MSc

The investigation entitled "comparative study of the soils of cardamom
plantations and virgin forests" was taken up at the College of Agriculture,
Vellayani, during 1994 - 96. The study has been made on the soils of cardamom
plantations of the Idukki district of Kerala with a view to assess and compare
physico-chemical and nutritional status of cardamom cultivated soils and virgin
forests. A comparison was also made between healthy cardamom plantation
with those where a decline in yield is observed. For this, surface soil samples
and soil profiles excavated from various selected locations were subjected to
detailed chemical analysis. The plant samples were also collected from the
cardamom plantations and subjected to chemical analysis to find out whether any
plant nutrient factors are involved in the yield decline in cardamom.
A study of the soils of cardamom plantations in comparison with adjacent
forests has shown that considerable variation in the physico-chemical properties
of the forest soils did not take place due to the influence of the cardamom
plantations.
In all these soils, the sand and silt content decreased and clay content
increased with depth. The soils of cardamom plantations have higher sand
content and lower clay content compared to the soils of adjacent forests.
A higher content of the clay in the forest soils compared to cardamom plantation
indicates a greater degree of weathering and clay formation. Healthy cardamom
plantation soils contained a significantly higher amount of coarse sand and lower
content of fine sand than the soils of the location which show a decline in yield.

12D
The physical properties such as bulk density, particle density and WHC
and exchangeable properties such as CEC, ECEC, exchangeable acidity were
found to be positively influenced by organic matter content of the soils and were
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more or less similar in all the locations.
Total P and K content of soils of the cardamom plantations were low



when compared to the


adj acent forest indicates inefficient bio-cycling



associated with the cardamom plantation and loss of bases from the system by
leaching and soil erOSIOn. A lower P content of the soils of the cardamom
plantation which show a decline in yield when compared to the healthy
plantation is due to t,he inherent properties of the former.
Inspite of the similarity in the content of total nitrogen, the available N of
the adjacent forest soils was significantly higher indicating a rapid rate of
mineralisation of organic matter in the soils of adjacent forest. The total P
content of the soils of the healthy cardamom plantations was significantly higher
than that of the location which show a decline in yield.~\.Jhe specific influence of
--'
the plantations m making more of available P from the unavailable pool is
evident.
The total and exchangeable potassium status m the soils of the
cardamom plantation recorded a lower value than the soils of the adjacent
forest. This situation may indicate a lower release as well as grater uptake of
this element. The content of micronutrients such as Fe, Mn, Zn and Cu were
more or less same in the soils of cardamom plantation and adjacent forest
indicating the same parent material and similar climatic conditions prevailed in
the locations under study.



The analysis of plant leaves showed a higher content of P, K, Ca, Mg, Fe,
Mn, Zn and Cu in the leaves of the healthy cardamom plantation. This point to
a situation where the soil nutrient factors are not a single factor for declining the
yield of cardamom but the plant nutrient factors were also responsible for the
decline in yield.


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