Soil Quality Evaluation and Classification System: Criteria for Determining Fertility Classes for Agricultural Production

Abstract

Soil functions are numerous and diverse considering the different uses and roles played by the soil in both managed and natural environments. An evaluation system was developed and applied to three soil units or sites in a mangrove (Rhizophora spp.) forest ecosystem by reason of the environment being a peculiar terrain exhibiting both land and water features with recurrent or semi-diurnal, alternating, oxidation-reduction processes. A minimum data-set (MDS) of soil properties was chosen and each property was rated on a 5-point scale according to criteria for fertility classes in agricultural production and these were transformed into soil quality classes. Soils in quality classes 1 and 2 that require minor to moderate management inputs are deemed to be ideal agricultural soils in sustainable agriculture while those in class 3 represent low productivity with high production costs. Soils in classes 4 and 5 are non-agricultural even on a short-term basis. The soils in the study area belong to class 3 in subclasses 3(i) and 3(ii) described as fairly (50-60%) and marginally (40-50%) fertile, respectively, in productive agriculture, which also reflects the health of the soils in ecological functions such as ecosystem buffering. Soils with scores below 50% are best preserved as environmental filters and, perhaps, for rejuvenation rather than their instant use in agriculture since production or crop yield is not likely to be sustainable in the long-run.