Nutrient cycling and greenhouse gas emissions from soil amended with biochar-manure mixtures

Abstract Integrating biochar into cattle diets has recently emerged as a potential management practice for improving on-farm productivity. Yet, information concerning the cycling of biochar-manure mixtures is scarce. A 70-d incubation experiment was conducted within two surface (0–15 cm) Mollisols with contrasting textures, i.e., sandy clay loam (Raymond) and clayey (Lethbridge), to evaluate the effects of biochar (3 Mg ha–1) on cumulative greenhouse gas (GHG) emissions and related fertility attributes in the presence or absence of cattle manure (120 Mg ha–1). Five treatments were included: i) non-amended soil (control, CK), ii) soil amended with pinewood biochar (B), iii) soil amended with beef cattle manure (M) (manure from cattle on a control diet), iv) soil amended with biochar-manure (BM) (manure from cattle on a control diet, with pinewood biochar added at 20 g kg–1 of diet dry matter), and v) soil amended with B and M at the aforementioned rates (B+M). A total of 40 soil columns were prepared and incubated at 21 ° C and 60%–80% water-holding capacity. On average, total CO2 fluxes increased by 2.2- and 3.8-fold under manure treatments (i.e., M, BM, and B+M), within Raymond and Lethbridge soils, respectively, relative to CK and B. Similarly, total CH4 fluxes were the highest (P