Effects of Soil Water on Rhizobium japonicum Infection, Nitrogen Accumulation, and Yield in Bragg Soybeans1
- P. G. Hunt,
- A. G. Wollum and
- T. A. Matheny2
Low soil water contents may be involved in the lack of success of soybean inoculation in southeastern U.S. soils having high indigenous populations of Rhizobium japonicum. This study was conducted to assess the effect of soil water on the inoculation, biomass, N accumulation, and yield of soybean [Glycine max (L.) Merr.]. ‘Bragg’ soybeans were noculated with 108 cells/cm row of R. japonicum (strain 110) and grown under both irrigated and nonirrigated conditions on a Norfolk loamy sand (Typic Paleudult) in a split plot design. Rainfall maintained the surface soil above −250 mb matric potential until the late flowering stage of growth. Subsequently, a seasonal drought created treatment differences between irrigated and nonirrigated plots resulting in a twofold increase in seed yield due to irrigation (3,160 vs. 1,682 kg/ha). Inoculation increased the percentage infection by strain 110 from practically 0% background to about 20%. Inoculation increased growth and total N accumulation in pods, petioles, and leaves of Bragg soybeans under irrigated conditions. Under nonirrigated conditions, the increased infection of strain 110 appeared to induced a negative response in the vegetative growth of Bragg soybeans. Nitrogen concentration was also significantly lower in the leaves and pods of nonirrigatedinoculated plants. These differences were not observed in N content of the mature seed, and inoculation did not significantly affect seed yield. These findings indicate that R. japonicum strain ✕ environment interactions may be important for soybean growth and yield in the southeast United States.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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