OREGON STATE UNIVERSITY
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Wheat is most often grown as a grain crop, but it can be a useful winter pasture and forage source. It is an annual grass grown as winter- or spring-sown types.
Winter types are planted at the end of the summer. It overwinters and then starts growing and maturing towards the end of spring and beginning of the summer. It has good winter hardiness and can tolerate a range of soils but does not tolerate flooding. Spring types are planted in early spring and are harvested in late summer. Facultative types can be planted either in the Fall or in the Spring.
Bunch-type grass with upright tillers growing up to 3.9 feet (1.2 m) tall.
Growth habit: Erect bunchgrass
Temperature: Wheat can survive temperatures above -20 °F (-29 °C), but only 0.5 days at -15 °F (-26 °C), and 6 days at 5 F (-15 °C). If crown temperatures remain above -4 °F (-20 °C), successful overwintering is expected. Three inches (7.6 cm) of snow is usually sufficient to keep crown temperatures in this range.
The optimum growth temperature for wheat ranges from 54 to 72 °F (12 to 22 °C), with particular temperature sensitivity during the grain-filling stage. Every 1.8 °F (1 °C) increase above this mean temperature decreases wheat yield by about 10%.
Precipitation: Wheat requires about 12 to 15 inches (31-38 cm) of water per growing season to produce a good dryland crop.
pH: Tolerant of strongly acid to moderately alkaline soils (5.1-8.4).
Al3+: Somewhat tolerant of aluminum (persisted at 1–2 ppm Al3+ and pH 4.0).
Drainage: Suited to well drained and moderately well drained soils (WD-MWD).
Flooding: Tolerant of brief flooding only (3-6 days).
Salinity: Higher tolerance of salinity than other cereals, 6-12 dS/m (millimhos/cm).
| Suitability | July Max Temp (C°/F°) | Jan Min Temp (C°/F°) | Annual Precipitation (mm/in) | Soil pH | Drainage Class | Soil Salinity (dS/m) | ||||||
| Low | High | Low | High | Low | High | Low | High | Low | High | Low | High | |
| Well-suited | 22/72 | 22/72 | 1780/70 | |||||||||
| Moderately-suited | 28/82 | 13/55 | 635/25 | |||||||||
| Marginally-suited | 31/88 | 9/48 | 380/15 | |||||||||
| Marginally-unsuited | 33/91 | 6/43 | 300/12 | |||||||||
| Unsuited | 35/95 | 3/37 | 250/10 | |||||||||
Based on literature and expert wheat specialist counsel, climatic and soil tolerances were compiled. Nine maps were created for winter wheat, one for each of 3 climate factors and one for each of the soil factors, one combined climate factors map, one combined soil factors map, and a map for all of the factors combined. This allows for each factor to be examined and addressed to improve suitability through management. Small images of maps are provided below, with larger maps linked by clicking. For spring wheat, all factors except for Tmin values would be the same.
US Production Areas
A general suitability map was provided in the Sustainable Agriculture Research and Education publication “Managing Cover Crops Profitably”:
It shows that wheat is suitable to almost all parts of the US, except for far northern regions of MT, ND, MN WI and ME and southern regions of the arid northwest and southwest and FL. However, this map is not able to distinguish conditions of sensitivity or potential yield.
Major and minor US Wheat production areas were graphed by the USDA Agricultural Weather Assessments unit. Data were obtained from the National Agricultural Statistics Service (http://www.naas.usda.gov).
Numerous types of wheat are grown in Northern MT, ND, MN, southern ID, NV, southern AZ and NM.
Profile
Wheat is a cool-season grass with optimum growth rates between 64 and 68 ̊F (18-20 ̊C).
Spring wheat can be planted early into cool soils [~40 ̊F (4.4 ̊C)] and can be harvested for forage in 58-65 days. The sigmoidal growth curve of plant height vs days after planting of spring barley is illustrated in this Kansas State University figure (see extensive list of publications and wheat growth and development links:
https://www.agronomy.k-state.edu/extension/crop-production/wheat/wheat-publications.html
https://bookstore.ksre.ksu.edu/download/wheat-growth-and-development-poster-20x30_MF3300
Winter wheat is planted in late summer or early autumn, growing sufficiently for light grazing before growth stops due to low temperatures. Spring harvest at the soft-dough stage is early enough to allow a double-cropping system with corn, sorghum, or other warm-season annual grasses.
Irrigation Requirements
Adequate soil moisture during germination and early seedling growth is important for cool-season annuals planted for forage. When managed grazing or as a hay crop, emphasis should be focused on meeting the plant’s water needs during rapid growth stages (see Figure 7 of this web link from the University of Nebraska-Lincoln: https://extensionpublications.unl.edu/assets/html/g2012/build/g2012.htm: Jerry D. Volesky, Extension Range and Forage Specialist and Aaron L. Berger, Extension Educator).
Even moderate water stress during vegetative stages is likely to reduce yield, although it may lead to improved forage quality.
Note: For winter wheat, irrigation requirements during August and early September can be relatively high, reducing water-use efficiency, especially when compared to spring-planted systems.
Wheat cultivars are classified primarily according to their growing season. Winter wheat is planted in the fall and harvested in the spring and summer. It accounts for approximately 75% of wheat grown in the US. Spring wheat is planted in the spring and harvested in late summer or early autumn. Wheat is further categorized according to its hardness (hard or soft), color (red or white), and shape of its kernel. Although all grain-type wheats can be used for forage, there are dual-purpose cultivars that can provide good quality forage during late fall and winter, and then production the next summer. In addition, there are some forage-type wheat cultivars developed specifically for pasture, silage, or hay. They are typically winter-hardy, taller, awnless growing types, with a high leaf-to-stem ratio.
