Response of Soybeans to Commercial Soil-Applied Inoculants1
- D. W. Nelson,
- M. L. Swearingin and
- L. S. Beckham2
Recent development of soil-applied inoculants, which have been advertised in midwestern states as increasing yields by an average of 10%, has stimulated a great deal of interest among soybean (Glycine max (L.) Merr.) producers. Field studies with two soybean varieties were conducted over 2 years (three different cultivars were used), to evaluate crop response to application of commercial soil-applied Rhizobium japonicum inoculants. Conventional seed-applied inoculants were also studied for comparison of effectiveness. Plots were established on a highly productive silty clay loam soil which had not been cropped to soybeans for more than 15 years (the native population of rhizobia was assumed to be low). Grain yields, nodulation, and leaf and grain composition were measured. Inoculation of soil or seeds with commercial inocultants did not increase yield, nodule mass per plant, or leaf and grain N concentration. Small, but inconsistent, changes in total P concentration of grain were obtained from inoculation. Soil inoculants were not superior to seed-applied inoculants for soybeans. These results combined with recent findings of other investigators (personal) communications from E. Ham and R. E. Smith) suggests that yield responses to soil or seed inoculants are unlikely in Cornbelt soils where soybeans are grown with some regularity because of a sufficient population of “native” rhizobia. There appears to be little justification for recommending in. oculation of soybeans except where soybeans are to be planted in a field for the first time or where a previous crop was poorly nodulated.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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