Winter wheat is planted in the fall and harvested in the middle of the summer. Spring wheat is planted in the spring and harvested in late summer. There are both hard and soft varieties of white spring wheat. Hard wheat usually has small grains and is richer in proteins called gluten; soft wheat has larger grains and is richer in carbohydrates.
Gluten is a form of protein that makes wheat chewy and helps it rise. Soft wheat lacks a high content of gluten and has more carbohydrates; it is made into flour for baking crackers and pastries. Hard wheat has a high content of gluten, making it useful for baking breads. Durham wheat, which has the highest gluten content, is preferred for making pasta. Hard wheat and durum wheat that have high gluten content (and usually bring higher prices than soft wheat), but soft wheat delivers higher yields.
Agronomists at the University of Wisconsin recommend that growers use the number of seeds per pound and not pounds of seeds in determining sowing rates of spring wheat. They recommend sowing 1.2 to 1.4 million seeds per acre. Spring wheat should be sowed 1 inch deep so the seeds will be warmed by the sun. If the seeds are sowed deeper than 1 inch, cool night temperatures can delay their germination.
Wisconsin agronomists say applying too much nitrogen to spring wheat encourages the growth of stems at the expense of the grain and can cause lodging. Lodging is when the plant stem bends or breaks at a 45-degree angle or more making it difficult to harvest the grain. Applying 60 lbs. of nitrogen per acre is adequate for most soils.
Spring wheat is most often affected by head scab, leaf and stem rust, Septoria leaf blotch and smut. Severe infections of Fusarium head scab can reduce the yield of grain by 50 percent or more; diseased kernels may be shriveled and carry toxins that are harmful to animals and humans. Fungicides applied to the foliage may increase yield if the lower leaves are infected, if moderate temperatures and humid weather are forecast for long periods or if spring wheat is sowed in land where wheat was previously grown.
To qualify as dark northern spring wheat, which brings a premium price, at least 75 percent of the kernels must be what buyers call DHV (dark, hard, vitreous). Growers commonly suffer a 9 percent penalty per bushel if the number of DHV kernels is below 25 percent, a 6 percent penalty for DHV levels between 25 and 50 percent and a 3 percent penalty if 50 and 75 percent of the kernels are DHV.
Discounts and premiums for DHV levels are calculated when the wheat is delivered. Buyers often require that spring wheat contain at least 14 percent protein. If the protein content is lower than 14 percent some elevators will reject it. Spring wheat that is blended with winter wheat cannot be sold on the market.
The amount of rain just before harvest can significantly decrease the protein content of spring wheat. Tests reported by Washington State University found that protein levels dropped significantly when the wheat was harvested two or three weeks after receiving an inch of rain.