Final answer:
Elden used Crop Rotation to conserve his soil by rotating wheat with soybeans, which helps to improve soil health and reduce pest cycles.
option B. crop rotation is correct .
Step-by-step explanation:
The soil conservation method that Elden used by rotating wheat with soybean is called Crop Rotation. This agricultural technique involves alternating the types of crops grown in a particular field from season to season. Crop rotation offers several benefits, such as improving soil nutrient levels, breaking cycles of pests and diseases, and reducing the need for chemical pesticides.
Rotating cereal crops like wheat with legumes such as soybeans not only conserves the soil but also helps fix nitrogen in the soil, which benefits the subsequent crop. Farmers have been using crop rotation since around 8000 BCE as a way to sustain soil fertility and boost overall yields.