Characterisation of Soils Under Reed (Ochlandra Travancorica Benth.) In the Western Ghats
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Date
1999
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Department Of Soil Science And Agricultural Chemistry,College Of Horticulture,Vellanikkara
Abstract
A study was carried out at the Kerala Agricultural University and the
Kerala Forest Research Institute during 1993-1996 mainly to characterise the reed
growing soils of Western Ghats. The study comprises four parts, viz., pedological
/ taxonomical characterisation of reed growing soils, evaluation of fertility status of
reed growing soils, assessment of growth performance of reed in relation to soil
fertility and study on litter decomposition and nutrient release from reed leaf litter.
The pedological / taxonomical characterisation was carried out by digging
representative soil profile (with 3 replications) at two different types of topography
(flat-undulating and sloping) in two different elevations (200-300 m and 600-800
m) at four locations viz. Vazhachal, Pooyamkutty, Adimali and Pamba. Reed
growing soils were found to carry litter on soil surface which was. under varying
stages of decomposition. The colour of the surface soils was mostly in the hue of
7.5 YR and subsurface layers were dominated by either 5 YR or 10 YR. Fine
fibrous roots were found to mat the soil surface giving granular and crumb
structure. The subsurface layers were generally massive without any distinct
structural development. Reeds were found to flourish on both shallow and deep
soils. In pure reed brakes where upper canopy was closed, the undergrowth was
completely absent.
The content of gravel, especially the secondary gravel, was very low in these
soils. In most of the cases the textural make up turned from sandy loam to sandy
clay loam from top to bottom of the profiles. Bulk density was found to increase
with increase in depth of the profiles while porosity and water holding capacity to
showed a diminishing trend.
These soils were strongly to moderately acid in reaction and in pure reed
areas surface soils were more acid than subsurface soils. But in areas where reed
was growing as undergrowth in teak and moist deciduous forest, surface soils were
less acidic than subsurface soils. In general, exchangeable bases, exchange acidity,
cation exchange capacity and percentage base saturation were found to show a
diminishing tendency from surface to bottom of the profiles. Distribution of organic
carbon, total and available N, total and available P and available K was in a
decreasing trend with increase in depth of the profiles while total K was found
concentrated in lower layers.
In general, the change in location, elevation and topography was not found
to exert any definite impact on the depth wise distribution of soil properties in these
soils.
These soils were classified under Ustic Kandihumult, Ustic Palehumult,
Ustic Haplohumult,' Ustic Kanhaplohumult, Typic Kanhaplustult, Ustic
Hurnitropept, Ustoxic Hurnitropept, Ustic Dystropept, Ustoxic Dystropept, Oxic
Ustropept and Lithic Dystropept at sub group level.
The content of gravel, especially the secondary gravel was low in the 'Surface
soils of reed growing soils. These soils were sandy loam in texture with low bulk
density and moderately high water holding capacity and porosity.
In general, these soils were strongly acidic in reaction with high content of
organic carbon and available N and K. But the status of available P was very low.
Contents of available Ca and Mg were in moderate quantities. Cation exchange
capacity was also high, but the percentage base saturation was low.
Significant variation with respect to various soil properties viz., gravel, silt,
clay, bulk density, porosity, water holding capacity, pH, organic carbon, available
N, K, Ca, Mg and percentage base saturation was observed due to change in
location. Change in elevation was found to exert significant impact on bulk density,
porosity, organic carbon and cation exchange capacity. In general variation in
topography was not found to exert any significant and definite impact on various
soil properties. Results in general reveal that reed bamboo play a significant role in
conserving soil and its fertility.
Number of matured culms / ha was found to be a better parameter injudging
the growth performance of reed and Class I reed was found to have higher number
of matured culms / ha than Class II and Class Ill. Soils of Class I reed was
significantly acidic and contained higher organic carbon but lower available N and K
than the class Ill. The model fitted through stepwise regression relating number of
culms to different soil properties viz., soil pH, organic carbon, available N, P and K
was Y = 501.0420 - 179.881920xI + 16.1516x12 + ! .9450XIX2 where Y= number of
culms / ha, XI = soil pH and X2 = organic carbon.
Dry weight of both culms and leaves per hectare and uptake of N, P and K
were significantly high in Class I than the other two classes. The models fitted
through stepwise regression relating dry weight of culms and leaves with the uptake
ofN, P and K were YI=-1294.29 + 37.265N + 321.410 P + 226.442K, Y2=2.1 +
38.403 + 187.2 K where YI is the dry weight ofculms / ha and Y2 is the dry weight
of leaves / ha.
Reed growing soils were found to conserve comparatively higher content of
soil moisture. Mass loss during decomposition of reed leaf litter was highly
influenced by rainfall and the annual decomposition rate constant did not vary
significantly (0.229 and 0.234) at two sites studied. The time required for 50 per
cent and 95 per cent decomposition was 3 and 13 months respectively. Based on
the concentration and absolute content, the nutrient mobility from decomposing
reed leaf litter was in the order K > N > Mg > Ca > P.
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171628