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The impact of fertilizer damage on cotton production cannot be ignored

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In recent years, while promoting new cotton varieties and providing technical services in cotton-growing areas, we have frequently encountered problems caused by farmers' mistakes in fertilizer application. First, when preparing soil for cotton nutritional-pot seedling raising, some applied too much farmyard manure or chemical fertilizer to the pot soil, so that after sowing, some cotton seeds rotted or the seedlings died; in some cases, although emergence was fairly uniform, root burn and seedling death followed. Second, after the cotton seedlings emerged in the seedbed, excessive application of water-soluble flush fertilizer scalded and scorched both cotyledons of the cotton seedlings. Third, when applying base fertilizer before transplanting cotton pot seedlings, some broadcast chemical fertilizer into the plow furrow, or applied chemical fertilizer into the pot holes, without separating the pot seedlings' root system from the applied fertilizer with fine soil; after transplanting, the cotton seedling roots came into direct contact with the chemical fertilizer, and the young roots and young stems turned brown or black after fertilizer damage. In mild cases, the cotton seedlings became stunted and did not grow; in severe cases, the young seedlings withered and died. Fourth, during the bud stage, excessive single application of nitrogen fertilizers such as urea or ammonium bicarbonate, or excessive input of high-efficiency multi-element compound fertilizer, with no regard for cost and a blind pursuit of building a high-yielding cotton framework early, resulted in excessive vegetative growth, premature row closure, severe shading in the cotton field, and serious outbreaks of pests such as mirids, causing massive shedding of buds and bolls. This phenomenon was especially common in rainy years. Fifth, during the flowering and boll stage, some rushed to broadcast urea before heavy rain arrived. Urea dissolved very quickly upon contact with rain, and the fertilizer concentration in the cotton field suddenly increased. After the rain, the weather suddenly cleared, cotton leaf transpiration was high, and water in the cotton plant rapidly underwent reverse osmosis and severe water loss, so that the lower stems and leaves of the cotton plant appeared scorched; in severe cases, the entire cotton plant withered and died and could no longer be saved.

In recent years, while promoting new cotton varieties and providing technical services in cotton-growing areas, we have frequently encountered problems caused by farmers' mistakes in fertilizer application. First, when preparing soil for cotton nutritional-pot seedling raising, some applied too much farmyard manure or chemical fertilizer to the pot soil, so that after sowing, some cotton seeds rotted or the seedlings died; in some cases, although emergence was fairly uniform, root burn and seedling death followed. Second, after the cotton seedlings emerged in the seedbed, excessive application of water-soluble flush fertilizer scalded and scorched both cotyledons of the cotton seedlings. Third, when applying base fertilizer before transplanting cotton pot seedlings, some broadcast chemical fertilizer into the plow furrow, or applied chemical fertilizer into the pot holes, without separating the pot seedlings' root system from the applied fertilizer with fine soil; after transplanting, the cotton seedling roots came into direct contact with the chemical fertilizer, and the young roots and young stems turned brown or black after fertilizer damage. In mild cases, the cotton seedlings became stunted and did not grow; in severe cases, the young seedlings withered and died. Fourth, during the bud stage, excessive single application of nitrogen fertilizers such as urea or ammonium bicarbonate, or excessive input of high-efficiency multi-element compound fertilizer, with no regard for cost and a blind pursuit of building a high-yielding cotton framework early, resulted in excessive vegetative growth, premature row closure, severe shading in the cotton field, and serious outbreaks of pests such as mirids, causing massive shedding of buds and bolls. This phenomenon was especially common in rainy years. Fifth, during the flowering and boll stage, some rushed to broadcast urea before heavy rain arrived. Urea dissolved very quickly upon contact with rain, and the fertilizer concentration in the cotton field suddenly increased. After the rain, the weather suddenly cleared, cotton leaf transpiration was high, and water in the cotton plant rapidly underwent reverse osmosis and severe water loss, so that the lower stems and leaves of the cotton plant appeared scorched; in severe cases, the entire cotton plant withered and died and could no longer be saved.

Increasing fertilizer input is originally an effective yield-increasing measure for supplementing cotton field nutrients, improving the soil's fertilizer supply capacity, and improving the nutritional status of cotton. However, blind fertilization without scientific basis is a man-made disaster for cotton, and the resulting reduction in cotton yield and income is caused by one's own actions. We should seriously sum up experience and lessons, scientifically grasp cotton fertilization techniques, and obtain the greatest cotton-growing benefit with the least input.

First, fertilizer should be applied according to the fertilizer requirements of cotton. Cotton generally requires little fertilizer in the early stage, steady amounts in the middle stage, and more in the late stage. Therefore, cotton fertilization should achieve the following: apply sufficient base fertilizer, apply seedling fertilizer quickly, apply bud fertilizer steadily, apply flowering and boll fertilizer generously, and apply boll fertilizer universally.

Second, fertilizer should be applied according to weather, soil, and variety. For example, for early-maturing varieties, sufficient boll fertilizer should be applied to prevent premature senescence; for transgenic hybrid insect-resistant cotton, potassium fertilizer should be increased, with no less than 60 jin per mu. On soils with high fertility, fertilizer should be applied appropriately less; on poor soils, organic fertilizer should be applied more. In dry weather, fertilizer should be applied when soil moisture is available, using water to regulate fertilizer, and when topdressing, attention should be paid to applying fertilizer after rain.

Third, costs should be calculated and fertilizer should be applied economically. First, the input-output ratio should be considered. Taking a seed cotton yield of 600 jin per mu as an example, fertilizer input per mu should generally not exceed 300 yuan. Second, fertilizer should be applied deeply, and fertilizer should not be applied on the soil surface to let it volatilize or be lost, still less should it be broadcast before rain; fertilization must not damage the root system. Third, topdressing fertilizer should be applied in split applications, and a single application should not be too large. Controlled-release fertilizers have good prospects and can be gradually expanded and promoted on the basis of trials and demonstrations. Fourth, fertilization must be closely combined with chemical regulation, so that limited fertilizer can be applied fully and evenly, and the cotton can present a robust, high-yielding plant type.

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