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Difficulty: EasyConservation of Natural Resources and Environmental Management

In sustainable soil management, farmers alternate cereal crops with legumes such as cowpeas or groundnuts in successive seasons. Which of the following environmental management outcomes is primarily achieved by this crop rotation practice?

  1. Natural replenishment of soil nitrate levels through symbiotic nitrogen-fixing bacteriaAnswer
  2. B
    Direct conversion of soil nitrates into atmospheric nitrogen by denitrifying bacteria
  3. C
    Complete removal of soil organic matter to initiate primary ecological succession
  4. D
    Increase in soil salinity through the release of mineral salts during rapid transpiration

Answer

The correct option is the natural replenishment of soil nitrate levels through symbiotic nitrogen-fixing bacteria.
Crop rotation utilizing leguminous plants promotes natural soil conservation because root nodules of legumes contain symbiotic Rhizobium bacteria. These microorganisms fix gaseous atmospheric nitrogen into nitrates, naturally replenishing nutrients taken up by previous crops without causing chemical pollution.

Step-by-Step Solution

1
Identify the biological mechanism associated with leguminous plants in crop rotation.
Legumes form a mutualistic association with Rhizobium bacteria residing in their root nodules.
Rhizobium bacteria fix atmospheric nitrogen (N2N_2) into usable ammonium and nitrate ions (NO3−NO_3^-).
2
Relate biological nitrogen fixation to environmental management and soil conservation.
Alternating nitrogen-demanding crops (like cereals) with nitrogen-fixing legumes restores soil nutrient levels naturally.
This practice maintains soil fertility, minimizes dependence on synthetic inorganic fertilizers, and reduces agricultural runoff pollution.

Key Concept

Soil Fertility Conservation via Crop Rotation and Biological Nitrogen Fixation
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Topics

Conservation of Natural Resources and Environmental Management

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