MORPHOLOGY AND TAXONOMY OF RED AND BLACK SOILS OF EDLAPADU MANDAL OF GUNTUR DISTRICT, ANDHRA PRADESH
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Date
2007
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY, RAJENDRANAGAR, HYDERABAD
Abstract
Eight profiles from Turlapadu, Jaggapuram, Edlapadu, Solasa,
Kondaveedu, Changeej Khan Peta, Boyapalem and Timmapuram villages of
Edlapadu mandal of Guntur district, Andhra Pradesh were studied. Four were
red soil profiles and other four were from black soil areas. Soil samples from
each horizon were described in the field and characterized in the laboratory.
Surface soil samples were also collected from sixty locations throughout the
madnal for fertility evaluation. Based on the morphology, physical, physicochemical,
electro-chemical and chemical properties of the soils, the soil profiles
were classified as per USDA soil taxonomy.
The study area was confined to semi-arid cliamte with well-defined dry
and wet periods. The red soils were formed and developed on weathered
granite-gneiss at higher elements of topography whereas, the black soils were
occurring on granitic gneiss parent material mixed with calcareous murram
relatively at lower elements of topography. The red soil profiles were relatively
more weathered than black soil profiles.
The colour varied from gray to very dark gray in black soil profiles and
reddish brown to dark reddish brown in red soil profiles. The texture was loam
to clay loam and clay loam to clay in red and black soil profiles, respectively.
The structure of black soil profiles was mostly granular in surface, sub-angular
or angular blocky in lower layers in red and black soil profiles.
Granulometric data indicated that the black soils had lower and higher
percent of sand and clay content, respectively than red soils. The ratios of
different fine earth fractions revealed, absence of lithological discontinuity
among the adjacent horizons in red and black soil profiles. The black soils had
recorded higher water holding capacity, volume expansion and sticky point
than the red soils.
The CEC, base saturation, saturation of bases (calcium, magnesium,
sodium and potassium) and CEC/clay ratios were higher in black soil profiles
compared to red soil profiles.
The results of physico-chemical properties revealed that the red soils
were neutral to slightly alkaline in reaction. The soils were non-saline and noncalcareous.
The black soils were slightly alkaline to strongly alkaline, nonsaline
and slightly to moderately calcareous in nature.
The chemical composition of soil samples exhibited the siliceous nature
of the soils by the broad and large silica/sesquioxides and silica/alumina ratios.
These molar ratios were relatively narrower in black soils than in red soils.
While the alumina/iron oxides ratios were higher in black soil profiles than in
red soil profiles.
The soils of the mandal were low in organic carbon, low in available
nitrogen, medium in available phosphorus, high in available potassium,
sufficient in available sulphur and micronutrients except zinc, which was
deficient in both red and black soils.
From X-RDA, it was clear that black soil clays were dominated by
montmorillonite, with small quanities of illite and kaolinite, while red soil clays
had illite, kaolinite and montmorillonite type of clay minerals. Small amount of
quartz was also recorded in clays of certain soil profiles.
Black soil profiles were having the moderate limitations of soil (restricted
drainage, fine texture and vertic features) besides the influence of semi-arid
climate. Red soil profiles were formed on higer elements of topography having
slight to moderate limitation of erosion and semiarid climate. Hene, the black
soil profiles were grouped under IIIsc land capability sub-class and red soil
profiles were grouped under land capability sub-class IIIec.
The taxonomic units of the eight soil profiles were as following.
Black soils:
Profile 1: Very - fine, montmorillonitic, isohyperthermic, Chromic Haplustert
Profile 2: Fine, montmorillonitic, isohyperthermic, Typic Haplustept
Profile 4: Very - fine, montmorillonitic, isohyperthermic, Typic Haplustert
Profile 8: Fine, montmorillonitic, isohyperthermic, Leptic Haplustert
Red soils:
Profile 3: Loamy, mixed, isohyperthermic, Typic Haplustalf
Profile 5: Loamy, mixed, isohyperthermic, Typic Haplustept
Profile 6: Loamy, mixed, isohyperthermic, Typic Haplustept
Profile 7: Loamy, illitic, isohyperthermic, Typic Haplustalf
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Keywords
MORPHOLOGY, TAXONOMY, RED, BLACK, SOILS, EDLAPADU, MANDAL, GUNTUR DISTRICT, ANDHRA PRADESH