How earthworms can help your soil Department of Primary Industries How earthworms can help your soil improve crop productivity by more than 50 percent improve crop productivity by more than 50 percent improve crop productivity by more than 50 percent improve crop productivity by more than 50 percent 7-inch layer topsoil from scratch “worm castings” that act like fertilizer the workhorses of your soil improve crop productivity by more than 50 percent improve crop productivity by more than 50 percent put some earthworms in it vermicompost as an organic fertilizer improve crop productivity by more than 50 percent improve crop productivity by more than 50 percent