Pouria Shirian, Mohammad Mahdi Matinzadeh, Mohammad Shayannejad, Mahdi Gheisari,
Volume 30, Issue 3 (10-2026)
In many Iranian agricultural farms, center-pivot sprinkler irrigation is widely used as a modern irrigation method. However, improper design, installation, or operation of these systems can reduce their actual irrigation efficiency. Consequently, non-uniform water distribution along the lateral may occur, resulting in localized waterlogging or runoff. These conditions can adversely affect plant growth and alter nitrate distribution and salinity levels in the soil. Two existing center pivot irrigation systems were evaluated at the farm of Qiam Agricultural and Industrial Company in Isfahan. In this evaluation, the average indices of the Christian-Sen uniformity coefficient CU (C), the distribution uniformity coefficient DU, the Hayman and Hein uniformity coefficient CU (H), the potential efficiency of application in the lower quadrant PELQ, and the actual efficiency of application in the lower quadrant AELQ for the two irrigation machines were calculated to be 67%, 57%, 65%, 45%, and 54%, respectively. Comparison of the results with the acceptable ranges for these indices showed that the two systems did not achieve acceptable irrigation efficiency. The results of the study also showed that the volume of water discharged from the different spans varied, with the highest and lowest volumes of discharged water observed in the first and last spans, respectively. Therefore, due to the non-uniform distribution of water across the spans in the studied center-pivot irrigation system, soil samples were collected from beneath different spans to investigate residual soil nitrate concentrations, the salinity of the saturated soil extract, and rapeseed yield. A completely randomized block design was used to compare their means. The results showed that the first span with higher water intake had the highest canola dry weight (1.19 kg/m2), the lowest saturated soil extract salinity (1.67 dS/m), and the lowest residual nitrate in the soil (4.93 mg/kg). The last span with lower water intake had the lowest canola dry weight (0.44 kg/m2), the highest saturated soil extract salinity (3.33 dS/m), and the lowest residual nitrate in the soil (2.203 mg/kg). There was a significant difference at the 1% level between the parameters in different spans. Therefore, it is recommended to use accurate, real-time management tools suited to the crop and climatic conditions of the region to achieve more uniform crop performance across all spans of the center-pivot irrigation system.
