Which one of the following crops enriches the nitrogen content in soil ?

Pea is a leguminous pulse crop that forms a symbiotic association with Rhizobium bacteria in root nodules; these bacteria biologically fix atmospheric nitrogen into plant-available forms such as ammonia and nitrates, thereby enriching soil nitrogen [3]. Pulses, including pea, are specifically noted for maintaining and restoring soil fertility through biological nitrogen fixation and can add substantial nitrogen (for example, up to about 40 kg N/ha) to the soil, making them soil-enriching crops in rotations [2]. Non-leguminous crops listed (potato, sorghum, sunflower) do not form such nodules and therefore do not contribute similarly to biological nitrogen enrichment of soil [3].

Sources

1. [1] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 5: Geomorphic Processes > Biological Activity > p. 45
2. [3] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > The Nitrogen Cycle > p. 20
3. [2] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 12: Major Crops and Cropping Patterns in India > Pulses (Legumes) > p. 28