Wednesday, 9 November 2005
4

Response of Genetically Diverse Soybean Cultivars to Various Bradyrhizobium Japonicum Inoculants.

Fawzy M. Hashem1, Robert Dadson1, Larry Butler2, Iqbal Javaid1, Thomas Devine3, and Jagmohan Joshi1. (1) University of Maryland Eastern Shore, Department of Agriculture, Princess Anne, MD 21853, (2) Becker Underwood, Inc., 801 Dayton Avenue, P.O. Box 667, Ames, IA 50010, (3) USDA/ARS, SASL,, 10300 Baltimore Ave, Bldg 001, Rm 242, Beltsville, MD 20705

The economy of the Delmarva Peninsula of the United States is highly dependant mainly on the productivity of soybean. The low cost of soybean production is essential in enhancing the prosperity of farming communities in this region. This can be achieved by minimizing the use of expensive nitrogen fertilizers, and substituting with inexpensive and environmentally friendly rhizobia inoculants. Field studies were conducted in a Randomized Complete Block Design during the last four soybean growing seasons to examine the effect of various Bradyrhizobium japonicum strains and commercial inoculants on nodulation, growth and yield of diverse grain and forage soybean cultivars grown under the Delmarva Peninsula environmental conditions. Surface sterilized soybean seeds were coated with each of the following inoculants before sowing: TA11 NOD+, NOD+, NOD+ with Extender, NOD+ with Subtilex (Bacillus subtilis MBI600), Nitragin Cell Tech Sci, Nitragin Optimize, HiStick L N/T containing B. japonicum and B. subtilis MBI600, soybean inoculant containing strains 532c, NSI and Urbana 212 or uninoculated controls. Soybean nodulation and nitrogenase activity were determined eight weeks after planting while soybean seed and biological yields were determined at maturity. Nodulation, nitrogenase activity and soybean yield varied significantly, and this variation depended on the soybean cultivar tested and the inoculant applied. Inoculants NOD+ with Subtilex and NOD+ with Extender produced the highest nodule number and seed yield on soybean cv. AG4903. However, forage soybean cv. Tyrone indicated best nodulation and highest grain yields when inoculated with TA11NOD+ inoculant.

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