Quality improvement of an erosion-prone soil through microbial enrichment

Biological soil crusts on bare land have undeniable roles in reducing soil degradation through improving soil quality. Enriching soil crusts biological properties by increasing soil microorganisms' population can be an effective strategy to improve soil chemical properties. Accordingly, native nitrogen-carbon fixing cyanobacteria and bacteria were individually and combined inoculated on 0.25 m2-plots filled by an erosion-prone, bare, and low quality soil collected from Marzanabad Region, Northern Iran. The important soil chemical properties, viz., total organic nitrogen, total organic carbon, soil organic matter, and total organic carbon-to-total organic nitrogen ratio were measured at time spans of 7-8 days for a period of 60 days. The results indicated that the total organic nitrogen, total organic carbon and soil organic matter increased significantly (p < 0.01) in all treatments. The total organic nitrogen and, total organic carbon and soil organic matter in the cyanobacteria, bacteria, and combined inoculated treatments increased up to 240, 188, and 172%; and, 40, 39, and 33%, respectively, compared to the control conditions. Additionally, the total organic nitrogen and total organic carbon in the study treatments were 46, 32, and 37%; and 40, 33, and 33% higher than those reported for the control plots. The rate of nitrogen fixing in all inoculated treatments had an increasing trend up to 38 days after which it declined. Nonetheless, carbon and organic matter storage increased throughout the experimental period. Meanwhile, the ratio of carbon-to-nitrogen were not significantly (p > 0.17) changed during the study period. Based on the study results, the positive role of microorganisms, especially cyanobacteria, was demonstrated in improving the chemical properties of the study soil.