Biochar Source and Application Rate Effects on Soil Water Retention Determined Using Wetting Curves

Abstract

Biochar is a stable carbon substance produced by the pyrolysis of biomass and used as a soil amendment. Biochar application to soil has resulted in agronomic benefits, including improved water-holding capacity. However, limited studies exist quantifying different biochars' roles in soil water retention, especially when the soil is drier than field capacity. The objective of this study was to investigate the effects of poultry litter and woodchip biochars, applied at various rates (i.e., 0, 5, and 10 Mg•ha −1 incorporated to a depth of 10 cm) to a loam soil, on the relationship between soil water potential and water content across a wide range of moisture conditions. Based on analysis of variance, the relationship between water potential and water content differed (P < 0.05) between biochar sources based on differing (P < 0.02) power-function coefficients, with poultry litter biochar having greater water retention capacity across a wide range of water potentials, but was unaffected by application rate. Based on regression analyses, application rate affected the relationship between water potential and water content for poultry litter biochar. Results indicate that biochar may not generally improve water retention at all water contents with one-time application rates. Additional experiments will be necessary to understand the impact on water retention of biochars produced from different feedstocks under varying pyrolysis conditions.

Dynamic effects of biochar concentration and particle size on hydraulic properties of sand

“…Using meta-analysis of existing publications covering a range of feedstocks, pyrolysis temperature, and soil types, Omondi et al (2016) concluded that biochar amendments significantly improved soil-water-retention properties and hydraulic conductivity of soil. Several other studies, however, have reported contradictory results ranging from a decrease to no significant effects of biochar on water retention and hydraulic conductivity (e.g., Barnes et al, 2014;Brantley, Brye, Savin, & Longer, 2015;Jeffery et al, 2015;Novak et al, 2009). The cause of this discrepancy is not clear.…”

Making hydrochar suitable for agricultural soil: A thermal treatment to remove organic phytotoxic compounds

“…Many studies have now proved this hypothesis to be true: biochar improves the composition and water retention and increases nutrient uptake and crop yields [6][7][8][9] and also modifies soil microbial habitats and supply nutrients to soil microbes [10]. It has been said that biochar can be considered "as a slow releasing reservoir of nutrients in soils" [2,11].…”

Production of Biochar from Date Palm Fronds and its Effects on Soil Properties

“…control treatments showed 7X10 4, while for treatments received biochar, the fungi numbers grown in the range of 12-22 millions X10 4 . The significant differences in bacteria, and fungi population were observed between biochar and control [40][41][42].…”