Fertilizing Cotton by Seedling Condition During the Flower and Boll Stage Requires Careful Judgment

In June, after cotton in the Hubei cotton region enters the squaring stage, plum rains occur frequently, and combined with differences in field management, cotton growth progress is uneven. For earlier-developing cotton, a single plant has already set 1 to 2 mature bolls, while later-developing cotton has just begun to square, with a growth progress difference of 20 to 30 days. Therefore, different measures should be adopted in cotton fertilization management.

From the field survey of cotton seedling conditions, among Wang Hua's 26 mu of cotton in Team 5, Nihu Brigade, Diaodong Farm, Hanchuan City, the leaves on half the area showed an obvious deficiency of potassium fertilizer, and he was advised to supplement potassium fertilizer immediately. Xiao Qihua's 40 mu of cotton in Group 8, Sujiapu Village, Taodian Township, Huangzhou District had generally begun flowering and was growing steadily; he had originally planned to apply ammonium bicarbonate and phosphate fertilizer, but we advised him to switch to a high-content compound fertilizer and apply it together with potassium fertilizer. Zhang Xiangbing's nearly 20 mu of cotton field in Group 1, Qunfeng Village, Zhuru Town, Caidian District was generally deficient in potassium and nitrogen, with boron deficiency also very prominent; we required him to quickly apply nitrogen and potassium fertilizers deeply and spray boron fertilizer.

The flower and boll stage is the key period when cotton gradually shifts from vegetative growth to reproductive growth, and it is also the peak boll-setting period that cotton is about to enter. Based on many years of cotton growth patterns, the concentrated boll-setting period for cotton is from late July to early August. This period is the golden period for cotton boll setting and also the period of greatest fertilizer demand for cotton, but for different cotton fields specifically, it must vary according to the seedlings.

For cotton in the full flowering stage, because vegetative growth is still proceeding alongside reproductive growth, a biased application of nitrogen fertilizer at this time will cause cotton to grow excessively and then run wild, not only intensifying bud and boll shedding but also triggering premature senescence. After running wild, the cotton field becomes too shaded, with high humidity, no ventilation or light penetration, and the lower cotton bolls are extremely prone to mildew and rot, ultimately causing reduced cotton yield. Therefore, for some cotton that has entered the flowering stage, compound fertilizer should be the main application, applying 15 to 20 kg of high-content compound fertilizer per mu, or applying a small amount of urea together with phosphate and potassium fertilizers. In particular, farmers who choose insect-resistant cotton varieties should apply more potassium fertilizer, with no less than 15 kg of potassium fertilizer per mu. Flowering-stage fertilizer should be applied deeply with intensity, and soil should be hilled up to form ridges.

For cotton that has already set bolls, boll fertilizer should be applied. In places with a relatively large area of hybrid insect-resistant cotton, boll fertilizer should be applied 2 times. When a single cotton plant has an average of 2 to 3 mature bolls, about 15 kg of urea should be applied per mu. When a single plant has an average of about 10 mature bolls, about 15 kg of urea should be applied again. When cotton has set many bolls, there is no need to worry about excessive growth from applying urea, because after cotton sets bolls, the direction of nutrient transport has shifted from the vegetative organs of branches and leaves to the cotton bolls. Timely supply of sufficient nutrients can not only increase boll weight and seed index weight but also improve quality. However, the application period of boll fertilizer must not be too late; applying it too late will only cause delayed greenness and late maturity.