Drip irrigation
Cotton is an important economic crop with a growth period of 5 to 6 months (depending on the variety). Cotton prefers warmth and sunlight, with an optimal temperature range of 25–30 °C and a daily optimal sunlight duration of 12 hours. It is quite sensitive to moisture, and its yield and quality are closely related to irrigation. Proper cotton irrigation management can optimize cotton growth, ensuring high yield and the formation of high-quality cotton fibers.
Cotton can be irrigated using drip or sprinkler irrigation methods, but it is more recommended to use drip irrigation for precise irrigation. Unlike sprinkler irrigation systems, drip irrigation waters the plant roots rather than the plant canopy, so humidity levels are not affected. Sprinkler irrigation can cause moisture to be distributed over the entire plant, including the cotton boll, which may lead to the surface of the cotton boll becoming wet, increasing the possibility of boll rot and affecting fiber quality. Compared to traditional furrow irrigation and overhead sprinkler irrigation, drip irrigation can increase cotton yield per cubic meter of water by 20% under different agro-ecological conditions without reducing cotton quality.
| Growth Stage | Emergence Stage | Seedling to Bud Stage | Bud to Flowering Stage | Flowering and Boll Stage | Boll Opening Stage |
|---|---|---|---|---|---|
| Irrigation Rate | 2–4 mm/day | 4–6 mm/day | 6–8 mm/day | 8–10 mm/day | 4–6 mm/day |
| Irrigation Frequency | Usually irrigate once a week, depending on soil moisture | 1–2 times per week | Twice a week | 1–2 times per week | Once a week or stop irrigation |
| Irrigation Method | Sprinkler or drip irrigation. The irrigation amount at this stage is relatively small, aiming to keep the soil moist, promote smooth seed germination, and healthy seedling growth. |
Sprinkler or drip irrigation. At this stage, the root system of cotton gradually develops, and the water demand increases. Moderate irrigation can promote robust growth of the cotton plants. |
Sprinkler or drip irrigation. This is a critical period for cotton's water demand. Adequate irrigation helps prevent bud and boll shedding, ensuring flowering and fruit development. |
Drip irrigation. This is the stage with the highest water demand for cotton. Deep irrigation can meet the needs of cotton boll expansion and fiber development, ensuring yield and quality. |
Neither irrigation nor drip irrigation. The water demand for cotton gradually decreases, and excessive irrigation may affect cotton quality. It is necessary to reduce or even stop irrigation. |
Drip irrigation
Sprinkler irrigation
Suitable soil conditions are very important for cotton growth. Cotton prefers deep soil layers, fertile, and loose-textured soil. The optimal soil temperature is generally 18–25 °C, with soil moisture content at 60%–70% of field capacity, and a suitable soil pH value of 6.5–8.5.
The required amounts of nitrogen, phosphorus, and potassium vary with different cotton yields. Generally, for every 100 kilograms of lint cotton produced, about 12–18 kilograms of nitrogen, 4–6 kilograms of phosphorus pentoxide, and 12–16 kilograms of potassium oxide are absorbed, with an N:P2O5:K2O≈ 100:33:100 ratio. As the yield increases, the required amount of fertilizer tends to decrease. Therefore, increasing yield is not solely dependent on fertilizer factors, but is the result of the combined effects of various cultivation measures.
During different growth stages, the amount of nitrogen, phosphorus, and potassium absorbed by cotton also varies. Cotton's absorption of nitrogen accounts for about 5% of the total nitrogen absorption during the entire growth period from emergence to the budding stage, about 10% from the budding to flowering stage, and the most during the flowering stage, accounting for about 55%. The absorption of phosphorus and potassium is characterized by less in the early stage and more in the middle and late stages, with the absorption after flowering accounting for about 70% and 80% of the total growth period, respectively.
