Assessment of Improved Ladder Terraces in Controlling Soil Erosion on Uluguru Mountains-Tanzania

摘要

This study assesses effectiveness of improved ladder terraces in controlling soil erosion on steep slopes of Uluguru Mountains in Morogoro Region, where runoff collection tanks were located downstream of the divisor system were all runoff from the catchment upstream where improved ladder terraces were located. The soil properties percentage weight for sand, silt and clay were average 40, 10 and 50 respectively. Half of the terraces were left barely and half were planted with maize crop. Runoff and soil loss generated during every rainstorm was collected from six field plots of improved ladder terraces to the tanks. There was statistically significant different between reductions of soil loss in bare improved ladder terrace and cropped improved ladder terrace. The amount of runoff on the bare soil was high by 15% to 18% compare to runoff on cropped soils. It was found that cropped improved ladder terrace reduced soil loss by 74% while bare improved ladder terrace reduced soil loss only by 41%. Simple linear regression shows runoff water generated from rainfall amount with soil losses from different land cover. Bare soils behave with linear relationship (r2 = 0.85) unlike cropped soil were r2 = 0.36 because of gradual increase of crop canopy at every crop stage hence less impact to the soil. Soils losses from the bare soil ladder terrace and that of cropped soil ladder terrace was significantly difference with correlation coefficient of 0.863 at vegetative stage and 0.928 at the full booting stage.