The Rundown on Ryegrass

Mike Trammel, Oklahoma State University Southeast Area Extension Agronomist

 

Lately, I have fielded several questions from producers regarding ryegrass. In the south, annual ryegrass is interseeded into over 2 million acres of Bermudagrass or Bahiagrass every year and is grown on as much as a million more acres as an annual forage or cover crop. From the start, let me be clear that we are talking about annual ryegrass and not rye. Though a lot of folks refer to annual ryegrass simply as rye, these are two distinct species. Annual ryegrass (Lolium multiflorum) is dark green with shiny leaves that have smooth edges. Cereal Rye (Secale cereale) is a small grain species that is usually bluer green in color with dull and somewhat waxy leaves. I have also received some questions about perennial ryegrass (Lolium perenne), which is the other major ryegrass forage species. Perennial ryegrass is usually grown in cooler, milder climates of the northern tier of the U.S. It is sometimes called the “Goldilocks” grass, as it prefers places where it doesn’t get too hot or too cold, it likes it just right. The ryegrass that is most grown for forage in Oklahoma is annual ryegrass.

 

Annual ryegrass is adapted to a wide range of conditions. It grows well on soils ranging from poorly drained clays to deep sands. However, production of annual ryegrass on sands is not as great as on heavier textured soils except under higher rainfall. Ryegrass will grow in areas receiving 20 inches of rainfall, but production is much greater in higher rainfall areas. In Oklahoma, the best ryegrass production area is east of I-35. However, annual ryegrass can produce well in many years from southwest Oklahoma north to Kansas in rainfall belts of 25 inches or more. It will also grow on acid soils, although growth is limited when the soil is below a pH of 5.5.

 

Diploid vs. Tetraploid

One of the more common questions I have been asked is what the difference between diploid and tetraploid ryegrass. Annual ryegrass is naturally a diploid species, meaning it carries 2 sets of chromosomes (2n). Plant scientists in the 1930s began experimenting with ryegrass hybrids and discovered mutants that had 4 sets of chromosomes (4n) and were substantially larger plants with wider leaves and stems. Researchers in the Netherlands expanded upon this early work, and ultimately, German plant breeders introduced the first tetraploid varieties into the U.S. in the early 1960s. Plant breeders have since developed many diploid and tetraploid varieties. Because the tetraploid varieties have larger tillers, wider leaves, and are simply bigger plants in general, they are impressive to look at compared to the diploid varieties.

 

Apparently, cattle think so, too. A grazing preference trial in Mississippi showed that forage provided by tetraploid variety plots was consumed 54% faster than diploid varieties. Yet, when researchers there looked at long-term yield data from their variety trial program, the yields of diploid and tetraploid annual ryegrasses were not different in most locations and only tended to give slightly more yield (less than 10%) in their southernmost location (Poplarville, MS). Further, when they conducted a grazing trial comparing diploid and tetraploid varieties, their stocker steers showed no difference in ADG or gain per acre. Their conclusion from all this research is that there is more difference within diploid and tetraploid varieties than there is between them. So, look for a high yielding variety that is recommended for your area and disregard the ploidy level. However, one practical consideration is that tetraploid seed is usually 50 to 100% larger than diploid seed. Though there is no difference in the seeding rate recommendations for the diploid versus tetraploid varieties (20-25 lbs./acre if drilled; 25-30 lbs./acre if broadcasted), it is important to calibrate, check, and adjust the drill to account for these differences in seed size.

 

In Oklahoma, annual ryegrass is usually planted by overseeding warm-season perennial grasses such as bermudagrass to provide grazing earlier in the late winter and spring. Annual ryegrass is also widely planted with small grains to extend the grazing season into late spring or early summer. Given adequate spring moisture and cool temperatures, annual ryegrass will remain productive into late May or mid-June. Annual ryegrass is sometimes planted in mixtures with legumes to provide earlier grazing and reduce the potential of bloat from the legumes.

Just remember, when planting annual ryegrass, do your homework. Select a variety that has adequate winter hardiness, good germination, a high purity percentage, and is adapted to your area to better optimize your cool season grazing system.

 

References

http://extension.msstate.edu/publications/annual-ryegrass-performance-mississippi-long-term-yield-production#:~:text=Annual%20ryegrass%20is%20the%20most,wide%20range%20of%20soil%20types.

https://www.noble.org/regenerative-agriculture/pasture-and-range/management-of-annual-ryegrass/


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