Since the content of available potassium (including water-soluble potassium and available potassium) in the soil decreases year by year, effective potassium has become the largest demand for cotton nutrition physiology. When 30 to 40 kg of high quality potassium fertilizer is applied to the base fertilizer, due to the consumption of cotton growth and development, and the leaching after heavy rain, the effective potassium content in the soil will fall to the original level by August.
In August, with the deterioration of soil permeability and the decrease of ground temperature after ridge-sealing in cotton fields, soil potassium supply capacity has been weakened. If potassium fertilizer cannot be added in time, it will show a clear shortage of potassium. The lack of potassium in cotton is first manifested in the lower old leaves. In general, the veins remain green, while the leaf parts gradually become chlorotic. Because of the strong activity of potassium in plants, most of them are concentrated in young and metabolically strong parts. When cotton plants are deficient in potassium, potassium is transferred from old leaves to young tissues first. For example, in the middle and early September, the potassium-deficient cotton fields were suddenly exposed to low-temperature rainfall, and the available potassium supply in the soil was almost interrupted. When the basic potassium nutrition of the cotton leaves could not be maintained, the cotton plants would suddenly become physiologically depleted, and the cotton leaves would change rapidly within two or three days. Yellow or red, and then dry off, stems dead, cotton plants died, also known as red stem blight, then take any measures are too late.
Therefore, in the middle and early August, it is a critical period for potassium supplementation in cotton, and spraying potassium on the foliage is the most economical and effective method for potassium supplementation. Effective potassium supplementation must be applied before the cotton strain is seriously deficient in potassium. If the cotton plant is in a state of severe potassium deficiency in August, it cannot be timely and effectively replenished. It will cause the upper bell to be reduced or no bell, the bell is delayed, the bolling is not smooth, the lint is reduced, the leaves fall off, and the whole plant will die. Serious consequences have been a lot of hard lessons in previous years.
What kind of potash fertilizer is best for spraying? There are four principles of fertilizer selection: (a) the principle of high potassium; (b) the principle of high solubility; (c) the principles of easy absorption and utilization and safety and harmlessness; and (iv) the principle of low input. According to the above four principles, potassium sulfate is the best type of foliar spray fertilizer: (1) High-quality potassium sulfate contains more than 50% potassium oxide, which is much higher than any other compound potassium fertilizer, if each shot of potassium sulfate 1 pound, can provide cotton for the production of 10 pounds of seed cotton potassium required; (b) soluble in water, at 30 degrees Celsius can dissolve 13 grams of potassium sulfate per 100 grams of water, easy to spray under any conditions; (three ) Easy to be absorbed and used by cotton, safe and reliable within a certain spraying concentration; (4) Calculated according to the unit effective component, the price is lower than any other potash fertilizer.
Fertilizer spraying method: Concentration of 2% is appropriate, 60 pounds of acre spray, only spray the top half of the cotton plant, the front and back of the blade are sprayed wet, spray time to avoid after 10:00 to 3 pm During the period with the largest amount of evaporation, the finer the fog point, the more secure the cotton is, and the cotton field that pays attention to the headland should not be re-sprayed. It should be sprayed once every 78 days and sprayed 3 times. If mixed with pesticides, it is necessary to reduce the amount of fertilizer and increase the frequency of spraying fertilizer. According to the practical experience of cotton farmers, spraying powdered potassium sulphate produced by Russia has the best effect, containing up to 52% of potassium oxide, rapid dissolution, and almost no precipitation. Unsatisfactory dissolution of large particles of potassium sulfate is not recommended for foliar spraying. The second and third grade potassium sulfate is low in potassium, and has many filling materials. It is not suitable for spraying fertilizer. Potassium chloride contains up to 60% potassium oxide and is dissolved well, but cotton leaves are more sensitive to chloride ions, such as foliar spraying fertilizer, it is preferable to use 1% concentration to ensure safety.
Potassium dihydrogen phosphate is an outdated cotton foliar fertilizer with low potassium content and high phosphorus content, low spraying concentration and high input. It is suitable for cotton fields with few potassium deficiency in the 1970s and 1980s. In a cotton field that is severely deficient in potassium, spraying potassium dihydrogen phosphate is far from satisfying the cotton's desire for potassium. In the field of premature decay, early maturing cotton fields, cotton fields with fertile reproductive growth and weak nutrient growth, no additional phosphorus can be sprayed. Potassium dihydrogen phosphate is suitable for use in cotton fields where vegetative growth is too prosperous and late maturing.
Potassium nitrate is a gunpowder and industrial raw material. It is expensive and has high input. It is suitable for use in cotton fields that are depleted in both potassium and nitrogen.
"Sulfate-type compound fertilizer" belongs to compound fertilizer, not potash fertilizer, and has low potassium content and cannot be used as potassium fertilizer.
It is the most convenient and economical way to spray high-quality potassium sulfate in the general cotton field. Practice has proved that it can achieve a good effect of potassium supplementation.
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