DETAILED SOIL RESOURCE INVENTORY OF VARATHURU WATERSHED IN CHITTOOR DISTRICT OF ANDHRA PRADESH USING REMOTE SENSING AND GIS
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Date
2024-05-23
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Acharya N G Ranga Agricultural University
Abstract
The present investigation entitled ''Detailed soil resource inventory of
Varathuru watershed in Chittoor district of Andhra Pradesh using remote sensing and
GIS'' involves study of twentyone (21) typical pedons for morphological, physical,
physico-chemical and chemical properties in the Varathuru watershed. Inaddition, two
hundred and fifty six (256) surface soil samples (0-15 cm) were collected with GPS
coordinates and were analyzed for pH, EC, organic carbon, macronutrients (N, P2O5,
K2O and S) and micronutrients (Zn, Cu, Fe and Mn) and were mapped by using
ArcGIS v 10.3.
The study area was characterized by semiarid monsoon climate with distinct
summer, winter and rainy seasons. The pedons occurs in plains (P7 and P8), very
gently sloping (P1, P2, P5, P11, P14 and P18), gently sloping (P3, P4, P15 and P17),
moderately sloping (P6, P9, P10, P12, P13 and P16), Very strongly sloping (P19 and
P20) and moderately steep sloping (P21) topography. All the pedons in watershed
were developed from granite-gneiss.
The morphological features indicated the presence of AC/AR (P3, P15, P19
and P21), ABC (P1, P2, P5, P7, P8, P9, P11, P13, P14, P17, P18 and P20), A-AB/BA C (P4, P6, P10 and P16) and A-A/B-C (P12) profiles. The soils were shallow to deep
in depth, dark reddish brown to light yellowish brown in colour, gravelly sandy loam
to sandy clay loam in texture and exhibited single grain, granular and sub-angular
blocky structures.
The clay content in P3, P9, P12, P13, P16 and P20 exhibited an increasing
trend with depth whereas no specific trend with depth was observed in the remaining
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pedons. Physical constants like water holding capacity and volume expansion
followed the trend of clay content.
The soils of Varathuru watershed were slightly acidic to moderately alkaline
(6.03 to 8.35) in reaction (pH), non-saline (0.02 to 0.40 dS m-1
) and low to medium
(0.04 to 0.74%) in organic carbon. The CaCO3 content was ranged from 0.60 to 8.68
per cent and ESP was low (0.39 to 10.80 %). The CEC values were ranged from 4.68
to 33.49 cmol (p+
) kg-1
and the exchange complex was dominated by Ca2+ followed
by Mg2+, Na+
and K+
.
The Varathuru watershed soils were low (25.10 to 262.50 kg ha-1
) in
available nitrogen, low to high (8.91 to 94.05 kg P2O5 ha-1
soil) in available
phosphorous and potassium (116.45 to 551.60 kg K2O ha-1
) and deficient to
sufficient (1.75 to 52.56 mg kg-1
) in available sulphur. The soils were
sufficient in DTPA extractable Cu and Mn and deficient to sufficient in
DTPA extractable Zn and Fe.
The mineralogy class for all these was mixed based on CEC / clay ratio.
Based on the morphological, physical, physico-chemical, mineralogical and
meteorological data, the soils were classified as Entisols, Inceptisols and Alfisols and
these soils were further classified at family level as:
Pedons 1, 4, 6, 7,
10, 12, 16 and 20
: Fine loamy, mixed, isohyperthermic, Typic Haplustepts
Pedon 3 and 15 : Fine loamy, mixed, isohyperthermic, Typic Ustorthents
Pedons 2, 5, 9, 11,
13, 14 and 18
: Fine loamy, mixed, isohyperthermic, Typic Hapustalfs
Pedon 8 : Fine loamy, mixed, isohyperthermic, Ultic Haplustalfs
Pedon 17 : Coarse loamy, mixed, isohyperthermic, Typic Haplustepts
Pedons 19 and 21 : Skeletal, mixed, isohyperthermic, Typic Ustorthents
Fifteen (15) soil mapping units at phase level were identified in Varathuru
watershed and were mapped into ten (10) soil series. These ten soil series were
classified into four land capability sub-classes such as IIIs (VRT3), IVs (VRT2,
VRT5, VRT6 and VRT7), IVes (VRT1, VRT4 and VRT8) and VIIes (VRT9 and
VRT10).
Similarly, the soils of Varathuru watershed were grouped into four land
irrigability sub-classes namely, 3s (VRT2 and VRT6), 4s (VRT1, VRT3, VRT4,
VRT5, VRT7 and VRT8), 5s (VRT9) and 6s (VRT10).
The soil series viz., VRT1, VRT4, VRT5 and VRT8 were moderately suitable
(S2) for growing groundnut, redgram and sugarcane and not suitable (N) for growing
rice crop whereas the soil series namely VRT2 was marginally suitable (S3) for
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growing redgram and sugarcane and not suitable (N) for growing groundnut and rice
crop. The soil series such as VRT3 was highly suitable (S1) for growing groundnut,
moderately suitable (S2) for redgram and sugarcane and not suitable for rice crop. The
soil series namely VRT6 was moderately suitable (S2) for growing redgram,
marginally suitable (S3) for growing groundnut and sugarcane and not suitable (N) for
rice. The soil series of VRT7 was moderately suitable (S2) for growing redgram,
marginally suitable (S3) for sugarcane and not suitable (N) for growing groundnut and
rice. However, the soil series VRT9 was marginally suitable (S3) for growing
redgram and not suitable (N) for growing groundnut, sugarcane and rice crops
whereas the soil series of VRT10 was not suitable for growing groundnut, redgram,
sugarcane and rice crops
Production potential revealed that, actual productivity of soil series were poor,
average and good whereas potential productivity of soil series were average, good and
excellent. The coefficient of improvement (Ci) varied from 1.43 to 4.46 indicating the
implementation of judicious soil and water management practices to sustain soil
productivity.
Soil fertility maps were also prepared for watershed for various parameters
such as pH, EC, organic carbon, available macronutrients (N, P2O5, K2O and S) and
micronutrients (Zn, Fe, Cu and Mn) under GIS technology using ArcGIS 10.3
version