Biochar and compost application synergistically enhance soil microbial activity in coastal savanna Acrisol

The use of organic fertilizers such as compost and biochar have received much research attention but their potential synergistic effects on soil biological properties have not been sufficiently investigated. This study investigated the effects of combined application of empty fruit bunch biochar and/or compost on soil biological activities in a coastal savanna Haplic Acrisol. Six treatments were evaluated; sole biochar 10 t ha − 1 (B10) and 20 t ha − 1 (B20); sole compost 20 t ha − 1 (C20); biochar + compost 10 + 20 t ha − 1 (B10 C20); and biochar + compost 20 + 20 t ha − 1 (B20 C20) respectively, and the control. Treatments were added to 1 kg of soil, incubated for 30 days and soil biological activities including protease, β-glucosidase, urease activities, and key soil physicochemical properties were monitored over the period. Results showed significant increases in bacterial and fungi counts in all amended soils compared to the control. Pearson correlation indicated a diverse association among soil enzymatic and microbial properties. Soil pH positively correlated with microbial biomass carbon (MBC) ( p < 0.01, r = 0.59) and urease activity ( p < 0.05, r = 0.94). Soil electrical conductivity (EC) also showed strong positive correlations with β-glucosidase and MBC. These indicate that co-application of biochar and compost can potentially improve soil microbial communities and soil health.