Seasonal variability in forage growth creates ongoing challenges for Ohio livestock producers. This occurs especially during the summer slump when hot, dry conditions slow the growth of cool-season grasses commonly used in Ohio. Adding warm-season annual grasses to a forage system can help fill this gap by boosting summer forage production and strengthening the overall resilience of the system. Species such as browntop millet, foxtail millet, pearl millet, teff, and sorghum-sudangrass are well-suited for summer conditions, offering fast forage growth, strong tolerance to heat and drought, and good nutritional value during summer, compared to cool-season perennials.
This fact sheet highlights key agronomic practices for establishing warm-season annual forages, including proper seedbed preparation, recommended planting periods, and potential cropping systems. It also reviews important risks associated with prussic acid development after frost, nitrate buildup during drought, and offers considerations to reduce these hazards. This publication is intended for livestock producers, forage managers, and agricultural professionals looking for research-based guidance to improve forage productivity, decrease reliance on purchased feed, and increase the resilience of forage systems under unpredictable weather conditions.
Benefits of Warm-Season Annual Grasses
Most pastures in Ohio are dominated by cool-season grasses such as tall fescue, orchardgrass, and timothy. These species grow most vigorously in the spring and again from late summer into early fall. However, their growth slows or ceases during the hot, dry conditions typical of June through August. This summer slump often results in reduced forage quantity and quality, making it difficult to meet the nutritional needs of grazing livestock.
Recent trends toward hotter summers and severe drought in 2024 and 2025 have been intensifying this seasonal decline in forage production, and are expected to worsen the summer slump, making it even harder to maintain sufficient year-round forage production for livestock. Incorporating annual warm-season grasses into existing forage systems is one practical way to address this challenge. These species grow best at temperatures between 80 degrees Fahrenheit and 90 F, which helps fill summer feed gaps, support more consistent forage availability, and improve the overall resilience of livestock operations.
Annual warm-season grasses offer several advantages when added to a forage system. Under suitable conditions, they establish quickly, grow fast, and produce high biomass, making them useful for both grazing and harvested forage. These species are typically more tolerant of heat and drought than cool-season grasses, which makes them well-suited for Ohio’s summer weather patterns. During the summer slump, warm-season annual grasses also tend to provide better nutritional value, including higher crude protein levels and improved digestibility compared to cool-season perennial grasses. As an example, a Virginia trial observed late-summer crude protein levels of 13%–19% for annual warm-season grass plots when adjacent cool-season plots had protein levels of 10%–13% and native warm-season perennial grasses had protein levels of 5%–10%. In the same trial, neutral detergent fiber levels were consistently lower for annual warm-season grasses as compared to cool-season and native warm-season perennial grasses.
In addition, rapid growth and the strong summer tolerance of warm-season annual grasses can add flexibility to a forage program. Many of these species can produce multiple cuttings per season, making them effective for both grazing and stored feed. They also fit well into crop rotations or serve as a bridge during pasture renovation, helping suppress weeds while providing forage between terminating an old stand and establishing a new one. During periods of limited summer forage, warm-season annuals can also function as an emergency feed source, helping reduce the need for purchased hay.
While warm-season forages provide many advantages, they also come with management challenges. The growth and development of these species is very sensitive to temperature, so it is important for producers to make decisions about when to cut, fertilize, graze, terminate, etc., based monitoring the forage versus dates on the calendar. This type of adaptive management can be challenging for individuals who have limited experience with warm-season grasses. If these crops are harvested after heading, they will be overmature, which reduces forage quality and limits their ability to regrow. Additionally, the establishment costs of annual crops vary depending upon fluctuating input costs. As with all new seedings, a risk of stand failure exists due to unpredictable rainfall in late-spring and early-summer.
Warm-season grasses can be planted alongside warm-season annual legumes such as cowpea. Incorporating legumes increases both management complexity and establishment costs. In some cases, later plantings of warm-season grasses can be effectively mixed with brassicas. Additionally, rotating warm-season annuals with cool-season annuals can enhance forage productivity. Many small grain crops have the potential for successful inner-seeding into warm-season annual stubble, which can extend the grazing season.
Planting time for warm-season grasses in Ohio can range from early May to late July, depending on the weather conditions. Warm-season annual grasses need warm soil conditions—at least 65 F. To reach the appropriate developmental stage for grazing or harvesting, most warm-season annuals will need 45–60 days of growth. The planting date should take place after the last frost.
