Spatial Variation in Soil Quality across Selected Fruit Tree Plantations in Bacnotan, La Union, Philippines

Authors

• Jay Mark G. Cortado, Graduate School, University of the Philippines, College, Los Baños, Laguna 4031 Philippines; Ilocos Sur Polytechnic State College, Santa Maria, Ilocos Sur 2705 PhilippinesFollow
• Roberto G. Visco, Institute of Renewable Natural Resources, College of Forestry and Natural Resources, University of the Philippines, College, Los Baños, Laguna 4031 Philippines
• Jenielyn T. Padrones, Institute of Renewable Natural Resources, College of Forestry and Natural Resources, University of the Philippines, College, Los Baños, Laguna 4031 Philippines
• Pastor L. Malabrigo Jr, Department of Forest Biological Sciences, College of Forestry and Natural Resources, University of the Philippines, College, Los Baños, Laguna 4031 Philippines

Publication Date

6-1-2026

Abstract

Sustaining soil quality on any plantation is critical to increasing productivity and responsible land use. However, spatial variation in soil quality across fruit tree plantations under existing field and management conditions remains insufficiently documented. This study aimed to assess the soil quality of monocropped plantations of banana, calamansi, coffee, and rambutan in northern Luzon, Philippines, evaluate the extent of degradation or improvement relative to a reference forest using the Soil Quality Index (SQI) approach, and identify the soil indicators that significantly influence soil quality in these plantations. The objectives were to determine which fruit tree plantations could enhance soil quality and which soil indicators most strongly influence it. The soil quality at 0 to 30 cm (upper), 30 to 60 cm (lower), and the combined data from both portions (0 to 60 cm depth) were assessed using 17 soil physical, chemical, and biological indicators, and rated from low to high. The soil quality in the upper portion of the banana plantation decreased, while the rest of the plantations improved. In contrast, the soil quality in the lower portion improved only under the banana plantation. Compared with the forest area, the coffee plantation alone showed improved soil quality across the 0 to 60 cm depth. Water holding capacity was the physical indicator that contributed most to the SQI across sites and soil depths. Among the chemical indicators, cation exchange capacity and exchangeable potassium exerted the strongest influence on the SQI, while the biological indicators that contributed most to the SQI were earthworm and bacterial counts. Overall, these plantations exhibited spatial and depth-dependent effects on soil quality relative to the forest area, with coffee showing net improvement across the 0 to 60 cm soil profile. This demonstrates that not all conversions of forest lands to fruit tree plantations result in reduced soil quality.

Recommended Citation

Cortado, Jay Mark G.; Visco, Roberto G.; Padrones, Jenielyn T.; and Malabrigo, Pastor L. Jr (2026) "Spatial Variation in Soil Quality across Selected Fruit Tree Plantations in Bacnotan, La Union, Philippines," The Philippine Agricultural Scientist: Vol. 109: No. 2, Article 14.
Available at: https://www.ukdr.uplb.edu.ph/pas/vol109/iss2/14