Consider Relative Reproductive Maturity of Grasses Seeded With Alfalfa
Our breeders continue to advance genetics of many cool-season grass species. When considering a particular cool-season grass species or variety, factor in the time of harvest of the alfalfa as well as the grass variety’s Reproductive Maturity (RM). This is most important for the first cutting each year of alfalfa-grass mixtures, as the crop grows longest during this period. Ideally, select a grass species variety in which the RM is similar to alfalfa, so that maximum yield and quality are achieved. Furthermore, the goal is at time of harvest the yield and quality of alfalfa is maximized (approximately at the bud stage, depending on animal needs), while the grass species yield and quality is also maximized.
Figure 1.
The relationship between alfalfa maturity stage and total forage, stem, and leaf yield and forage digestibility. Source: C. Sheaffer. In Undersander et al., 2014. Alfalfa Management Guide
O-Indicates ideal harvest timing of forage grass to maximize yield and quality.
Figure 2.
Generalized relationship between forage yield a forage quality as affected by stage of maturity of grasses. Source: https://extensionpubs.unl.edu/publication/g2185/2013/html/view
O-Indicates ideal harvest timing of forage grass to maximize yield and quality.
DLF’s Forage Maturity Index (Fig. 3) has been designed to accommodate the broader range of species and maturities utilized in the North American forage industry. It has a 9 point index with a maturity difference of approximately 3 days per unit, reflecting Oregon conditions. Variance with this index may occur in different regions since some cultivars are more temperature dependent, while others may be more day length dependent in maturity. With all species using the same Maturity Index Rating System, the maturity range of various forage species can now be directly compared on the same chronological maturity index (the black index scale at the top of the matrix). The gradient blocks in the Forage Maturity Matrix Species reflect the maturity range of available varieties within the species. The respective maturity of public varieties using the traditional nomenclature of each early, medium, and late is superimposed on the index. A maturity index in one species corresponds to the same maturity in another forage species.
Figure 3.
Generally depicts cool season grass species’ relative reproductive maturity and other legumes, and includes alfalfa so a cross reference can be achieved.
This tool allows producers to select grass varieties that best align with alfalfa harvest. It is also important to note that post first crop harvest, the frequency of harvest typically eliminates chances of grass varieties to approach heading in consecutive cuts.
Primary Cool-Season Grass Species Seeded with Alfalfa
Orchardgrass
When selecting an orchardgrass variety, it is important to select a late-maturing orchardgrass. Older genetics of orchardgrass tend to mature too early when seeded with alfalfa and have the potential to reduce overall quality of the alfalfa-grass mixture if it enters reproductive stages prior to harvest. New varieties classified as “late” will align with alfalfa in regard to harvest and maximize yield and quality potential at alfalfa harvest. Selecting a late maturing orchardgrass to be a companion with alfalfa is recommended.
Tall Fescue
When considering a tall fescue as a companion, select a late-maturing tall fescue. Older genetics of tall fescue, like orchardgrass, tend to be on the earlier side of RM when compared to alfalfa. Select a late maturing tall fescue to be a companion with alfalfa.
Meadow Fescue
When selecting a Meadow fescue, select a mid-late maturing variety. Meadow fescue maturity at alfalfa harvest tends to align fairly well; however, it is still important to evaluate variety comparisons.
Timothy
This species is very late-maturing compared to alfalfa’s optimum harvest timing. New varieties classified as “early” will align best so that the yield and quality of the timothy at the time of alfalfa harvest is maximized.
Festulolium
Some challenges may exist when selecting a festulolium variety, as it is a cross between ryegrass and tall fescue or ryegrass and meadow fescue. Typically festulolium’s RM will be closely linked to the more dominant parent of the cross, so it is important to know the cross of the festulolium.
Perennial Ryegrass
When selecting a perennial ryegrass, some challenges exist as relative reproductive maturities tend to be broad. Ideally selecting a variety that is close to beginning bloom of alfalfa will maximize yield and quality of the perennial ryegrass at the time of alfalfa harvest.
Summary
DLF’s Forage Maturity Index is a continuous work in progress, but does provide information on selecting the optimal varieties available today. This useful tool allows producers and agronomists to match cool-season grass species with alfalfa while managing the maturity range of each and helping maximize their yield and quality. Keep in mind, there is a variance in genetic and environment interaction between varieties and species.
Additionally, a Forage Grass Maturity Working Group was formed in 2016 to further evaluate and develop a uniform system for measuring grass variety maturity. The group was comprised of various seed industry representatives and university researchers, including but not limited to Kim Cassida (Michigan State University) and Ray Smith (University of Kentucky). As a result of the initial 5 year study, 8 reference varieties were defined in order to make particular comparisons. The reference varieties are available as check varieties at the University of Kentucky in which Smith indicates will be available for the next 3 years, and additionally available beyond that.