OREGON STATE UNIVERSITY
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Oat is a cool-season, small grain species used for both grain and forage. It is the least winter hardy species of the small grains. It is used as a summer annual planted in the spring for silage or hay but sometimes used as pasture. It is often used in companion seedings with legumes, especially alfalfa. Straw, after grain harvest, is often used as forage and as bedding, due to its soft, relatively dust-free, and absorbent nature.
Growth habit: Upright bunch growth
Persitance: Summer Annual
Oat is a cool-season annual grasses. It is more winter-sensitive than other small grains. Winterkills in Hardiness Zone 6 and colder and much of Zone 7. Optimum growth temperature is between 68 and 70°F (20-21 °C). Growth and development are substantially reduced at temperatures above 82 to 86°F (28-30 °C). Most oat production is in areas where annual precipitation is between 18 and 53 inches (450-1350 mm), especially in areas where March to August precipitation is greater than 18 inches (450 cm).
Suited to well-drained and moderately well-drained soils (WD-MWD). Tolerant of brief flooding only (3-6 days). Tolerant of strongly acid to moderately alkaline soils (5.1-8.4). Somewhat tolerant of aluminum (persisted at 1–2 ppm Al3+ and pH 4.0). Moderately tolerant of salinity, 3–6 dS/m (millimhos/cm).
Nine maps have been developed. For the climate factors: 1) Minimum temperature (Tmin), 2) Maximum temperature (Tmax), 3) annual precipitation from 30 year average, 4) a combined climate factors map. For the soil factors: 5) soil pH, 6) soil drainage, 7) soil salinity, 8) a combined climate factors, 9) all climate and soil factors combined.
Oat is a cool-season grass with optimum growth rates between 68 and 70°F (20-21 °C).
It can be planted when the 3-day soil temperature is 40 ̊F (4.4 ̊C) (https://extension.sdstate.edu/soil-temperature-planting-spring-crops) and can be harvested for forage in about 60 days. The growth curve of plant height vs days after planting of spring barley is illustrated in a Kansas State University publication sourced from this document: http://courses.missouristate.edu/WestonWalker/AGA375_Forages/Forage%20Mgmt/References/2Forages/4Annual/2Cool
Stage of maturity at harvest should be governed by the livestock being fed. For lactating dairy cattle, oat forages should be harvested as the first grain heads appear (late boot stage). Oat forage at this stage will provide a feed with more energy and similar protein levels to late-bud alfalfa and similar energy but higher protein content than corn silage. Many producers harvesting oats for feeding to gestating beef cows will delay harvest until the dough stage, to gain slightly more forage yield.
Irrigation Requirements
Adequate soil moisture during germination and early seedling growth is important for cool-season annuals planted for forage. When managed as a grazing or hay crop, emphasis should be focused on meeting the plant’s water needs during rapid growth stages (see Figure 7 of this web link: https://extensionpublications.unl.edu/assets/html/g2012/build/g2012.htm).
Even moderate water stress during vegetative stages is likely to reduce yield, although it may lead to improved forage quality.
Ma, Qianhu et al. (2022) reported on APSIM modeling of both nitrogen and irrigation strategies to improve forage oat yield and quality. There is a great need for improving oat forage production and quality. Simulations showed that the N rate of 90 kg ha−1 resulted in the best performance for oat under rainfed conditions. Under irrigated conditions, irrigation promoted oat nitrogen uptake. Thus, overall an N rate of 120 kg ha−1 in combination with irrigation of 120 mm applied during the vegetative growth period performed the best.
FAO Irrigation Document: https://www.fao.org/3/s2022e/s2022e02.htm#2.2%20influence%20of%20the%20crop%20type%20on%20the%20crop%20water%20needs
Oat cultivars are classified on the basis of maturity rating (early-, mid-, or late-season) and projected use (grain or forage type). A mid-season cultivar will mature more rapidly than a very late-season cultivar, regardless of growing season (spring or fall), or planting date within season. Two other characteristics of oat cultivars also are important. First, cultivars selected specifically for production of forage generally exhibit much slower maturation characteristics than grain-type cultivars. Secondly, oats has a long-day photoperiod requirement for flowering that is disrupted by a late-summer planting date. As a result, the maturation rate for all cultivars is generally much slower in the fall, and differences between cultivars of diverse maturity classes tend to be more separated.
See http://ipm.ucanr.edu/PMG/r730000411.html; https://smallgrains.ucdavis.edu/cereal_files/OatCvDescLJ11.pdf
Forage yield and feeding value of the harvested crop change as the oat plant matures through its growth stages. When harvested for silage or hay, very high quality forage is obtained when it is harvested in the boot stage, with higher yields when harvested later (mild or dough stage of the grain).
Nitrate poisoning, grass tetany, bloat, and ergot are antiquality issues of concern. Nitrate toxicity can occur with oats when over-fertilized with nitrogen (either commercial fertilizer or manure) and when drought-stressed. Ensiling reduces the nitrate level 40 to 60 percent. Have suspected forage tested before feeding to cattle. Dilute suspected forage by mixing with low nitrate forages and/or energy feeds such as molasses or corn. Grass tetany (hypomagnesemia) is a magnesium (Mg) deficiency of ruminants associated with their grazing of cool-season grasses during spring. Bloat: Although normally associate 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. Ergot or ergot fungi refers to a group of fungi of the genus Claviceps, often Claviceps purpurea ("rye ergot fungus"). They transform the ovary into a sclerotia that produces mycotoxins.
See descriptions of these antiquality components provided in the “Growing Cereals Grains for Forage” document.
