# Biochar Amended Soils and Water Systems: Investigation of Physical and Structural Properties
## 1 Introduction
[31] reported positive effects of a biochar from forest biomass, pyrolyzed at 450 \({}^{\circ}\)C, on the soil retention and structural properties of a desert sandy soil, indicating that BC significantly decreased bulk density, improved water retention, and increased the amount of PAW of the BC amended sand, by increasing the amount of storage pores. They also found that BC improved soil aggregate stability [32], and the specific surface (BET-SSA) of the BC amended soil. With reference to medium and/or to fine textured soils (i.e., soil containing clay), mixed and sometimes contrasting effects of BC on soil-water retention, on the amount of PAW and on soil hydraulic conductivity have been published. [PERSON] et al. [33] compared the effect of BC on three differently textured soils, i.e., a sandy-loam, a silt-loam and a clay loam. They found that BC had a clear positive effect on the PAW only for the sandy soil, concluding that sandy soils have the most to gain from BC amendment, as previously suggested also by [PERSON] et al. [34]. [PERSON] et al. [35] found that BC applications increased the saturated water content and decreased the residual water content of a silty clay soil and of a sandy loam soil, indicating that BC increased macroporosity and decreased microporosity. [PERSON] et al. [36] recognized that BC improved aggregate stability and water retention of a sandy-clay soil, increasing inter-aggregate porosity at the highest application rates. [PERSON] and [PERSON] [27] reported significant positive changes in aggregate stability, water retention and pore-size distribution after addition of biochar to a clay soil, but only at the larger BC dose (90-135 tons ha\({}^{-1}\)). Instead, [PERSON] et al. [37] did not find clear positive effects of BC on soil hydraulic conductivity of a clay soil and showed that significant increases of soil water retention were detected only close to water saturation (\(0<|\,h\,|<10\) cm) and only at the highest BC concentration. [PERSON] et al. [38] also reported almost non-significant increases in the PAW of a silt-loamamended with BC. [PERSON] et al. [39] also found non-significant effects of BC on field capacity and PAW of a heavy clay soil. A comparison between the different research results is difficult because different soils, different BC and different BC application rates have been used in published papers. The analysis above shows that contrasting results on the effect of BC on the physical and structural soil properties have been found, thus this issue needs to be further investigated. The objective of this study was to investigate the effects of amending three differently standard textured soils (LUFA) classified as loamy sand, loam and clay, with a BC from forest biomass waste produced in Italy, pyrolyzed at 450 \({}^{\circ}\)C, having distinct soil physical and chemical properties. The effects of BC, at a selected application rate (\(f_{BC}\) = 0.091), on soil water retention, plant available water (PAW), aggregate stability, and specific surface area (BET-SSA) of the soil-BC mixtures were evaluated.