The Impact of Agricultural Land Cover Change on Soil Hydraulic
Properties: Implications for Runoff Generation
Abstract
Infiltration and hydraulic conductivity ( K) play a key role in
streamflow generation and groundwater recharge. The impact of
agriculture on soil infiltration and K has been widely
investigated. While many studies show decreases in infiltration and
K, others show an increase or no change in both parameters. These
variations highlight the importance of conducting local scale
investigations. We investigated the impact of agricultural development
and land cover changes on infiltration and K. Unsaturated
hydraulic conductivity (K unsat) was measured at the
soil surface during both dry and wet seasons and saturated hydraulic
conductivity (K sat) was measured at 25, 45, and 65 cm
below the surface. Our results show that there were no significant
differences in K unsat between perennial crop cover and
natural forests; however, agroforests did have significantly higher K
unsat than natural forests, which was attributed to
higher soil moisture. There were no significant differences in K
sat among the perennial crops, agroforests and natural
forests at the 45 and 65 cm depths; however, at 25 cm natural forests
had significantly higher K sat, which was attributed to
the higher soil organic matter and lower bulk density in natural forest.
The study showed that the impacts of agriculture and land cover change
on K sat does not extend to deeper soil layers. We used
two years of rainfall intensity data, observed K unsat
and K sat , and HYDRUS-1D modelling to infer any changes
to runoff. We show that footpaths and perennial crop cover may generate
more surface runoff than natural forests. This study adds to the
literature on agricultural impacts on infiltration and K. More
importantly it shows that differences in crop type, management practices
and topographic location all play an important role on infiltration and
K, showing the need for local field based studies.