Microbial Ecology in Submerged Soils as Revealed by Using TTC (Triphenyl Tetrazolium Chloride) (Part 2)

Abstract

A few aspects of microbial lives associating with decomposition of rice straw and sesbania leaf in the submerged three Thai paddy soils (one sandy soil and two clayey soils) were examined rather in detail under a microscope using the TTC technique. Water-soluble substances extracted from these plant debris were confirmed to be preferred substrates for soil microorganisms. Removal of these substances somewhat affected the decomposition process of the plant debris themselves, mode of affection being different between rice straw and sesbania leaf. A succession of microorganisms including protozoa was recognized during decomposition of the plant debris. This succession was considered to proceed from r-strategists to K-strategists. Additional evidence was obtained to support the assumption that sesbania leaf contained some organic compounds toxic to microorganisms and in the initial period of decomposition this compounds were more effective in the sandy soil than in the clayey soils because these compounds were adsorbed by clay particles. Contrary to the widely accepted concept, the decomposition rates of these two plant debris were higher in the clayey soils than in the sandy soil. This may be caused not only by the effect of the toxic substances but also by the difference in microflora. Available information suggested that microbial decomposition of rice straw in the Thai soils were some what different from that in Japanese soils.