Cereal rye is an excellent winter cover crop because it rapidly produces a ground cover that holds soil in place against the forces of wind and water. Rye’s deep roots help prevent compaction in annually tilled fields, and because its roots are quite extensive, rye also has a positive effect on soil tilth. Do not let it overmature, because the rye ties up the nutrients in the stems the older it gets.Cover Crops are sold in pound bags.