| Summary: | Extensification of the agricultural land by utilizing peat soil can be a solution to
enhance soybean production, however peat soil has low pH which affect rhizobial
growth and soybean production. The objective of this study was to select rhizobia
isolates based on their ability to form nodules and fix nitrogen on soybean (Glycine
max) grown in peat soil.
This study used 106 rhizobia isolates, collection of the Laboratory of Agricultural
Microbiology, Gadjah Mada University. These isolates were assayed and compared
with Bradyrhizobium japonicum USDA 122 and B. japonicum THA 7. They were
grown on peat soil without ameliorant. Uninoculated soybean grown either on fertilized
and unfertilized peat soil were used as negative controls. Rhizobia which had ability to
nodulate as well as to fix nitrogen were then examined to nodulate and fix nitrogen on
soybean grown on ameliorated peat soil. Uninoculated soybean grown either on
ameliorated-fertilized and ameliorated-unfertilized peat soil were used as negative
controls.
The result showed that 19 isolates could nodulate soybean roots in peat soil
without ameliorant, but only 10 isolates were able to fix nitrogen. They were AII3a2,
AIII1a1, AIII7a2, BIod2, C10c)4.3, C10c)8.3, C10c)13.1, C10c)13.5, C10c)14.1,
C11a)11.2, and B. japonicum USDA122 respectively. When they were grown on
ameliorated peat soil, 10 isolates could nodulate soybean roots, but only 3 isolates were able to fix nitrogen. They were AII3a2, BIod2 and C10c) 4.3 respectively. Based on the phenotypic test, all the 19 isolates were gram negative, and only 12 isolates were slow grower, similar to B. japonicum USDA 122 and B. japonicum THA 7.
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