Improving soil properties, especially in arid and semiarid regions, is an urgent need for sustainable food production. This study aims to evaluate the effect of applying two types of anionic polyacrylamide polymers (PAMs) with different molecular weights on: (1) soil aggregate stability, (2) infiltration rate and (3) saturated hydraulic conductivity of sandy loam soil and introduce a novel modelling approach to predict the effect of PAM addition on the mentioned soil properties. Polymers were applied at five different concentrations; 0, 100, 250, 500 and 1000 mg L⁻¹. Direct positive relations between the concentrations of PAM (low and high molecular weight) and saturated hydraulic conductivity and infiltration rate were observed. Nevertheless, the relations were more pronounced in case of low molecular weight PAM. The difference between the effect of the two PAMs on infiltration rate was statistically significant at α = 0.05. On the other hand, the differences were not significant except for the 1000 mg L⁻¹ concentration in case of saturated hydraulic conductivity. Meanwhile, concentration has an effect on increasing soil aggregate stability only in case of low molecular weight PAM. At the concentration 1000 mg L^-1 of low molecular weight PAM, aggregate stability and saturated hydraulic conductivity increased 3-fold while infiltration rate increased by more than 7-fold compared to the control. It is hypothesized that the change in the mentioned properties is correlated to the amount of PAM adsorbed by the soil and hence they can be used as surrogate parameters of adsorption. Modified versions of the Langmuir and Freundlich isotherm equations were used to model the change in aggregate stability and saturated hydraulic conductivity in response to the PAM concentration. The pseudo-first and second kinetics models were applied to predict the change in infiltration rate. The models showed excellent fit to the experimental data, thus supporting our hypothesis. The results suggest that low molecular weight PAM is more efficient in improving the physical properties of sandy loam soil. The modelling approach presented in this work may be extended to other types of soil. Other isotherm models may be used to predict the response of soil to PAM concentration where the Langmuir or Freundlich isotherms do not apply. This modelling approach provides land managers with a decision support tool to optimize PAM application.

改善土壤特性，特别是在干旱和半干旱地区，是可持续粮食生产的迫切需求。这项研究旨在评估应用两种不同分子量的阴离子聚丙烯酰胺聚合物（PAM）对（1）土壤团聚体稳定性，（2）渗透率和（3）沙壤土的饱和水导率的影响，并介绍一种新颖的建模方法来预测PAM添加对上述土壤特性的影响。聚合物以五种不同的浓度使用。0、100、250、500和1000 mg L ^-1。观察到PAM（低分子量和高分子量）的浓度与饱和导水率和渗透率之间存在直接的正相关关系。但是，在低分子量PAM的情况下，这种关系更为明显。两种PAM对渗透率的影响之间的差异在α= 0.05时具有统计学意义。另一方面，在饱和水力传导率的情况下，除了浓度为1000mg L ^-1以外，差异不显着。同时，仅在低分子量PAM的情况下，浓度才具有增加土壤团聚体稳定性的作用。浓度为1000 mg L ^-1与对照相比，低分子量PAM的聚集体稳定性和饱和水力传导率提高了3倍，而渗透率提高了7倍以上。假设上述性质的变化与土壤吸附的PAM量有关，因此可以将其用作吸附的替代参数。Langmuir和Freundlich等温方程的修改版本用于模拟响应PAM浓度的骨料稳定性和饱和水力传导率的变化。使用伪第一和第二动力学模型来预测渗透率的变化。模型显示出与实验数据的极佳拟合，从而支持了我们的假设。结果表明，低分子量PAM在改善砂壤土的物理特性方面更为有效。在这项工作中提出的建模方法可以扩展到其他类型的土壤。在不适用Langmuir或Freundlich等温线的地方，可以使用其他等温线模型来预测土壤对PAM浓度的响应。这种建模方法为土地管理人员提供了决策支持工具，以优化PAM应用。