1.   Because farmers own their land, they have every incentive to rotate crops and keep the soil fertilized.

2.   But ideas tend to take root when the soil has been fertilized by social and economic trends.

3.   Earthworms are a valuable tool in the garden as they aerate and fertilize the soil.

4.   For example, there were so many lobsters here, they were used to fertilize the soil.

5.   The fires sustained the prairies by clearing dead thatch, fertilizing the soil and destroying trees.

6.   They scatter wildflower seeds, aerate and fertilize soil, help rid the world of carrion, and, perhaps best of all, kill lots of irritating insects.

7.   Signs explain that human waste is piped from toilets to fertilize the soil.