Correlations between soil microbial and physicochemical variations in a rice paddy: implications for assessing soil health.
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2009-12
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Abstract
This study was conducted to test the hypothesis that spatial variations in soil microbial variables in a Thai rice paddy
are accurately described by multivariate profi les of the soil bacterial communities. We found that community-level
physiological profi les of soil bacterial communities could better describe the population density of Rhizoctonia
solani in soil than the physicochemical profi les do. However, soil dehydrogenase levels were closely correlated with
soil fertility (P<0.05), and these were better described by the physicochemical profi les. Hence, the hypothesis was
rejected, and we suspect that soil microbial variables react differently to the same physicochemical changes. The
average population density of R. solani (35 colony-forming units/g dry soil) was relatively high in the soil we studied,
and the soil fertility was found to be among the poorest in Thailand. The soil quality was comparable to the most
degraded bare ground soil in an adjacent bioreserve in terms of Shannon diversity index based on the communitylevel
physiological profi le as well as values of soil fertility indices. Overall, the soil microbial and physicochemical
indicators showed that the paddy soil needs to be supplemented with soil nutrients. Otherwise, R. solani may cause a
signifi cant reduction in rice production.
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Doi Ryoichi, Ranamukhaarachchi Senaratne Leelananda. Correlations between soil microbial and physicochemical variations in a rice paddy: implications for assessing soil health. Journal of Biosciences. 2009 Dec; 34(6): 969-976.