Question

crop rotation improved harvest yields by: reducing the amount of land used using more fertilizers maintaining soil fertility through varied planting increasing water usage

Explanation:

Crop rotation involves growing different crops in sequence on the same land. This helps maintain soil fertility as different plants have different nutrient - requirements. For example, legumes can fix nitrogen in the soil, benefiting subsequent crops. It doesn't reduce land use, use more fertilizers (in fact, can reduce the need for some fertilizers), or increase water usage as its main goal is soil - health improvement.

Answer:

Maintaining soil fertility through varied planting