Agriculture is one of the most important environmental factors influencing the growth and development of plants, especially in the arid and semi-arid regions of Iran. However, due to the rising cost of water consumption and the decreasing availability of water in these areas, considerable attention has been paid to water scarcity stress and its effects on plants. This highlights the necessity of managing water resources with a comprehensive and precise approach. Therefore, this study aimed to investigate the effects of surface and subsurface irrigation methods at different irrigation levels (100%, 90%, and 80%) on potato yield, land productivity, and water use efficiency at the research station of the South Kerman Agricultural Research Center in Jiroft.

Keywords: ELP, Water Productivity, Water needs, Under-irrigation

Introduction
Considering the shortage of water resources in the country, the high water requirement of potato plants, and the climatic conditions of Jiroft — located in one of the arid regions of Iran — planning for the optimal use of water resources in this area is both necessary and inevitable. Furthermore, due to the limited number of studies on subsurface drip irrigation in potato cultivation in Iran, the implementation of appropriate irrigation systems, along with targeted planning, can contribute significantly to sustainable agriculture. Therefore, this study was conducted to evaluate potato cultivation under different irrigation methods and levels in the climatic conditions of Jiroft. The results of this research can serve as a useful reference for future irrigation planning and design.

.Methodology
Considering the shortage of water resources in the country, the high water requirement of potato plants, and the climatic conditions of Jiroft — located in one of the arid regions of Iran — planning for the optimal use of water resources in this area is both necessary and inevitable. Furthermore, due to the limited number of studies on subsurface drip irrigation in potato cultivation in Iran, the implementation of appropriate irrigation systems, along with targeted planning, can contribute significantly to sustainable agriculture. Therefore, this study was conducted to evaluate potato cultivation under different irrigation methods and levels in the climatic conditions of Jiroft. The results of this research can serve as a useful reference for future irrigation planning and design.
.Results and Discussion
The study of the effect of irrigation levels on yield showed that reducing the irrigation level by up to 10% compared to the optimal level did not lead to a significant decrease in yield. However, a 20% reduction resulted in a statistically significant decline, consistent with the findings of Mousavi Fazl and Akhyani (2020), Ebrahimi Pak and Pezra (2008), Niu et al. (2024), and Hassan et al. (2002), which confirmed the negative impact of deficit irrigation on yield. Based on the analysis of variance in the study of irrigation levels on water use efficiency, there was no significant difference between the full irrigation treatment (100%) and the 90% treatment. However, both of these levels were significantly different from the 80% treatment. Therefore, 90% irrigation was identified as the optimal level for maximizing water use efficiency. At this level, 354.2 cubic meters of water per hectare were saved. The findings of Afshar et al. (2011) also support this conclusion; in their study on different irrigation levels in potato cultivation, full irrigation (100%) decreased water use efficiency, while 75% irrigation increased it.These results suggest that reducing irrigation to approximately 90% of the crop water requirement improves water use efficiency without significantly compromising yield. This irrigation level not only ensures efficient water use but also maintains high yield levels. Furthermore, other studies such as Lamm et al. (2005) and Wang et al. (2018) have demonstrated that subsurface irrigation methods can significantly enhance water use efficiency compared to surface irrigation.
Conclusion
Overall, the results indicated that both the individual and interactive effects of irrigation level and irrigation method were significant for crop yield, water use efficiency, and the land value index. The highest yield and land value index were observed at the 90% irrigation level with subsurface irrigation, while the lowest values for these parameters occurred under 80% irrigation with subsurface irrigation. Therefore, it is recommended that farmers adopt a 90% irrigation level in combination with efficient subsurface irrigation systems to achieve optimal water use efficiency and crop performance.