The dry end of the soil water retention curve (WRC) plays an important role in various hydrologic, solute transport, plant, and microbial processes. Despite increasing application of biochar as a soil amendment, knowledge about water retention in biochars and biochar‐amended soils under dry conditions is lacking. Mechanistic models are presented to predict the WRC for biochars and biochar‐amended soils at matric potential (ψ) < ~−1 MPa. For biochars, the amount of water retained is linked to biochar surficial oxygen content and pore volume and surface area distributions. The WRC for soils at dry conditions is predicted using specific surface area. The WRC model for biochar‐amended soils is the sum of the contributions of models for biochar and soil. The model's utility was examined for three natural soils and a uniform sand, a wood‐based biochar, and 10 different combinations of these soils and biochar. The accuracy of the model for biochars was further tested for six other pyrogenic carbonaceous materials (PCMs). The models agreed well with experimental data: for the biochar and PCMs, soils, and biochar‐amended soils, the root mean square error normalized to the range of water content was almost always <10%. The line of best fit for predicted versus measured gravimetric water content at permanent wilting point had slope of 0.935 ± 0.013 and a coefficient of determination of 0.997. The applicability of these models for different biochars, soils, and their mixtures is discussed.

中文翻译：

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低含水量的热碳（生物炭）和生物炭改良土壤中保水量预测模型

土壤保水曲线（WRC）的干燥端在各种水文，溶质运移，植物和微生物过程中起着重要作用。尽管越来越多地使用生物炭作为土壤改良剂，但缺乏关于在干燥条件下生物炭和生物炭改良过的土壤中保水的知识。机理模型被呈现给预测WRC在基质势（生物炭的生物炭和修订的土壤ψ）<  〜 -1兆帕 对于生物炭，保留的水量与生物炭的表面含氧量，孔体积和表面积分布有关。使用比表面积可预测干燥条件下土壤的WRC。生物炭改良土壤的WRC模型是生物炭和土壤模型的贡献之和。该模型的效用针对三种天然土壤和均一的沙子，一种木质生物炭以及这些土壤和生物炭的10种不同组合进行了检验。对于其他六个热解碳质材料（PCM），进一步测试了生物炭模型的准确性。这些模型与实验数据非常吻合：对于生物炭和PCM，土壤和生物炭改良过的土壤，归一化到含水量范围的均方根误差几乎总是<10％。预测的和测得的重量百分比在永久萎wil点的最佳拟合线的斜率为0.935±0.013，测定系数为0.997。讨论了这些模型对不同生物炭，土壤及其混合物的适用性。