TAXONOMIC STUDIES ON SOILS OF THOTAPALLI AYACUT AREA OF NORTH COASTAL REGION OF ANDHRA PRADESH
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Date
2018
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Acharya N.G. Ranga Agricultural University
Abstract
Six soil profiles from Devarapalli, Gujjangivalasa, Cheepurupalli, Gangada, Aamity and Maddivalasa villages belonging to Srikakulam and Vizianagaram districts of north coastal Andhra Pradesh were selected and described for their site and morphological features. Horizonwise soil samples were collected from each profile and subjected to laboratory analysis. Surface soil samples were also collected from one hundred locations throughout the study area for fertility evaluation. Based on the morphology, physical, physico-chemical, electro-chemical and chemical properties of the soils, the soil profiles were classified as per USDA soil taxonomy (Soil Survey Staff, 2014).
The study area was characterized as semi-arid to sub-humid climate with distinct wet and dry seasons. The profiles were derived from granite-gneiss and mixture of granite-gneiss with calcareous murram. Topography was gently sloping cultivated lands to nearly level cultivated plains. The soils were moderately deep to very deep. Surface cracks of deep and wide and intersecting slickensides were observed in Gangada and Maddivalasa profiles, while argillans and iron nodules were found in profiles of Devarapalli, Gujjangivalasa and Aamiti. Profile 1 and 2 developed argillic horizon and profile 3, 4 and 5 had cambic horizon and calcic horizon was noticed in deeper layers of profile 4. The colour of the soils varied from yellowish brown to dark grayish brown. In general the textural classes were sandy loam to sandy clay loam in red soils while, it was clay loam / clay in black and associated soils. The structure varied from granular to sub-angular blocky in surface horizon and subangular blocky to
angular blocky in subsurface. The soil physical constants like bulk density was recorded low at surface horizon compared to subsurface layers, whereas other properties like maximum water holding capacity, pore space and volume expansion were followed the trend as that of clay.
The soils were acidic to alkaline in reaction, non saline with respect to soluble salt concentration, low to medium in organic carbon content. The CEC values ranged from 6.4 to 32.5 cmol (p+) kg-1 and the soil exchange complex was dominated by calcium followed by magnesium, sodium and potassium. The ratio of CEC / clay was low in profile 2, medium in profiles 1, 3 and 5, while high in profiles 4 and 6. Chemical composition of soils revealed that silica and sesquioxides were the dominant fractions followed by calcium and magnesium oxides. The X-ray difractograms of soil fine earth fraction revealed the presence of quartz mineral in sand and silt fractions of all the six profiles, while in clay fraction profiles 1, 3 and 5 showed evidence of kaolinite, montmorillonite and illite, profiles 4 and 6 exhibited presence of montmorillonite and profile 2 showed kaolinite and illite.
In respect of available nutrient status, the soils in general were low in nitrogen, medium in phosphorus and high in potassium, while the micronutrients were sufficient in manganese however remaining micronutrients (Fe, Zn and Cu) were deficient to sufficient. Montmorillonite was the dominant clay mineral with small amounts of illite, kaolinite, hematite, magnetite, calcite and traces of quartz in all the profiles.
Based on morphological, physical, physic-chemical, mineralogical and meterological data the soils were classified as follows
Profile 1: Fine loamy, mixed, isohyperthermic, Typic Haplustalf
Profile 2: Fine loamy, kaolinitic, isohyperthermic, Typic Haplustults
Profile 3: Fine loamy, mixed, isohyperthermic, Typic Ustochrepts
Profile 4: Clayey, montmorillonitic, isohyperthermic, Vertic Ustochrepts
Profile 5: Fine loamy, mixed, isohyperthermic, Typic Ustochrepts
Profile 6: Clayey, montmorillonitic, isohyperthermic, Chromic Haplustert.
The laboratory analytical results of surface soil samples from one hundred locations covering 5 mandals of the study area and five villages in each mandal and four locations in each village were revealed that the soils were slightly acidic to alkaline in reaction, non saline with respect of soluble salt concentration, low to medium in organic carbon content and low in available nitrogen status, low to medium in available phosphorous and medium to high in potassium, deficient to sufficient in available zinc and iron, while sufficient in available copper and manganese.
Description
D5664
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