Abstract Although plastic-film mulching has played an important role in agriculture production in arid areas, the practice has resulted in the accumulation of large amounts of residual plastic film (RPF) in the soil. This intensely impedes the movement of the water and solutes in soil by seriously affecting the physical and hydraulic properties of soil, in particular the soil water characteristic curve (SWCC). Despite the severity of the problem, studies on how RPF affects soil properties and the SWCC remain scarce. This paper thus aims to achieve a better understanding of the influences of RPF on soil pores and SWCC. In this study, SWCCs were measured under five concentrations of RPF (0 kg·hm−2, 50 kg·hm−2, 100 kg·hm−2, 200 kg·hm−2 and 400 kg·hm−2) and three soil textures (sandy soil, sandy loam and loam soil) based on the pressure plate extractor test. A model for estimating SWCC for soil with residual plastic film (RPF-SWCC) based on an improved pore-size distribution is proposed, and its performance was evaluated and compared with those for existing models, including the van Genuchten (VG), Brooks-Corey (BC) and log normal distribution (LND) models. The results showed that there is a clear influence by the RPF in soil on the shape of the SWCC, and the order of the different soil types in regards to soil water holding capacity was loam soil > sandy loam > sandy soil, with or without RPF. The RPF-SWCC model accounted for the effects of water blocking by RPF, thereby achieving improved fitting accuracy compared to that by the VG, BC and LND models, especially for soil with high RPF concentration. The average Nash-Sutcliffe efficiency coefficient (NSE), mean absolute percentage error (MAPE) and symmetric mean absolute percentage error (SMAPE) for achieved for the RPF-SWCC model were 0.9943, 3.37% and 3.43%, respectively, which was an improvement on the 0.9938, 5.94% and 5.06% achieved for the VG model, 0.9926, 4.43% and 4.25% for the BC model and 0.9923, 15.00% and 7.53% for the LND model, respectively. In addition, the correlation between the parameters of the RPF-SWCC model and RPF concentration showed that the saturated soil water content and residual soil water content decreased and increased with increasing RPF concentration, respectively. In addition, soil RPF increased and decreased the proportion of macropores and soil water holding capacity, respectively. This study can provide a theoretical and technical basis for research into soil water movement and the efficient utilization of water and fertilizer in areas with high agricultural film residue.

中文翻译：

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基于改进孔径分布的含残膜土壤水分特征曲线估算

摘要 虽然地膜覆盖在干旱地区的农业生产中发挥了重要作用，但这种做法导致土壤中积累了大量的残留地膜（RPF）。这通过严重影响土壤的物理和水力学性质，特别是土壤水分特征曲线（SWCC），强烈阻碍了土壤中水和溶质的运动。尽管问题很严重，但关于 RPF 如何影响土壤特性和 SWCC 的研究仍然很少。因此，本文旨在更好地了解 RPF 对土壤​​孔隙和 SWCC 的影响。在本研究中，SWCC 在五种 RPF 浓度（0 kg·hm-2、50 kg·hm-2、100 kg·hm-2、200 kg·hm-2 和 400 kg·hm-2）和三种土壤质地（沙土，砂壤土和壤土）基于压力板提取器试验。提出了一种基于改进的孔径分布来估计残留塑料膜土壤 SWCC 的模型 (RPF-SWCC)，并对其性能进行了评估，并与现有模型的性能进行了比较，包括 van Genuchten (VG)、Brooks- Corey (BC) 和对数正态分布 (LND) 模型。结果表明，土壤中RPF对SWCC的形状有明显的影响，不同土壤类型土壤持水能力的顺序为壤土>砂壤土>砂土，有无RPF . RPF-SWCC 模型考虑了 RPF 阻水的影响，从而与 VG、BC 和 LND 模型相比，提高了拟合精度，特别是对于高 RPF 浓度的土壤。RPF-SWCC 模型实现的平均 Nash-Sutcliffe 效率系数 (NSE)、平均绝对百分比误差 (MAPE) 和对称平均绝对百分比误差 (SMAPE) 分别为 0.9943、3.37% 和 3.43%，这是一个改进VG 模型分别为 0.9938、5.94% 和 5.06%，BC 模型分别为 0.9926、4.43% 和 4.25%，LND 模型分别为 0.9923、15.00% 和 7.53%。此外，RPF-SWCC模型参数与RPF浓度的相关性表明，饱和土壤含水量和残余土壤含水量分别随着RPF浓度的增加而减少和增加。此外，土壤RPF分别增加和减少了大孔隙比例和土壤持水量。