RAS question
Which micronutrient deficiency is most widespread in the soils of Rajasthan as per soil fertility mapping studies?
Correct answer: (C) Zinc (Zn).
Zinc deficiency is the most widespread micronutrient deficiency in Rajasthan's soils according to soil fertility mapping studies.
Explanation
Rajasthan's agricultural soils are largely alkaline, and high pH reduces the bioavailability of zinc to crops. The cited soil fertility appraisal for hot arid Rajasthan analysed 5,655 geo-referenced soil samples from rainfed croplands, irrigated croplands and rangelands across 12 districts. It found zinc and iron inadequate in large parts, while copper and manganese were adequately supplied in most areas. The key discriminator is the nutrient index: DTPA zinc had a low nutrient index value of 1.51, whereas iron was only marginal, copper adequate and manganese high. This matches the wider ICAR/NBSS&LUP-style finding cited in the question explanation that over 40-50% of Rajasthan agricultural soils are zinc-deficient, affecting wheat, bajra and soybean yields and making ZnSO4 application a standard recommendation.
Why the other options are wrong
- (A) Iron deficiency is reported in large parts of hot arid Rajasthan, but the cited appraisal classifies iron as marginal while DTPA zinc falls in the low nutrient-index category.
- (B) Boron deficiency may occur in specific pockets, but the given soil fertility evidence identifies zinc, not boron, as the most widespread micronutrient constraint in Rajasthan.
- (D) Manganese is not the leading deficiency because the cited appraisal reports manganese as adequately supplied in most areas and gives it a high nutrient index value.
Concept
This tests Rajasthan soil fertility and nutrient-management mapping, especially micronutrient constraints in arid and alkaline soils. It recurs in RAS because soil constraints directly link physical geography with agriculture, crop productivity and state-level input recommendations.