Soil- Classification Of Soils
Soils can be grouped into categories based on their present properties. The most general soil category is called order. All world soils are place into 10 orders.1. Entisols: Those soils that have natal, if any, profile development are known as entisols. Soils in desert belong to this classification. The productivity of these soils varies with their location and properties. With controlled water supply and proper fertilization, these soils have good productivity and good for vegetables, groundnut, citrus, wheat, paddy, etc.
2. Inceptisols: These soils have better profile development than entisols but are less developed. The horizons are formed mostly from alteration of the parent materials with accumulation of clay. The productivity is limited due to poor drainage. Found in humid regions.
3. Histosols: These are organic soils (pleats and mucks) consisting of variable depths of accumulated plant remains in bogs, marshes and swamps that have developed under water saturated environment. Highly rich in organic matter i.e. Org. C ranges from 12 to 18% in soils with low to more than 50% clay content.
4. Aridisols: Soils found in arid or dry areas with light in colour, poor inorganic matter and are not subjected to leaching, used for cultivation with irrigation. Process a horizon of CaCO3 (lime), Calcium sulphate (Gypsum) or more soluble salts. These are desert soils.
5. Mellisols: Mostly these are grasslands having thick surface horizon of dark colour, dominated by divalent cations. Process normal granular or crub structure, do not harden on drying and with moderate to have fertilization soil are productive.
6. Vertisols: These have a high content of clays that swell when wetted (more than 30%). During the dry season, these soils on tract and give rise to deep cracks which disappear in the wet season or after irrigation. Found in sub humid or semi arid (Temperate to tropical) climates where temp. are moderate to high. Good for crop production with fine texture which are plastic and sticky when wet and hard when dry. Difficult to manage due to very little time for their proper preparation by tilling good for the production of cotton, millet, sorghum, wheat, paddy, etc.
7. Alfisols: Develop in humid and sub humid climates (500 mm to 1300 mm rainfall) with gray to brown surface horizons. Soils are slightly too moderately acid and quite productive with good texture. Soils are frequently under forest vegetation.
8. Spodosols: Soils belong to forests with low content of bases, having coarse texture (sandy). Found in humid climates where temperatures are low. The subsurface horizons have accumulation of org. matter and sesquioxide.
9. Ultisols: These are strongly acid, normally forest soils with low content of bases extensively weathered soils of tropical and subtropical climates, respond to good mgt. practices, have clay of 1:1 type and give good crop production with adequate fertilization.
10. Oxisols: These are most developing in tropical and subtropical climates. The subsurface horizons are high in clay and acid. The soils are productive with supplements of ‘P’ micro-nutrients.