|Watts, Donald - Don
|CANTRELL, KERI - Former ARS Employee
|JOHNSON, MARK - Environmental Protection Agency (EPA)
Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2015
Publication Date: 1/15/2016
Citation: Novak, J.M., Sigua, G.C., Watts, D.W., Cantrell, K., Shumaker, P.D., Szogi, A.A., Johnson, M., Spokas, K.A. 2016. Biochars impact on water infiltration and water quality through a compacted subsoil layer. Chemosphere. 142:160-167.
Interpretive Summary: Many soils in the Southeastern United States Coastal Plain region have compacted subsoil layers which limits root penetration and water movement. During drought periods, shallow roots cannot find sufficient water for transpiration which impacts crop productivity. Deep tillage practices are often used to fracture the compact subsoil layer, however, this requires large farm machinery which also consumes copious amounts of fuel. Studies have investigated improving water movement characteristics of compacted horizons with the additions of composts, peat/manures, and crop residues. Unfortunately, these amendments do not last in the hot and humid soils of the Southeastern United States. We investigated if biochar produced from pine chips, poultry litter, and blends added to columns containing a compact sandy soil layer could improve physical properties and allow faster water movement rates. This was determined by applying water to the top of the soils and measuring the amount of water moved as a function of time. Except for the biochar produced from poultry litter, all other applied biochars resulted in faster rates of water movement compared to the control. We concluded that biochars produced from pine chips and blends of pine chip and poultry litter can be a suitable amendments to improve water movement through sandy compacted soil layers.
Technical Abstract: Soils in the Southeastern United States Coastal Plain region frequently have a compacted subsoil layer, which is a barrier for water movement. Four different biochars were evaluated to increase water movement through a compacted horizon from a Norfolk soil (fine-loamy, kaolinitic, thermic, Typic Kandiudult). In addition, we also evaluated biochar effects on water quality. Biochars were produced by pyrolysis at 500° Celcius from pine chips, poultry litter 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-millimeter pellets. Each biochar was mixed with the subsoil at 20 grams per kilogram of soil and the mixture was placed in columns. The columns were leached four times with water over 128 days of incubation. Except for the biochar produced from poultry litter, all other applied biochars resulted in significant water movement increases compared to the control. However, water movement rates in each treatment were influenced by additional water leaching. Leachates were enriched in anions and cations 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 movement, 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.