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KERALA

Geographic position and climate

The state of Kerala located at the southern most end of the country along the coast of Arabian
Sea with latitude 8°18' to 12°48' N and with longitude 74°52' to 72°22' E. Though, Kerala is a
narrow strip of land with 580 km length and with a width varying from 35 to 120 km along the
coast of Arabian sea, it has got a wide spectrum of soils developed under different topography,
micro-climate and variation in intensity and pattern of rainfall. Kerala, is blessed with humid
tropical wet climate with an annual rain fall of 3107 mm from seasonal monsoons. The extreme
eastern parts experience a drier tropical wet and dry climate, while the mountainous eastern
highlands of Idukki district experience wet and cool climate. Kerala's rains are mostly the result
of seasonal monsoons. The entire state could be visualised as a macro watershed with 41 rivers
originating from the eastern boundary of Western Ghats flowing down to the western side
through the foot hills, the midlands and converging to the coastal lakes and finally to Arabian
sea. The alluvium from these rivers together with marine deposits due to inundation of brackish
water resulted in the formation of the potentially acid sulphate/acid saline soils all along the
coastal area of the state.

Soils

The soils of Kerala have beendeveloped from acid igneous parent rocks under tropical humid
climate. Rainfall and moisture regimes are the most important climatic factors along with relief
which influenced the soil forming processes of this region. Thus based on the variation in climate
and topography along with influence of sea water, the state is covered by soil orders with major
share of Ultisols and Alfisols (the laterite and lateritic soils), Inceptisols or Entisols and Histosols
in Kuttanad, Kole, Pokkali and Kaipad, and quite different Vertisols in eastern Palakkad with a
semi arid climate. These soils are fertile with respect to available nutrient status, but are
constrained with salinity, acidity, iron and aluminium toxicity. High seasonal variability is
observed with respect to nitrates, potassium, magnesium and boron resulting from tidal influence
and rainfall pattern.

Ninety two per cent of total area of the state is acidic in nature of which 54% is extremely to
strongly acidic, which essentially requires amelioration. The lowest pH (≈3) is usually observed
in the acid sulphate/ acid saline areas.The high organic matter status in acid sulphate/acid saline
soils is attributed to colluvial deposition and slow rate of decomposition under submerged
environment. In general, the laterite and sandy soils of Kerala are very poor in available
phosphorus (Bray 1 P) status due to fixation under acidic environment. However, high available
P status in more than 64% of soils was recorded across the state during the recent fertility
assessment. The reserve potassium on solid phase in the soils of the state is negligible due to the
absence of potassium fixing minerals. Medium level of potassium fertility is usually noticed due