How should potassium fertilizer be applied when growing cotton?
How should potassium fertilizer be applied when growing cotton? Please give an introduction. In cotton fertilization, people generally focus on applying phosphorus fertilizer and nitrogen fertilizer, and do not pay enough attention to the application of potassium fertilizer. According to data, for every 50 kg of lint cotton produced, 9 kg of pure nitrogen, 3 kg of pure phosphorus, and 8 kg of pure potassium must be absorbed from the soil. If 100 kg of lint cotton is produced, then...
How should potassium fertilizer be applied when growing cotton? Please give an introduction.
In cotton fertilization, people generally focus on applying phosphorus fertilizer and nitrogen fertilizer, and do not pay enough attention to the application of potassium fertilizer. According to data, for every 50 kg of lint cotton produced, 9 kg of pure nitrogen, 3 kg of pure phosphorus, and 8 kg of pure potassium must be absorbed from the soil. If 100 kg of lint cotton is produced, then 13 kg of pure nitrogen, 4.5 kg of pure phosphorus, and 13 kg of pure potassium are needed. It can be seen that the ratio of the three is 1:0.35:1, which also shows that cotton is a potassium-loving crop. Cotton production practice in recent years shows that no matter which type of insect-resistant hybrid cotton variety it is, the demand for potassium fertilizer is relatively large, especially under continuous cropping, and particular attention should be paid to supplementing potassium fertilizer.
Applying potassium to cotton can enhance physiological activity, improve the utilization rate of nitrogen fertilizer, promote the growth of cotton roots, stems, leaves, and reproductive organs, prolong the functional period of leaves, and prevent premature senescence. Especially in cotton areas with severe Fusarium wilt, applying potassium can enhance disease resistance and stress resistance and reduce its harm. Because potassium is very active in the cotton plant, it can undergo replacement and substitution with other elements, which helps increase the concentration of cell sap and the permeability of membranes, thereby promoting the plant's absorption and synthesis of nitrogen and phosphorus, improving cotton's cold tolerance and economic water use capacity, and providing a very defensive effect for early-sown cotton and cotton planting in arid areas. In production, because people emphasize nitrogen and neglect potassium, cotton field soil cannot get supplemental potassium nutrition, and coupled with predatory management of the soil year after year, the potassium resources in cotton soil decrease year by year, obstructing the transport and conduction of nutrients in the cotton plant, leading to a decline in yield year by year, and it has become an obstacle factor restricting high cotton yields.
When cotton lacks potassium, the first sign is yellow-white patches on the leaves; afterward, the leaves gradually turn light green, and yellow spots appear between the veins. The central parts of these spots die first. At the same time, many brown dirty spots appear at the tips and edges of the leaves, and after rotting they curl downward and droop. Finally, the entire leaf becomes brown and then dries up and falls early. In potassium-deficient cotton plants, the lateral roots also become noticeably shorter, the root mass is also small, the stems are short and thin, boll shedding becomes more serious, there are few and small bolls, and it is difficult for them to mature and open, and fiber quality declines. In severely potassium-deficient cotton plants, because too many leaves fall too early, the plants die prematurely, which is the so-called red leaf stem blight. Even if some large bolls have formed, in the later stage a large number of large bolls will also shed, causing severe yield reduction. Potassium deficiency in cotton is relatively common, but generally it only becomes fairly obvious in the later stage, and by then it is too late to supplement potassium fertilizer, so emphasis should be placed on increasing organic fertilizer application to cotton fields that have historically been deficient in potassium. In addition, according to the nitrogen and phosphorus application situation in the cotton field, a certain amount of potassium fertilizer should also be applied in combination, with the potassium application rate per mu of cotton field being no less than 15 kg, and potassium-deficient cotton fields can increase it to 20-25 kg. The input ratio of nitrogen, phosphorus, and potassium should preferably be 1:0.3:0.8-0.9. The specific application is: at sowing or transplanting, on the basis of applying 2500-4000 kg of high-quality farmyard manure per mu, mix in 10-15 kg of potassium chloride or potassium sulfate, or 40-50 kg of plant ash or 2-3 kg of potassium dihydrogen phosphate as base fertilizer, which can meet the cotton's potassium needs throughout the entire growth stage. For cotton fields with insufficient potassium fertilizer in the early stage, 10-15 kg of potassium chloride can be buried and applied at the bud stage, and 5-7.5 kg of potassium chloride per mu can be buried and applied at the flowering and boll stage. In the middle and late stages, because root absorption capacity weakens, 0.2% potassium dihydrogen phosphate can be used for foliar spraying 2-3 times. Spray 50-60 kg of fertilizer solution per mu each time. This can not only enhance the cotton's staying power and prevent premature senescence, but also play a role in setting more bolls and larger bolls. It is an important measure to improve cotton yield and quality.
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