AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
(C) Phosphoric content
Black soils are rich in calcium carbonate, magnesium, potash and lime, but are generally poor in phosphoric contents.
Source: Resources and Development, Black Soil section
The textbook explicitly states: "These soils are generally poor in phosphoric contents." All other options (calcium carbonate, magnesium, potash) are nutrients that black soil is rich in, making (C) the only correct answer.