Geographic Information System-Assisted Approach in Soil Erosion Hotspot Assessment of Banga Microcatchment

Abstract

The study aimed to characterize the biophysical environment of the microcatchment, predict soil loss (t/ha/yr.), quantify soil loss for six months, estimate carbon and primary nutrients nitrogen (N), phosphorous (P), potassium (K) loss of major land uses using Universal Soil Loss Equation (USLE) modified through Manifold System Version 8.0 and recommend doable mitigating measures. The Sibalew-Torralba Microcatchment (431.87 ha) is located in Banga, Aklan (122°19'845" and 122°19'449" East Longitude, 11°32"329" and 11°32'586" North Latitude). The two soil types were Sigcay and San Manuel clay loam with compacted surface value of 1.33-147g/cm, a pH of 4.7-6.1; with low N, P, K but medium in soil organic matter (SOM). The microcatchment belonged to Type III climate with mean annual rainfall of 2,183.47 mm. The topography is flat to undulating, rolling, and steep slopes. There are seven major land uses namely agricultural land, mixed vegetation, orchard/agroforestry, coconut-based, grassland, built-up, and water tributaries. Results revealed that the average soil loss at different land utilization types (LUT) was 159.51-1205.32 t/ha/yr. The average actual soil loss range from 19.98-1074.06 kg/ha for six months. Soil erosion hotspots (high-very high soil loss category) was predicted in four LUTs: agricultural land (upland rice, 206.29-618.73 t/ha/yr.; mix vegetation (natural vegetation,  fruit trees associated with banana, and corn-vegetables, 75.15, 87.04 and 913.78 t/ha/yr., respectively); coconut-based (coconut-based perennial and mahogany, with underneath of upland rice, 96.37 and 154.77 t/ha/yr.), and built-up (institutional and roads going to provincial roads, 41.69 and 70.42-332.09 t/ha/yr.).  Further, carbon loss range from 2.60 to 137.26 kg/ha/6 months; available N loss range from 3.65-172.27 kg/ha/6 months; available P loss range from 74.13-9297.25 kg/ha/mo. while exchangeable K loss range from 8.42-452.39 kg/ha/yr. Thus, application of best crop and soil conservation management practices (natural farming/organic farming and multi-story fruit based agroforestry) is recommended to mitigate soil erosion.