Is there any way to improve the effect of urea topdressing?

Is there any way to improve the effect of urea topdressing? Please introduce the use of urea topdressing can refer to the following methods: 1. The amount of topdressing is determined according to soil fertility. The practice shows that increasing the amount of fertilizer applied to the middle and low yield fields can significantly increase the yield. For the high-yield fields, the general fertilization level can be maintained. Generally, on the basis of fully applying agricultural fertilizer and chemical fertilizer as base fertilizer, taking corn and sorghum as an example, 20 kg per mu is applied in high fertility soil, 23 kg per mu in medium fertility soil, and 27 kg per mu in low yield soil. two。 Topdressing at the peak of crop nutrition. The main function of topdressing is to use fertilizer to adjust the growth of crops, to meet the nutrition needs of crops in the middle and later stages of growth, and to achieve the purpose of increasing yield. The key to improve the utilization rate of topdressing chemical fertilizer is to grasp the critical period and maximum efficiency period of nutrient absorption by various crops, and to topdressing in the peak period of crop nutrition as far as possible in order to improve the utilization rate of fertilizer. Corn should be in jointing to big trumpet stage; sorghum should be in jointing to booting stage; rice from turning green to tillering stage; sunflower in budding stage; wheat in three-leaf stage; soybean topdressing urea in early flowering stage. 3. To cover the soil deeply. Practice has proved that after urea is applied to the ground surface for 4-5 days at room temperature, most of the nitrogen will be ammoniated and volatilized, and its utilization rate is only about 30%, especially on the surface of calcareous and alkaline soil, the loss of ammonia volatilization is more serious. Therefore, when topdressing upland crops with urea, it is best to apply less than 10 cm deep in pits or trenches, so that urea can be placed in wet soil, which is beneficial to the transformation of urea, and is also beneficial to the adsorption of ammonia fertilizer by the soil and reduce volatilization loss. When topdressing rice with urea, the depth of the water layer should not exceed 3-5 cm. 4. Keep a distance from the crops. Urea has great hygroscopicity because of its high nitrogen content and high nutrient concentration. Therefore, when topdressing, it is necessary to prevent urea from being applied near the polar system of crops, not to mention dropping urea into the heart leaves of crops, so as not to burn seedlings and affect growth, and be sure to keep a certain distance from crops. 5. Apply ahead of other nitrogen fertilizers. Because urea is a low molecular weight organic compound, it has to be ammoniated after being applied to the soil and transformed into a highly volatile ammonium carbonate before it can be absorbed by crop roots. Therefore, topdressing crops with urea should be applied about 7 days earlier than other nitrogen fertilizers. 6. Do not mix with alkaline fertilizer. Urea is a neutral fertilizer, so do not mix it with alkaline fertilizer when topdressing, so as to prevent the fertilizer efficiency from being reduced. If it must be mixed with alkaline fertilizer, the date of fertilization should be staggered, usually every 5 days. However, when urea is mixed with potassium chloride, phosphate rock powder and calcium superphosphate, the yield increase effect is very significant. 7. Water should not be irrigated immediately after topdressing. After urea is applied into the soil, it can not be absorbed by the soil until it is decomposed and transformed. If you irrigate immediately after the chase, it will cause a large amount of urea loss. When the soil is seriously short of water and must be irrigated, small water should be irrigated frequently, and flood irrigation must be avoided. When topdressing rice, the fluidity of urea before transformation should be taken into account, and it is more difficult to irrigate immediately after topdressing. Generally, it is appropriate to irrigate once every 3-5 days after topdressing. 8. Make top dressing outside the root. Urea has less damage to crop leaves, is easily soluble in water, has strong diffusivity, is easy to be absorbed by leaves, and is not easy to cause plasmolysis after entering the leaves, so it is very suitable for extra-root topdressing. However, urea with biuret content not more than 2% should be selected to prevent the loss of leaves. The concentration of urea as extra-root topdressing varies with different crop types. The concentration of extra-root topdressing for Gramineae crops is 1.5%-2%; the concentration used for extra-root topdressing for double-leaf crops is 1%, which should be lower during the flowering period. Generally, the amount of topdressing outside the root of urea per mu is 0.5-1.5 kg. The suitable spraying time is after 4: 00 p. M., when the transpiration is less, the leaf stomata open gradually, and the diluted urea solution can be absorbed overnight, which greatly improves the utilization rate of urea. Click to get more nitrogen, phosphorus, potassium application techniques click to get more chemical fertilizer application techniques