Operations and Timing
Most crops in the U.S. are planted in the spring. The exception is winter wheat, which is planted across the U.S. but concentrated in the central and southern Great Plains and the Pacific Northwest. Winter wheat is planted in the fall, goes into dormancy during the winter, and is harvested for grain the following spring.
The table below shows the "usual planting dates" for six major crops. Planting dates vary by region, following the weather. For simplification, the usual range of planting dates for the top-producing states are shown; if planting dates vary widely, more than one is given. The actual planting dates may begin earlier and extend later, but these are considered the most common. Over the past ten years, planting dates have typically shifted a couple days backward.
Source:USDA NASS Field Crops Usual Planting and Harvesting Dates (October 2010) (PDF) (51 pp, 1.96 MB, About PDF)
|Crop||Usual Planting Dates (most active period) in Top-Producing States||Top Producing States||Total Acreage (million acres)|
|Barley||Apr 7 - May 11 (ID, MT); Apr 26 - May 25 (ND)||ND, ID, MT||
|Corn (grain)||Apr 25 - May 18 (IA); May 5 - May 26 (ID)||IA, ID||
|Wheat (spring)||Apr 24 - May 25||ND||
|Soybeans||May 8 - June 12||IA, IL, MN||
|Wheat (winter)||Sep 1 - Oct 20||KS, CO, WA||
Drills - are implements used to plant crops in closely spaced rows (typically four to ten inches); drills are commonly used for cereal crops such as wheat and can be used to plant soybeans. Grain drills are typically equipped with disks to open a small trench in the soil, a metering system to deliver a measured, controlled amount of seed to drop tubes which guide the seed to the seed trench. There must be some means (wheels or drag chains) of gently closing the seed trench with soil to cover the seeds.
Tractors - are traction machines that provide mechanical, hydraulic, and/or electrical power to implements to perform a wide range of crop production and handling operations. Tractors are most often used to perform drawbar work and PTO (power take-off) work. Tractors can be equipped with rubber tires, rubber belts, or steel tracks. A modern farm tractor is almost always equipped with a diesel engine and tractor size is measured by the amount of power that the tractor can produce at the PTO. Tractor sizes range for those with less than 40 PTO horsepower to ones that produce more than 500 horsepower. The cost of a large tractor is between $200,000 and $300,000.
Planters - are implements used to plant row crops (typically in row spacings ranging from 10 to 40 inches). Planters open a seed trench, meter seeds one-at-a-time, drop seeds into the seed trench, and gently cover the seed. Some planters can cut through residues and till a small strip of soil in each row at the time of planting. Planters can also be equipped to apply fertilizer, pesticides, and herbicides during planting. Planters come in sizes as large as sixty feet wide - that is twenty-four rows with a typical 30-inch row spacing, or thirty-six rows with a narrower 20-inch row spacing. Such large planters can cost in excess of $140,000.
Potential Environmental Concerns
One current controversy related to planting is the choice of seeds. More and more of the seeds planted in the U.S. are genetically modified (GMOs) to make crop production more efficient, to better withstand environmental stresses such as drought, flood, frost, or extreme temperatures, to protect crops against pests such as weeds, insects, or diseases, and to be resistant to herbicides.
Environmental concerns related to GMOs include increased pest resistance, development of weed tolerance, and decreased genetic diversity. For example, insects exposed to a genetically engineered crop with the Bt gene (Bt is a natural toxin taken from the Bacillus thuringiensis bacteria, which is toxic to a number of insects) may become more resistant to pesticides. This is a serious concern for organic farmers who use Bt on their crops as an alternative to chemical insecticides. Another environmental concern is that, over time, some weed species could develop a tolerance to herbicides that are applied repeatedly to a crop tolerant to that herbicide. A transgenic crop might cross with another crop or weed, resulting in an undesirable crop or weed species. Others are concerned that reliance on a few genetically modified crops may reduce biological diversity. Also, a lack of genetic diversity in the food supply could increase the risk of catastrophic crop failure and threaten our food security.
Crops; Wheat. GMO Compass, 4 Dec. 2008. Web. <http://www.gmocompass.org/eng/grocery_shopping/crops/22.genetically_modified_wheat.html>.
Best Management Practices
To reduce the risk of insect resistance to Bt, a certain percentage of crop acreage on every farm is normally devoted to non-genetically modified variety.