Sprinkler Irrigation System Performance in Winter Wheat Fields: A Comprehensive Study

A solid set sprinkler irrigation system with portable sprinklers was evaluated in a cluster of winter wheat fields in a semiarid area in the south of Iran. Irrigation performance indicators, including coefficient of uniformity (CU), distribution uniformity (DU), application efficiency (AE), potential application efficiency of the lower quarter (PELQ), application efficiency of the lower quarter (AELQ), deep percolation (DP), wind drift and evaporation losses (WDEL), and irrigation adequacy (ADirr) were analyzed in six irrigation events over three fields. Crop water productivity (WP) and final grain yield (GY) were also analyzed to assess the irrigation system efficiency. The results showed that in most irrigation events, the values of CU, DU, AE, PELQ, and AELQ were lower than 81%, 70%, 75%, 65%, and 65%, respectively, as the minimum recommended values in the literature. Furthermore, the ADirr values were between 0% and 80% in the irrigation events. The performance of different irrigation scheduling methods, including NETWAT software (known as the national reference method for irrigation scheduling), Penman–Monteith and Kc, Penman–Monteith and measured Kc, and calibrated Penman–Monteith and Kc were investigated based on monitoring the soil moisture deficit (SMD). Analysis showed that NETWAT estimated the lowest evapotranspiration for all of the wheat growth stages, which indicates an improper choice of irrigation scheduling method. This means that NETWAT highly underestimated the crop water requirement and resulted in a high soil water deficit, whereas the Penman–Monteith and measured Kc had the best match with the SMD. Moreover, in different fields, GY and WP varied between 2.7 and 3.55 Mg ha−1, and 0.36 and 0.48 kg m−3, respectively. Our detailed analysis revealed that the main reasons for the inefficient performance of the irrigation system were primarily related to the irrigation system design, scheduling, and setup. Therefore, accountability for the outdated design and subsequent system failure can be attributed to the irrigation system designer(s), the public agricultural agency responsible for approving the system design, and the scientific representative(s) responsible for the irrigation system. This study underscores the detrimental impact of inadequate management and design on the modern irrigation systems, highlighting their potential to reduce crop yields and water productivity significantly.