LAUSR

Abstract Biochar and arbuscular mycorrhizal fungi (AMF) are found to improve crop productivity affecting the nutrient availability in the soil and favoring build-up of beneficial microbes. The effects of AMF and bamboo biochar (BB) on the growth of cacao, estimated number of mycorrhizal spores, and soil chemical properties were investigated. Cacao seedlings were grown in unsterilized and oven-sterilized acidic soil. After 15 months, AMF generally increased most growth traits of cacao plant over the control. Bamboo biochar at 15%, gave the best plant growth regardless of soil sterilization. When biochar was added to AMF, 15% consistently provided the heaviest total plant dry weight, especially in unsterilized soil. Likewise, all treatments improved the height and stem diameter increments of those grown in unsterilized soil. Percentage of mycorrhizal root colonization was higher in mycorrhizal (+AMF) plant and addition of biochar proliferated AMF spores in the rhizosphere. Biochar showed positive effect in enhancing the soil chemical properties. The results imply that biochar and AMF can improve the overall growth and can positively increase the yield of cacao plants, which will provide impact in improving cacao production in acidic soils in the Philippines.