Abstract:
The objective of this study was to quantify the effects
of cultivation on selected soil properties in the northern highland of
Iran. Three adjacent land-use types including cultivated lands (which
have been converted from pastures and forests for 18 years), a native
forest and pasture lands were studied. Soil samples were collected from
four sites in each of the three different land use types in the depths
of 0-10 and 10-20 cm. Results showed that conversion of native pasture
and forest soils into cropland during the 18 year-period increased soil
Bulk Density (BD) by 16%, plasticity index by 30% and soil erodibility
by 51%. In addition, it decreased Soil Organic Matter (SOM) and Total
Nitrogen (TN) by 50% each, tilth index by 40% and available water capacity
by 40% for the 0-20 cm soil depth. There were significant differences
in soil BD between depths in the pasture and cropland, but not in the
forest. Depending upon the increases in soil BD and disruption of pores
by cultivation, total porosity decreased accordingly. The Mean Weight
Diameter (MWD) and Water-Stable Aggregates (WSA) were greater in the pasture
and forest soils in comparison with the cultivated soils and did not change
with the depth for each land use type. The distribution of Organic Carbon
(OC), Total Nitrogen (TN) and available Phosphorus (P) within WSA showed
preferential enrichment of these elements in the macroaggregate fraction
(4.76-2.0 mm) for the uncultivated soils and microaggregate fraction (>0.25
mm) for the cultivated soils. These results suggest that the cultivation
of native forests and pasture lands in the northern highlands of Iran-degraded
soil properties left soil more susceptible to erosion. Since smaller aggregates
are preferentially removed by erosion, there is a need to consider appropriate
management practices for increasing soil sustainability and productivity.
Mostafa Emadi, Mehdi Emadi, Majid Baghernejad, Hamed Fathi and Mahboub Saffari, 2008. Effect of Land Use Change on Selected Soil Physical and Chemical Properties in North Highlands of Iran. Journal of Applied Sciences, 8: 496-502.
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