With reference to agricultural soils, consider the following statements: 1) A high content of organic matter in soil drastically reduces its water holding capacity. 2) Soil does not play any role in the sulphur cycle. 3) Irrigation over a period of time can contribute to the salinization of some agricultural lands. Which of the statements given above is/are correct?

Only statement 3 is correct, so B is right. Irrigation water carries dissolved salts, and in arid and semi-arid regions with poor drainage these are left behind as water evaporates. Over years they build up in the root zone, which is secondary salinisation. Over-irrigation also raises the water table and causes waterlogging, which worsens the problem. The Indira Gandhi Canal command area in Rajasthan and parts of Punjab and Haryana are often cited for this.

Statement 1 is wrong. Organic matter improves soil structure, aggregation and porosity, and it holds water itself, so water holding capacity rises. Statement 2 is wrong because soil is central to the sulphur cycle. Soil microbes mineralise organic sulphur and oxidise sulphides to sulphate, which plants absorb, and decomposition returns sulphur to the soil.

Core concept: soil degradation through salinity, alkalinity and waterlogging. It links to Mains questions on the side effects of the Green Revolution and on water-use efficiency through drip and sprinkler irrigation.

Trap: aspirants often assume that since organic matter is good for soil, it must help water holding in every sense, or they dismiss statement 2 without knowing that soil microbes drive the sulphur cycle.