Marginal Uplands in the Philippines: Characteristics, Occurrence, and Management for Improved Crop Production and Environmental Quality

Marginal uplands are defined in this paper as undulating and steep lands ranging in elevation from near sea level to about 1000 m elevation and having low crop productivity due to poor soil fertility. Deforestation, shifting cultivation, and unsustainable cultivation practices have resulted in the widespread occurrence of these problematic lands in the Philippines. The common plant species in marginal uplands which can be used as indicator plants are (A). Cogon (Imperata cyclindrica), (B). Bugang or Talahib (Saccharum spontaneum), (C). Carabao grass (Paspalum conjugatum), and (D). Hantutuknaw (Melastoma malabathricum). Native guava (Psidium guajava) is almost always present in marginal uplands. The soils in marginal uplands possess various constraints to crop production that vary with the soil genesis and land use history. The constraints include physical such as shallow depth, compaction, unfavorable slopes, and low infiltration rates as well as chemical constraints such as acidic or alkaline pH, low OM, and nutrient contents. The soil fertility constraints vary widely among marginal upland soils. Agroforestry is widely accepted as the sustainable form of management strategy for marginal upland soils. The use of native tree species to rehabilitate denuded lands called Rainforestation Farming has been proven effective at various sites throughout the country and has been adopted as part of the national strategy to rehabilitate marginal or degraded uplands. Lastly, contour farming is also a proven strategy to improve soil and environmental quality in marginal uplands.