For summer-annual crops such as corn or soybeans, cover is needed in fall, winter, and spring. For winter-annual crops such as winter wheat or barley, cover is needed in late summer or fall. Regardless of the cover crop, it must be killed or suppressed so it doesn't interfere or compete with the primary crop.
Cover crops can be annual, winter annual, biennial, or perennial plant species.
Winter annuals such as rye can be used as a fall and winter cover, whereas crownvetch, a perennial, can serve as a living mulch for all seasons. Several of the more commonly used cover crops are described in Table 9-1 . Volunteer oats that come in after the August oat harvest make excellent growth and even may head out before frost. If the volunteer oats are spread more evenly with a straw spreader at harvest time, no additional groundcover is needed. If oats are seeded as a groundcover, seeding should be done as early as possible and certainly before September 15.