Evaluation of Rhizobium japonicum Inoculants in Soils Containing Naturalized Populations of Rhizobia¹

Abstract

An important question in current soybean (Glycine max (L.) Merrill) production is whether inoculation is beneficial when seed is planted in soils where effectively nodulated plants have been produced previously. These studies were conducted to measure the effective of inoculating soybeans with commercial cultures of R. japonicum on seed yield and protein percentage when soybeans were grown on soils which had grown nodulated soybeans previously. Paired samples of different lots of soybean seed taken before and after commercial inoculation with R. japonicum were planted at two Minnesota locations in 1967. More extensive studies were conductedi in 1968 at five locations in cooperation with various inoculant companies. Seed from a common lot was sent to the participating companies to be inoculated. Two treated samples and an uninoculated check were returned from each company. Two samples were treated immediately prior to planting with humus samples from each inoculant company. Three humus cultures of single strains of R. japonicum, selected from the more effective strains in an inoculation study on rhizobia free soils in Minnesota, also were used as inoculants. Soybean seed yields and seed protein percentage were not significantly increased by inoculating soybean seeds with Rhizobium japonicum at planting time. The uninoculated checks were adequately nodulated by rhizobia which were in the soil from previous soybean crops. Serotyping of single strain inoculants indicated a substantial range of recovery (0–17%) depending on the strain and location.

Persistence and competitiveness of threeBradyrhizobium japonicum inoculant strains in clay loam Nile valley soil

“…Such response was extended to the second season with no additional inoculation. Similar results with soybean inoculation were obtained by Ham et al (1971) in soil with naturalized population of rhizobia and by Hamdi et al (1981) and Nassib et al (1983) in soils void of B. japonicum. There were no significant differences in seed yield between inoculated treatments within the same season or between the two seasons.…”

SURVIVAL OF Bradyrhizobium japonicum IN CANADIAN PRAIRIE SOILS

“…Similar results were reported for the U.S.A. by Abel and Erdman (1964), Caldwell and Vest (1970), and Bezdicek et al (1978). However, in the traditional soybean-growing areas of southern Ontario and the U.S.A., on soils where soybean has grown previously, inoculation frequently does not increase yield of soybean (Abel and Erdman 1964;Ham et al l97l; Nelson et al 1978;Muldoon et al (1980) because B. japonicum strains survived in the soil and the population was adequate for effective nodulation and N2-fixation (Weaver et al 1972; Muldoon et al 1980). (Mills et al 1977;' Bailey 1988).…”

Nitrogen fixation(N-15 dilution) with soybeans under Thai field conditions. III. Effects of Bradyrhizobium japonicum strains and herbicides in northeast Thailand.

“…The benefits depend greatly on the selection of appropriate bacterial strains, since bacterial strain-soybean cultivar specificity has been found in many cases (3)(4)(5)(6). Native populations of Bradyrhizobium japonicum cannot be relied upon to supply adequate amounts of N for commercial soybean production since they vary considerably in their competitiveness and N2-fixing abilities (7,8). There are no published comparisons of B, japonicum strains for use in sandy, low-fertility, low-pH tropical soils such as occur in northeast Thailand.…”