Use this fact to answer the question: crop rotation has a positive impact on soil quality

The field a farmer plants with varied crops over the years is richer than

Choices:
[-] a field where apples, beans and squash is planted;
[-] a field where only grain is planted;
[-] a field where rice, corn and beans are planted;
[-] a field where fruits and vegetables are planted;

The answer is:
a field where only grain is planted