Soil organic matter status changes with cultivation of overgrazed pastures in Semi-dry West Central Iran

Abstract

The native intensively grazed and degraded pastures in dry areas are initially low in soil organic matter content. Therefore, frequently cultivation and conversion of these lands to croplands might have a positive influence on soil properties including soil organic matter. This study was conducted to determine the impacts of cultivation of overgrazed pasture on selected soil organic matter components in Javanmardi Plain, west central Iran. Total Organic Carbon (TOC), Particulate Organic Carbon (POC) compounds, total nitrogen and carbohydrate fractions were measured. Two sites including a pasture overgrazed by sheep in adjacent with one pasture converted to wheat fields for more than 23 years were used. Soil samples were taken from 0-5 and 5-15 cm depths in each site. Land use change resulted in significant (p<0.05) increases in TOC, POC, total nitrogen and carbohydrates contents in both depths. In most cases, the amounts of TOC in macroaggregates (0.25-2 mm) were significantly higher than those of micro aggregates (0.05-0.25 mm) and large portion of TOC was stored in the macroaggregates. Cultivation of overgrazed pasture considerably increased the percentage of POC/TOC, reflecting more plant residue inputs under plantation. Although, land use change considerably increased TOC and carbohydrate amounts of intact soil, in most cases positive impact of land use change on storage of TOC and carbohydrate in aggregates were not (p>0.05) significant. © 2011 Academic Journals Inc.