The main categories of soils in India are: (i) Alluvial soils (ii) Black soils (iii) Red soils (iv) Laterite soils (v) Mountain and hill soils (vi) Terai soils (vii) Desert (or Arid) soil and (viii) Peat soils.
India has various types of soil ranging from the fertile alluvial of the Indo-Gangetic plains to the black and red soils of the Deccan Plateau. For example, if one is travellers through the State of Tamil Nadu, one may observe that the ploughed fields in the districts of Salem and Periyar are red while those in Coimbatore and Ramanathapuram are black.
Each type of soil benefits different types of crops through their unique physical, chemical and biological properties. Alluvial soil is a fertile soil rich in potassium. It is highly suitable for agriculture, especially for crops such as paddy, sugarcane and plantain. Red soil has high iron content and is fit for crops like red gram, Bengal gram, green gram, groundnut and castor seed. Black soil is rich in calcium, potassium and magnesium but has poor nitrogen content. Crops like cotton, tobacco, chilly, oil seeds, jowar, ragi and maize grow well in it. Sandy soil is low in nutrient content but is useful for growing trees such as coconut, cashew and casuarinas in areas with high rainfall.
Soil may sometimes get eroded through factors such as wind, running water, overgrazing of animals and human activities such as construction. In addition, soil may also be depleted of its fertility if a particular crop is cultivated repeatedly in the area. This is when soil testing is vital. The quality of soil available in an agricultural area may be tested at soil testing laboratories. Here, the sample of soil is analysed and recommendations are made about what elements are needed to optimize it. Quality soil is one of the most important farming inputs. High yields and good produce can be achieved only when the right type of soil is used for a certain crop. For areas in which suitable soil is not available, one may add nutrients in the form of fertilizers to enrich it.