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First, it is necessary to topdress according to the soil conditions. Since the structure of each soil is different, the necessary tests can be carried out on the soil during topdressing. According to the difference in soil acidity and alkalinity, it is determined that the type of fertilizer should be applied, so that the fertilizer can be used in a timely and rational manner, such as in low-lying land. Acidic fertilizers such as ammonium sulfate should be used. In acidic soils, alkaline or neutral fertilizers such as urea, ammonium bicarbonate and ammonia should be applied. In sandy and sandy loam soils with poor water retention and fertility, it is necessary to apply non-volatile ammonium chloride. Fertilizers such as urea. At the same time, in the period of topdressing, we must grasp the amount of fertilization, do not apply it at one time, and apply the amount of topdressing several times to reduce the amount of fertilizer applied. It can not only prevent excessive fertilizer burning, but also prevent chemical fertilizer from volatilizing and losing. .
Second, it is necessary to apply fertilizer according to the variety of fertilizers. Most fertilizers are salt-based, acidic, alkaline and neutral. When fertilizing, it must be treated differently according to the nature and composition of the fertilizer to prevent the production of the wrong fertilizer and reduce the quality of the crop. The application of ammonium chloride and urea in paddy field can inhibit nitrification and reduce leaching, but it should not be used in saline soil to avoid accumulation of chloride in the soil and increase salt damage. Potassium chloride-type compound fertilizer can not be applied to crops such as watermelon, tobacco, sugar beet and potato, so as not to reduce its yield and quality, resulting in watermelon is not sweet; urea is suitable for various crops and various soils, but it is The transformation in the soil releases the fertilizer and is absorbed by the crop. Therefore, when using urea as a top dressing, it is a few days ahead of other nitrogen fertilizers, and at the same time, deep application of soil, thereby increasing the utilization rate of fertilizer.
Third, it is necessary to topdress according to different crops. Different types of crops and even different varieties of the same crop require different types and amounts of fertilizer. Therefore, it is necessary to select a suitable fertilizer according to the type of crops and supply it as needed. Field crops are mainly applied to nitrogen fertilizer, and economic crops such as vegetables, tobacco, grapes, cotton, etc., in addition to nitrogen fertilizers, should be applied to potash fertilizer. After the test, the spring corn was first applied to half of the base fertilizer at the time of sowing, and the other half was applied as top dressing at the end of July and early August, and the nitrogen fertilizer utilization rate could be increased by 10-20%. The amount of topdressing required for each crop is different. Rice can be topdressed with 230-370 kg of ammonium sulfate or 180-200 kg of urea per hectare. Soybeans are crops that require more nitrogen fertilizer. The nodule nitrogen fixation can only satisfy the soybean growth period. It takes about 50% of nitrogen fertilizer, and it is very effective to apply nitrogen fertilizer in time. It can topdress 130-170 kg of urea per hectare. However, the method of applying nitrogen and potassium fertilizer in summer must be carried out to cover the soil, avoiding the loss of nitrogen volatilization caused by nitrogen application and the potassium fixation caused by the alternating dry and wet of potassium fertilizer on the surface.
Fourth, we must choose the best fertilization period for crops to topdress. The key issue of top dressing is to grasp the critical period and maximum efficiency period of various crop nutrients. Good steel is used in the cutting edge to carry out top dressing during the nutrient period of the crop. At this time, the absorption of nutrients reaches the highest peak, which is the best time for topdressing. . For example, the critical period of nitrogen in wheat is from tillering to panicle differentiation, and the critical period of phosphorus is in tillering. The nitrogen critical period of maize is in the panicle differentiation stage, and the phosphorus critical period is in the 3-5 leaf stage. The critical period of nitrogen and phosphorus in cotton is around the beginning of the bud. During the maximum efficiency of crop nutrition, crops have the most demand for one or several nutrients. At this time, the application of chemical fertilizers can best exert its potential for increasing production. For example, the maximum efficiency of nitrogen fertilizer application in wheat is from jointing to heading stage. Nitrogen fertilizer should be applied once in the three-leaf stage. Soybean can topdress secondary nitrogen fertilizer at the early flowering stage, which can reduce the rate of falling and falling, and can prolong the life of the plant and increase the grain. Weight and yield; corn is the peak period of nutrient absorption after jointing to large bell mouth. It should be applied to the second fertilizer, or second fertilizer before heading; rice should be topdressed in the greening, jointing and heading stages. once.
Fifth, we must grasp the amount of fertilizer. In the top dressing, it is necessary to use different fertilization amount for each crop. It should not be too much or too little. The nitrogen fertilizer is over-fertilized, which is easy to cause crops to grow prosperously, and the disease resistance and lodging resistance are reduced, especially in summer. After the storm, a lot of corn fell to the ground, causing a reduction in production. Excessive application of phosphate fertilizer will shorten the growth period, premature ripening, and the quality of crops will decrease, while the lack of topdressing will not increase the yield, resulting in a decrease in yield. Therefore, in the topdressing, not only the quantity should be paid attention to, but also the combination should be done. It is not necessary to apply some kind of fertilizer. Although other nutrients are sufficient, when a certain nutrient is lacking, the crop growth will still be affected, resulting in low crop yield or quality. Decline, only when the various nutrients are matched with the appropriate amount of fertilizer, will the purpose of less investment and more output.
Summer is hot and rainy, and the sun is abundant, which is beneficial to the photosynthesis of the leaves. It is the maximum efficiency period of crop rapid growth period and crop nutrition. Moreover, the carbohydrates produced by crop photosynthesis require a large amount of nitrogen to form amino acids, proteins and nucleic acids. At this time, the topdressing and nutrient absorption and utilization efficiency of the crops are high. Farmers in some places like to use the nitrogen fertilizer in the whole growth period of crops as a base fertilizer for one-time application at the time of sowing. The nitrogen fertilizer stays in the soil for a long time, while the early growth of the crop is slow and the absorption is less, resulting in the loss of nitrogen fertilizer, waiting for the high temperature and rain. When the season comes, the crop enters the rapid growth stage and needs a lot of nutrients. At this time, the nitrogen fertilizer has been applied to the soil, some of which have been lost, and the nutrient supply is insufficient, which will cause the phenomenon of post-fertilization and de-fertilization, and reduce the yield and quality. Increasing crop yields plays a larger role. However, according to the author, many farmers are used to applying nitrogen fertilizer to the ground after the rain. They think that the nitrogen fertilizer can be quickly melted into the ground, the crop can be absorbed quickly, and some are directly poured. Spreading, these practices not only waste a lot of fertilizer, but also cause serious pollution. Therefore, when topdressing in summer, you must pay attention to science in order to achieve high yield.
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