Efficacy of Biochar-biofertilizer-vermicompost Treatment on Theobroma cacao and Rhizosphere Soil Microbial Population

Abstract

Abstract The study investigated the effects of a novel biochar-biofertilizer-vermicompost formulation on the rhizosphere soil microbial community and growth of mature T. cacao trees planted in three farms in the provinces of Batangas (Lipa) and Laguna (Liliw and Magdalena), Philippines. Cacao trees were amended with MYKORICH® (MR) without or with 15% bamboo biochar (15% BB) and vermicompost. In the three years span of the experiment, stem diameter increments of BB-treated cacao in Magdalena and Lipa were 5% and 19% higher than the control (56.09 mm and 49.08 mm), respectively, whereas MR and MR + BB-treated trees in Liliw were 34-35% higher relative to control. Soil microbial analysis showed that mycorrhizal spore counts in BB-amended soils were 133% (Liliw), 262% (Magdalena) and 109% (Lipa) higher than the control. Nitrogen-fixing bacteria obtained from MR + BB-amended soils in Liliw were 216% higher than control, and 81% higher relative to control in BB-treated soils in Lipa. Soil nitrogen and potassium contents of the three cacao farms also improved by 26-85%. With the significant effect of bamboo biochar and mycorrhizal fertilizer, alone or in combination, on the growth of cacao, the microbial community and nutrient status of the cacao rhizosphere soil, this technology would be beneficial to cacao farmers and to almost all crops in an agroforest ecosystem.