Regulated Deficit Irrigation for Transplanted Cotton after Winter Wheat Harvest

Abstract

【Background】 The Yellow River basin is one of the most important grain and cotton production bases in China, with wheat-cotton rotation as one of the dominant cultivation methods in which inter-wheat rows are reserved for cotton drilling. Such cultivation, however, reduces wheat yield and damages the cotton seedlings when harvesting the wheat. As an improved agronomic practice, transplanting the cotton after wheat harvest rather than directly drilling it has become increasingly popular due to its convenience for machine harvesting without compromising cotton yield. The transplantation reduces the growth duration of the cotton in the field and makes it more sensitive to soil moisture. Regulating water deficit is hence particularly important for transplanted cotton. 【Objective】 This paper is to experimentally seek suitable regulated deficit irrigation for transplanted cottons in Yellow river basin. 【Method】 The experiment was conducted in a field with different water deficits imposed at bud stage, or blossoming and boll-forming stage, respectively. In each treatment, we measured the growth, yield and quality, and water utilization efficiency of the cotton. 【Result】 Moderate or severe water deficit, especially that occurring at the bud stage, inhibited growth of the height and stem diameter of the cotton, while a slight water deficit occurring at either stage did not show significant effects on cotton growth and development. Relative water content in cotton leaves decreased with degree of the water deficit, and a slight water deficiency at the bud or boll stage enhanced accumulation of above-ground dry matter. Compared with control without water deficit, a moderate water deficit at the bud or blooming stage saved irrigation water by 5.45% and 9.09% respectively, increased cotton production by 9.16% and 2.34% respectively, and improved irrigation water use efficiency by 15.05% and 12.90% respectively. Regulated deficit irrigation did not show a noticeable impact on macron value and elongation of the cotton. A moderate water deficit at the bud or boll stage, or a slight water deficit at the bud or blossoming and boll-forming stage, improved length, uniformity and fracture specific strength of the cotton fiber. 【Conclusion】 When water supply is seriously scarce, imposing a slight water deficit at the bud stage gives the highest cotton-seed yield and irrigation water use efficiency. In contrast, when available water for irrigation is limited, sufficient irrigation at the bud stage coupled with a moderate water deficit at the flowering and boll stage is most effective for saving water while in the meantime improving water utilization efficiency and maintaining high cotton yield.

Keywords

• cotton transplanting
• drip irrigation
• cotton yield
• fiber quality
• wheat-cotton rotation
• irrigation water utilization efficiency