Synthetic polymers, such as polyacrylamide (PAM), and biochar are generally used as soil amendments to improve soil properties. This paper explores a laboratory column experiment conducted to investigate the effects of biochar (pyrolysis at 400–450 °C) and polymers, with different application rates, on the hydro-physical properties of sandy soil. The experiment evaluated four rates each of biochar (0.0% (C), 2% (B1), 4% (B2), 6% (B3) and 8% (B4)) and polymers (0.0% (C), 0.2% (P1), 0.4% (P2), 0.6% (P3), and 0.8%(P4)), as well as a mixture of them. The infiltration rate decreased significantly when a mixture of biochar and polymers was adopted. B1 showed a decrease of 32.73% while a mixture of 8% (B4) and (0.8%) P4 exhibited a decrease of 57.31%. The polymers increased the infiltration rate at low concentrations (P1 and P2) and reduced it at high concentrations (P3 and P4). The cumulative evaporation decreased significantly for most treatments. B1 recorded the highest decrease in cumulative evaporation with a percentage decrease of 31.9%. The highest decrease in hydraulic conductivity (Ks) was for B1. However, the mixture of B4 and P4 resulted in the highest increase in soil moisture content at field capacity compared to the control and other treatments. P4 and the mixture of B2 and P2 showed significant (p < 0.05) increases in the percentage of stable aggregate (SA) in fraction size (0.25–0.125 mm). Although the mixture of B4 and P4 had the highest increase in soil moisture content, this study recommends using the B1 treatment on sandy soil in arid environments due to its strong hydro-physical properties and affordability.

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This study aims to evaluate the Partial Root Zone Drying Irrigation System (PRD) as one of the modern technologies that provide irrigation water and increase the efficiency of its use on potato crop. The effect of applying the PRD conventional deficit irrigation (CDI) on the efficiency and water saving in potato crops using the drip surface (S) and subsurface (SS) irrigation methods were investigated. SALTMED model used to predict soil moisture and salinity distribution, soil nitrogen dynamics, and yield of potato crop using the different irrigation levels (150%, 100%, and 50% of Crop evapotranspiration (ETc)). The study showed that the water use efficiency (WUE) decreases with increasing levels of irrigation water, as it ranged between 2.96 and 8.38 kgm−3, 2.77 and 7.01 kgm−3 for surface irrigation PRD and CDI, respectively, when the amounts of irrigation water varied from 308 mm to 1174 mm, respectively. The study showed that the irrigation efficiencies were the highest when using PRD system in all treatments when irrigating the potato crop during the spring season, and it was more efficient in the case of using subsurface irrigation method. The results show that the soil moisture (SM) was high in 25–45 cm at 150% of ETc was 0.166 and 0.263 m3m−3 for the first and last stages of growth, respectively. 100% of ETc, (SM) was 0.296 m3m−3 at 0–25 cm, 0.195 m3m−3 at 25–45 cm, 0.179 m3m−3 at 45–62 cm, depths, respectively. whereas 50% of ETc, (SM) was 0.162 m3m−3 at 0–25 cm, 0.195 m3m−3 at 25–85 cm, depths. At 100% of ETc, soil salinity was 5.15, 4.37, 3.3, and 4.5 dSm−1, whereas at 50%, ETc, these values were 5.64, 9.6, 3.3, and 4.2 dSm−1. Statistical indicators showed that the model underestimated yield, for 150%, 100%, and 50% of ETc. Therefore, it can be concluded that yield and WUE using PRD systems were the highest in the potato crop compare to CDI surface and sub-surface, and SALTMED model can predict the moisture distribution, salinity, and yield of potatoes after accurate adjustment.