The top-dressing of crops is an important means to increase production and income, but it is necessary to pay attention to science when top-dressing, so as to achieve a multiplier effect.
One must adapt to local conditions.
The structure of the soil is different. When topdressing, the soil must be subjected to the necessary tests. According to the difference in soil acidity and alkalinity, the types of chemical fertilizers must be determined. Under normal circumstances, low-alkali alkali to use ammonium sulfate, ammonium nitrate and other acidic fertilizers; acid soil topdressing urea, ammonium bicarbonate, ammonia and other alkaline or neutral fertilizers; poor water retention and retention capacity of sand and sandy loam, to chase Application of volatile ammonium nitrate, ammonium chloride, urea and other fertilizers. At the same time during the top-dressing period, it is best to increase the frequency of topdressing and reduce the amount of fertilizers each time to prevent evaporation and loss of chemical fertilizers.
Second, it should be due to fertilizer.
Most chemical fertilizers are salts, which are acidic, alkaline, and neutral. When fertilizing, it must be treated differently depending on the nature and composition of the chemical fertilizer. Ammonium nitrate can be used as a top-dressing fertilizer in dry farms, but not as a top-dressing fertilizer in rice. Mixed application of ammonium chloride and urea in paddy fields can inhibit nitrification and reduce leaching, but it must not be used in salted soil to prevent chlorides from accumulating in the soil and increase salt content. harm. At the same time can not be applied to tobacco, sugar beet and potato and other chloride-resistant crops, so as not to reduce its yield and quality; urea applies to all kinds of crops and all kinds of soil, but it can only be released in the soil through the transformation of fertilizer efficiency, absorbed by crops . Therefore, when using urea as topdressing, it is necessary to advance several days ahead of other nitrogenous fertilizers, and at the same time apply deep soil and improve fertilizer efficiency.
The third must be based on physical conditions.
Different types of crops are even different varieties of the same crop, and the type and amount of chemical fertilizer required are different. Therefore, according to the type of crops, the right medicine should be supplied on demand. For example, rice can be topdressed with 230-370 kg of ammonium sulfate or 180-200 kg of urea per hectare; corn and sorghum need more nitrogen, and the application of base fertilizer and seed fertilizer alone can not meet the needs of nitrogen fertilizer, but also timely recovery of a certain number of Nitrogen fertilizer, dressing 230-250 kg ammonium nitrate or 150-190 kg urea per hectare; soybeans also need more nitrogen fertilizer crops, root nodules and nitrogen fixation can only meet about 50% of the required nitrogen fertilizer in the whole growth period of soybean, timely topdressing nitrogen fertilizer. good results. Each hectare can be topdressing 150 to 230 kilograms of ammonium nitrate or 130 to 170 kilograms of urea; sunflowers have higher plant weights, deeper roots, and larger discs, and the amount of fertilizer needed is also higher than that of the gramineous crops, and can be applied from 220 to 240 kilograms per hectare. Ammonium nitrate or 170-190 kg urea.
Fourth, it must be adjusted according to the times.
The key issue of topdressing is to grasp the critical period and the maximum efficiency period of nutrients for various types of crops, so that topdressing can be carried out during the peak season of nutrition. The jointing of sorghum to heading is the period between vegetative growth and reproductive growth. At this time, the absorption of nutrients reaches the highest peak, which is the best time to top-dressing; the early-stage topdressing of wheat has a significant effect of increasing yield, and nitrogen fertilizer should be topdressed at the three-leaf stage for cultivation. Strong seedlings and knots lay a good foundation; soybeans can be topdressed with nitrogen fertilizers at the early flowering stage, which can reduce the rate of falling flowers and plants, and can prolong the lifespan of plants, increase grain weight and yield; corn is the period from jointing to the big bell-mouth period. During the peak period of absorbing nutrients, the first fertilizer should be applied, and the second fertilizer should be applied before heading; the rice should be top-dressed once during rejuvenation, jointing, and heading; the millet should be top-dressed at the jointing stage to the booting stage; Top dressing.
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