Effects of biochar and manure amendments on water vapor sorption in a sandy loam soil

Over the last decade, the application of biochar (BC) as a soil amendment to sequester carbon and mitigate global climate change has received considerable attention. While positive effects of biochar on plant nutrition are well documented, little is known about potential impacts on the physical properties of soils, especially on water retention at low matric potentials. To overcome this knowledge gap, the effects of combined BC (0 to 100Mgha^-1) and manure (21 and 42Mgha^-1) applications on water vapor sorption and specific surface area were investigated for a sandy loam soil. In addition, potential impacts of BC aging were evaluated. All considered BC-amendment rates increased water retention, especially at low matric potentials. The observed increases were attributed to a significant increase of soil organic matter and specific surface area (SSA) in BC-amended soils. Hysteresis of the water vapor sorption isotherms increased with increasing BC application rates. Biochar age did not significantly affect vapor sorption and SSA.