Morphometrical analysis of cracks and crevices on a cyanobacterized soil surface subjected to a freeze-thaw cycle using image processing

Abstract

The present study was conducted with the aim of feasibility study of inoculation of soil cyanobacteria in improving soil crack patterns and controlling surface runoff under freeze-thaw conditions in erosion sensitive area of Badranlou in North Khorasan Province, Northeastern Iran. This study identified the dominant and safe cyanobacteria available in the micro-bank of the soil and inoculated them on prepared small experimental plots of 0.5 m × 0.5 m in three replications subjected to rainfall simulation. The crack pattern morphometry of the soil surface was comparatively studied using an image processing technique. Samples inoculated with cyanobacteria were compared to controls. The results showed that cyanobacterization influences the soil cracking patterns. So that a few deep and large cracks in the control treatment were significantly improved to shallow, small, frequent, and well-connected crevices with a larger area (226%; p < 0.04), longer length (101%; p < 0.05), and smaller width (70%; p < 0.03). The positive effects of changes in crack properties on runoff resulted from a simulated rain having 70 mm h−1 intensity and 30 min duration on the plots with a slope of 20% were also found. Compared to the control soil, the results showed that the soil cyanobacteria treatment by secreting polysaccharides and creating a spider-like system on the soil surface caused agglutination of aggregates and improved rheological properties of the soil, leading to increase runoff start time (274%; p < 0.01) and decrease runoff volume (-147%; p < 0.001). The results suggested that modifying soil surface conditions through inoculation of the soil cyanobacteria can be an innovative method to improve soil rheologic indices. These results would improve the understanding of soil cracks morphometry and the use of microorganisms in reducing the detrimental effects of extreme climatic conditions on soil hydrologic behaviors.