Microbial Activities as Affected by Peat Dryness and Ameliorant

Abstract

Problem statement: Acceleration of microbial activities and thus of CO₂ emission in drained peat soils used for agriculture, is of the main environmental concern. The objectives of this study were to (i) examine microbial activities in peat samples treated with different levels of water contents and ameliorants and (ii) evaluate the relative contribution of microbial groups to peat respiration. Approach: Surface (0-20 cm) and subsurface (30-50 cm) peat samples were collected from Tanjung Jabung Barat, Jambi Province, Indonesia. Peat samples were categorized as saprist (mature stage), acidic (pH <4.5), low bulk density (<0.12 g cm^-3) and high carbon content (C >500 g kg^-1). Each peat sample was treated with four different levels of water contents (7-66%, v/v) and four levels of ameliorant applications (without and with 600 kg ha^-1 furnace slag and/or lateritic-soil). Another set of peat samples was treated with three different lethal doses of chemical agents to inhibit the growth of selected microbial group (bacteria, actinomycetes and fungi). The rate of respiration and the number of individual microbial group population were estimated by alkali absorption method and spread-plate counting technique, respectively. Results: Application of furnace slag and/or lateritic soil at the level of 600 kg ha^-1 did not affect peat respiration. However, respiration rates increased as the water content of peat samples increased, namely from 4.23-18.2 μg CO₂ g^-1 h^-1 in the surface samples and from 6.19-15.84 μg CO₂ g^-1 h^-1 in the subsurface samples. Bacteria were the dominant microbial group in both samples ranging from 9.39-12.76 log₁₀ cell g^-1 and contributed to 82 and 58% of surface and subsurface peat respiration, respectively. Conclusion: Microbial activities, notably bacteria were affected by peat water content and less affected by ameliorants of furnace slag and lateritic soil. Increasing water content up to 66% increased peat respiration, indicating the preference of the microbes to moist condition.