How to Control Weeds in Cotton Fields? A Detailed Guide to Practical Methods
How to control weeds in cotton fields? Please provide methods. When growing cotton, you can refer to the following methods for weed control: (1) Types and occurrence characteristics of cotton field weeds. China is one of the world's major cotton-producing countries, with Shandong, Hebei, Henan, Jiangsu, Hubei, Xinjiang, and Anhui among the main cotton regions. Cotton field weeds mainly include 2...
How to control weeds in cotton fields? Please provide methods.
When growing cotton, you can refer to the following methods for weed control:
(1) Types and occurrence characteristics of cotton field weeds
China is one of the world's major cotton-producing countries, with Shandong, Hebei, Henan, Jiangsu, Hubei, Xinjiang, and Anhui among the main cotton regions. Cotton field weeds mainly belong to 24 families and about 60 species. Among grass weeds, the highest densities are found in large crabgrass, goosegrass, Chinese sprangletop, barnyardgrass, green foxtail, jointed signalgrass, and Bermuda grass; broadleaf weeds are mainly false daisy, redroot pigweed, mugwort, oakleaf goosefoot, Asian copperleaf, and velvetleaf; among sedge family weeds, purple nutsedge is the main one.
Weed damage is an important problem in cotton production. According to sampling surveys by the National Farmland Weed Survey Group, moderate or worse weed damage in cotton fields nationwide affects 47 million mu, accounting for 56% of the total cotton planting area. In the Yangtze River Basin, Yellow River Basin, and Northwest Inland cotton regions, weed-infested cotton field areas account for 82.7%, 75.2%, and 81.0% of the planting area respectively, with moderate or worse damage areas at 61.7%, 50.0%, and 44.0%. Nationwide, weed damage causes a 14.8% loss in cotton, reducing lint cotton output by about 255,000 t. Some weeds are also hosts for cotton diseases and pests, and the occurrence of weeds can increase damage from diseases and pests.
The extent of yield loss caused by weed damage to cotton is closely related to the type and density of weeds. When weed type and density remain relatively constant, the degree of yield reduction from weed damage is also closely related to the length of coexistence with weeds and the different growth stages during coexistence. According to test results from Xinyang Farm in Jiangsu Province, weeds strongly inhibit cotton growth and development, and the damage intensifies with longer coexistence time. Cotton without weed control treatment from sowing to June 15 had 19.7% fewer leaves and 33.9% greater plant height than treated cotton, forming thin, tall, spindly seedlings, and weed control at this point also caused serious yield reduction; cotton without weed control from sowing to August 25 was 66% shorter, had 40.8% fewer leaves, 85.7% fewer fruiting branches, and 94.2% fewer fruiting nodes than treated cotton, rarely flowering or setting bolls, and even some cotton plants died after being shaded by weeds, resulting in severe yield reduction or total crop failure.
In the Yellow River Basin cotton region, as cotton is sown and temperatures rise, various weeds in cotton fields begin to sprout one after another, forming the first emergence peak in the field by late May, dominated by green foxtail, large crabgrass, barnyardgrass, and lambsquarters; afterward, with rainfall and irrigation, a smaller weed emergence peak may occur; by July, as the rainy season arrives, weeds such as purple nutsedge emerge in large numbers, forming a second weed emergence peak. At the same time, weeds that emerged earlier enter their period of most vigorous growth, making severe damage to cotton likely.
For plastic-film-mulched cotton fields, because the soil temperature in the tillage layer is higher after mulching, the subsoil moisture is relatively good, and conditions change little, weed germination and emergence are relatively favored. Generally, weeds begin to emerge successively 5-7 days after mulching, and under good moisture conditions, an emergence peak forms in about 15 days. Although the time for the emergence peak to form may be long or short, the characteristic is that weeds emerge early and concentrated.
(2) Cotton weed control strategies
1. Control of weeds in cotton seedbeds
In cotton seedbeds, the main weeds are large crabgrass, green foxtail, goosegrass, lambsquarters, and redroot pigweed. These weeds are relatively easy to control. In production, amide herbicides, dinitroaniline herbicides, oxyfluorfen, oxadiazon, and other herbicides can be used.
Apply after sowing and before mulching, diluted with water and sprayed on the soil surface. You can use 50% acetochlor emulsifiable concentrate 50-75 ml/mu, or 72% metolachlor emulsifiable concentrate 75-100 ml/mu, or 72% pretilachlor emulsifiable concentrate 75-100 ml/mu, or 33% pendimethalin emulsifiable concentrate 75-100 ml/mu, or 50% acetochlor emulsifiable concentrate 50 ml/mu + 24% oxyfluorfen emulsifiable concentrate 10 ml/mu, or 12% oxadiazon emulsifiable concentrate 100 ml/mu, diluted with 50-80 kg/mu of water and sprayed on the soil surface. During the cotton seedling stage, low temperature, excessive moisture, water accumulation in the seedbed, or excessive herbicide dosage can easily cause herbicide injury. The symptoms of herbicide injury are leaf wrinkling. After cotton grows to 3 compound leaves, when temperatures rise, normal growth can resume, with basically no effect on cotton seedlings.
2. Control of weeds during the cotton growth period
For most cotton fields, large crabgrass and green foxtail cause severe damage and make up the vast majority of weeds. When weeds have basically all emerged and are at the seedling stage, apply herbicide promptly. Specific agents are as follows: 5% quizalofop-p-ethyl emulsifiable concentrate 50-75 ml/mu, or 10.5% haloxyfop-R-methyl emulsifiable concentrate 20-40 ml/mu, or 12.5% sethoxydim emulsifiable concentrate 50-75 ml/mu, or 24% clethodim emulsifiable concentrate 20-40 ml/mu. When applying, determine the dosage according to weed condition and soil moisture. When weeds are large and moisture is poor, appropriately increase the dosage. Dilute with 30 kg/mu of water and spray evenly.
For certain cotton fields, because cultivation management cannot keep up in the middle and late stages of cotton production, more weeds occur in the field. When cotton has reached a certain height, non-selective herbicides can be applied for control. You can use 20% paraquat aqueous solution 200-300 ml/mu; when applying, add 40 kg of water to prepare the solution and spray directionally between cotton rows. After cotton squaring and when plant height is above 60 cm, apply directionally between cotton rows. After cotton squaring and when plant height is above 60 cm, at the 4-leaf stage of weeds, use 10% glyphosate aqueous solution 200-250 ml/mu; when weeds are above 6 leaves, use 400-600 ml/mu. When applying, add 40 kg of water to prepare the solution and spray directionally between cotton rows. During operation, a protective shield should be added to the nozzle, and the nozzle should be kept low to prevent the solution from contacting cotton young buds or leaves. Rain within 4 hours after application does not affect efficacy.
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