Annual Summer Forages for West Texas
Calvin Trostle, Extension Agronomy,
TAEX-Lubbock ,c-trostle@tamu.edu, (806) 746-6101
February, 2001

General Principles for High Quality Forage: For any forage, quality and energy level of the forage declines with maturity. This decline is rapid once the forage matures past boot stage. If you seek quality forage for grazing or haying (vs. tonnage) do not allow forage to head out. Maximum tonnage for most forages occurs in the soft dough stage though quality is lower. For best regrowth after haying or grazing leave a minimum of 6" of stubble. Remember that seed size will differ among forage types. Seeding rates on irrigated land are roughly 1.5 to 2.0 times higher than dryland; grazing seeding rates are slightly higher than rates for hay or silage. For long-term grazing consider plugging your drill to have ~20-22" spacing between rows. Livestock tend to walk between the rows thus regrowth is better.

Seeding rate cost comparisons below are for 10-inch drilled dryland at targeted seeding rates as noted in 'Suggested Summer Forage Seeding Rate Targets for West Texas' by Calvin Trostle (February, 2001). The following prices are from two seed companies, which will help producers evaluate relative seed costs among forage types.

Conventional sorghum/sudan. Haygrazer. Adequate for numerous uses and highly productive, but slightly more than 50% of yield comes from stem. Often the best all-round producer for hay or grazing. Better vigor, regrowth, and drought tolerance than forage sorghum. Depending on the hybrid it may be sweet or not, or have coarse or fine stems. These are normally about 16,000 seed/lb. Grazing may be initiated when the plants are 24-30" tall.

Companies A & B at $12 to $18/bag ($3.60 to $5.40/A at 15 lbs./A).

Sorgo-sorghum/sudan. This class of forage is sweeter than sorghum/sudan, which is believed to increase consumption and palatability for livestock. Seed size (20,000-24,000 seed/lb.) is smaller than conventional sorghum/sudans thus seeding rates should be 20% less. Sorgo-sorghum/sudan has the good regrowth and drought tolerance of conventional sorghum/sudan.

Companies A & B at $18/bag ($4.32/A at 12 lbs./A).

Brown mid-rib (BMR) sorghum/sudan. The management of BMR sorghum/sudan (16,000 seed/lb.) is similar to conventional sorghum/sudan for seeding, planting date, and harvesting. The brown mid-rib trait is just that, a brown midrib in the leaves. The important characteristic for BMRs is lower lignin concentration in the leaves and stalk. This can result in 20 to 50% less lignin than conventional sorghum/sudan when harvested at comparable maturities. High lignin lowers the digestibility {i.e., the negatives of higher Neutral Detergent Fiber (NDF) and Acid Detergent Fiber (ADF)} of the forage. Thus BMR forage has higher feed value and forage palatability for livestock (grazed or baled). One concern with BMR may be standability (lodging). This is generally only a concern if the forage heads out. Higher seeding rates increase lodging potential. Lower seeding rates than conventional sorghum/sudans and lower applied N may be appropriate for BMRs if the forage will head out. Genetics are slightly different among BMRs with bmr-6 and bmr-12 genes believed to stand better than bmr-18. Also, BMR forage sorghum silage is available.

Companies A & B at $25.00/bag ($6.00/A at 12 lbs./A).

Photoperiod-sensitive sorghum/sudan and forage sorghum. Current photoperiod sensitive forages remain in the vegetative stage until daylength is less than ~12 h, 20 min (about September 20th for West Texas) at which time it will initiate the reproductive stage (and head out about 4 weeks later). Thus forage potential (grazed, baled, ensiled) is higher due to long-season growth, especially if planted early. While producers run the risk of conventional forages heading out due to delayed harvest (rainy weather, no time to harvest) photoperiod sensitive forage simply continue adding more leaves. This puts the producer in control and greatly reduces the risk of losing forage quality due to heading. The general management of photoperiod sensitive forages (16,000 seed/lb. for forage sorghum or sorghum/sudan) is the same as conventional hybrids for planting date, seeding rate, regrowth, etc. Photoperiod sensitive traits are now available in forage sorghum from several companies and even in hybrid pearl millet.

Company A, photoperiod-sensitive forage sorghum with some sudan background, $28.50/bag ($8.55/A at 15 lbs./A).

Forage sorghum. Old names such as ‘Red Top Kandy', ‘Cane', ‘Sweet sorghum'. Many forage sorghums are multi-purpose, but are most often planted for silage rather than hay or grazing because of their limited regrowth potential. These materials are often very tall and coarse stemmed in part due to their strong daylength sensitivity. Forage sorghums have sweet, juicy stems, relatively small grain heads, and may mature late. Traditionally, some grain production was expected from forage sorghums produced for silage, but the widespread availability of feed supplements has made this less important. Prussic acid potential tends to be higher than sorghum/sudans. Seed size varies, but averages near 16,000 seed/lb. Forage sorghum is the best choice for after frost grazing.
Somewhat similar is ‘Red Top Cane,' an old ‘early sumac' forage sorghum cross, which has higher seeding rates than conventional forage sorghums. It provides a lot of bulk, grows fast, is susceptible to prussic acid when short, but has done well on high pH soils or those with caliche. Also, Hegari, is popular with some growers. It produces chalky or starchy-white seeds, and is sweet. Hegari is suitable for shallow soils or chlorotic soils. It is an older ‘workhorse type' forage with good drought tolerance, but low disease resistance. Over time, Hegari has evolved to a lower-class forage placed on less productive soils. A downside of full maturity in both Red Top Cane and Hegari forages is tannin in the grain which when consumed by livestock inhibits nutrient uptake.

Company A, forage sorghum, $28.50/bag ($8.55/A at 15 lbs./A).
Company B, forage sorghum, $18-20/bag ($6.00/A at 15 lbs./A).
Company B, red top BMR, $25.00/bag ($10.00/A at 20 lbs./A).
Company A, conventional red top, $25.00/bag ($10.00/A at 20 lbs./A).
Company A, Hegari, $20/bag ($6.00/A at 15 lbs./A).

Hybrid pearl millet. This leafy forage is similar to conventional sorghum/sudans, but with some key differences. Seed size is much smaller (75,000-90,000 seed/lb.) than sorghum/sudan thus seeding rates must decrease. Due to small seed size, a shallow seeding depth of 0.75 to 1.5" is recommended, which may limit establishment under dry conditions. Relative to sorghum/sudans (60-65 F) warm soils are critical for success for hybrid pearl millet (65-70 F). Yields are somewhat lower than sorghum/sudans but this leafy forage tends to have higher quality. In West Texas hybrid pearl millet is much more tolerant than sorghum/sudan of iron (Fe) deficiency induced by chalky or caliche soils. Thus millets may produce comparable or even higher yields on these soil types relative to conventional sorghum/sudans. Hybrid pearl millet is drought tolerant, can be grazed by horses, and does not develop prussic acid problems (a good forage choice for fall grazing when light frosts are possible). This material may be grazed sooner (18-24") than sorghum/sudan. It should be harvested in boot stage for maximum total digestible nutrients per acre, or in pre-boot if higher quality is desired. Regrowth potential is somewhat less than sorghum/sudan so if haying leave 8" of stubble or if grazing do not allow livestock to trample the stalks.

Company A, $25/bag ($5.00/A at 10 lbs./A).
Company B, $35-40/bag ($7.00/A at 10 lbs./A).

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