Abstract:
The local communities residing in Timble watershed Fagita Lekuma district are actively
engaged in expanding Acacia decurrens plantation on different land use types, primarily for
charcoal production and construction purposes. However, their influence on catchment
hydrology and soil aggregate stability was not well studied and appropriately characterized.
The objective of this study was examining the effect of different land use types on catchment
hydrology and soil aggregate stability. Two factors were involved in the experiment that is land
use types (cropland, grazing land, 0 year stand, 2
nd
year stand, and 4
th
year stand age) and soil
depths (0-15, and 15-30cm). Acacia decurrens plantation was further subdivided into three
stand age groups (0 year, 2
nd
year and 4
th
year stand ages). The design was 5* 2 factorial
arrangements in a randomized complete block design (RCBD) and replicated 4 times. A total of
40 (5*2*4) composite soil samples were collected for the analysis of selected soil
physiochemical properties. Semi structured questionnaire was used to investigate the perception
of purposefully selected farmers on catchment hydrology. Two way analysis of variance
(ANOVA) was performed and significance difference was declared at p<0.05. Results showed
that soil particle sizes (sand, silt and clay) and SOC contents significantly varied in all studied
land use types and soil depths. However, soil pH did not vary with soil depths (p=0.5605). The
soil organic carbon content was significantly lower (p<0.05) under crop land and grazing as
compared to other studied land use types. Significantly different and higher values of wet
aggregate stability (WAS), mean wet diameter (MWD) and geometric mean diameter (GMD)
were observed under fourth age and second age stands of Acacia decurrens plantation
(p=0.0264, p<0.0001 and p=0.0161, respectively). In addition, WAS, MWD and GMD values
are strongly and positively correlated with clay, and SOC contents. Most of the interviewed
households believe that flow of water, quality of water, and severity of soil erosion due to runoff
has been improved due to the recent land use land cover change to Acacia decurrens plantation
This study recommends the implementation of land use planning assisted Acacia decurrens
plantation for the improvement of soil physico-chemical properties and catchment hydrology of
the study area soils. Moreover, local farmers could be benefited more from the Tangua system if
they harvest Acacia decurrens plantation at the fourth stand age
