Studies on the soils in rice-fields. 3. Microbiological analyses of soil profile in a rice-field and a dry-farm
Itano, Arao; Arakawa, S.
Ber Ohara Inst Landw Forsch 4(1): 55-66
From microbiological and biochemical investigations on the profile of a rice field and of dry farm land, the following conclusions may be drawn: Samples were taken from each of 3 distinct strata. Soil from the rice field contained more humic substance than that of the dry farm, and showed the wider C:N ratio. In both cases, the p H was slightly less than 7 in the 1st stratum and approached 7 as the depth increased. The numbers of bacteria, actinomycetes and fungi were determined aerobically by use of 4 media, albumin agar giving best results. The number of bacteria per gm. of drv soil decreased as the depth increased, in both cases. The number of actinomyces per gm. of dry soil in the rice field showed a similar tendency in respect to the depth, amounting to 20.7%, 20.5% and 28.4% in the 1st, 2nd and 3rd, strata, respectively. In the dry farm, the numbers of bacteria amounted to 23.4%, 25.1% and 11.2%, in respective strata. The majority of colonies (95-100%) were grayish white. The numbers of fungi were 20,080, 2,310 and 1,170 in the rice field; and 20,260, 6,280, and 2,610 in the dry farm soil, in the respective strata. Forty-seven strains of bacteria were isolated from the rice field and 44 from the dry farm; all were subjected to morphological, biochemical and cultural study; the organisms were grouped and their percentages were determined. As to biochemical action of soils, it was found that those from the dry farm manifested much more vigorous action.