Urea is not a waste of topdressing
Determine the amount of topdressing according to soil fertility
Practice has proved that increasing the amount of fertilizer applied to the middle and low-yield fields can significantly increase the yield. For high-yield fields, maintain the level of general fertilization.
Topdressing in the season of crop nutrition
The key to improving the utilization rate of fertilizers is to grasp the critical period and maximum efficiency period of nutrient absorption of various crops, and try to topdress the crops during the nutrient period.
Doing deep application
Practice has proved that after applying urea to the surface of the ground for 4 to 5 days at normal temperature, most of the nitrogen will be ammonia volatilized, and its utilization rate is only about 30%, especially on the surface of calcareous and alkaline soils. The loss of volatilization is more serious. Therefore, when using urea to topdress the dry crops, it is best to apply the pits or trenches to a depth of 10 cm, so that the urea can be placed in the moist soil, which is beneficial to the conversion of urea, and is also beneficial to the ammonia fertilizer. Adsorption reduces the loss of volatilization.
Keep a certain distance from the crop
Urea has a high nitrogen content, a large nutrient concentration, and a large hygroscopicity. Therefore, in topdressing, it is necessary to prevent urea from being applied to the roots of the crops, and it is also impossible to drop urea into the heart leaves of the crops so as not to burn the seedlings and affect the growth, and it must be kept at a certain distance from the crops.
Early application
Urea is a low molecular organic compound that needs to undergo an ammoniation process after being applied to the soil and converted into a highly volatile ammonium carbonate before it can be absorbed by the crop roots. Therefore, the application of urea to the crop should be applied about 7 days earlier than other nitrogen fertilizers. Not mixed with alkaline fertilizer
Urea is a neutral fertilizer. When topdressing, it should not be mixed with alkaline fertilizer to prevent reducing fertilizer efficiency. If it is not mixed with alkaline fertilizer, the date of fertilization should be staggered, usually 3 to 5 days. However, when urea is mixed with fertilizers such as potassium chloride, phosphate rock and superphosphate, the yield increase effect is remarkable.
It is not advisable to fill the water immediately after the application
After urea is applied to the soil, it cannot be adsorbed by the soil before it is decomposed and transformed. If you fill the water immediately after chasing, it will cause a large loss of urea. Soil water shortage is serious, non-irrigation is not time, but also to do small water diligent irrigation, avoid flooding. When topdressing rice, the characteristics of urea with greater fluidity before conversion should be considered. After the application, it is not possible to immediately irrigate the water. Generally, it is better to pour a small water 3 to 5 days after the chasing.
Suitable for root dressing
Urea has less damage to crop leaves, is soluble in water, has strong diffusibility, and is easily absorbed by leaves. It is not easy to cause separation of the walls after entering the leaves, so it is very suitable for top dressing. However, high-quality urea with a biuret content of not more than 2% should be used to prevent damage to the leaves. The concentration of urea top dressing varies with crop types. The concentration of top dressing of gramineous crops is 1.5% to 2%; the concentration of top dressing for double-leaf crops is 1%, and the concentration of crops at flowering stage It should be smaller. Generally, the amount of top dressing per urea is 0.5 to 1.5 kg. The spraying time is preferably around 4 pm. At this time, the amount of transpiration is small, and the leaf pores are gradually opened. The diluted urea solution can be absorbed completely in one night, which greatly improves the utilization rate of urea.
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