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|
Browntop Millet |
Foxtail Millet |
Pearl Millet |
Teff |
Sorghum-Sudangrass |
|
|
Planting Date |
5/1–7/20 1 |
5/1–7/20 1 |
5/1–7/20 1 |
5/15–7/01 1 |
|
|
|
Seeding Rates (lb/acre) |
Broadcast |
20–25 2 |
20–30 5 |
20–30 3 |
Not generally recommended |
30-35 3 |
|
Drilled |
15–20 2 |
15–20 5 |
15 3 |
8–12 if coated, |
20–25 3 |
|
|
Planting Depth (inches) |
0.5–1 2 |
0.25–0.5 5 |
0.5–16 |
0.125–0.25 1 |
0.5–1 8 |
|
|
Optimal pH |
7–7.5 2 |
5.5–6.5 5 |
5≥ 2 |
6–6.5 4 |
5.5≥ 3 |
|
|
Nitrogen Recommendations (lb N/acre) * |
100 1 |
100 1 |
100 1 |
50–60 1 |
100 1 |
|
|
Soil Test Phosphorus Critical Level (ppm) ** |
20 9 |
20 9 |
20 9 |
20 9 |
20 9 |
|
|
Soil Test Potassium Critical Level [ppm, for Cation Exchange Capacity (CEC) > 5] ** |
100–120 9 |
100–120 9 |
100–120 9 |
100–120 9 |
100–120 9 |
|
|
Mechanical Harvest Recommendations |
|
Limited to no regrowth 5 |
Mower-conditioner needed before hay curing 3 |
Best for dry baling 4 |
Mow at ≥4 inches ( requires wide windrows management) 10 |
|
|
Minimum Height for Grazing or Harvest (inches) |
18 5 |
18 5 |
18 3 |
2–3 if not easily uprooted 4 |
24 3 |
|
|
Leave For Regrowth (inches) |
N/A 2 |
N/A 5 |
6–10 6 |
3–4 4 |
6–10 10 |
|
|
Yield Range Estimates (tons/acre) |
1–2 2 |
1–3 5 |
3–4.5 7 |
2–4 4 |
3.5–5 7 |
|
|
Nutritive Value Range Estimates |
|
8%–17% CP |
8%–17% CP |
13%–16% CP |
9%–15% CP |
|
|
Considerations |
Yields less than pearl but better for hay curing 11 |
Limited to no regrowth, not recommended for horses 5 |
Seed before summer rains; very dependent on moisture 3 |
Easily uprooted; typically grown for hay 4 |
Hay curing is difficult; more suitable for bailage or grazing 3 |
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* These rates are intended to be applied half at planting, with the rest split between each cut/graze. For more specific information on N rates based on previous crops or yield goals, visit Table 7.11 in the Ohio Agronomy Guide, 16th edition. ** These critical levels represent the amount of phosphorus (P) or potassium (K) present in the soil needed for adequate growth based on a Mehlich-3 soil test. If soil tests show concentrations below these numbers, fertilization is recommended. See Nutrient Management of Forage Crops Intended for Hay for more information on calculating specific P and K rates based on a soil test or crop removal rate. |
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Table 1 References 1Barker, D. J., Chiavegato, M. B., Essman, A., Fulton, J., Haden, R., LaBarge, G., Lentz, E., Lindsey, A., Lindsey, L., Lopez-Nicora, H., Michel, A., Noel, J., Ortez, O., Paul, P., Rakkar, M. K., Sulc, R. M., Tilmon, K., Wilson, A., & Witter, J. (2024). Ohio agronomy guide (16th ed.). Ohio State University Extension. 2Sheahan, C.M. (2014). Plant guide for browntop millet (Urochloa ramosa). USDA-Natural Resources Conservation Service. 3Kallenbach, R., Roberts, C., & Bishop-Hurley, G. (2001). Warm-season annual forage crops. University of Missouri Extension. 4Kreager, D., Gelley, C., & Jagger, C. (2025). Teff for forage production. Ohioline, Ohio State University Extension. 5Teutsch, C., Keene, T., Smith, R., & Henning, J. C. (2018). Foxtail millet. University of Kentucky Cooperative Extension Service. publications.ca.uky.edu/sites/publications.ca.uky.edu/files/AGR233.pdf 6Teutsch, C., Keene, T., Smith, R., & Henning, J. C. (2018). Pearl millet. University of Kentucky Cooperative Extension Service. publications.ca.uky.edu/sites/publications.ca.uky.edu/files/AGR231.pdf 7Sulc, M., & Weiss, B. (2019). Emergency forage for planting early to mid-summer. Forages, Ohio State University Extension. 8Teutsch, C., Keene, T., Smith, R., & Henning, J. C. (2018). Sorghum-sudangrass hybrids. University of Kentucky Cooperative Extension Service. 9LaBarge, G., & Beers, L. (2022). Nutrient management of forage crops intended for hay. Ohioline, Ohio State University Extension. 10Curtis, Z., & Duppstadt, L. (2023). Planting forage sorghum, sudangrass, and sorghum-sudangrass hybrids. Penn State Extension. 11Baker, R. D. (2004). Millet production. New Mexico State University Cooperative Extension. |
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Browntop Millet (Urochloa Ramosa)
Browntop millet is a fast-growing but generally low-yielding crop that is usually planted for hay, pasture, or cover. It can germinate within five days of planting in ideal conditions—quicker than other millets—which is useful for situations that need fast results. It naturally reseeds itself and, when not managed correctly, can become a challenge. Its stems are thin, allowing for easier hay curing than pearl millet. While Browntop millet performs best in soils with pH around 6.5–7, it is much more tolerant of acidic soils compared to other warm-season annuals and can still grow in environments with pH as low as 5.
