Cover Crop Planting Methods And Seeding Rates

DR. ERICK LARSON 

 MISSISSIPPI STATE, MISSISSIPPI

Cover crops can be seeded in agricultural fields using various methods commonly used to plant small grains or forages. These methods commonly range from using a grain drill, to various methods of broadcasting seed. Utilizing a drill offers more precision than other planting methods as well as the ability to place seed in direct contact with soil moisture. However, not everyone has a drill, and there are some complications which may limit advantages of using a drill to plant cover crops. On the other hand, broadcast seeding is an efficient and generally more common method to seed cover crops in agricultural fields in Mississippi.

Row crops are commonly grown on raised beds in the Midsouth. Raised beds are created using tillage in the fall and lay undisturbed over the winter to facilitate spring planting and improve drainage. This is a critical component of stale seedbed systems which promote early planting, which improves row crop productivity. This irregular soil surface of raised beds makes it difficult for a drill to maintain uniform seeding depth in this system. However, drills do offer an opportunity to manipulate the lateral placement of rows of seed. Alternatively, broadcast seeding is a practical seeding method for raised bed systems.

Cover crops normally consist of a blend of cereal grains, legumes and brassicas, which differ dramatically in seed size and emergence capability. Therefore, there must be some adaptation to establish various species. Small seeded legumes are suited to emerge from very shallow soil depth (less than ¼-inch depth), while the optimum seeding depth for cereals is considerably deeper (1-inch). Accordingly, the ability of drills to control seed placement at a moderate depth may confound emergence success of clovers by placing them too deep. Therefore, broadcast seeding is a viable compromise which can produce successful emergence of cover crop blends.

Broadcast seeding on freshly tilled soil enhances seed to soil contact and typically produces successful cover crop establishment. Of course, seed germination depends on sufficient fall rainfall, but our high rainfall climate is generally conducive to establishment. Hard-packed soil or no tillage systems will likely limit cover crop emergence success and make seed germination more dependent upon ample rainfall and moist soil. For instance, using a bedder-roller which packs beds or receiving a hard, compacting rain prior to seeding will likely limit cover crop establishment.

The purpose of cover crops is to provide sufficient soil coverage to provide protection and generate beneficial plant biomass during a period during a fallow period. Thus, typical cover crop seeding rates are considerably more modest than normal for grain or forage production. Furthermore, high seeding rates increase expense of cover crops, which do not directly generate income. Since cover crops are usually comprised of a blend of cereals and legumes, seeding rates of each species are normally reduced at least 50% compared to a normal monoculture rate. ∆

DR. ERIC LARSON: Mississippi State University