2010 Volume 1 Issue 1 Pages 152-157
Agricultural management significantly influences soil microbiological properties, such as microbial biomass carbon, microbial biomass nitrogen and respiration rate. Besides soil parameters, microbial diversity is useful for monitoring changes in soil quality to evaluate sustainable agriculture. This study aims to develop and use microbial diversity in rice soil as an indicator of soil quality for sustainable organic rice farming. An experiment was carried out using the existing rice fields (Kao Dawk Mali 105 variety) in Surin Rice Research Center, Thailand. Four plots of rice received different management practices for over 11 years, including (1) conventional farming (CF) with a normal rate of chemical fertilizer applied, (2,3) two plots of organics: one with green manure (GM) and the other with rice straw (RS) and (4) a control plot (CT) without external sources of plant nutrients. Soil microbial communities were determined by cultural and molecular methods such as total plate counts, community level physiological profiling (CLPP) with BIOLOGTM Ecoplate, and PCR-amplified (16S rDNA) and analysed by denaturing gradient gel electrophoresis (DGGE). Two-way ANOVA of results revealed that total plate counts were significantly (P<0.05) affected by the four different management practices. However, the GM plot (2.3x106 CFU g-1 of dry soil) and CF plot (1.8x106 CFU g-1 of dry soil) were not significantly different (P>0.05). Likewise soil management practices influenced the microbial diversity, both in functional and genetic diversity in the rice plots studied. Further a narrow range of Shannon-Weaver diversity index (Hf’) was obtained with values between 2.77 for CT and 3.01 for GM. Statistical analysis (ANOVA) performed using substrate richness (S) from potential substrate utilization patterns as the input data, showed that the GM treatment increased the microbial diversity.
