Response of the Clover-Rhizobium Symbiosis to Soil Acidity and Rhizobium Strain1
- Frank C. Thornton and
- C. B. Davey2
Thirty-three strains of Rhizobium trifolii were tested for the effects of soil acidity on nodulation, nitrogen fixation, and dry matter production with ‘Mt. Barker’ clover (Trifolium subterraneum L.). Clover plants were grown in a Norfolk loamy sand (Typic Paleudult, fine loamy, silicious thermic) adjusted to 7, 34, and 57% Al saturation at acidity levels of pH 5.9, 5.1, and 4.4, respectively. Results from this experiment confirm that R. trifolii exhibits a large and varied tolerance to soil acidity in symbiotic association with the host. Laboratory prescreening of R. trifolii in liquid medium, based on the ability of rhizobia to grow in acid media (pH 4.2) containing Al (15 µM), identified 54% of the strains that proved symbiotically acid sensitive. Over 70% of the strains prescreened as acid tolerant ranked in the top half of all strains in total N accumulation in the most acid soil treatment. In some cases acid-resistant effective strains of R. trifolii formed symbiotic associations that produced between 90 to 99% of the yield of the N-amended controls.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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