Poor cotton growth, management must keep up in the middle and late stages this year

Since the beginning of this year, our province has experienced prolonged overcast and rainy weather with scant sunshine, severe occurrence of seedling diseases, and cotton growth generally poorer than in previous years. At present, cotton has entered a critical period of growth, so we must make full use of the current characteristics of higher temperatures and rapid cotton growth to do a good job in cotton field management. Management in the middle and late stages of cotton should focus on the following aspects:

1. Early stubble clearing, early management. Stubble clearing and intertillage can not only provide a good environment for cotton seedling growth and development, but also eliminate cotton bollworm pupae. Once cotton seedlings enter the field, the word "management" must be put first, and all localities should suit measures to the seedlings and carry out classified management. Category 1 cotton seedlings grow and develop quickly and have vigorous vegetative growth, so they should be reasonably regulated to shape an ideal plant type and promote early boll setting, more bolls, and large bolls; Category 2 cotton seedlings should combine promotion and control, with promotion as the main approach, to urge the plants to build a high-yield framework early; Category 3 cotton seedlings develop late and grow weakly, so the method of promoting both water and fertilizer should be adopted, and if necessary, "biased fertilizer" can be applied to promote early plant development.

2. Scientific fertilizer and water management. First, apply flower and boll fertilizer heavily. Generally in early to mid-July, when 1-2 large bolls appear on the lower part of the plant, topdressing should be carried out, applying 15-20 kg of urea per mu. When fertilizing, it should be flexibly controlled according to cotton appearance and weather changes. If the weather is dry, base fertilizer and bud fertilizer were applied relatively little, and the soil fertility is relatively poor and the cotton plants grow weakly, flower and boll fertilizer should be applied early and heavily, so as to "apply at flowering for use at boll setting." Second, supplement with topping fertilizer. Generally in early August, for cotton fields with medium to high fertility, in order to strive for more bolls per plant, increase boll weight, and obtain a higher yield, 2.5-3 kg of urea can be topdressed per mu, and for cotton fields showing a trend of premature aging, 5 kg of urea can be topdressed per mu. Topping fertilizer should not be applied too late or too much. Third, foliar fertilization. Generally, in cotton fields, when cotton begins to open bolls, if premature aging is found in the cotton plants, foliar spraying should be carried out promptly. For late-developing cotton fields, a 2%-3% calcium superphosphate solution or an 800-1000 times potassium dihydrogen phosphate solution can be sprayed, and nitrogen fertilizer must absolutely not be topdressed.

3. Deep intertillage, high hilling. At the end of June and beginning of July, cotton is at the stage of full bud and early flowering, when excessive growth is very likely to occur, so on the basis of stubble clearing and hilling during the bud stage, deep intertillage and high hilling should be carried out. The depth of intertillage should preferably be 6-7 cm, and the hilling height should be about 16 cm. Doing so can promote deep rooting, control excessive plant growth, prevent lodging, and prevent premature aging, and is also beneficial for drainage and irrigation during the rainy season. In addition, weeds in cotton fields should be removed promptly when they appear.

4. Chemical regulation. On the basis of light control at the cotton seedling stage, at the early flowering stage generally 2-2.5 g of mepiquat chloride per mu is used, mixed with 15-25 kg of water for spraying; or 500-600 times Xuebo brand cotton high-efficiency liquid fertilizer can be sprayed, so as to shape an ideal plant type, promote early boll setting and more inner bolls per plant, and enhance root activity. Seven to eight days after cotton topping, when the plant is at the stage of full flowering and boll setting, generally 3-5 g of mepiquat chloride per mu is used, mixed with 15-25 kg of water, and then sprayed on the top and side tips of the cotton plants. Its main effect is to increase the setting of early autumn bolls, increase boll weight, and prevent the plants from remaining green and late maturing.

5. Reasonable pruning. First, remove vegetative branches. Change the past practice of "rolling up the trouser legs" to removing vegetative branches, that is, remove leaf branches and retain main stem leaves. For places with missing seedlings, 1-2 vegetative branches can be retained to use the space for more bolls. Second, top at the appropriate time. After entering the middle stage of cotton growth (around July 20), topping and pruning can be carried out appropriately according to the seedlings and the field. The main effect of topping is to control vertical growth of the cotton plants and promote the transport of nutrients to reproductive organs. Topping too early is not conducive to high cotton yield; topping too late increases ineffective buds. For cotton fields with medium fertility, the topping time is generally around July 20, and for high-fertility and high-water plots it can be postponed to the end of July. Generally, the density of spring cotton is 3000-4000 plants/mu, and 14-16 fruit branches can be retained per plant; the density of summer cotton is 6000-8000 plants/mu, and 6-8 fruit branches can be retained per plant.

6. Grasp both drought prevention and drainage. During the flowering and boll stage, cotton plants grow vigorously, and the temperature is also high, so transpiration is intense, making this the period of greatest water demand in the entire life of cotton. If the soil lacks water at this time, it will affect the exertion of fertilizer efficiency, leading to premature aging of cotton plants and shedding of buds and bolls, and in severe cases the plants will stop growing. Therefore, when drought occurs during the flowering and boll stage, watering must be timely to regulate fertilizer with water and meet the needs of normal cotton growth for water and fertilizer. However, the flowering and boll stage of cotton in our province coincides with the flood season. If watering overlaps with rainwater, it will lead to excessive growth of cotton plants, oversized vegetative mass, field shading, massive shedding of buds and bolls, and can also cause boll rot. Therefore, during the flowering and boll stage, both drought prevention and drainage must be grasped. When drought occurs, alternate-row furrow irrigation should be used (flood irrigation is not suitable), and when waterlogging occurs, drainage should be timely. The watering period should be determined according to the weather and cotton appearance. Generally, when there have been more than 7-10 consecutive sunny days, or when drought signs appear in cotton (slow plant growth, dark green and lusterless leaves, thickened leaves, top leaves wilting and drooping at noon and still unable to recover after 3 p.m., and the proportion of red stems has reached more than 90%), watering should be carried out. The specific watering time should preferably be chosen in the evening or morning, and after watering, the soil should be loosened in time to preserve moisture.

7. Integrated control of diseases, insects, and pests. Because of the warm winter last year, cotton diseases, insects, and pests will all occur relatively heavily this year. All localities must attach great importance to this, strengthen forecasting and prediction, and grasp the appropriate control period. In the control of cotton bollworm, it is necessary to distinguish insect-resistant cotton from non-insect-resistant cotton, adopt appropriate measures, and control it at the right time. For the control of cotton leaf mites, pesticides such as Shamiewang and Chongmanke can be selected. For cotton aphids, the yellow board aphid trapping method can be used for trapping and killing, or pesticides such as Yashijing and Huifeng Jingzhi can be selected for chemical control. For the control of cotton fusarium wilt and verticillium wilt, there is currently no effective pesticide, so prevention should be the main approach, and pesticides such as Guangkuling and Shiteling can be selected.