Effect of Biochar on Soil-Water Characteristics of Soils: A Pore-Scale Study

Abstract

The mechanical and hydraulic properties of soils are largely governed by their soil-water characteristics, which are influenced by factors such as pore size distribution (PSD). While biochar is commonly used as an additive to alter soil properties, its effect on PSD and the soil water retention curve (SWRC) at the pore scale remains unclear. This study aims to investigate the impact of biochar on PSD and SWRC in soils of different types. The study utilized nuclear magnetic resonance (NMR) and the filter paper method to obtain the particle size distribution (PSD) curve and soil water retention curve (SWRC) of various types of soils, ranging from fine-grained to coarse-grained, with different amounts of biochar. The results and discussion revealed that the impact of biochar on soil PSD and SWRC varied depending on the soil type and biochar content. In fine-grained soils, the addition of 8% biochar resulted in the greatest decrease in mesopore size and percentage, while in medium-grained soils, 6% biochar had the most significant effect, and in coarse-grained soils, the optimum biochar content was 2%. At low suction states, the addition of 8% and 2% biochar improved the water retention of fine-grained and medium-grained soils, respectively, but had little effect on coarse-grained soils. Overall, the effect of biochar on soil-water characteristics was non-monotonic and depended on the relative sizes of biochar and soil particles. Therefore, selecting the optimum biochar-to-soil ratio requires careful consideration of these factors.

Influence of Date Palm-Based Biochar and Compost on Water Retention Properties of Soils with Different Sand Contents

“…In the case of biochar, this can be explained by the small surface area measured on the biochar (Table 1), since the permanent wilting point is closely related to the specific surface area of soil [36,37]. This is in agreement with Chen et al [38], which showed that the addition of biochar had little effect on soil water contents at a matric potential of higher than 10,000 hPa (pF > 4). Amendment with biochar led to a significant increase in AWC for A1 and A2 soils but not for the original soil A (Figure 3).…”

Effect of Humic Amendment on Selected Hydrophysical Properties of Sandy and Clayey Soils

“…The hydrophysical properties of soil, such as porosity, saturated hydraulic conductivity, soil water repellency, and water retention capacity, are the most important factors that affect the soil environment. Some authors found that the soil water retention capacity and porosity increased in sandy soil after biochar amendment [7][8][9] decreased saturated hydraulic conductivity and bulk density [10,11] and had no effect on soil water repellency [12] or altered it [13,14]. The impact of biochar on clayey soil is studied to a lesser extent, and the results are different.…”