Passage Summary: Usually, plants struggle if you grow them in the same spot for years because they eat up all the nitrogen in the dirt. Alfalfa actually puts nitrogen back into the dirt, but for some reason, it still grows worse and worse every year it's replanted.

Reasoning: Most crops grow poorly over time because they deplete nitrogen, but alfalfa, which adds nitrogen to the soil, also grows poorly when planted repeatedly in the same field.

Analysis: We are faced with a classic 'even though' paradox: alfalfa fixes the very problem (nitrogen depletion) that usually causes the observed effect (poor growth). Since the usual culprit is absent, there must be another factor at play that negatively impacts alfalfa specifically. To resolve this, we need a piece of information that introduces a different cause for poor growth, such as a different nutrient being depleted or a specific pest that thrives on alfalfa. Look for an answer that provides a reason for declining health that is independent of nitrogen levels.