Pedogenesis and Physiographic Divisions of Uttar Pradesh Soils
The soils of Uttar Pradesh have evolved through complex pedogenic processes dictated by the Indo-Gangetic geomorphology, climate variations, parent material depositions by Himalayan river systems, and native vegetation. Uttar Pradesh is broadly divided into three main physiographic zones: the Himalayan region in the north, the vast Indo-Gangetic alluvial plain (central and eastern expanse), and the southern plateau/bundelkhand region.
- Alluvial Soils (Bangar and Khadar): Covering nearly three-fourths of the state, these soils are formed by the continuous deposition of sediments brought down by the Ganga, Yamuna, Ghaghra, and Gandak rivers. Bangar represents the older alluvial upland soils which are less fertile, heavier in texture, and occasionally contain calcium carbonate nodules known as kankar. Khadar represents newer alluvial flood plain soils, sandy to loamy in texture, renewed annually by seasonal river floods, and highly fertile.
- Bundelkhand Soils (Southern Plateau): Developed in the southern districts (Lalitpur, Jhansi, Banda, Hamirpur, Jalaun) from ancient gneiss, granite, and Vindhyan rocks. These are categorized into distinct local types: Parwa (light sandy-loam), Mar (heavy black clay), Kabar (heavy clay-loam), and Rakar (sloping, eroded red soils).
- Terai and Bhabar Soils: Located along the foothills of the Himalayas (Shivalik range). Bhabar soils are coarse, gravelly, and excessively drained where rivers disappear underground. Terai soils are moist, swampy, fine-textured, rich in organic matter, and naturally supporting tall grass and high-water-demanding cropping systems.
Taxonomic Classification and Physico-Chemical Properties
Under USDA Soil Taxonomy, the soils of Uttar Pradesh predominantly belong to the orders Inceptisols, Entisols, Alfisols, and Vertisols, reflecting their stage of weathering and mineralogical composition.
- Inceptisols: The most dominant soil order across the central Gangetic plains. These are young yet moderately developed soils with cambic subsurface horizons, neutral to mildly alkaline pH, and good base saturation.
- Entisols: Young, weakly developed soils found mainly in active floodplains (Khadar tracts) and sandy tracts (Bhurs) with little or no pedogenic horizon differentiation.
- Alfisols: Found in areas of higher effective precipitation or older uplands, characterized by argillic horizons with illuvial clay accumulation and slightly acidic to neutral reaction.
- Vertisols: Occurring in the southern Bundelkhand zone (Mar and Kabar formations), these are shrink-swell clay soils rich in smectite minerals, exhibiting deep vertical cracks during dry summer months and high plasticity when wet.
- Nutrient Status: Most UP soils are deficient in total nitrogen (N) and available zinc (Zn). Phosphorus (P) availability ranges from low to medium, whereas potassium (K) is generally medium to high due to illite-dominated clay mineralogy.
Problem Soils of Uttar Pradesh: Saline, Sodic, and Ravine Lands
Uttar Pradesh possesses significant tracts of degraded and problem soils that constrain agricultural productivity unless scientifically managed.
- Sodic (Alkaline/Usar) Soils: Extensively distributed in districts like Rae Bareli, Sultanpur, Unnao, Pratapgarh, Kanpur, Aligarh, and Etah. Characterized by high exchangeable sodium percentage (ESP > 15), high pH (> 8.5), and sodium carbonate/bicarbonate dominance, causing dispersion of clay particles and poor hydraulic conductivity.
- Reclamation and Management of Sodic Soils: Gypsum (CaSO4·2H2O) is applied as the primary chemical amendment to replace exchangeable sodium with calcium. Leaching of salts, green manuring with Sesbania aculeata (dhaincha), and cultivation of salt-tolerant rice varieties (e.g., CSR-36) are standard agronomic practices.
- Ravine and Eroded Soils: Found along the Chambal, Yamuna, and Betwa river basins in western and south-western UP. Accelerated gully erosion has stripped the topsoil, necessitating contour bunding, gully plugging, and afforestation with species like Acacia nilotica and Dalbergia sissoo.
Agro-Climatic Zones and Soil-Crop Suitability
Uttar Pradesh is partitioned into nine distinct agro-climatic zones by the Indian Council of Agricultural Research (ICAR) based on rainfall, temperature, topography, and soil characteristics, ensuring targeted crop zoning.
- Western Plain Zone: Loamy to sandy-loam soils; highly suitable for intensive wheat (Triticum aestivum), sugarcane (Saccharum officinarum), and basmati rice (Oryza sativa) cultivation.
- Central Plain Zone: Deep alluvial soils supporting diversified cropping systems including maize (Zea mays), potato (Solanum tuberosum), and mustard (Brassica juncea).
