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Soil organic matter (SOM) is one of the most important components of soil when evaluating soil structure and its impact upon the environment. The discovery of a unique glycoprotein, glomalin, in 1996 challenged what was known about the composition of SOM. In an effort to better understand the presence of glomalin in SOM, the current research focused on glomalin concentrations in soils as it relates to the key soil properties, such as pH, clay (%), total C (%), C/N ratio, organic C/N ratio, inorganic C (%), and soil organic matter (%). Twenty soils collected from undisturbed rangelands throughout the United States, representing a wide range of the aforementioned soil properties, were analyzed for easily extractable glomalin (G1) and for total glomalin (G2). The G1 and G2 extracts were analyzed for protein content using the Bradford assay, and their respective immunoreactive fractions (IR-G1 and IR-G2) were determined using the enzyme-linked immunosorbent assay (ELISA). Statistical correlations indicated that pH, total C, and SOM were the best predictors of glomalin in soils (R2 values of 0.43, 0.42, and 0.46, respectively). Inorganic carbon and C/N ratio were determined to be the best predictors of the immunoreactive fractions of soil glomalin (R2 values of 0.63 and 0.55, respectively). Multiple regression analysis revealed that 75% of variation in the G2 fraction and 73% of variation in the IR-G2 fraction could be explained by the collective soil properties. Overall, the results indicate that G1 and IR-G1 measurements may be ambiguous and that G2 and IR-G2 are the most accurate representation of total glomalin and immunoreactive glomalin in soils.
Melissa J. Haddad received her M.S. degree in environmental science from the University of Texas at San Antonio. Her thesis research focused on glomalin and its relationship with soil properties. Prior to this, Haddad served in the U.S. Army as a Medical Service Corps officer, completing assignments in Germany, Bosnia–Herzegovina, and Fort Bragg, North Carolina. She completed her undergraduate studies at Mercer University, where she received a B.S.E. degree in biomedical engineering with minors in environmental engineering and mathematics.Dibyendu Sarkar is an assistant professor and director of the Environmental Geochemistry Laboratory at the University of Texas at San Antonio. Sarkar received his Ph.D. from the University of Tennessee and did his postdoctoral training at the University of Florida. His areas of expertise include soil chemistry, environmental quality and remediation, and risk assessment. Sarkar is also an associate editor of Environmental Geosciences.