Effect of Bacillus subtilis S37-2 on Microorganisms in Soil and Growth of Lettuce (Lactuca sativa)

The present study evaluated the variations in soil microbial population of controlled horticultural land used for lettuce (Lactuca sativa) cultivation by their fatty acid methyl ester and chemical properties. We utilized four treatment groups, no treatment (NT), culture medium (CM), Bacillus subtilis S37-2 (KACC 91281P) ${\times}10^6CFU\;mL^{-1}$ (BS1), and Bacillus subtilis $S37-2{\times}10^7CFU\;mL^{-1}$ (BS2) and analyzed these variations throughout the before treatment and harvesting stage. The chemical properties such as pH, organic matter, available phosphate, and electrical conductivity in soils before treatment and harvesting stage showed no significant difference among the treatments. Total numbers of bacteria and microbial biomass C in soil treated with BS1 were larger than those of NT, CM, and BS2, whereas total number of fungi at the harvesting stage was significantly lower in the BS1 soil than in the NT and CM soils (P < 0.05). On basis of leaf length, leaf width, leaf number and leaf weight, the growth characteristics lettuce on the soil treated with BS1 and BS2 was faster than those of NT and CM soils. Yield of lettuce with treated BS1 and BS2 were 35% and 29% more than that of NT, respectively.