Abstract
This study evaluated land cover change and slope gradient on selected soil quality parameters in the Gumara watershed, northwestern Ethiopia. 36 soil samples were collected from 0- to 20-cm depth under four land cover types across three slope gradients. The collected soil samples were analyzed for selected soil quality parameters. Result indicated that the bulk density of the soil is different (P < 0.001) in the watershed because of land cover change and slope gradient. Cultivated land and steeper slopes have the highest bulk density and lowest total porosity. On the other hand, the forestland and gentler slopes have lowest bulk density and high total porosity. Intensive cultivation accompanied by continuous conversion of forestland to cultivated land caused high bulk density and low total porosity. Cation exchange capacity, exchangeable magnesium total nitrogen, available phosphorus and potassium negatively correlated with slope gradient. Conversion of forestland to cultivated land contributed to changes in pH (P < 0.05) exchangeable calcium (P < 0.01), potassium (P < 0.001), available phosphorus (P < 0.01) and nitrogen (P < 0.01) content. The soil degradation index results showed that soil organic carbon, nitrogen, available phosphorus and exchangeable potassium contents declined and bulk density increased because of the land cover change. This negative effect on agricultural development and environmental health of the watershed makes an integrated land resource management approach vital for sustaining agricultural productivity and the environment health of the Gumara watershed.
Highlights
Soil as a fundamental natural resource performs key environmental, economic and social functions
Some research has been done on land use/cover change and its impact on soil quality dynamics (Lambin et al 2001)
Since the main purpose of assessing soil quality in this study is to evaluate its status for crop production, only the soil parameters that are crucial for plant growth such as soil organic carbon (SOC), N, P, K and bulk density were considered
Summary
Soil as a fundamental natural resource performs key environmental, economic and social functions. These functions of soil vary over space and time governed by a soil quality. The quality of soil is its capacity to function within ecosystem and land use boundaries, to sustain biological productivity, maintain environmental quality and promote plant, animal and human health (Doran et al 1996). Studies of impacts of land-use change on soil fertility quality in the highlands of Ethiopia (Woldeamlak and Stroosnijder 2003; Mulugeta 2004; Negassa and Heluf 2004) indicate that forest and shrub lands have high fertility quality compared to grass and cultivated areas. In western Ethiopia, Nega and Heluf (2009) conclude that conversion of natural forest land into grazing land and cultivated lands caused loses of
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