Abstract:
Removal of the topsoil layer reduces soil health, water retention capacity, and carbon
sequestration ability while contaminating reservoirs and increasing runoff and flooding.
Therefore, accurate assessment of soil erosion is very important for sustainable land
management and building aclimate-resilient environment. This study was conducted to quantify
soil erosion rates using the Fallout Radio Nucleotide (FRN) technique in the Gregory Lake
Catchment. The study further investigated the relationship between soil chemical properties and
soil erosion under selected land uses including natural forest, tea land, vegetable land, grassland
and municipal area. Sediment samples from Gregory Lake were also analyzed. Three soil samples
(0 – 40cm) were collected from each land use and analyzed for radioisotopes of 137Cs and 210Pb
activities using High Purity Germanium Gamma detector. These radioactivity values were
converted to soil erosion/deposition rates using the mass balance model. Soil samples were also
tested for chemical properties such as pH, EC, available phosphorus, exchangeable potassium and
organic matter content. Using Turkey’s mean separation, differences (p<0.05) in erosion
estimates and chemical properties among land uses were identified. The study revealed that soil
erosion rates vary significantly with land use type. The highest soil erosion was observed under
vegetable cultivation (43.56t/ha/yr), which is highly influenced by human activities and a high
rate of sediment deposition was observed in Gregory Lake (16.53t/ha/yr). There was a significant
negative correlation between soil erosion and soil organic matter percentage. Since there was a
strong correlation between soil erosion rates measured using 137Cs and 210Pb methods both Cs
and Pb radioisotopes can be used to measure soil erosion rates with comparable accuracy. This
method aids long-term erosion assessment in highland catchments by quantifying soil erosion
rates, identifying suitable conservation methods, locating critical erosion-prone areas and
preventing degradation of agricultural lands, tea plantations and forests.
