Reduction in soil detachment capacity by inoculation of bacillus polymyxa strain BcP26 in deforested lands

Abstract

The beneficial effects of rhizobacteria in increasing plant growth, nutrient uptake and rhizosphere soil aggregation are well known. However, few investigations have explored the impacts of these bacteria on soil erosion processes, particularly for the parameters used in rill erosion. To fill this gap, this investigation has evaluated the effects of growth of Zoysia grass roots induced by bacillus polymyxa strain BcP26 on the rill detachment capacity (Dc) and rill erodibility (Kr) in the treated soil, compared to the control soil by a paired sample t-test with six replications for each experiment in deforested lands of Northern Iran. For measuring Dc, a hydraulic flume was used at five slopes (4.3%–38.2%) and five water discharges (0.29–0.69 l m−1 s−1). Three characteristics of roots including the length, biomass and weight density of roots were measured. Dc was lower (on average - 24% for the average slopes) in the treated soil with the bacillus strain (PB) compared to the control soil (AB). Rill erodibility (Kr), obtained by the relationship between Dc and the shear stress, also was significantly lower (−60%) in the PB soil compared to the control soil. A principal component analysis provided a significant combined factor (the first principal component) that revealed an obvious discrimination in rill detachment capacity between treated and control soils. This value of rill erodibility for deforested lands is contributory for modelling purposes of soil resistance to rill erosion. It is concluded that, thanks to the bacillus strain used as one of plant growth promoting rhizobacteria, soil erosion is significantly (at p < 0.01) reduced, and this strain contributes to reduce the risk of soil degradation.