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AP Environmental Science · Question of the Day

AP Environmental Science Question of the Day

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Friday, August 7, 2026

In a rice paddy, farmers intentionally flood fields. If flooding increases nitrogen loss from the soil to the atmosphere, which nitrogen-cycle process is most likely responsible for that loss?

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Question of the Day

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In a rice paddy, farmers intentionally flood fields. If flooding increases nitrogen loss from the soil to the atmosphere, which nitrogen-cycle process is most likely responsible for that loss?

  1. Denitrification (correct answer)
  2. Nitrification
  3. Assimilation
  4. Ammonification

Explanation: Denitrification is promoted in flooded rice paddies, where anaerobic conditions allow bacteria to convert NO₃⁻ to N₂ gas, causing nitrogen loss to the atmosphere. Flooding limits oxygen, favoring denitrifying bacteria like Pseudomonas over aerobic ones. These bacteria use nitrate in anaerobic respiration, releasing N₂. This process explains the increased nitrogen loss in such agricultural systems. Nitrification would decrease due to low oxygen. Therefore, choice A correctly points to denitrification as responsible.