Organic fertilizer, but not heavy liming, enhances banana biomass, increases soil organic carbon and modifies soil microbiota

Low soil pH and low soil organic matter content are major factors limiting banana production in acid soils. A pot experiment was conducted to determine whether liming or organic fertilizer is effective in mediating banana growth and soil health. The experiment comprised an unamended control and two treatments, lime and OF (organic fertilizer) and sampling was conducted twice, 65 and 280 days after planting. Soil nutrient concentrations, soil microbial communities and enzyme activities, and banana biomass and nutrient uptake were determined. As expected, the application of lime or organic fertilizer significantly increased soil pH and mineral nutrient concentrations and decreased Al3+ concentration. At both harvests an increase in bacterial and fungal diversity in the lime treatment and a shift in the soil bacterial and fungal communities did not translate into increased plant biomass. Organic fertilizer application significantly increased soil organic carbon content and enzyme activities, root length density down the soil profile, plant biomass and nutrient uptake compared to the lime treatment and the control. Changes in the soil microbial community in the organic fertilizer treatment compared to the control followed the same direction as in the lime treatment. However, the relative abundances of Actinobacteria and Ascomycota increased significantly 280 days after planting and potential pathogenic fungi including Fusarium decreased. Our results indicate that heavy liming alone may not be a viable approach to overcome the growth limiting factors in banana production on acid soils. In addition to the increased soil organic matter and nutrient availability, organic fertilizer may prime microbial activities and act as biologically active agent and/or enhance synergistic interactions within the soil microbiome in enhancing plant biomass. Increased soil biological activities after organic fertilizer application emphasize the importance of soil health in promoting the yield of banana crops.