying is often used at higher temperatures. In order to prevent it from having a negative effect, water must be watered after burying to reduce the concentration of the fertilizer applied.
　　 4  Facility chasing
In recent years, with the development of protected cultivation technology, with the support of drip irrigation technology is widely used, the method of fertilization took to the track automation. Specific Methods dressing drip irrigation facilities are: mounted fertilizer in water entering the drip directors parts, was dissolved in the fertilizer in the fertilizer, the fertilizer drip director's suction pipe inserted into the filter, with watering fertilizer can automatically enter the crop root In the surrounding soil. The advantage is that the film is covered, the fertilizer is almost non-volatile, no loss, the fertilizer is concentrated, but the concentration is small, so it is safe, labor-saving and labor-saving, and the effect is very good. This is a relatively scientific and highly promising method of topdressing, but it is difficult to promote and apply it in large-scale production because of too much investment.
　　 5  Top dressing
Top dressing is foliar spray. In cultivation, because of artificially created environment more conducive to meet the environmental requirements of crop conditions, crop exhibit fast growth, high yield, results and more features. In production, it is often combined with spraying to carry out foliar topdressing to supplement the shortage of crop nutrients. The method with less fertilizer fast, active ingredient and avoid soil fertilizer is fixed, it is a cost-effective fertilization methods. It can be used in the case of obvious lack of nutrients and root senescence in the late stage of crop growth. Foliar fertilizer, in addition to urea, potassium dihydrogen phosphate, potassium sulfate, potassium nitrate, and other common fertilizer macronutrient fertilizer, in recent years, many manufacturers have developed around suitable for a large number of crop spraying plus fertilizer containing trace elements or elements more amino acid composition, such as fertility hormone, Penshibao, phytoalexins, etc., all have a certain effect. But it must be noted that the basic nutrients required for the growth and development of crops, mainly from basal and top dressing fertilizer in other ways, as a foliar application only auxiliary measures.
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