A grower in Rowan County, N.C., has developed a row-crop/cover crop system that is profitable and sustainable. A winter cover crop of crimson clover is planted in the fall. Seed is harvested from the crimson clover the following spring, and a double-crop of soybeans is no-till planted into the crimson clover stubble. That fall, crimson clover seed left on the surface germinates and grows similar to a fall-planted, interseeded crop below the fall-harvested soybeans. Crimson clover is grown through the winter and no-till corn is planted into the clover residue in the spring. All crops are no-till and the grower produces three crops in a two-year rotation: crimson clover seed>soybeans>corn. The farmer does not use nitrogen on the soybean crop and reduces the nitrogen application rate for corn due to the crimson clover residue and soybean stubble. The system is not only profitable but also reduces erosion and builds soil organic matter due to continuous no-till and crop residue buildup.
Sod-Based Tomato Production
A grower in the Southern Piedmont region of North Carolina has been able to utilize a sod-based system to grow hay and vegetables. This grower harvests a hay crop in the spring on a bottom soil near a stream. Following hay removal, a strip-till implement is used to cultivate beds 8–12 inches wide for tomatoes. Tomatoes are transplanted into the cultivated strips and grown using standard bare-soil production practices. During the summer, the sod is mowed with a riding mower. Inter-row areas receive considerable foot traffic due to twice-a-week harvesting, yet the sod holds the soil in place and provides a cleaner environment. The potential for soil to be splashed on tomatoes when it rains is reduced. Fields can be walked on immediately after rain due to the sod between the rows. Chapter 8 has more information about sod management and growing hay in dormant sod.
This sod-based system will work for conventional producers and may have promise for organic producers. Conventional producers can keep the tomato rows free of grass weeds with an herbicide. Organic producers could use a mulch to reduce grass growing into the tomato rows. Trickle chemigation, or the delivery of nutrients or pesticides through a closed irrigation system, can be used for these crops, reducing overhead spray. The grower produces hay and a vegetable crop in this conservation tillage system. Peppers, eggplants and tobacco will work in this system. As with tomatoes, the potential for soil to splash on to vegetables is reduced.
Steve Gibson is a retired North Carolina State University agricultural Extension agent in Cleveland County. He remembers that producers in the Southern Foothills region of North Carolina faced real challenges getting land prepared for small-grain planting after the summer crop (soybeans, cotton, corn or grain sorghum). Tillage operations following summer harvest usually meant late small-grain plantings and, sometimes, poor stands. Beginning in the late 1980s, producers started adopting no-till planting of wheat following their summer crop, and by the mid-1990s nearly all of the small grains in the region were no-till planted. Improvements in no-till drills really helped farmers successfully make this change. Also, the availability of combine straw choppers and chaff spreaders made planting even into heavy corn or grain sorghum stubble possible. In 1989, the Cleveland County Extension program decided to no-till plant all variety tests and demonstrations. This helped promote the practice to the point where the vast majority of crop fields are now under continuous no-till.
Many of the problems producers thought would arise by switching to continuous no-till did not materialize. Instead, producers have learned over the past 20 years that seeding rates for no-till are about the same as conventional tillage, and establishment is similar. The incidence of Hessian fly and head scab has not increased with no-till, even with no-till wheat planted into corn residue. Diseases like leaf and glume blotch remain as troublesome as they were in conventional systems. Gibson says the keys to successfully growing no-till wheat are careful variety selection, timely but not too early planting, appropriate seeding rates, and using scouting and weather forecasts to dictate the need for foliar fungicides.
Producers are discovering many unforeseen advantages to continuous no-till systems, such as improvements in soil quality. A field in Cleveland County was monitored with extensive soil sampling after the conversion to continuous no-till. In four years the soil's humic matter and cation exchange capacity doubled. No-till has indeed made field-crop production much more sustainable.
Corn Silage No-Till System
Ray Styer, a livestock farmer from Rockingham County, N.C., uses a cover crop seed mixture of 20 pounds of Abruzzi rye, 8 pounds of hairy vetch, 4 pounds of Daikon radish, 10 pounds of winter peas and 5 pounds of crimson clover per acre in his no-till corn-silage production system. The mixture of winter cover crops, rather than just one species, pays dividends on production costs and provides the bonus of soil improvements. The only time he deviates from this mix is when experimenting.
Planted early and allowed to achieve a reasonable level of maturity before termination, the rye residue provides summer-long ground cover to conserve moisture, while the legumes supply nitrogen for the corn. The rye also scavenges any residual soil nitrogen not taken up by the previous summer crop, thus reducing the possibility of nitrate leaching into the groundwater. The radishes will winter kill, so they need to be planted early to maximize growth. Styer cautions that a high-biomass cover crop may negatively affect water availability to the following crop at planting. On the other hand, a thick mulch helps conserve moisture later in the growing season. Styer points out that it is important to ensure the planter is getting through the residue and that seeds are placed at the proper soil depth.
Styer stopped applying nitrogen fertilizer in 1996 and stopped applying a starter fertilizer a few years later after taking tissue samples. Instead, cover crops and manure have improved water-holding capacity, stopped erosion and supplied nutrients to grow his crops. He relies on the legume to provide fixed nitrogen and on the rye to supply some nitrogen scavenged from the previous year. Lots of farmers think cover crops cost too much, but in 2004 Styer figured if he applied nitrogen alone at 125 pounds per acre it would cost $34.50. On the other hand, the cover crop system per-acre costs were $32. (At that time he was planting a rye/hairy vetch/crimson clover mix: $8 for rye seed, $12 for hairy vetch seed, $5 for crimson clover seed and $7 for planting.) For a fewer dollars, he gets the nitrogen, plus the ground cover and soil improvements.
While it may seem impossible for every farm to use an extensive cover crop system like Styer’s, he thinks there are systems that can work for just about every situation. A rotation can be implemented to include a cover crop. Each species has a particular benefit. All of them accomplish the basic goal of covering the soil. Styer believes the soil should be covered at all times of the year, preferably with a growing crop, or at least with heavy residue.