When there is a lot of rain, prevent the cotton from drying up
Changzhou Ziying Metal Products Co., Ltd , https://www.ziyingmetal.com
In 2008, the Hubei Jianghan Plain experienced a sudden and heavy rainfall in mid to late August, which led to an early withering phenomenon in some cotton fields. This resulted in a significant drop in cotton production. According to surveys conducted by the author and relevant experts, approximately 30% to 40% of the cotton fields suffered from this issue, with varying degrees of damage. On average, the seedling death rate reached 35.9%, and in severe cases, it exceeded 70%. Some plants recovered after the rain but still experienced major yield losses. A typical household survey revealed that even those cotton fields that were heavily affected showed signs of short-term recovery, yet their output reduction was generally between 30% and 50%, with some cases exceeding 70%. To prevent similar issues from occurring in our province, we now present a detailed analysis of the situation.
I. Symptoms of Early Withering
Two heavy rain events occurred on August 15–16 and August 28 last year, with total rainfall exceeding 150 millimeters. After the rains, some cotton fields exhibited partial wilting of entire plants. By the end of the day, these plants turned brown and eventually died. Some cotton plants wilted from top to bottom, while others gradually died or partially recovered but still suffered from significant yield reductions. In addition, some plants developed blue discoloration and dryness after wilting.
II. Relationship Between Early Withering and Related Factors
1. Variety Influence: According to an investigation of 54 local cotton varieties at the Qianjiang Experimental Station of Guoxin Cotton Research Institute, the average seedling death rate after the rain was 39.5%. Among them, 9 varieties had less than 10% mortality (16.6%), 15 varieties had 10–30% mortality (27.8%), 23 varieties had over 70% mortality (42.6%), and 7 varieties had more than 70% mortality (12.9%). Under the same conditions, there were significant differences among varieties. Generally, varieties with fewer bolls and longer growth periods had lighter damage, while those with more bolls and pods had heavier losses. Varieties with strong resistance to yellowing and wilting also showed less damage.
2. Terrain Influence: Surveys indicated that areas with high groundwater levels (less than 1 meter) and poor drainage had more severe cases of early withering.
3. Fertilization Influence: Most farmers applied topdressing during the flowering period, usually between July 15 and 20, using 20–25 kg of urea per mu. This practice was not significantly related to the occurrence of early withering. However, insufficient fertilization and weak sandy soils led to heavier losses. Some farmers applied topdressing too late or in excessive amounts, which also caused serious damage. Additionally, potassium deficiency in the fields contributed to higher rates of early death.
III. Causes of Early Withering
Experts concluded that the sudden rainstorms caused premature aging of cotton seedlings, leading to early withering. Susceptible varieties, early-maturing types, and those with more bolls were more vulnerable. High groundwater levels and poor drainage were key factors. Urea-based topdressing, when not fully dissolved before heavy rain, caused localized nutrient concentration, which prevented cotton from absorbing nutrients and led to withering. Some plants could recover, but potassium deficiency often caused yellow or red leaf blight. These symptoms typically started at the leaf margins and spread inward, resembling yellow wilt but without stem discoloration upon cutting.
IV. Prevention and Remediation Measures for Early Withering
1. Use disease-resistant and anti-mite varieties. This is the foundation for preventing early withering. Choose varieties suited to local conditions. For longer-growing varieties, transplant early to avoid peak rain seasons. Select early-maturing varieties for wheat and rapeseed planting to prevent late ripening from affecting yields.
2. Improve drainage systems. Fields with good drainage showed lighter damage. Especially in areas with high groundwater levels, proper ditch digging ensures smooth drainage after rain.
3. Implement effective management practices to delay root aging. The root development peak occurs during the bud stage to early flowering. After blooming, focus on root cultivation and delay root senescence. Avoid intensive cultivation post-flowering, and apply topdressing in small, spaced amounts. If large amounts are needed, apply after rain or irrigation. Apply two rounds of fertilizer in high-yield fields: once during the first bloom and again when bolls are full. Avoid applying fertilizer too close to the roots, and place it deeper in the furrow. In late July to early August, apply 5–7.5 kg per mu of fertilizer. Spray foliar fertilizer every seven days using a 2% compound fertilizer solution.
4. Increase potassium application. If potassium is lacking, supplement it through flower and boll fertilizers. After entering potassium-deficient stages in August, spray 0.3% potassium dihydrogen phosphate every seven days.
5. Post-occurrence recovery and management. After early withering occurs, take appropriate measures based on severity and causes. First, drain excess water to reduce waterlogging. For mild cases, remove dead plants, improve air circulation, and perform shallow soil loosening. Reduce field humidity and restore normal growth as soon as possible. For fertilizer-related damage, water the field to dilute nutrient concentration and promote healthy plant growth.