Unsaturated soil hydraulic conductivity (Kh) and soil resistance under different land uses of a small upstream watershed in Mt. Banahaw de Lucban, Philippines

Issue Date

12-2021

Abstract

Soil hydraulic conductivity influences hydrologic processes and the ability of watersheds to provide ecosystem services. Like most soil properties, however, it is highly spatially variable at different scales due to biophysical and anthropogenic factors. To quantify spatial variability, the study assessed the influence of land use/land cover (LULC) on soil hydraulic conductivity and compaction, as reflected by soil resistance in a small upstream watershed. Compaction was measured using a soil compaction tester and the unsaturated soil hydraulic conductivity (Kh) was estimated in the field using the inverse auger hole method. Measurements were made across six LULC: agriculture (Agri), coconut with agricultural crops (Coco + Agri), coconut with pasture (Coco + Grass), coconut with forest (Coco + Forest), reforestation area (Refo), and forest (Forest). Measurements were taken at 0–30 cm and 0–50 cm soil depths. Results showed that soil hydraulic conductivity and resistance significantly differed across LULC and soil depths. Soil resistance averages 0.83 MPa for all LULC at 0–30 cm depth, which was significantly lower (p = 1.184e–04) than 0–50 cm depth. Coco + forest recorded the highest soil resistance (1.01 MPa at 0–30 cm and 1.82 MPa at 0–50 cm), while Coco + Agri has the lowest resistance. Pairwise comparison of means also revealed that Forest at 0–30 cm depth had significantly higher (p < 0.01) Kh at 1.18 cm min–1 compared with other LULC across depths. Kh at 0–30 cm depth averages 0.57 cm min–1 for all LULC, which is significantly higher (p = 3.229e–02) than 0–50 cm depth. This indicated a decreasing hydraulic conductivity with increasing soil depth. This implies that strategies for promoting groundwater recharge and sustaining freshwater supply for lowland communities, in general, should be founded on LULC decisions, especially in upstream watersheds.

Source or Periodical Title

Philippine Journal of Science

ISSN

0031-7683

Volume

150

Issue

6A

Page

1407-1415

Document Type

Article

Frequency

quarterly

Physical Description

illustrations; table

Language

English

En – AGROVOC descriptors

SOIL STRENGTH; SOIL PROPERTIES; SOIL COMPACTION; SOIL CHEMICOPHYSICAL PROPERTIES; HYDRAULIC CONDUCTIVITY; SPATIAL VARIATIONS; LAND USE; LAND COVER; LAND MANAGEMENT; WATERSHEDS; PHILIPPINES

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