Arid/desert soil

Arid and desert soils form in regions receiving less than 50 cm of annual rainfall, predominantly in western Rajasthan, the Rann of Kutch in Gujarat, and parts of southern Haryana and Punjab. In India's traditional eightfold soil classification adopted by the Indian Council of Agricultural Research (ICAR), these are listed as a distinct group; under the USDA Soil Taxonomy they correspond to aridisols and entisols. They develop under arid and semi-arid climatic conditions where evaporation greatly exceeds precipitation, producing sandy parent material derived largely from the mechanical disintegration of rock and the wind-borne deposition of sand from the adjacent Thar Desert and the Indus basin. The soil is reddish to brown in colour, owing to the absence of leaching and the presence of iron oxides.

The defining features of arid soils flow directly from the moisture deficit. Because rainfall is scant, soluble salts are not washed away but accumulate, making the soils saline and alkaline; in lower horizons calcium carbonate concentrates to form a hard impermeable layer called kankar, which restricts the infiltration of the little water that is available and impedes root penetration. Nitrogen and humus are deficient because sparse vegetation yields little organic matter, but the soils are surprisingly rich in soluble salts and phosphates, lacking chiefly nitrogen and organic content. Soil texture is coarse and porous, with high permeability at the surface but poor water-retention capacity, and the surface is frequently disturbed by aeolian action producing shifting sand dunes (the dhrian of Rajasthan).

With irrigation and proper management these soils become cultivable, a fact demonstrated by the Indira Gandhi Canal (Rajasthan Canal), completed in stages and drawing water from the Sutlej–Beas system, which has converted large tracts of the Thar into productive land growing wheat, cotton, bajra (pearl millet), pulses and guar. Where salinity and the kankar pan are absent, the phosphate-rich character supports drought-resistant crops. As of 2026 desertification and soil salinisation remain pressing concerns, addressed through the National Action Plan to Combat Desertification and India's commitments under the UN Convention to Combat Desertification (UNCCD), hosted at COP14 in New Delhi in 2019, where India pledged to restore degraded land.

For the UPSC examination, arid and desert soil is tested primarily in the General Studies Paper I (Indian and World Geography) and in Geography optional Paper II (Geography of India). Prelims questions typically probe the correct matching of soil type to region, the chemical character (salinity, nitrogen deficiency, phosphate richness) and the kankar layer; a common trap is confusing arid soils with red soils on the basis of colour. Mains answers should integrate the soil's properties with reclamation strategies — gypsum application to counter alkalinity, canal irrigation, dune stabilisation and agro-forestry — and link them to broader themes of desertification, food security and sustainable land management under the UNCCD framework.