Document Type : Research Paper
Authors
1
Professor, Department of Soil Science, College of Agriculture, Vali-e-Asr University of Rafsanjan University, Iran.
2
MSc Graduated, Department of Soil Science, College of Agriculture.Vali-e-Asr University of Rafsanjan. Iran.
3
Assistant prof., of Irrigation and Drainage, Pistachio Research Center, Horticultural Sciences Research Institute, Agriculture Research Education and Extension Organization (AREEO), Rafsanjan, Iran.
4
Associate prof., of Soil Science, Pistachio Research Center, Horticultural Sciences Research Institute, Agriculture Research Education and Extension Organization (AREEO), Rafsanjan, Iran.
5
Assistant prof., of Soil Science, Pistachio Research Center, Horticultural Sciences Research Institute, Agriculture Research Education and Extension Organization (AREEO), Rafsanjan, Iran.
Abstract
This study evaluated the performance of a low-pressure subsurface irrigation system using perforated PVC pipes in pistachio orchards of Anar County (Kerman Province), focusing on soil moisture and salinity distribution. The HYDRUS-2D numerical model was applied to simulate two-dimensional water and solute movement in the soil. Treatments were based on a factorial combination of four design parameters, each at two levels: channel depth (40 and 60 cm), pipe diameter (110 and 160 mm), hole spacing on perforated PVC pipes (15 and 25 cm), and hole diameter (9 and 12 mm). Model evaluation based on the NRMSE index confirmed the HYDRUS-2D model's strong ability to simulate both moisture and solute distribution in the system. Simulation results revealed that treatments with 60 cm channel depth, 110 mm pipe diameter, 9 mm hole diameter, and 15 or 25 cm hole spacing (T15 and T16) achieved the most favorable salinity distribution by reducing salt accumulation in the root zone. Furthermore, treatments with 160 mm pipe diameter, 12 mm hole diameter, 60 cm channel depth, and 15 or 25 cm hole spacing on perforated PVC pipes (T9 and T10) showed superior moisture distribution compared to other treatments. These configurations provided the best overall performance in terms of moisture and salinity distribution under subsurface irrigation using perforated PVC pipes. In contrast, treatment T4 (40 cm channel depth, 160 mm pipe diameter, 9 mm hole diameter, 25 cm hole spacing) demonstrated the poorest performance regarding uniform water distribution and salinity control. Based on these findings, it is recommended that subsurface irrigation systems for pistachio orchards adopt the identified optimal design parameters, tailored to local soil and environmental conditions.
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