Biochar and manure additions increased above- and belowground wood decomposition, and soil enzyme activities in a sandy loam soil

Abstract

While biochar and manure can provide considerable benefits to soil properties, how these amendments may alter soil microbial activity and decomposition processes remains unknown. In a split-split-split-plot experiment, we amended a sandy loam soil with three rates of manure (whole plot; 0, 3, 9 Mg ha⁻¹) and biochar (split-plot; 0, 2.5, 10 Mg ha⁻¹), and installed three species of wood stakes (split-split-split plot; triploid poplar, Populus tomentosa Carr.; trembling aspen, Populus tremuloides Michx.; and loblolly pine, Pinus taeda L.) on the soil surface and in the mineral soil (split-split plot) to serve as a substrate for microbial degradation. Wood stakes were sampled 3 years after installation to assess decomposition rates (mass loss), and changes in wood carbon (C) and nitrogen (N). In addition, soil extracellular enzyme activities at the 0–20 cm depth were examined. Biochar alone, especially 10 Mg ha⁻¹, increased wood stake decomposition and moisture content on the soil surface and in the mineral soil. Manure at the rate of 9 Mg ha⁻¹ increased soil N-acetyl-β-D-glucosaminidase, α-glucosidase, and aryl sulfatase activities by 91%, 17%, and 48% respectively. Because of the synergistic benefits of biochar and manure, we suggest that, in this climatic regime and soil texture, 10 Mg ha⁻¹ biochar can be used for soil C sequestration and soil quality improvement, and 9 Mg ha⁻¹ manure can be used in combination with biochar to build soil organic matter in plantations.