LSAT 28, Logical Reasoning I, Q8, LSATHacks

QUESTION TEXT: Generally speaking, if the same crop is sown in a field…

QUESTION TYPE: Paradox

PARADOX: If you plant the same crop again and again, it will grow poorly. This is because it sucks nitrogen out of the soil.

Alfalfa beans add nitrogen to the soil. But they too grow poorly if you plant them over and over.

ANALYSIS: The stimulus never said that lack of nitrogen is the only reason a plant could grow poorly.

Maybe alfalfa beans suck some other nutrient out of the soil.

For this reason, good farmers rotate their crops. The soil does better if you mix nitrogen fixing and non-nitrogen fixing plants.

___________

1. The stimulus never said whether the plants were grown all alone, or with other plants in surrounding fields.
2. This shows that how alfalfa helpfully adds nitrogen to the soil. It doesn’t explain why alfalfa eventually grows poorly.
3. CORRECT. This shows that alfalfa gradually poisons its own soil, if you plant it year after year.
4. Presumably the bacteria is present often. The stimulus says alfalfa does increase the amount of nitrogen.
5. Umm…do black walnut trees suddenly sprout up if you plant alfalfa for a few years in a row? That seems unlikely. Either the black walnuts will hurt alfalfa right from the beginning, or they won’t be nearby to hurt alfalfa.

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