Green waste compost with wood ash additive improves physico-chemical and biological parameters of an Oxisol, and soybean (Glycine max L) yield

A greenhouse study was conducted to assess the potential of green waste wood ash compost on a tropical acid soil. Four types of compost (prepared with 0, 5, 10 and 15% of wood ash prior composting) were used to amend an Oxisol from the centre region of Cameroon. The different composts were mixed with the soil in 1/4 proportions (w/w); the experimental design was a completely randomized block with three replicates per treatment. The different treatments were planted with soybean (Glycine max L.) for three month growing period. Compost amendment increased the soil pH, organic carbon, total nitrogen and total phosphorus. Bacterial and fungal biomass together with cellulase and protease activities also increased in amended soil. Following soil chemical, physical and chemical parameters, plant growth and yield also improved in compost treated sols. However, compost prepared with 15% wood ash additive showed trends of inhibition of the soil microbiota. It can be concluded that green waste wood ash compost could be used as a suitable soil fertilizer for tropical acid soils, although precautions are to be taken when using these composts prepared with addition of wood ash ≥ 15%.