Foxtail Millet (Setaria italica)
Foxtail millet (or German millet) is often grown for hay due to its lack of prussic acid and sufficient growth in dry conditions. As hay, it is highly palatable but may only produce one or two cuttings because it struggles to regrow after harvest. It should not be a major part of horse diets due to its glucoside setarian content, which is harmful to horses.
Pearl Millet (Pennisetum americanum (L.) Moench.)
Pearl millet is a common warm-season annual grass grown for forage. It produces high yields and can be grazed or cut multiple times during a season. It is fairly tolerant of acidic soils and drought conditions. Like foxtail millet, pearl millet does not have prussic acid. It depends on heavy moisture to establish, so planting before the end of spring is recommended due to increased rainfall. Brown midrib (BMR) varieties are available and typically exhibit lower lignin content, resulting in higher fiber digestibility than non-BMR varieties.
Sorghum-Sudangrass (Sorghum bicolor x Sorghum bicolor var. sudanese)
Sorghum-sudangrass is a hybrid crop that combines the regrowth ability of sudangrass with the increased foliage of forage sorghum. It can be cut or grazed multiple times, unlike sorghum. This crop depends heavily on moisture, and when harvested it requires extra care to dry properly. It is usually harvested for chopped silage, baleage, or hay, although hay curing can be challenging because of its coarse stems. Like all grasses in the sorghum family, sorghum-sudangrass is not recommended for horses and can pose a prussic acid risk to all livestock. Brown midrib (BMR) varieties are available and typically exhibit lower lignin content, resulting in higher fiber digestibility than non-BMR varieties.
Teff (Eragrostis tef (Zuccagni) Trotter)
Teff is a crop growing in popularity due to its uniform stands, ability to aid weed control, and reputation for palatability. It can be harvested for hay or silage for livestock, including horses. Equine managers are often interested in teff for horses with metabolic disorders due to teff’s low non-structural carbohydrate content. Unlike some other warm-season annual forages, it does not accumulate prussic acid. Grazing is generally not advised because of its delicate root system that can be easily uprooted, but it can be grazed lightly with careful foot traffic. Its very small seeds require a firm, well-prepared seedbed to establish. It cannot tolerate frost or germinate in soils below 65 F.
Preparation and Establishment
Tilled Seedbeds
Tillage generally warms the soil and can disturb weed populations, which helps warm-season annual grasses establish more quickly. Planting with a drill works well when the seedbed is firm. Another option is finely cultivating the seedbed, broadcasting seed, and then cultipacking the seedbed. Broadcast methods usually require about a 1/3-higher seeding rate compared to drilled plantings.
No-till
When tillage is not used for seedbed preparation, chemical weed control before planting becomes more vital. If chemical control is used, always read and follow all label directions. Contact your local Ohio State University Extension office for assistance with weed identification and development of an effective control plan.
Using a no-till drill helps ensure proper seed-to-soil contact with less soil disruption than tillage. Among the species discussed in this publication, teff grass establishment would be the most limited in no-till seeding conditions due to its small seed that is often buried too deeply by a drill.
Termination
In Ohio, annual warm-season grasses naturally die back with the first fall frost. These species are not cold-tolerant and start to decline when temperatures approach freezing. Fall frost in Ohio typically occurs between mid-October and early November, depending on location and weather. Frost is classified by temperature:
- light frost (33–36 F)
- freeze (32 F)
- heavy freeze (28 F or lower), which usually results in the complete die-off of these grasses
Cautions Based on Environmental Conditions
Prussic Acid Concerns Following Frost
Some grasses contain dhurrin as part of their defense mechanisms. When plant cells are damaged, the dhurrin reacts with other compounds in the plant to form prussic acid. Prussic acid contains cyanide, which can interfere with oxygen transport in mammals and may be toxic even at relatively low levels (toxicity begins at 500–750 ppm cyanide in feed on a dry-matter basis).
Frost damage is the main cause of widespread prussic acid formation in pastures and hayfields. The level of prussic acid varies depending on the severity and timing of the damage, as well as the species and variety of forage. Sorghum-sudangrass typically has higher prussic acid levels than other species cited, including weeds such as johnsongrass. Shattercane can also produce prussic acid. Millets and teff have a very low potential to accumulate prussic acid.
