Improving runoff behavior resulting from direct inoculation of soil micro-organisms

Surface hydrology can significantly influence biological soil crusts through altering runoff behavior. Hence, micro-organisms enrichment of degraded soil crust may be a novel and practical strategy to improve soil quality and surface runoff behavior. This study evaluated the impact of inoculating (i) bacteria, (ii) cyanobacteria and (iii) bacteria + cyanobacteria on soils, with the hypothesis this would improve runoff properties. Accordingly, we assessed the influence of microbial enrichment after inoculating the native cyanobacteria (Nostoc, Oscillatoria and Lyngbya) and bacteria (Azotobacter and Bacillus) on runoff onto a degraded soil under laboratory conditions. The cyanobacteria and bacteria were isolated from the studied soil, purified and proliferated in the laboratory, and then inoculated in individual or combined treatments onto soils placed into small experimental boxes. After 15, 30 or 60 days, the treatments were subjected to a simulated rainfall. We observed a significant (p < 0.01) decrease in both coefficient and peak of runoff in the bacteria, cyanobacteria, and bacteria + cyanobacteria inoculated boxes relative to the control boxes. There was also a significant (p < 0.01) delay in runoff start time (38-205%) and time to peak runoff (48-52%), and decrease in coefficient (74-96%) and peak of runoff (48-86%) in the bacteria, cyanobacteria, and bacteria + cyanobacterial-treated boxes compared to the control boxes. The most effective treatment was the inoculation of cyanobacteria after 60 days (p < 0.01). In this treatment, the runoff coefficient was reduced 96%, the peak reduced 83%, the start time delayed 168% and time to peak reduced by 34% compared to the control. While these results need verification in the field, they suggest that inoculation of native micro-organisms particularly cyanobacteria, can be practically used to restore local hydrological cycles in the soil.