Detailed Q&A on Cotton Squaring Stage Management Techniques

1. What is the squaring stage?

Answer: When triangular flower buds the size of buckwheat grains appear on the first fruiting branch of the cotton plant, it is called squaring. When 50% of the cotton plants in the field have squared, it is called the squaring stage; when 50% of the cotton plants have squares on the fourth fruiting branch, it is called the peak squaring stage. The squaring stage generally lasts between 25-30 days. The saying "twenty-eight (days) from square to flower" refers to the squaring stage. Depending on cultivation methods and temperatures, the squaring stage varies slightly. In areas north of the Yellow River, the squaring stage generally runs from early June to early July.

2. Why should attention be paid to squaring stage management?

Answer: This stage is a period when vegetative growth and reproductive growth advance simultaneously. Cotton is relatively sensitive to water and fertilizer. If water and fertilizer are insufficient, especially nitrogen fertilizer, it will cause poor vegetative growth and less dry matter accumulated through photosynthesis. The result is small plants, few squares, an inability to build a high-yield framework, and premature senescence leading to reduced yield. If water and fertilizer are excessive, especially too much nitrogen, vegetative growth will be excessive, and a large amount of dry matter accumulated through photosynthesis will be consumed by vegetative growth, causing the cotton plants to grow wildly and a large number of squares and bolls to shed. Therefore, during this period, the plants need both to grow out and to grow steadily. It is the key period for building a good high-yield framework.

3. How can the appearance and growth trend of high-yield cotton be judged?

Answer: (1) The appearance of high-yield cotton is: "roots deeply penetrating and leaves oily green, thick stalks with short internodes and steady plant growth, flat and even tops with plump buds, many and large squares with little shedding." The growth trend of high-yield cotton is: in northern regions, the daily increase in plant height from squaring to peak squaring is between 1-1.5 cm, and the daily increase in plant height from peak squaring to early flowering is between 1.5-2.5 cm.

2 The appearance of excessively vigorous cotton growth is: "thick stalks with slender branches and long internodes, 3 slender petioles and large leaves, 4 sunken growing point and tall stems and leaves, 5 small and lean squares with severe shedding." The growth trend of excessively vigorous cotton growth is: in northern regions, the daily increase in plant height from squaring to peak squaring exceeds 2 cm, 6 and the daily increase in plant height from peak squaring to early flowering is greater than 3 cm.

7 The appearance of 8 poor cotton growth is: red and slender stems, small plant type, 9 thin and small leaves with yellow color, 10 cotton tips protruding prominently above the top, 11 few small and lean squares. The growth trend of poor 12 cotton growth is: in northern regions, the daily increase in plant height from squaring to peak squaring is less than 1 cm, 13 and the daily increase in plant height from peak squaring to early flowering is less than 2 cm.

14 What are the principles of cotton field management during the squaring stage: The most suitable temperature during the squaring stage is 26-30°C. Suitable temperatures are very favorable for rooting, plant growth, squaring and framework building. Temperatures below 19°C affect squaring; above 30°C, the terminal bud grows vigorously, 15 and vegetative growth accelerates. Therefore, 16 the principles of cotton field management during the squaring stage are: strive to coordinate the contradiction between vegetative growth and reproductive growth of cotton, 17 apply scientific management by "observing the sky, the soil, and the plant appearance," 18 and achieve "promoting the weak and controlling the vigorous."

5. What are the main measures for cotton field management during the squaring stage?

Answer: (1) For cotton fields with droughty weather, poor soil fertility, and weak cotton growth: water appropriately and apply a small amount of nitrogen fertilizer to promote the seedlings, generally 5 kg of urea per mu. Phosphate fertilizer and potassium fertilizer can also be added at the same time (depending on the situation, generally 5 kg each of diammonium phosphate, potassium sulfate, or potassium chloride per mu). (2) For cotton fields with excessively vigorous growth: control water and fertilizer and appropriately practice seedling restraint. Common methods of seedling restraint include: a) Intertillage. Intertillage can cut the lateral roots of cotton and can control the cotton plants from growing vigorously within one week. Generally, cut one side and preserve the other. For cotton fields using wide-narrow row planting with plastic film mulching, intertillage along both sides of the film is sufficient, that is, intertillage on the ridge back. b) Chemical control with mepiquat chloride. According to research results from China Agricultural University, full-process chemical control is better for cotton. Chemical control during the squaring stage can shape the plant directionally, promote roots and strengthen seedlings, reduce square shedding, and enhance resistance.

Generally, chemical control is applied twice during the squaring stage: the first time at the early squaring stage, with a dosage of about 0.3 g per mu (powder); the second time from peak squaring to early flowering, with a dosage of about 2 g per mu (powder). c) Manual pinching for seedling restraint. This method can be used where human resources are abundant. For some slender and tall seedlings, pinch the tender green part at the fourth leaf from the top with the thumb and index finger until a cracking sound is felt. Some people summarize the benefits of this method as: with one crack, it does not grow for three days; it does not grow the main stem and only grows bolls. Control tall seedlings, promote short seedlings, let tall seedlings wait for short seedlings, let short seedlings catch up with tall seedlings, so that growth is uniform, and both squaring and boll retention are ensured. (3) Do a good job in pest monitoring and forecasting, and control pests during the squaring stage such as red spider mites, aphids, corn borers, cotton bollworms, mirids, and small gray weevils as early as possible. (4) Combine intertillage with hilling. Make preparations for drainage and drought prevention. (5) Where conditions permit, cover the cotton field with 1-2 cm of chopped crop straw, which can preserve soil moisture and resist drought, resist disease, and reduce disasters.