Which of the following crops would be preferred for sowing in order to enrich the soil with nitrogen?

To enrich soil with nitrogen, leguminous crops are preferred due to their unique ability to perform biological nitrogen fixation (BNF). Gram (also known as Bengal-gram or chickpea) is a major pulse crop that maintains and restores soil fertility by fixing atmospheric nitrogen through a symbiotic relationship with Rhizobium bacteria residing in its root nodules [3]. Pulse crops like gram can add up to 40 kg of nitrogen per hectare to the soil, making them essential for sustainable farming and crop rotation [4]. In contrast, crops like wheat (a cereal), mustard (an oilseed), and sunflower are non-leguminous and typically deplete soil nitrogen rather than enriching it [2]. Legumes are often grown before non-leguminous crops to ensure the soil is enriched with organic matter and nitrogen for the subsequent crop's growth.

Sources

1. [1] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 5: Geomorphic Processes > Biological Activity > p. 45
2. [3] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 9: Agriculture > 11. Less Area under Leguminous and Fodder Crops > p. 9
3. [4] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > 25.6.1. Principles of crop rotation > p. 360
4. [2] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 12: Major Crops and Cropping Patterns in India > Pulses (Legumes) > p. 28