Effects of Superabsorbent Polymer on Cyanobacterial Biological Soil Crust Formation in Laboratory

Numerous attempts have been made to control desertification and restore soil by inducing biological soil crusts (BSCs) formation through inoculation with cyanobacteria or application of soil fixing chemicals. In this study, combined application of biological (cyanobacteria) and chemical (superabsorbent polymer: SAP) materials to sand particles was conducted under laboratory conditions. Nostoc sp. was applied to sand at 5 to 25 mg fresh weight (FW)/cm2 and incubated at 25°C under 100 μmol photons m−2 s −1 for 12 hr per day for 3 months. MWD (Mean Weight Diameter) analysis showed that the minimal cell dose for artificial BSCs induction was 10 mg FW/cm2, and the resulting BSC was stable enough to resist various destructive factors. Aggregate stability of the combined biological and chemical treatment (ACSAP) was higher than that of samples treated with Nostoc cells alone (AC) in the fast and slow wetting tests, but less stable than that of AC treatment in the wet stirring test. The SAP showed no harmful effect on Nostoc cell growth because of increased biomass during ACSAP treatment. However, the levels of extracellular polysaccharides (ESP) were lower upon ACSAP treatment than AC treatment. The wet stirring test demonstrated that ESP content was more important than cyanobacterial biomass for maintaining stability of the induced BSC. Overall, this study provides useful information regarding the interaction of Nostoc cells and superabsorbent polymer during artificial BSC formation. The results indicate that future studies investigating application of combined treatment of Nostoc cells and SAP in the field are warranted.