When pastures containing species that can produce prussic acid experience a light frost, wait at least two weeks before grazing again. The waiting period allows the plant tissue to release some of the prussic acid in its gas form. Some prussic acid will usually remain, but the waiting period also allows the plants to grow larger, which decreases the risk of toxicity since plants under 18 inches tall are more likely to develop toxic levels of prussic acid. High prussic acid levels are unlikely in hay because the cyanide in prussic acid breaks down during the drying process. However, hay can also be tested at commercial labs for prussic acid and cyanide levels before feeding.
Nitrate Concerns During Droughts
Nitrates can build up in plants during droughts when they are unable to efficiently turn nitrates into proteins. High nitrate levels in forages can harm the hemoglobin in animals’ blood, reducing its capacity to carry oxygen. Elevated nitrate levels are usually linked to dry conditions, as drought decreases photosynthesis and stops plants from turning soil-absorbed nitrate-nitrogen into proteins.
Nitrates can be built up in any plant species, but usually only in dry conditions. Other factors that increase the risk of nitrate buildup include too much nitrogen fertilizer or high stem-to-leaf ratios. While ensiling forages can cut nitrate levels by about a third, drying forages to make hay will not reduce their nitrate content.
| KNO3 | NO3-N | NO3 | Interpretation |
|
0%–1% |
0%–0.15% |
0%–0.65% |
Generally safe for livestock |
|
1%–1.6% |
0.15%–0.23% |
0.65%–1% |
Caution: Potential toxicity; dilute or limit in forage mixtures |
|
>1.6% |
>0.23% |
>1% |
Danger: Do not feed; high toxicity risk |
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Table 2 Reference Ensley, S., & Barnhart, S. K. (2012). Nitrate toxicity. Iowa Beef Center, Iowa State University. |
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Nitrate tolerance in livestock can be improved through feeding management. Allowing animals to consume feed gradually helps reduce the risk of toxicity, and feeding grain alongside forage can further increase tolerance. Ensiling forages can significantly reduce nitrate levels and lower the risk of toxicity. However, nitrate exposure from both feed and water sources is cumulative. Suspect forages should be introduced gradually over several days to allow animals time to adapt, and forages should be tested whenever there is uncertainty about nitrate levels.
Conclusion
Annual warm-season grasses can be a valuable tool for Ohio livestock producers looking to fill forage gaps during the summer slump. Warm-season grasses offer fast growth, good nutritional value, and drought tolerance, making them well-suited for Ohio’s increasingly hot and dry summers. With proper planning and management, they can be used for grazing, hay, or silage, and fit well into crop rotations or pasture renovations. Producers should consider their farm’s goals, soil conditions, and available equipment when selecting species and planting methods. Producers should also be mindful of environmental conditions that can lead to prussic acid or nitrate accumulation, as these issues can pose risks to livestock. Incorporating warm-season annuals into forage systems can help maintain summer forage supplies, lower feeding expenses, and strengthen the overall resilience of the operation.
References
Duiker, S. W., & Williamson, J. A. (2019). Extending the grazing season with plant diversity.
extension.psu.edu/extending-the-grazing-season-with-plant-diversity
Frankson, R., Kunkel, K.E., Champion, S. M., & Easterling, D. R. (2022). Ohio State climate summary 2022. NOAA Technical Report NESDIS 150-OH. NOAA/NESDIS.
statesummaries.ncics.org/chapter/oh
Henning, J. (2020). Cyanide poisoning and nitrate toxicity – Do you know the difference? Ohio BEEF Cattle Letter.
u.osu.edu/beef/2020/10/28/cyanide-poisoning-and-nitrate-toxicity-do-you-know-the-difference
Marsalis, M. A., Lauriault, L. M., & Trostle, C. (2012). Millets for forage and grain in New Mexico and West Texas. New Mexico State University—BE BOLD. Shape the Future.
pubs.nmsu.edu/_a/A417/
Oppedahl, D., & Jorgensen, C. (2023). Climate change and risks to Midwest agriculture. Federal Reserve Bank of Chicago.
chicagofed.org/publications/blogs/midwest-economy/2023/climate-change-agriculture-risks
Teutsch, C., Smith, R., Keene, T., & Henning, J. C. (2018). Warm season annual grasses in Kentucky. University of Kentucky Cooperative Extension Service.
publications.mgcafe.uky.edu/sites/publications.ca.uky.edu/files/AGR229.pdf
Tracy, B. F., Maughan, M., Post, N., & Faulkner, D. B. (2010). Integrating annual and perennial warm-season grasses in a temperate grazing system. Crop Science, 50(5), 2171–2177.
doi.org/10.2135/cropsci2010.02.0110
Vittetoe, R. (2023). Alternative forage options: Tips for seeding warm season annuals. Integrated crop management. Iowa State University Extension.
crops.extension.iastate.edu/post/alternative-forage-options-tips-seeding-warm-season-annuals