Cereal plants produce nutritious roughage for livestock maintenance during winter. Wheat forage can be as high quality as oat forage. When cut at the boot stage or at very early head emergence, wheat forage is very palatable and has a high nutritive value. When cut later (at the early milk to soft dough stage of the grain), its nutritive value is lower.
Nitrate Poisoning
Nitrate (NO3-) accumulates in plant tissue because of luxuriant uptake of soil N when plant metabolism of N is slow or stopped. This condition is promoted by cool temperature, drought, or other physiological stress that slows growth (Wright and Davison, 1964; Adv. Agron. 16:197-247). Plant nitrate is not toxic to animals but is reduced to nitrite (NO2-) in the rumen which causes methemoglobinemia that may lead to acute poisoning of animals. Non-ruminants, such as horses, are also subject to methemoglobinemia, however, at higher consumed concentrations.
Nitrate is the most common form of nitrogen in soil solution. Plants need nitrogen to make amino acids and proteins which results in plant growth and increased yield, however, excessive applications of N fertilizers can result in appreciable amounts of nitrate accumulation. For silage, ensiling more than 30 days, may entirely or partially degrade the nitrate concentration. Nevertheless, high nitrate level forages should be checked before feeding by submitting samples to an accredited forage lab. Farm workers can develop Silo-Filler’s disease from inhaling nitric and nitrous oxides emitted from fermenting forages containing high N concentrations. Ensure good air ventilation to reduce the health hazard.
Livestock suffering from methemoglobin poisoning, will have brownish-colored blood and brownish discoloration to the nonpigmented areas of skin and mucous membranes. Clinical signs include staggering, rapid pulse, frequent urination, and labored breathing followed by collapse, coma and death. Sub-lethal toxicity, which is primarily unrecognized in livestock, includes early-term abortions in pregnant females. This can also manifest as open cows or ewes at calving and lambing.
Plants with < 0.44% dry matter nitrate are considered safe. Forages containing 3,400 to 4,500 mg N/g as nitrate should be considered potentially toxic and should be mixed with safer feeds prior to use.
Hypomagnesemia (grass tetany) is a magnesium (Mg) deficiency of ruminants associated with their grazing of cool-season grasses during spring. It occurs in all classes of cattle and sheep, but is most prevalent among older females early in their lactation. Magnesium must be supplied daily because it is excreted in urine and milk. Symptoms are nervousness, twitching and staggering, collapsing, and convulsions that may cause death.
Vegetative and early jointing stage cereal grains, like other lush growing pastures, may have a low Mg content. Many factors affect Mg concentration and availability to livestock. The principal factor is high potassium (K) which negatively affects soil Mg uptake by plants and animal absorption and low calcium (Ca) levels. Forage Mg levels greater than 0.2 percent (2.0 mg/g) and a milliequivalent ratio of less than 2.2 for K/(Ca+Mg) are considered safe.
Grass tetany often occurs when the crop has received large amounts of water (from spring rains or irrigation) and has been heavily fertilized with N and K because soil Mg is leached by water and K is preferentially absorbed in early spring. Agronomic practices to increase forage Mg include splitting applications of N and K fertilizers, liming acid soils with dolomitic limestone, spraying Mg on herbage, or choosing cultivars higher in Mg. Mg can be supplemented to livestock by applying Mg fertilizer to pasture, providing other higher Mg-containing forages (e.g. legumes), adding Mg to drinking water, providing stock salt-mineral, molasses licks, or other energy sources to reduce the incidence.
Although usually associated with legume grazing, cereal grain pastures can cause frothy bloat. Pasture bloat is caused by rapid release of cell contents of succulent, immature forage during rumen fermentation. The material has a rapid rate of cell rupture, releasing the soluble proteins and fermentable carbohydrates. Soluble proteins are foaming agents, causing the formation of a stable foam in the rumen. This prevents eructation (belching) of rumen gases formed by the fermentation.
Bloat typically happens on lush pastures, with low dry matter and fiber content, and high protein and soluble nitrogen fractions. These conditions may occur in autumn or early spring. To prevent bloat, hungry cattle should be supplemented with more fibrous forages. Low concentrations of Ca may make bloat more likely by reducing rumen motility. High levels of soluble protein are also associated with increased occurrence of bloat.
Bloat can be controlled by feeding antifoaming agents such as poloxalen (Bloat Guard) or laurenth-23.
Ergot
Ergot or ergot fungi refers to a group of fungi of the genus Claviceps, often Claviceps purpurea ("rye ergot fungus"). This fungus grows on rye and related plants, and produces alkaloids that can cause ergotism in humans and other mammals who consume grains contaminated with its fruiting structure (called ergot sclerotium). It most commonly affects outcrossing species such as rye (its most common host), as well as triticale, wheat, and barley. It affects oats only rarely. It also affects quackgrass, smooth bromegrass, and great basin wildrye.
An ergot kernel, called a sclerotium, develops when a spore of fungal species of the genus Claviceps infects a floret of flowering grass or cereal. The infection process mimics a pollen grain growing into an ovary during fertilization. The proliferating fungal mycelium then destroys the plant ovary and connects with the vascular bundle originally intended for seed nutrition.
Management practices to reduce ergotism include: crop rotation, tillage, managing grassy weed hosts, use of ergot-free seed, fungicides, varietal resistance, harvest strategy, and cleaning ergoty seed lots (https://www.ndsu.edu/agriculture/ag-hub/publications/ergot-small-grains).
Forage Information System
Oregon State University
Department of Crop and Soil Science
109 Crop Science Building
Corallis, OR 97331-3002