- Bundelkhand Zone: Mixed red and black soils suited for pulses like chickpea (Cicer arietinum), pigeonpea (Cajanus cajan), and oilseeds under rainfed conditions.
- Eastern Plain and North-Eastern Plain Zones: High moisture regimes and fine alluvial soils ideal for high-intensity lowland rice and wheat rotations, alongside jute (Corchorus olitorius) and vegetables.
Comparison of Alluvial Soil Sub-types: Bangar vs. Khadar
| Parameter | Bangar Soils | Khadar Soils |
|---|---|---|
| Geological Age | Older alluvium (Middle Pleistocene to Holocene) | Newer alluvium (Recent / Holocene) |
| Physiographic Position | Higher elevation, upland terraces above flood level | Low-lying floodplains adjacent to river channels |
| Flooding Frequency | Free from annual inundation | Subject to annual or periodic seasonal flooding |
| Texture & Structure | Heavier, clay-loam to sandy-clay with depth | Lighter, sandy-loam to silt-loam |
| Calcium Carbonate Content | Contains abundant calcareous nodules (Khadar/Kankar) | Usually devoid of Kankar nodules |
| Natural Fertility | Moderate fertility; requires nitrogen and phosphorus fertilization | High natural fertility due to annual fresh silt deposition |
Bundelkhand Soil Classification and Characteristics
| Local Soil Name | Soil Texture & Color | Dominant Clay Mineral | Agronomic Suitability |
|---|---|---|---|
| Mar | Heavy black clay, sticky when wet | Smectite (Montmorillonite) | High water retention; excellent for post-monsoon Rabi crops like chickpea |
| Kabar | Heavy clay to clay-loam, dark brown/black | Smectite and Illite | Moderate to high fertility; suitable for wheat and barley under adequate moisture |
| Parwa | Light sandy-loam to loam, reddish-brown | Illite and Kaolinite | Easy to till; requires irrigation; good for pearl millet, sorghum, and pulses |
| Rakar | Coarse, gravelly, eroded sloping soil, red/yellow | Kaolinite and quartz | Poor fertility and moisture retention; best suited for afforestation or hardy fodder grasses |
Memory Trick / Mnemonic
Bundelkhand Soil Types (MP-KR)
Modern Painters Paint Rooms (Mar, Parwa, Kabar, Rakar)
M stands for Mar (heavy black clay), P stands for Parwa (light sandy-loam), K stands for Kabar (heavy clay-loam), and R stands for Rakar (eroded sloping red soil). This helps instantly recall the four key soil types of the southern Bundelkhand region.
Memory Trick / Mnemonic
Major Problem Soils of UP (S-R-A)
Some Rivers Are salty (Sodic, Ravine, Acidic)
S represents Sodic (Alkaline soils requiring gypsum), R represents Ravine soils (Chambal/Yamuna gully erosion), and A represents Acidic soils (found in high rainfall Terai zones). Covers the broad degradation categories in UP.
⚡ High-Yield Exam Points (UP TGT / PGT Focus)
- Bangar soils represent older alluvium containing calcium carbonate nodules known locally as kankar.
- Khadar soils represent newer alluvium deposited annually by floodwaters, possessing high natural fertility.
- The southern plateau region of Uttar Pradesh is known as the Bundelkhand region, featuring Mar, Kabar, Parwa, and Rakar soil types.
- Sodic (Usar) soils of UP are reclaimed using agricultural grade gypsum (CaSO4·2H2O) as a chemical amendment.
- Bhabar soils are coarse, gravelly, and excessively drained soils located immediately south of the Shivalik Himalayan foothills.
- Terai soils are moist, swampy, fine-textured alluvial soils characterized by high organic matter content.
- Under USDA Soil Taxonomy, the majority of Indo-Gangetic alluvial soils in Uttar Pradesh belong to the Inceptisols order.
- Mar and Kabar soils of Bundelkhand exhibit high shrink-swell properties due to the dominance of smectite clay minerals.
- Zinc (Zn) and Nitrogen (N) are the most universally deficient plant nutrients across Uttar Pradesh soils.
- The nine agro-climatic zones of Uttar Pradesh were designated by ICAR to formulate localized agricultural research and extension strategies.
⚠️ Common Mistakes & Exam Pitfalls
- Confusing Bangar with Khadar: Bangar is older alluvium situated on uplands, whereas Khadar is newer alluvium in active flood plains.
- Assuming Bundelkhand soils are purely alluvial: Bundelkhand soils are residual soils derived from granites and gneisses, distinct from Indo-Gangetic alluvium.
- Treating sodic soils with lime: Sodic soils have high pH and sodium; they require gypsum (CaSO4), whereas acidic soils require agricultural lime (CaCO3).