Impacts of Soil Organic Matter on Microbial Community of Paddy Soils in Gyeongnam Province

Agricultural management of paddy soil depends on the effects of soil microbial activities. The present study evaluated the soil microbial community of 25 paddy soils in Gyeongnam Province by fatty acid methyl ester (FAME). The average of microbial communities in paddy soils were 32.2% of total bacteria, 16.7% of Gram-negative bacteria, 12.9% of Gram-positive bacteria, 2.0% of actinomycetes, 14.9% of fungi, and 1.3% of arbuscular mycorrhizal fungi. The communities of total bacteria (34.9%) and Gram-negative bacteria (19.4%) in soils with 30∼35 g kg-1of organic matter were significantly larger than those in soils with other organic matter levels. However, soils with 20∼30 g kg-1 of organic matter had significantly low ratio of cy17:0 to 16:1ω7c and cy19:0 to 18:1ω7c as compared with soils with 30∼35 g kg-1 of organic matter, indicating microbial stress decreased (p < 0.05). In principal component analyses of soil microbial communities, Gram-negative bacteria should be considered as a potential responsible factor for the obvious microbial community differentiation that was observed between the two different organic matter levels in paddy fields. Thus, soils containing 20∼30 g kg-1 of organic matter were responsible for strong effect on microbial biomass and stress in paddy fields.Ratio of cy17:0 to 16:1ω7c and cy19:0 to 18:1ω7c of paddy soils in Gyeongnam Province. Means by the same letter within a column are not significantly different at 0.05 probability level according to Tukey’s studentized range test. Bars represent one standard deviation of the mean.