Glomalin-Related Soil Protein and Its Relationship with Organic Carbon and Nitrogen in Water-stable Aggregates in Abandoned Agricultural Lands

Abstract

A large number of studies have shown that glomalin-related soil protein (GRSP) plays an important role in soil aggregate formation and soil carbon balance. However, to date, we lack understanding on the relationship between GRSP and water-stable aggregates (WSA) in abandoned agricultural lands of semi-arid region. We considered abandoned agricultural lands of different ages in Minqin Oasis as the research object. We discussed the changes of GRSP and the relationship between GRSP and WSA during land abandonment. The research results showed the following: the content of extractable glomalin-related soil protein (e-GRSP) and total glomalin-related soil protein (t-GRSP) is higher than that of traditional arable lands, and the content increases as the years of land abandonment increase. e-GRSP and t-GRSP contents are higher than the soil layer of 0–20 and 40–60 cm in terms of vertical section. The proportion ranges of e-GRSP and t-GRSP in soil total organic carbon (TOC) are 0.62%–2.0% and 1.97%–8.1% respectively in the abandoned agricultural lands. e-GRSP and t-GRSP also exhibit significant quadratic correlation with TOC (<i>P</i><0.05). e-GRSP and t-GRSP have significant positive correlation with mean weight diameter (<i>P</i><0.05). Significant and extremely significant positive correlations are observed between the e-GRSP and t-GRSP and the WSA with particle sizes between 0.25–1 and >2 mm and the organic carbon (OC) and nitrogen (N) existing in such sizes, respectively. In addition, significant and extremely significant negative correlation exist between the e-GRSP and t-GRSP and the clay and silt contents (<0.053 mm) and the OC and N in clay and silt. In general, land abandonment has raised the GRSP content. Moreover, the GRSP after land abandonment tends to promote large WSA formulation and organic matter enrichment in large aggregates. Organic matter accumulation in clay and silt was also inhibited. This phenomenon helps build a reasonable aggregate hierarchy and improve the stability of soil aggregates.