Premature aging of cotton is mainly due to the aging of cotton roots in the middle and late periods, and the ability to absorb nutrients and moisture is reduced. The nutrients and water transported by plants cannot meet the needs of cotton growth and development. Premature aging has a greater impact on the yield and quality of cotton. The sooner it occurs, the greater the impact. General reduction of production by 10% to 40%. According to field investigations, some cotton has experienced premature aging, so we must step up prevention.

First, the symptoms. There are two types of premature aging of cotton: yellow leaf type and red leaf type. The yellow leaf type is characterized by chlorotic chlorosis between the veins of the cotton after its peak period. The yellowing leaves begin from the farthest point away from the main stem, develop from the bottom up and outward, and the leaves gradually dry off. The red leaves are the leaves from green to dark green in the later growth period and the leaves become thicker and brittle. After that, the red spots on the leaves are scattered. Finally, the whole leaves turn red, and the veins remain green, which is the stem blight of red leaves. When the disease is serious, the base of the petiole becomes soft, and the water loss shrinks, causing the leaves to wither and fall off. The top of the stem is dry and coke-shaped, and some of them cause repeated infections of ring blotch and brown spot, which leads to the death of the diseased plant. Severe onset and early onset of plant dwarf, root dysplasia, the main root, lateral roots are short and thin. Some plant disease leaves can still grow axillary buds.

Second, the reasons for the occurrence. According to the field survey, the premature aging of cotton this year was heavier than in previous years, mainly due to the following points:

1. In early summer, frequent rain and frequent loss of nutrients.

In June and July of this year, there were many rains. The cotton aboveground grew fast and the plant type was large. However, the roots were shallow and the nutrient was lost. The nutrient was difficult to meet the needs of the later growth and development of cotton.

2. Late autumn and early autumn drought, insufficient water supply. Since mid-August, there has been no obvious rainfall. After a relatively long period of drought, the peasants did not timely flood, the drought in the cotton fields, the recent fine weather, large evaporation, soil moisture can not meet the needs of cotton. It also affects the absorption, transportation, and distribution of nutrients, resulting in the physiological imbalance of cotton plants. As a result, the disease is heavy and premature aging is aggravated.

3. Soil compaction, poor root development. Most of the cotton fields were planted without organic fertilizers and only chemical fertilizers, which resulted in a decrease in soil organic matter content, salt and alkaline buildup, poor root development, reduced nutrient range of cotton, reduced ability to absorb nutrients, and nutritional imbalance.

4. The application of blindness is large and the ratio is unreasonable. Farmers invest more in nitrogen and phosphorus fertilizers, and potassium fertilizers are not applied or used less. The lack of potassium in cotton induces physiological diseases such as stem blight of red leaves, leading to premature aging of cotton and reduced yield.

5. Successively revisited and reduced resistance. The cultivation of cotton is generally continued for many years, and the rotation is difficult. This results in the lack of nutrients and the accumulation of pathogens. Diseases increase year by year and affect the growth and development of cotton.

6. Early sowing, lack of stamina. Coverage of cotton mulch, sowing early, early exposure to low temperature, late frost hazards, triggering seedling disease; mid-float peach field, reproductive growth needs more nutrition, vegetative growth is affected, cotton plant physiological load is too heavy, plant resistance Reduced sex, it is difficult to build a high yield shelf, the formation of "early old cotton fields" and premature aging.

Third, preventive measures. Farmers should take early precautions based on the climate characteristics and cultivation and management conditions of their cotton fields.

1. Hold water tight. Some cotton farmers believe that cotton boils and there is not much water required. In fact, this understanding is wrong. After cotton bolling, although the vegetative growth basically stopped, but reproductive growth also needs a lot of water and nutrients, the supply of nutrients can not do without the participation of water. In case of drought and water shortage, it will cause the upper young age to fall off and the weight of the bell will be reduced. In particular, when soil moisture in the cotton fields is insufficient in the middle and early September, when the field water capacity is 60% to 55%, watering should be carried out once. The watering should not be excessive, and care should be taken to extend the cotton roots. Growth time, promote nutrient absorption and ensure normal maturation of cotton.

2. Leaf surface fertilizer. Use 50% potassium sulfate 100 times, or high-quality potassium dihydrogen phosphate 300 times urea and 100 times the foliar spray, spray every 10 to 15 days 1, even spray 3 to 4 times.

3. Continue pruning. The flowers that bloom after buds and white dew after the beginning of autumn are invalid. In order to reduce nutrient consumption and prevent premature aging, ineffective buds should be removed in time, and leggy branches, axillary buds and empty branches should be removed together. Density of closed cotton fields, due to poor ventilation and light transmission, can be in the 3 to 5 pieces of cotton leaf to protect a cotton boll under the premise of destroying the yellow leaves and some of the extra old leaves.

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