Journal of Agronomy and Field Innovations

Background: The reduction in freshwater supply, the increasing need for irrigation in agriculture, and the unpredictable amount of rainfall combine in jeopardizing the sustainability of irrigated cotton (Gossypium hirsutum L.) cultivation in dry agricultural conditions. Regulated deficit irrigation (RDI) is a technique whereby water supply is deliberately reduced to below full crop evapotranspiration (ETc) levels for specific periods.
Objective: This work explored the effect of four irrigation systems (100%, 80%, 60% and 40% ETc) on cotton cultivation (Gossypium hirsutum L.) in terms of growth, yield, as well as the water usability and productivity.
Methods: The experiment was carried out over one growing season in line with a randomized complete block design that had three replications. According to cumulative pan evaporation, ETc estimates produced the irrigation schedule. The irrigation regime was imposed during squaring, flowering, boll formation, and beyond, while the irrigation level remained the same in all cases. Data about cotton production and phenology was collected and analyzed.
Results: Full irrigation (100% ETc) results in the highest level of plant height, leaf area index, and seed cotton yield amounting to 2864 kg ha⁻¹, however, with the lowest water productivity of 0.47 kg m⁻³. Mild deficit irrigation (80% ETc) performs at a yield level similar to that provided by full irrigation with a lower amount of water used (20% less) and higher water productivity (0.55 kg m⁻³). With a moderate deficit irrigation (60% ETc), the highest water productivity index is attained (0.65 kg m⁻³) with a decrease in yield by 17%. Severe deficit irrigation (40% ETc) gives rise to significant yield reduction (36%) in spite of the highest water productivity achieved. 
Conclusion: Mild-to-moderate regulated deficit irrigation applied depending on 80% ETc may be regarded as a feasible and water-efficient option for cotton production. Mild and moderate regulated deficit irrigation will improve irrigation water productivity without any adverse consequences for yield levels.