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

• Biochar (BC) and manure (PS) application on soil water vapor sorption was assessed.
• BC and PS increased water vapor sorption, especially at low matric potentials.
• Soil specific surface area increased for BC-amended soils.
• Hysteresis of the water vapor sorption isotherms increased with BC application rate.
• No effect of BC aging on water vapor sorption and surface area was observed.

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 100 Mg ha− 1) and manure (21 and 42 Mg ha− 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.