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Effect of Rhizobium japonicum Inoculant Rates on Soybean Nodulation in a Tropical Soil 1
Author(s) -
Smith R. S.,
Ellis M. A.,
Smith R. E.
Publication year - 1981
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1981.00021962007300030025x
Subject(s) - rhizobia , bradyrhizobium japonicum , microbial inoculant , biology , nitrogen fixation , inoculation , agronomy , sowing , rhizobiaceae , symbiosis , horticulture , bacteria , genetics
Soybean [ Glycine max (L.) Merr.] research and production is expanding in tropical areas. Successful soybean nodulation in a soil free of Rhizobium japonicum is dependent totally upon viable rhizobia from the inoculant. This study examined soybean nodulation as influenced by the rate of applied R. japonicum in a tropical soil without indigenous R. japonicum. Rates of R. japonicum were evaluated with soybeans grown in a field experiment on a Puerto Rican Coto clay (Typic Haplorthox, clayey, kaolinitic, isohyperthermic) lacking indigenous R. japonicum . Eight rates of liquid inoculation were added to the seed furrow at planting and supplied number of R. japonicum from log 2.59 cells/cm row with 10 fold increases through log 9.59 cells/cm row. R. japonicum rates of log 2.59 and 3.59 cells/cm row were not successful in establishing nodulation. Nodule numbers increased with increasing rates of applied rhizobia from log 4.59 up to the highest rate of log 9.59 viable cells/cm. Regression analyses indicated linear relationships between the rate of inoculation with rhizobia and the number of tap root nodules, total number of nodules, and nodule weight/plant. An inverse relationship was observed between weight/nodule and total number of nodules. Inoculation levels above log 5.0 rhizobia/cm were necessary to establish effective nodulation in a R. japonicum free tropical soil.