ARARAGI, M., TANGCHAM, B., CHOLITKUL, W. and PHETCHAWEE, S., 1979, Studies on microflora in tropical paddy and upland farm soils
Tech. Bull., Trap. Agr. Res. Center, Japan, No.13.
The dynamic behavior of soil microorganisms related to the nitrogen cycle in the paddy and upland farm soils of Thailand was investigated and was compared with that of Japanese soils.
Microflora of tropical soils was found to be different from that of temperate soils.
Microflora showed marked variations among great soil groups, and was found to show seasonal variations. Relationships between populations of microorganisms, and soil chemical and physical properties were discussed. The tropical upland farm soils contained predominantly chromogenic actinomycetes with strong protease and cellulase activities and this trend was particularly evident in soils with low carbon content. In the field experiments, the populations of ammonia oxidizer and denitrifier showed distinctly lower values in Brackish Water Alluvial Soils than in Low Humic Gley Soils during rice growing season. Methane gas was hardly detected in the control plot of the former soils. The application of phosphate or rice straw (6 tons/ha) with and without N-fertilizers affected variously the population of microorganisms related to the change of mineral nitrogen. Following either phosphate or rice straw application, the amount of molecular nitrogen and methane in soil gas increased in both soil groups.