Effect of rice variety and fertilizer type on the active microbial community structure in tropical paddy fields in Sri Lanka

Factorial ANOVA on 13CCr revealed significant effects of variety, type of fertilizer and variety × fertilizer type on active C uptake by actinomycetes. Rice variety significantly influenced the active fungal and Gram-negative bacterial groups, while none of the factors affected Gram-positive bacteria. Active Gram-negative bacteria were higher with BG variety, whereas fungi and actinomycetes were higher with KH variety in both inorganic and organic fertilizer applied fields. Gram-negative and Gram-positive bacteria were the most active functional groups in the paddy soil microbial community, whereas actinomycetes only relied to a minor extent on rhizodeposit C to meet their energy requirement. It is concluded that rice microbial communities differ significantly as a function of cultivation practices, potentially showing a large impact on ecosystem processes such as greenhouse gas emissions and plant nutrient availability.