Effect of community-based soil and water conservation practices on soil glomalin, aggregate size distribution, aggregate stability and aggregate-associated organic carbon in northern highlands of Ethiopia

Abstract

BackgroundLand degradation is a major and widespread problem causing losses of ecosystem services in Ethiopia. Extensive utilization of the land resources for centuries resulted in severe land degradation in the Tigray region of northern Ethiopia. To reverse the problem, land restoration activities have been carried out for the past three decades. This study was initiated to determine the effect of community-based soil and water conservation interventions on soil glomalin, aggregate size distribution, water stable aggregates (WSA) and aggregate-associated organic carbon.MethodsSoil samples were collected from exclosures + terraces, exclosures alone, stone terraces and non-conserved grazing lands using systematic sampling based on slope positions.ResultsBoth easily extractable glomalin and total glomalin were significantly (p < 0.05) higher in exclosures compared to terraces and non-conserved grazing lands. The macroaggregate fraction of all SWC measures ranged 21.91–32.41%, where the lowest was in non-conserved grazing lands, while the highest was in exclosures with terraces. The micro-aggregate fraction ranged 19.9–26.66%, where the lowest was in exclosures, while the highest was in non-conserved grazing lands. The results also indicated that exclosures had significantly (p < 0.05) higher percent of WSA compared to terraces and non-conserved grazing lands. Mean weight diameter (MWD) was also significantly (p < 0.05) higher in exclosures. The WSA and MWD decreased in the order of exclosures with terraces > exclosures alone > terracess > non-conserved communal grazing lands. Comparison of aggregate-associated organic carbon (AAOC) showed relatively higher organic carbon in macroaggregates than in micro-aggregates. Besides, both macro- and micro-aggregate-associated SOC was higher in exclosures than in terraces and non-conserved grazing lands. The AAOC of both macro- and micro-aggregates follows the order exclosures alone > exclosures + terraces > terraces > non-conserved communal grazing lands.ConclusionExclosures and terraces are important strategies for rehabilitation of degraded lands through improving glomalin content, aggregate structure and stability, and aggregate-associated organic carbon.