The scientific classification of soils of Kerala is made based on classification system developed by USDA, the Soil Management Support Services. This multicategoric system is known as soil taxonomy. Each category is an aggregate of taxa, defined at about the same level of abstraction with smallest number of classes in the highest category and largest number in the lowest category. These categories are Order, Suborder, Great group, Subgroup, Family and Series. There are 12 orders under the System viz., Gelisols, Histosols, Spodosols, Andisols, Oxisols, Vertisols, Aridisols, Ultisols, Mollisols, Alfisols, Inceptisols and Entisols. Of these, eight orders are encountered in Kerala. They are Histosols, Spodosols, Vertisols, Ultisols, Mollisols, Alfisols, Inceptisols and Entisols.
There are no large contiguous areas of peats in Kerala. These are organic rich soils with organic matter, Hemists or Saprists that develop in lower topographic positions in a permanent water saturated environment. High acidity and high content of sulphidic material are associated with Histosols. These soils present numerous nutrient management problems and need special management for optimum returns. Cultivation of Histosols with organic layers result in decomposition of organic matter with concomittent shrinkage of soils. Upon shrinkage, the permanent water table comes to the surface and reduces the soil quality. These soils are identified in Kuttanad Kari lands.