How to carry out field management of cotton during the flowering and boll stage? Technical Q&A

1. What is the flowering and boll stage?

The stage from flowering to boll opening, generally from early July to early September. There is a farming saying, "flowers see flowers forty-eight," but in fact in China's Yellow River basin it generally takes 50-70 days. When 10% of the cotton plants in the field have flowered, it is called the initial flowering stage; when 50% have flowered, it is called the flowering stage. When 50% of the cotton plants have the first fruiting node of the fourth fruiting branch flowering, it is called the full flowering stage.

2. What are the management principles during the flowering and boll stage?

The initial flowering stage is the transition from vegetative growth to reproductive growth, and management should focus on control to prevent excessive growth and achieve steady growth. The full flowering stage is the stage when vegetative growth shifts to being mainly reproductive growth. It is the period when cotton needs the most water and fertilizer in its entire life, and also the period when contradictions in growth and development are most concentrated. It is necessary both to meet the water and fertilizer needs for growth and development and to control the vegetative growth of the cotton plants so that nutrients are directed to reproductive growth. Management should adopt the method of promoting below and controlling above, or combining promotion and control, with the main application of flowering and boll fertilizer. The peak flowering and boll stage is the period when vegetative growth fully shifts to reproductive growth with mass flowering and boll setting. It is necessary to meet the water and fertilizer needs for cotton growth, adopt a policy of continuous promotion, promote more boll setting in the middle and upper parts, and strictly prevent premature senescence in the later stage.

3. What are the main causes of bud and boll shedding?

When flowering encounters rain, pollen absorbs water and loses its pollination ability or fertilization is poor. After rain, humidity in the cotton field is high, temperature rises, ventilation is poor, and the relationship among water, fertilizer, and temperature is not well coordinated, which intensifies physiological contradictions. Poor external environmental conditions lead to nutritional imbalance in the cotton plant and loss of control over physiological functions, such as insufficient or excessive soil moisture, excessive or insufficient nitrogen application, excessively high or low temperature, insufficient light, pest and disease damage, and mechanical injury.

4. How can the appearance of cotton plants during the flowering and boll stage be judged?

① Appearance during the flowering and boll stage:

Light green leaf color is normal; plants are strong if neither excessively vigorous nor declining; flowers and bolls all around the middle with little shedding; dark top leaves indicate water shortage; shiny top leaves indicate insufficient fertilizer; in cotton field management, first look at the appearance.

② Vigorous and healthy type:

At initial flowering, steady and full of potential, with large flowers and a full frame; at full flowering, vigorous but not excessively vegetative, growing robustly and setting bolls steadily; with bolls on the plant when rows close, the middle is not empty; with three crops of bolls well set, shedding is light.

③ Premature senescence type:

Cotton plants are short with few fruiting branches; the main stem is thin and weak and grows slowly; the stem is red all the way to the top and leaf color is yellow; autumn bolls are thin and small with heavy shedding.

④ Excessive vegetative growth type:

The stem is green with sparse branches and long internodes; leaves are tender and large, green with a yellow tinge; leaf tips droop and leaves are broad; rows close too early, tall and empty.

5. What are the basic measures for cotton field management during the flowering and boll stage?

Pruning: In the Yellow River basin, for cotton fields with no more than 3000 plants per mu in dry years and no more than 2500 plants per mu in wet years, simplified pruning cultivation techniques may be used (limited to "Guoxin" brand GK-12 and 95-1); otherwise, pruning measures must be adopted. That is, at the seedling and bud stage, first remove the lower vegetative branches. As cotton grows, promptly remove redundant buds on the main stem and fruiting branches to save nutrients, reduce consumption, control excessive growth, and reduce shading in the cotton field. After August 10, remove all the middle and upper edge tips, and remove redundant buds and ineffective flower buds on fruiting branches.

Topping: Topping too early causes the upper fruiting branches to extend too long, easily shading the lower part. Topping too late prevents the upper fruiting branches from spreading out, forming small late-autumn bolls. Flexibly control topping time according to different varieties, different soil fertility, and different densities, generally in mid-to-late July, and at the latest no later than the end of July. The general principle is: top early on poor land, top late on...; top early in dry weather, top late in wet weather; top early in dense planting, top late in sparse planting; top early when there are many lower bolls, top late when lower shedding is heavy; top early in early-developing cotton fields, top late in late-developing cotton fields. Strengthen pest forecasting and timely prevent and control pests and diseases. The main pests of insect-resistant cotton during the boll stage include mirids; in dry weather red spider mites are rampant, so pest forecasting must be strengthened, prevention and control carried out early, and pests eliminated at the egg and larval stages. Water reasonably. If dry at the initial flowering stage, water lightly; if dry at the full flowering stage, water heavily; be sure to water fully in case of summer drought and drain promptly in case of waterlogging. Pay attention to flowering and boll fertilizer. "Guoxin" brand GK-12 buds, flowers, and sets bolls early and concentratedly, so fertilizer should be applied early and combined with watering to promote vigorous growth during the flowering and boll stage. It has strong staying power, so prevent premature senescence. For cotton fields with general fertility, begin topdressing at the initial flowering stage; for cotton fields with sufficient fertility, topdress when 1-2 bolls have set in the lower part. For general fertility, apply 20-30 jin of nitrogen fertilizer per mu. Insect-resistant cotton has a high demand for potassium fertilizer. If staying power is insufficient, use 2-4 liang of potassium dihydrogen phosphate per mu mixed with 1.5% urea solution for multiple foliar sprays (5 days apart). Rationalize chemical regulation. In wet years, for vigorously growing cotton fields, use 3-4 grams of mepiquat chloride original powder at one time, mixed with 60-80 jin of water, and spray on the leaves; in dry years, reduce the amount as appropriate.

6. Which cotton fields need remedial measures?

For cotton fields with high density, such as more than 3000 plants (Yellow River basin), no-pruning cultivation techniques cannot be used, and pruning must be carried out in time. For cotton fields with severe shedding in the middle and lower parts due to improper mid-season management or excessive water and fertilizer causing vigorous growth, water and fertilizer should be appropriately controlled, topdressing time postponed, and the amount of topdressing reduced.