The study investigates the use of biochar as a soil improver to address various crop cultivation challenges by utilizing actinomycetes to enhance the available nutrients for plants. It aimed to examine the response of cocoa plants to different types of biochar and concentrations of actinomycetes for growth and productivity. This research began in Watu Toa Village, Marioriwawo District, Soppeng Regency, using 3-year-old MCC 02 plants. The research employed a split-plot design with main plots as the types of biochar (rice husk, coconut shell, and corn cob biochars). The subplots comprised various concentrations of actinomycetes, i.e., 0, 30, 60, and 90 mL L^-1. The results revealed significant interaction effects between the types of biochar and actinomycetes concentration on stomatal opening area (83.04 μm²), number of cocoa pods formed (43.11 pods), percentage of fallen flower cluster (32.39%), and 100 dry beans’ weight (171.68 g). However, the individual application of actinomycetes enunciated the most pronounced effects, particularly in the number of pods created (126.52 pods), the percentage of fallen cocoa pods (16.77%), the number of harvested fruits (15.67 fruits), and the production yield (618.84 g/tree and 687.53 kg/ha).

Keywords: Cocoa (T. cacao L.), biochar, actinomycetes, interaction effects, growth and physiological traits, productivity

Key findings: The combination of corn cob biochar and the highest concentration of actinomycetes (90 mL L^-1) provided the best effects on cocoa (T. cacao L.) for the stomatal openings, the lowest percentage of fallen flowers, and the maximum 100 dry seeds’ weight.