Synergic effect of Arbuscular mycorrhizal fungi and potassium fertilizer improves biomass-related characteristics of cocoa seedlings to enhance their drought resilience and field survival

Abstract

Drought stress has become the most widespread environmental factor that affects cocoa production in West Africa. This study assessed the effect of AMF and or potassium fertilizer on cocoa drought resilience and survival at the nursery stage to 2 years after transplanting to field. Nursery and field experiments were conducted at the FRNR Farm (60 43 N and 10 36 W), KNUST- Ghana from 2020 to 2022. A 3x3x2 factorial experiment with three cocoa varieties (V1, V2 and V3), three levels (0, 2 and 4g plant− 1) of potash and AMF spore treatment (AMF and Non-AMF) in a Randomized Complete Block Design was used. Soil samples (0-20cm depth) from cocoa rhizosphere in five farms were examined for native AMF spores and structures using the Wet Sieving and Decantation methodology and the Sucrose Centrifugation Technique. AMF inoculum was prepared using the trap culture technique. At the nursery, K levels with AMF recorded the highest stem diameter (8.3mm) than the non-AMF seedlings (7.9mm). 2g and 0g K with AMF in V2 and V3 had the highest (p < 0.05) plant heigh (50.27cm). 2g K x AMF in V1 and V2 had the highest aboveground (5.13g) and belowground (2.81g) biomass respectively. At 24 months, V1x0g and V3x4g both without AMF had mortality of 60% and 50% respectively, while V1x4g and V2x2g both with AMF had 2% mortality rate. This synergy improved the field survival of cocoa from the current 30–98%. This has implications for cocoa nutrients management and drought conditions that threaten sustainable cocoa production.