Natural Fluctuations in Carbon Substrate Utilizing Activity and Community-Level Physiological Profiles of Microorganisms in Rice Paddy Soils as a Basis for Assessing the Side-Effects of Pesticides on Soil Ecosystems
Kazuhito ITOH, Takahiro IKUSHIMA, Kumi FUJII, Kousuke SUYAMA and Hiroki YAMAMOTO
J. Pestic. Sci.
27, 360-364 (2002)
Natural fluctuations in carbon substrate utilizing activity and community-level physiological profiles of microorganisms in low input and conventional rice paddy soils were monitored using Biolog GN plates for almost two years in order to establish criteria for assessing side-effects of pesticides on soil microbial ecosystems. The activity changed seasonally showing a regular pattern with more activity observed during late summer in both soils. The level of activity seemed to be directly influenced by soil tempera-ture and/or redox potential. Soil microbial communities were grouped into three clusters, Aug”¾Dec, Jan”¾Apr, and May”¾Aug, based on the sampling season. The first cluster was further divided between the two paddy soils. The same microbial communities were reestablished in the same season for two successive years in both soils. Low soil temperatures and reduced soil conditions seemed to be influential in the establishment of the second and third clusters, respectively. Criteria are proposed for assessing the side-effects of pesticides on microbial function and structure in paddy soils.
