GENESIS, CLASSIFICATION AND EVALUATION OF SOILS IN RENIGUNTA MANDAL OF CHITTOOR DISTRICT, ANDHRA PRADESH
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Date
2008
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY, RAJENDRANAGAR, HYDERABAD.
Abstract
The present investigation involves study of genesis, classification and
evaluation of soils in Renigunta mandal of Chittoor district in Andhra Pradesh.
For this seven representative pedons were selected in seven different locations
of the study area covering all types of soils. All the seven pedons were
described for their morphological features in the field and horizon-wise
samples were collected and analyzed in the laboratory for physical, physicochemical
and chemical properties.
The study area was characterized by semi-arid monsoonic climate with
distinct summer, winter and rainy seasons. The pedons selected were confined
to plain and gently sloping topography. Pedons 4 and 7 were originated from
calcareous murrum and alluvium parent materials, respectively. However, the
remaining pedons were originated from granite-gneiss.
The morphological features indicated the presence of AC (Pedons 2, 3
and 7) and ABC (Pedons 1, 4, 5 and 6) profiles. The soils were deep to very
deep in depth, yellowish brown to dark yellowish brown in colour, loamy sand
to silty clay loam in texture and had sub-angular blocky, angular blocky and
single grain structure.
The clay content increased with depth in pedon 3 whereas pedon 6
showed an increasing trend from Ap to Bw2 horizon and later on decreased.
Pedons 1, 2, 4, 5 and 7 have shown no specific trend with depth. Physical
constants like water holding capacity, loss on ignition and volume expansion
followed the trend of clay content. All the pedons exhibited an irregular trend
in bulk density with depth.
The pedons were slightly acidic to strongly alkaline in reaction and low
in organic carbon content. All the pedons recorded less per cent of CaCO3.
The CEC values were low to medium and exchange complex was
dominated by Ca2+ followed by Mg2+, Na+ and K+. Chemical composition of
soils revealed that all the pedons registered higher silica content indicating
siliceous nature.
Regarding nutrient status, the soils were low in available nitrogen and
phosphorus, low to medium in available potassium and high in available
sulphur. However, the soils were deficient in available zinc and sufficient in
available copper and manganese. Further, the surface soils were sufficient and
sub-surface soils were deficient in available iron.
As far as clay mineralogy is concerned, pedons 1, 4, 5 and 6 showed the
dominance of illitic clay mineralogy whereas pedons 2, 3, and 7 exhibited
siliceous mineralogy due to higher silica content (>80%).
Based on morphological, physical, physico-chemical, mineralogical and
meteorological data, the soils of Renigunta mandal were classified as :
Pedon 1: Fine-loamy, illitic, iso-hyperthermic, Typic Haplustalfs
Pedon 2: Fine-loamy, siliceous, iso-hyperthermic, Typic Ustifluvents
Pedon 3: Fine-loamy, siliceous, iso-hyperthermic, Typic Ustorthents
Pedon 4: Fine, illitic, iso-hyperthermic, Typic Haplustepts
Pedon 5: Fine-loamy, illitic, iso-hyperthermic, Typic Haplustepts
Pedon 6: Fine-loamy, illitic, iso-hyperthermic, Typic Haplustepts
Pedon 7: Coarse-loamy, siliceous, iso-hyperthermic, Typic Ustipsamments
Based on the soil properties, the soils of the Renigunta mandal have
been classified into land capability classes and sub-classes viz., IIs (Pedons 4,
5 and 6), IIIe (Pedons 1 and 2), IIIes (Pedon 3) and IVs (Pedon 7).
Description
Keywords
GENESIS, CLASSIFICATION, EVALUATION, SOILS, RENIGUNTA, MANDAL, CHITTOOR DISTRICT, ANDHRA PRADESH