What is the effect of spraying potassium on cotton in August? Detailed explanation of cultivation techniques
What is the use of spraying potassium on cotton in August? Please explain: entering August, as soil aeration deteriorates and soil temperature drops after the cotton field canopy closes, the soil's potassium supply capacity gradually weakens. If potassium fertilizer is not supplemented in time, obvious potassium deficiency will appear. Potassium deficiency in cotton first shows on the lower old leaves; generally the veins remain...
What is the use of spraying potassium on cotton in August? Please explain
Entering August, as soil aeration deteriorates and soil temperature drops after the cotton field canopy closes, the soil's potassium supply capacity gradually weakens. If potassium fertilizer is not supplemented in time, obvious potassium deficiency will appear. Potassium deficiency in cotton first shows on the lower old leaves; generally the veins remain green while the mesophyll gradually loses its green color. Because potassium is highly mobile within the plant and tends to concentrate in young, metabolically active parts, when the cotton plant is deficient in potassium, potassium is first transferred from old leaves to young tissues. If in early to mid-September a potassium-deficient cotton field is suddenly hit by low temperature and rain, the supply of available potassium in the soil is almost cut off. When even the basic potassium nutrition of the cotton leaves cannot be maintained, the cotton plant will suddenly show physiological collapse; within two or three days the cotton leaves rapidly turn yellow or red, then dry up and fall off, the stems wither and die, and the cotton plant dies. This is also called red-leaf stem blight, and at this point no measure taken will be in time.
Therefore, early to mid-August is the key period for potassium supplementation in cotton, and foliar potassium spraying is the most economical and effective potassium supplementation method. Effective potassium must be applied before the cotton plants become severely potassium-deficient. If in August the cotton plants are in a state of severe potassium deficiency and cannot receive timely and effective supplementation, it will cause reduced boll setting or no bolls on the upper part, small and late-developing bolls, poor boll opening, reduced lint percentage, leaf shedding, and even the serious consequence of whole-plant death. There have been many painful lessons in previous years.
Which potassium fertilizer variety is best for foliar spraying? There are 4 principles for choosing fertilizer: (1) the high-potassium principle; (2) the high-solubility principle; (3) the principle of easy absorption and utilization and safety and harmlessness; (4) the low-input principle. According to the above 4 principles, potassium sulfate is the best foliar spray fertilizer variety: (1) high-quality potassium sulfate contains more than 50% potassium oxide, far higher than any other compound or blended potassium fertilizer variety. If 1 jin of potassium sulfate is sprayed per mu each time, it can provide the cotton with the potassium needed to produce 10 jin of seed cotton; (2) it is easily soluble in water; at 30°C, 100 grams of water can dissolve 13 grams of potassium sulfate, making it convenient to spray under any conditions; (3) it is easily absorbed and utilized by cotton and is safe and reliable within a certain spraying concentration; (4) calculated by unit of active ingredient, its price is lower than any other potassium fertilizer variety.
Spraying method: the concentration should preferably be 2%, spray 60 jin of liquid per mu, spray only the upper half of the cotton plants, and wet both the front and back sides of the leaves. The spraying time should avoid the period of greatest evaporation from after 10 a.m. to before 3 p.m. The finer the mist droplets, the safer for cotton. Be careful not to spray the cotton plants at the ends and edges of the field repeatedly. Spray once every seven or eight days, for 3 consecutive sprays. If mixed with pesticides, reduce the fertilizer amount and increase the number of fertilizer sprayings. According to cotton farmers' practical experience, powdered potassium sulfate produced in Russia has the best spraying effect, with potassium oxide content as high as 52%, dissolving quickly and with almost no sediment. Large-granule potassium sulfate that does not dissolve well is not suitable for foliar spraying. Second- and third-grade potassium sulfate has low potassium content and much filler, so it is not suitable for spraying. Potassium chloride contains as much as 60% potassium oxide and also dissolves well, but cotton leaves are relatively sensitive to chloride ions. If used for foliar spraying, a 1% concentration is advisable to ensure safety.
Potassium dihydrogen phosphate is an outdated cotton foliar fertilizer variety, with low potassium content and high phosphorus content, low spraying concentration and high input. It was suitable for cotton fields with not much potassium deficiency in the 1970s to 1980s. In severely potassium-deficient cotton fields, spraying potassium dihydrogen phosphate is far from enough to satisfy the cotton plants' craving for potassium. In prematurely aging cotton fields, early-maturing cotton fields, and cotton fields with vigorous reproductive growth but weak vegetative growth, phosphorus can no longer be sprayed. Potassium dihydrogen phosphate is suitable for cotton fields with excessive vegetative growth and a tendency toward late maturity.
Potassium nitrate is a raw material for gunpowder and industry, expensive and high-input, and is suitable for cotton fields deficient in both potassium and nitrogen at the later stage.
"Potassium sulfate type compound fertilizer" belongs to compound mixed fertilizer, not potassium fertilizer. It has low potassium content and cannot be sprayed as potassium fertilizer.
For general cotton fields, spraying high-quality potassium sulfate is the simplest and easiest, as well as economical and practical. Practice has proved that it can achieve a relatively good potassium supplementation effect.
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