An important part of our farm plan includes planting cover crops. We strive to plant cover crops in the late spring and in the fall. There are many benefits to planting cover crops, for example they add organic matter to the soil which reduces soil crusting. Organic matter will improve soil tilth, the stability of soil aggregates, and water infiltration. Increased organic matter can boost the population of beneficial soil microbes and earthworms. Cover crops can help reduce soil erosion by keeping the soil covered during periods of rain when the soil might normally be bare. August 5th was one of the last measurable rains we had. We received 6/10 inch of rain in about 30 minutes and the cover crops held the soil in place. I was relieved those particular areas were not fallow; they would have been subject to erosion. Cover crops can reduce weeds in subsequent crops. A big cover of winter rye and clover can choke out winter annual weeds and decomposing winter rye is mildly allelopathic; it releases chemicals that prevent or retard the germination or growth of some seeds or seedlings.
Cover crops can bring in a lot of beneficial insects and can aid in reducing fertilizer costs. Legumes such as clover, vetch, soybeans and cowpeas “fix” nitrogen for use by subsequent crops. They work in a symbiotic relationship with rhizobia bacteria to convert atmospheric nitrogen into a plant-available form of nitrogen. Legumes’ ability to fix nitrogen can be boosted by using a bacterial inoculate on the seeds prior to planting. Bacterial inoculants are commercially available and inexpensive. You will want to match your inoculants to your seed; for instance, use inoculants specific for clovers or specific to soybeans. Use all of the inoculant as it does not store.
We are working hard to rebuild our depleted soils; we do not count on a cover to provide all of the nitrogen for a cash crop. Grasses and grains do not “fix” nitrogen, but thanks to their massive, fibrous root systems, they do scavenge mineral nitrogen and other nutrients from the soil that could be subject to leaching and ground water contamination.
Generally, in the late spring we plant a combination of pearl millet and soybeans or pearl millet and cowpeas. If pearl millet is not available, we use brown top millet. We also like sorghum-sudangrass and it combines nicely with cowpeas. We cannot raise a crop of soybeans or cowpeas UNLESS they are sown inside of a deer fence, the deer just simply mow them down.
Pearl millet is a vigorous summer annual bunch grass. It grows over 4 feet tall. I think this is a good choice to smother annual summer weeds and it provides a lot of biomass. I try to mow millets before they start to flower.
Sorghum-sudangrass is an annual grass that tolerates hot, dry conditions. It is moderately tolerant of true drought conditions. It provides a lot of biomass when mowed and incorporated into the soil. Even though it will grow well over 6 feet tall, I try not to let it get that big. If the crop established is early enough I like mow it at about 3 foot and let it regrow before I mow it for the final time. This practice shocks the roots and encourages them to act like” biological subsoilers”, penetrating the soil and reducing soil compaction.
Cowpeas (aka blackeye peas or crowder peas) are a great choice for a heat-loving, drought-tolerant legume. Cowpeas fix nitrogen, suppress weeds, and attract beneficial insects. Cowpeas would be a good choice to provide nitrogen ahead of a fall cash crop. Soybeans are similar to cowpeas in that they will fix nitrogen and suppress weeds. They establish quickly and can sustain short periods of drought.
Buckwheat is another summer option. It does not fix nitrogen, nor does it provide tons of biomass. But it does grow quickly (it can go from seed to flower in about 30 days) and it scavenges phosphorous. Buckwheat flowers bring in a lot of beneficial insects as well. It is easily incorporated and decomposes rapidly. Our hoophouses are not mobile and since it can be difficult to kill and incorporate a cover crop, buckwheat works nicely in that situation. It grows so quickly that we can plant a couple of buckwheat crops from the time the early-season flowers are finished until it time to prep beds.
In regards to timing, the spring garden is finished in June. I mow the cash crops, disc and then seed the covers. Hopefully this occurs before a perfectly timed rain. The timeline for the late spring cover crops is mid June to early July.
For fall planting we like oats and crimson clover or winter rye (not annual rye grass) and crimson clover. Winter rye and hairy vetch is a great combination. Oats are quick to establish and they provide a cheap, reliable fall cover. They provide a lot of biomass, almost as much as winter rye. They smother weeds and the residue has allelopathic characteristics. Oats can be winter killed in some of zone 7 and generally winter killed from zone 6 colder.
Winter rye (aka cereal rye) is the workhorse of the fall cover crops. It provides a lot of dry matter and its extensive root system helps prevent erosion. It is a good weed fighter and it can be planted later than almost any other cover crop. For legumes we rely heavily on crimson clover. Not only does it fix nitrogen, but it fights erosion and is a good soil builder. When walking through an area of crimson and winter rye, I always find aphids, but I always find plenty of lady beetles at work. Clover is easily killed mechanically. To take advantage of the maximum available nitrogen, I try to mow it at mid-late bloom.
Hairy vetch is another reliable choice for parts of the Southeast. It fixes nitrogen and is a good soil builder. Its rapid growth in the spring chokes out weeds. Hairy vetch is a vine, so combine it with winter rye to give it a “trellis”. It may be helpful to note that a combination of oats and crimson will mature faster than rye and vetch.
Ideally, we sow the fall covers in September. This ensures plenty of time for the crops to get established before the onset of cold weather. I have sown crimson clover as late as October 1. Hairy vetch can be sown up to Oct 15 and winter rye grass can be sown as late as Nov 15 (Piedmont, North Carolina).
We spread the seed with a chest spinner. A PTO spinner works nicely, especially for the grains and grasses. If I am sowing a combination of grasses (grains) and legumes, I sow each crop separately. I spread the seed making an X across the field and then I spread the seed in a serpentine pattern. I probably use a little too much seed, but I would rather have a good stand than skimp on seed. I gently cover the seed with the tine weeder. Sometimes I use the disc and just let it roll across the ground. A cultipacker would be excellent in this situation, it would ensure good soil to seed contact and improve germination. However, our system suffices and rain dances are sure to follow!
We allow at least one month from the time we mow the cover crop until we plant the cash crop. We use a rotary mower on the cover crops. A flail mower would be ideal because it would lay the shredded residue right in place rather than cutting it into a windrow. After mowing, we disc and let the residue mellow a bit. We disc again and then prepare for planting.
For more information in regards to seeding depth, seeding rate and amounts of nitrogen supplied, refer to Managing Cover Crops Profitably. It is a publication of the Sustainable Agriculture Network. Once again I will refer to Debbie Roos’ website Growing Small Farms, at to go http://chatham.ces.ncsu.edu/growingsmallfarms/ and click on the Production link.
Cover crops are a great addition to the farm program. They just require a little planning and management.
This is my last report as Regional Director. I have learned a lot about the Association and how it operates. It has been a fantastic educational experience and my pleasure to give back to the ASCFG. I would like to welcome Susan Wright as the new Director. She is the owner operator of Shady Grove Gardens and Nursery in Vilas, North Carolina. I would like to thank Gary and Sybil Calder for tons of support through my stint as Regional Director. Finally, I would like to thank Vicki Stamback and Joe Caputi for encouraging me to take the job! Thanks y’all!