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Biochar impact on water infiltration and water quality through a compacted subsoil layer
Citation:
Novak, J., G. Sigua, D. Watts, K. Cantrell, P. Shumaker, A. Szogi, M. Johnson, AND K. Spokas. Biochar impact on water infiltration and water quality through a compacted subsoil layer. CHEMOSPHERE. Elsevier Science Ltd, New York, NY, , 8, (2015).
Impact/Purpose:
Biochars are a product of pyrolysis, a biofuels technique used to extract energy from biomass (lignocellulosic and manure feedstocks). Biochars can be used as a soil amendment to improve soil quality, sequester carbon in soils, and protect surface and groundwater quality. In this study biochar was formulated to improve hydrologic infiltration into soils that typically have compacted subsurface layers. Biochars were produced by pyrolysis at 500°C from pine chips (Pinus taeda), poultry litter (Gallus domesticus) feedstocks, and as blends (50:50 and 80:20) of pine chip:poultry litter and added to the subsoil at a rate of 20 g/kg (w/w) and the mixture was placed in columns. These columns were leached with Milli-Q water. With the exception of the biochar made from pure poultry litter, infiltration rates were increased compared to the control. Leachates were enriched in PO4, SO4, Cl, Na, and K after addition of poultry litter biochar, however, their concentrations declined in pine chip blended biochar treatments and after multiple leaching. Infiltration rates slowed as the number leaching events increased. Careful biochar feedstock selection and pyrolysis conditions are critical for remediating soil limitations. The results of this research will have widespread utility domestically and internationally as biochar is becoming widely used as a soil amendment. Incorporating the results of this research will improve soil quality and agricultural productivity while being protective of valuable water resources.
Description:
Soils in the SE USA Coastal Plain region frequently have a compacted subsoil layer (E horizon), which is a barrier for water infiltration. Four different biochars were evaluated to increase water infiltration through a compacted horizon from a Norfolk soil (fine-loamy, kaolinitic, thermic, Typic Kandiudult). In addition, we also evaluated biochars effect on water quality. Biochars were produced by pyrolysis at 500°C from pine chips (Pinus taeda), poultry litter (Gallus domesticus) feedstocks, and as blends (50:50 and 80:20) of pine chip:poultry litter. Prior to pyrolysis, the feedstocks were pelletized and sieved to > 2-mm pellets. Each biochar was mixed with the subsoil at 20 g/kg (w/w) and the mixture was placed in columns. The columns were leached four times with Milli-Q water over 128 d of incubation. Except for the biochar produced from poultry litter, all other applied biochars resulted in significant water infiltration increases (0.157 to 0.219 mL min-1; P < 0.05) compared to the control (0.095 mL min-1). However, water infiltration in each treatment were influenced by additional water leaching. Leachates were enriched in PO4, SO4, Cl, Na, and K after addition of poultry litter biochar, however, their concentrations declined in pine chip blended biochar treatments and after multiple leaching. Adding biochars (except 100% poultry litter biochar) to a compacted subsoil layer can initially improve water infiltration, but, additional leaching revealed that the effect remained only for the 50:50 pine chip:poultry litter blended biochar while it declined in other biochar treatments.
