On the basis of the morphological features and physio-chemical properties, the soil of the Kerala have been classified into red loam, laterite soil, costal alluvium, riverine alluvium, Onattukara alluvium, brown hydromorphic, saline hydromorphic, Kuttanad alluvium, black soil and forest loam.
Red Loam
Red loams of kerala are found mostly in the southern parts Thiruvananthapuram district. These soils occur in chain sequence along with laterite. The soil has red colour due to the presence of iron oxides. They are low in organic matter content.
Laterite
The major soil type found in Kerala is Laterite soil. Heavy rainfall and high temperature is suitable for the process of laterisation. They have poor water holding capacity with low organic matter content. The major crops that grown in the laterite soil of Kerala are Rubber, Cashewnut, Pepper and Coffee
Coastal Alluvium
These soils are seen in the coastal tracts along the west. They have been developed from recent marine deposits. These soils are acidic and of low fertility level.
Riverine Alluvium
These soil occurs mostly along the banks of rivers and their tributaries. They are very deep soils. They are moderately supplied with organic matter, nitrogen and potassium. Also they are acidic and poor in phosphorus and lime.
Brown Hydromorphic*
Hydromorphic soil are mostly confined to valley bottoms of undulating topography in the midland and to low lying areas of costal strip. They have been formed as a result of transportation and sedimentation of material from adjacent hill slopes and also through deposition by rivers. They are moderately supplied with organic matters.
Saline Hydromorphic*
The orgin, genesis and development of these soil have been under peculiar physiographic conditions. These souls are mainly found in the costal tracts of the districts of Ernakulam, Alappuzha, Thrissur and Kannur. They are not comparable with the salines soils occurring in the other parts of the country. The Pokkali(Ernakulam district) and Kaipad( Kannur district) soil come under this category.
Black Soil
They are dark, low in organic matter and high in clay content. In Kerala black soil is found in Chittur taluk of Palakkad district. Cotton and Groundnut are the major crops that grow in black soil of kerala.
Forest Loam
They are rich in nitrogen; but poor in the bases because of heavy leaching. They are restricted inoccurrance to the eastern part of the State.
Kuttanad Alluvium
A good portion of Kuttanad lies 1 to 2 meter below sea level and is submerged for major parts of the year. The soils of Kuttanad area are faced with the serious problem of hydrology floods, acidity and salinity. The construction of the Thanneermukkam bund, salinity hazards have been considerably reduced.
The soil of Kuttanad can be grouped into three categories, the Kayal soil, the Karappadam soil and the Kari soil which are dealt with in the zone of Problem Areas. Acid sulphate soils occur in Kerala in Kuttanad region.
Onattukara Alluvium
These soil confined to the Onattukara region comprising the Karunagapally, Karthikapally and Mavelikara of Kollam and Alappuzha district. They occur as marine deposits. These soil have very rapid permeability.
*Hydromorphic Soil - Soil formed by sedimentaion different things from other regions.