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Agronomy QUESTION #2031
Question 1
The most significant agronomic advantage of including a legume crop in a rotation sequence is:
  • It produces allelopathic compounds that suppress all subsequent weeds
  • It fixes atmospheric nitrogen through symbiosis with Rhizobium bacteria, reducing nitrogen fertilizer requirement for the subsequent crop✔️
  • It always produces higher economic yield than cereal crops
  • It prevents all fungal diseases in the subsequent cereal crop
Correct Answer Explanation
Legumes host Rhizobium or Bradyrhizobium bacteria in root nodules that fix atmospheric \(N_2\) into plant-available \(NH_4^+\). The residual nitrogen from legume roots and residues (typically 50–200 kg N/ha depending on species) benefits the following crop, reducing synthetic N fertilizer needs.