Effect of limited drip irrigation regime on yield, yield components, and fiber quality of cotton under Mediterranean conditions

Limited irrigation regime, known as deficit irrigation, is a common practice to cope with limited water availability. A two-year field experiment was conducted in order to determine the effect of limited irrigation regime on the growth, yield and fiber quality traits of cotton crop (Gossypium hirsutum L.). The experiment was set up as a split plot design with four replicates, two main plots (irrigation treatments) and two sub-plots (cotton cultivars). Plant water status, expressed in terms of the water potential index (WPI), growth in leaf area and biomass weight, seed yield, boll number, boll weight and fiber quality parameters were measured throughout the growing seasons. The adopted irrigation schemes produced a clear differentiation among cultivars concerning their plant water status. Water shortage resulted in more negative leaf water potential and water potential index and lower leaf area index and biomass values. Seed cotton yield and boll numbers per plant were positively affected by increased irrigation amounts while mean boll weight was less affected by irrigation levels. In particular, deficit irrigation resulted in 23% and 38% decreases in LAI, 29% and 27% in biomass, 16% and 28% in seed yield and 25% in boll numbers for Julia and Zoi, respectively, compared to the well-watered treatments. Fiber length was shortened in response to water stress while fiber strength, fineness and uniformity index were not consistently affected by irrigation levels. Negative linear functions of all parameters, with the exception of mean boll weight and lint percentage, against WPI values revealed significant differences in Y-intercepts and regression slopes between the two cultivars, indicating greater adaptability for ‘Julia’ in water stress conditions. In general, use of limited drip irrigation regime with 50% of water requirement had significant benefits in terms of saved irrigation water although it leads to a moderate decrease in yield without significant negative impact on the fiber quality parameters.