The major U.S. oilseed crops are soybeans, cottonseed, sunflowerseed, canola, rapeseed, and peanuts. Soybeans are the dominant oilseed in the United States, accounting for about 90 percent of U.S. oilseed production. Most U.S. soybeans are planted in May and early June and harvested in late September and October (see Usual Planting and Harvesting Dates for U.S. Field Crops for soybean dates by region).
Large-scale production of soybeans did not begin until the 20th century in the United States, but area planted to soybeans has expanded rapidly. Soybeans are the second-most-planted field crop in the United States after corn, with 77.5 million acres planted in 2009. Increased planting flexibility, steadily rising yield improvements from narrow-rowed seeding practices, a greater number of 50-50 corn-soybean rotations, and low production costs (partly due to widespread adoption of herbicide-tolerant varieties) favored expansion of soybean acreage. More than 80 percent of U.S. soybean acreage is concentrated in the upper Midwest, although significant amounts are still planted in the historically important areas of the Delta and Southeast. Acreage tends to be concentrated where soybean yields are highest. (See USDA's National Agricultural Statistic Service for historical data on soybean and other oil crop acreage, yields, and prices.)
Rising yields have also encouraged expansion of soybean acreage, as seed varieties, fertilizer and pesticide applications, and management practices have improved over time. Higher yields reduce per-bushel production costs, increasing profitability. ERS data indicate that soybean production costs and returns for each region vary from the national average. Midwestern soybean producers generally have higher yields and lower per-acre cash costs than Southern and Eastern producers.
Data from the 2007 Census of Agriculture indicated that 279,110 U.S. farms raised soybeans in 2007, down from 511,000 in 1982. Acreage planted to soybeans was also lower in 2007 than in 2002, as demand for corn rose dramatically in this year. Harvested soybean acreage per farm increased from 114 acres in 1978 to 229 acres in 2007. Although small farms with fewer than 250 acres accounted for 72 percent of the farms growing soybeans, these farms produced only 26 percent of the 2007 crop. Irrigation was used on 5.2 million acres of soybeans, or 8 percent of U.S. soybean acreage in 2007. Individual or family farms accounted for 81 percent of all soybean farms in 2007 and 69 percent of soybean production. The rest were largely partnerships and small family-held corporations, with other corporations accounting for less than 1 percent of soybean farms and soybean production.
In the United States, soybeans are most commonly grown in a crop rotation with corn (see Agricultural Production Management: AREI, 2006 Edition). Since the early 1980s, double cropping of soybeans with wheat in the South has declined. In recent years, an increasing number of soybean farmers have adopted conservation tillage practices. The development of better herbicide applications has allowed producers to use less intensive soil cultivation practices. Soybean pesticide use (nearly all of which are herbicides) ranks second only to corn. Commercial fertilizer was applied to less than 40 percent of soybean acreage, a much lower rate than for most row crops (e.g., corn and cotton). Unlike other crops, soybeans can fix their own nitrogen and require minimal nitrogen fertilizer. (More information on Crop Production Practices is available from the Agricultural Resource Management Survey.)
Soybeans were one of the first bioengineered crops to achieve commercial success. USDA now conducts a farm survey to determine the extent of the adoption of biotech crops. The data indicate that soybeans comprise the greatest share of biotech acreage of all major U.S. crops (see the annual Acreage report). Biotech soybeans are nearly all herbicide resistant.
The popularity of bioengineered soybeans among U.S. farmers has ramifications for resource use, marketing, and international trade. Herbicide-tolerant soybeans have lowered the cost and changed the type of herbicides used by farmers (see Estimating Farm-Level Effects of Adopting Herbicide-Tolerant Soybeans ). In response to consumer preferences, both domestic and foreign, grain handlers are assessing the value of segregating bioengineered soybeans from conventional varieties. The added cost for segregating nonbiotech corn and soybeans could be higher than for segregating value-enhanced crops. Differentiating biotech and nonbiotech commodities may become an issue for grain handlers (see Biotechnology: U.S. Grain Handlers Look Ahead ). Initially, the bioengineering of oilseed crop traits has focused on improving production attributes, such as higher yields and lower costs. But enhanced functionality characteristics will soon emerge, such as high oleic, high stearate, and increased omega-3 content (see Value-Enhanced Crops: Biotechnology's Next Stage ).