Reducing Surface Runoff from Soils Subjected to a Freezing-Thawing Cycle using Soil Cyanobacteria

Nowadays, the use of soil microorganisms as soil inoculators is being promoted to promote biotechnological methods to protect the environment. On the other hand, soil and climate conditions are among the important factors affecting the quantity and quality of soil erosion. So that, climatic agents such as freezing and thawing influence erosion dynamics. In this regards, soil conservation in watershed slopes and the significant role of freezing-thawing cycle in the production of surface runoff by the use of soil microorganisms such as cyanobacteria due to stability and proper sequence conditions of vegetation cover, adhesion and stabilization of soil for regeneration. Sustainable upgrading of ecosystems seems to be essential, while most soil and water conservation practices in the drainage network are engineered without considering the potential of biological methods for water and soil loss control. Therefore, the purpose of this study was to investigate the feasibility of inoculation of soil cyanobacteria in inhibition of surface runoff from soil under freezing-thaw conditions in a small plot.

For this purpose, the studied soil was taken from dryland and prone to erosion area of Badranloo in North Khorasan Province. Then, the most suitable native cyanobacteria in origin soil were identified, selected, purified and propagated, and ultimately inoculated on the plots in six replications for the capability assessment for soil and water conservation. Comparison of control and inoculated treatments with cyanobacteria under a freezing and thawing cycle was made under simulated rain conditions with intensity of about 72 mm.h-1 lasting for 30 min and on small erosion plots (0.5 x 0.5 m) with slope of 20% in the Rain and Erosion Simulation Laboratory of Tarbiat Modares University, Iran.

The results showed that inoculated cyanobacteria treatment after a freeze-thaw cycle significantly (p < 0.001) improved the surface runoff components compared to the control treatment. Statistical comparisons of the means also showed that cyanobacteria inoculation treatment significantly (p < 0.001) increased runoff commencement and time to peak at respective tune of 228 and 49%, and decreased runoff peak and volume at rates of 48 and 65% compared to those of the control treatment.

The results of the current study showed the positive effect of soil cyanobacteria inoculation for water conservation. It therefore could be supposed as an efficient, economic, and biological tool for improving the hydrological behavior of freezing-thawed soils. Hence, the results of this study could be used to designate the management patterns of water and soil conservation and extend to areas with similar conditions.