Conservation Tillage Systems in the Southeast

Cash Crop Selection and Crop Rotations

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Soybeans, corn, wheat and cotton occupy 39 percent, 20 percent, 17 percent and 8 percent, respectively, of the 1.2 million acres of harvested row-crop land in the Southern Piedmont region [12]. Corn acreage increased due to demand for its use in ethanol production. Other crops grown in the region include sorghum, tobacco, sweet potatoes, beans, orchard crops and vegetables.

The vegetable, fruit and wine-vineyard industries have grown rapidly over the past two decades, due in part to the rapid growth of urban centers that extend across the Southern Piedmont. Examples include Atlanta, Ga., Greenville-Spartanburg, S.C., and Petersburg-Richmond, Va. In North Carolina, urban centers include Charlotte, Winston-Salem-Greensboro and Raleigh-Durham. Land dedicated to vegetable production increased from 21,750 acres in 2002 to 32,104 acres in 2007, with the greatest increase seen in North Carolina, where the acreage doubled. Typically, vegetables and small fruits such as strawberries are produced using plasticulture. However, traditional organic mulch systems that incorporate cover crops and conservation tillage have increased to some extent. A variety of vegetables are produced in the region. Sweet corn, tomatoes, peppers, squash, eggplants, cantaloupes and peas are grown in the summer. Broccoli, cauliflower, cabbage, winter squash and pumpkins are grown in the fall.

Organic production is increasing, especially in areas near urban centers where the products are marketed directly to consumers and to the restaurant industry. Conservation tillage practices are not used to any appreciable extent in organic systems, though cover crops are used. Some innovative growers are using conservation tillage and heavy residue production as a way to reduce weed competition in their systems. Most organic growers recognize the soil quality improvements conservation tillage offers and would readily adopt the practice if improved methods of weed control were developed for organic systems. Weed management in reduced-tillage organic systems is discussed in Chapter 11.

Many producers in the Southern Piedmont include corn, wheat and soybeans in rotations. The most popular component of this rotation is double-cropping soybeans and wheat. The residue produced from a mature wheat crop increases biomass inputs and provides additional benefits associated with improved soil quality. Soybeans are also double-cropped following harvest of a small grain such as silage. Wheat and rye are good cover crops for this region because they produce significant amounts of biomass during the mild winter and early spring. These cover crops fit well within conservation systems for corn, full-season soybeans and cotton.

Row crop producers in the central South Carolina Piedmont focus on producing grains for dairy operations or as a cover crop in cotton production. Dairy operations create a demand for both grain and silage. Most use a corn>wheat>soybean>fallow rotation where wheat is planted in fields harvested for silage. Harvesting for corn silage occurs earlier than grain harvest, and most of the corn plant is removed, leaving little residue. When corn is harvested for grain, the stalks, cobs and husks are left on the field. Soybeans are planted directly into wheat stubble. The rotation is fallow after soybeans because there is little time for a cover crop to grow and mature between soybean harvest and early corn planting. The need for a good short-season winter cover crop is also apparent in other parts of the region. Soybeans, corn and wheat are planted with no-till grain drills. Rotary headers that can harvest with or across rows are used to harvest corn silage planted on 15-inch rows.

Cotton producers in the region use rye and wheat as cover crops but are often planting into winter weeds due to the lateness of cotton harvest. Winter weeds are controlled with 2,4-D in March and cotton is planted either no-till or strip-till in late April to early May following a burn down of weeds with glyphosate. The amount of residue at the time of cotton planting is often minimal. Cotton production in the region continues to decline due to rising corn and soybean prices and losses in infrastructure such as gins. Producers are reluctant to invest in new or used cotton pickers because they are much less versatile than a combine. However, small pockets of producers scattered throughout the region continue to grow cotton profitably.

Vegetable producers rely on alternating crops of different families to help with disease and pest control. Wheat or rye is usually used for a winter cover crop in vegetable production systems. Vegetables are grown later in the summer after the small-grain harvest. Producers that grow tomatoes, bell peppers, eggplants and other crops from transplants use no-till transplanters to plant directly into rye or wheat residue. Summer cover crops such as sorghum-sudangrass, millet, forage sorghum or buckwheat are grown to provide biomass and compete with weeds. Legumes such as cowpeas, soybeans, annual sweet clover, sesbania or velvet beans are used as summer cover crops to add nitrogen along with organic matter.

Organic producers in the region are experimenting with various cover crops. These include legumes such as crimson clover, lupine, winter peas and vetch; non-legumes such as oats, rye and brassicas; and mixtures of legumes and cereals. They are planted in the fall either by direct seeding or by overseeding a crop such as soybeans prior to leaf drop. A roller/crimper provides an optimum method for killing the cover crops. With this equipment, a roller is pulled over the cover crop at the flowering stage, crimping the stem and resulting in death of the plant (see figures 9.2–9.4 in Chapter 9). Corn, soybeans or another crop can be direct seeded into this vegetative mat using no-till planting practices. The vegetative mat remaining from the cover crop helps control weeds. Other benefits include improved soil moisture retention, increased organic matter, nitrogen added by the legumes and the biomass returned to the soil.

Download the tables from Chapter 20.