Survival of Rhizobium in an Oxisol Subjected to Incremental Simulated Erosion
- M. Habte and
- S.A. El-Swaify
The survival of four strains of Rhizobium was monitored as a function of time at constant moisture potential and temperature in soils from sites subjected to incremental simulated erosion. Populations of two of the strains were either stimulated or unaffected by simulated erosion representing up to 37.5 cm of surface soil removal. Populations of the remaining two strains were also stimulated or unaffected by simulated erosion not exceeding 15 cm of surface soil removal. Simulated erosion in excess of this level, however, significantly decreased the survival of these strains. Strain tolerance to erosional losses of soil closely paralleled tolerance to soil acidity. Declines in the populations of the erosion-intolerant strains were accompanied by declines in soil pH, organic C, total N, extractable P, and extractable Ca, Mg, and K. The adverse effects of simulated erosion on the sensitive rhizobia was eliminated, however, by liming the eroded soil samples to pH 6.0. Liming improved the survival of the bacteria in these soil samples largely by improving the supply of Ca. Our results demonstrate that the adverse effect of erosional soil losses on the survival of Rhizobium in the Wahiawa soil could be overcome either by increasing the supply of Ca or by selecting rhizobial strains that are insensitive to erosion.
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