Soil heterogeneity: A comparative assessment of soils from two different AESR, southern India

A comparative study was carried out to assess the nature and characteristics of soils from two agro-ecological sub regions (AESU and AESR) from two states of South India. Using sentinel-2 satellite data, google imagery and top sheet, a detailed soil survey was taken up in AESU and AESR. Major soils from upland as well as from lowlands were compared to assess the soils heterogeneity. Results showed that there was a high heterogeneity between properties of soils AESU and AESR. Variability existed in climatic conditions (tropical humid region in AESU and semiarid condition in AESR), physiographic (valley plain to gently, very gently, moderate, steep and very steep slopes in AESU and levelled to gently and very gently slopes in AESR ), geology (charnockite and granite gneiss in AESU whereas granite gneiss in AESR), land use (rubber, paddy, coconut in AESU and paddy, mango, pigeon pea, groundnut in AESR), soil classification (Ultisols and Alfisols in AESU whereas Alfisols and Inceptisols in AESR) and land capability (soil and water conservation measures must in AESU and slope was manageable with agronomic management practices in AESR). Soils varied in texture (clay, sandy clay and clay loam in AESU whereas sandy clay loam to sandy loam in AESR), consistency and depth of soils (shallow to very deep in AESU and shallow to deep in AESR). Clay content (32.9 to 63.5%) was dominant fraction in AESU whereas sand (52.1 to 72.1%) was in AESR. Soil acidity (strongly acid to very strongly acid) was a major problem (both hydrogen and aluminium saturation) in AESU whereas slightly acidic to neutral and slightly alkaline in AESR. Organic carbon content was high (up to 25.9 gkg-1) in AESU whereas it was up to 10.0 gkg-1 in AESR. Base saturation was <35% in AESU and >75% up to 100% in AESR. Calcium carbonate equivalent is >5% in AESR and not a problem in AESU. CEC was low (<12 cmol (p+) kg–1) in AESU and good (>12 cmol (p +) kg–1) in AESR.