Baseline Profile of Soil Samples from Upian River Watershed

Abstract

The Mines and Geosciences Bureau (MGB) in the Philippines is currently mapping out the entire Davao City Watershed Area (DCWA). There are 8 major watershed areas within DCWA that has been identified by the MGB and the largest is the Davao River Watershed Area (DRWA). A smaller sub-watershed within DRWA, the Upian River Watershed Area (URWA), was proposed of which its boundary and soil profile is yet to be established. This study focused on the analyses of the soil samples from URWA. The results for pH, organic matter, cation exchange capacity, N, P, K, Ca and Mg were then compared to the Bureau of Soil standard for its fertility rating. Analysis of lead (Pb) was also included as a pollutant indicator for possible soil contamination.

There are 4 sampling sites with unfavorable ratings for pH, 3 for both organic matter and phosphorus, and 2 stations for both nitrogen and calcium. Fertility rating is generally good for cation exchange capacity, potassium and magnesium. The Bureau of Soil has no existing standards for micronutrients. However, all sampling sites were found to be too low with micronutrients according to Gershuny and Smillie. No indication of lead contamination or pollution on all sites as far as natural levels of lead in surface soil is concerned. This study will provide baseline information that is useful to all stakeholders, to the people living near the area, farmers, planners, and resource managers. This can also provide inputs to key government agencies in the Philippines like the Department of Environment and Natural Resources (DENR) and the City Planning Office of Davao in formulating policies for sustainable management of the resource upon implementation of their programs and projects. Without the aforementioned information, planners would have difficulty in predicting the impact or recommend best management strategies for a specific land use.

doi:10.14456/WJST.2014.2