Sagers, J. , Extension Educator, University Of Idaho
J. Reed Findlay, Extension Educator, University of Idaho
Justin Hatch, Extension Educator, University of Idaho
Glenn Shewmaker, Professor, University of Idaho
Kevin Jensen, PhD, USDA ARS
Jon Hogge, Extension Educator, University of Idaho
Ron Roemer, University of Idaho
Jan Burr, USDA ARS

ABSTRACT

At elevations higher than 6000 ft., grasses are one of the better options available for producers to optimize potential forage production.  This study evaluates grass species intermediate wheatgrass (Rush), meadow brome (Regar), orchardgrass (Potomac II), perennial ryegrass (Journey), tall fescue (Teton), and tall wheatgrass (Alkar) grown at 6,120 ft. high elevation for dry-matter yield (DMY) and quality during the establishment year (2017), and 2018 and 2019 under irrigation. Higher yielding grasses such as tall fescue and tall wheatgrass produced lower RFQ values, while lower yielding grasses such as perennial ryegrass produced higher RFQ values.

Introduction

Grass hay production accounts for approximately 25% of the total hay produced in Idaho (https://www.nass.usda.gov). At elevations higher than 6000 ft, grasses are one of the better options available for producers to optimize potential forage production. Reduced forage yield at these higher elevations continues to be the largest determinant to economic return.  Selecting grass species with high yield potential and persistence is fundamental to success. (Shewmaker et al., 2010)

Grasses are typically used as a forage in these higher elevation pastures.  However, there are grass species available and it is important to understand their specific adaptation and agronomic performance and how it corresponds to the target area being planted (Robins et al., 2013). Forage yield and quality will vary across Idaho environments and operations. Growing grass at high elevations can be particularly difficult, due to a reduction in growing degree days for optimal production. These trials are designed to educate and assist producers in choosing hay and pasture grasses, especially at altitudes greater than 6000 feet in elevation.

Methods

Six different species of grasses; intermediate wheatgrass (Rush), meadow brome (Regar), orchardgrass (Potomac II), perennial ryegrass (Journey), tall fescue (Teton), and tall wheatgrass (Alkar), were planted at the University of Idaho Tetonia Experiment Station in Tetonia, Idaho (43°53'48.24"N 111°16'51.28"W. Elevation 6,120 ft.). In addition, a mixture of the six grasses in equal proportions by seed count was included. Plots were planted at a rate of approximately 2.6 million seeds per acre on a pure live seed calculation (Jensen et al., 2001). The trial was fertilized with 100 units of nitrogen each year applied in 2 applications (0.15 lbs. spread per application over 100 square feet). Weeds were sprayed in 2018 and 2019 with 2,4-D in late May. Plots were irrigated with approximately 2 inches of sprinkler applied irrigation weekly from June to September. Approximately 24 inches were applied throughout the growing year. Weeds were mechanically removed by hand throughout the season in addition to the herbicide application. The trial was planted on the 24^th of May 2017. Plots were irrigated, fertilized, and maintained weed free throughout the growing seasons. Plots were harvested once in 2017 and twice in 2018 and 2019. Plots were planted as randomized complete block design with four replications. Samples were ground through a Wiley Mill (Thomas Scientific, Swedesboro, NJ) to 0.079 inches in length, then ground with Udy Cyclone Sample Mill (Udy Corporation, Fort Collins, CO) to 0.039 inches.  Forage nutritive parameters were predicted by FOSS DS2500 Near Infrared Reflectance Spectroscopy (NIRS) using the NIRS Forage and Feed Testing Consortium (NIRSC) grass equations (https://www.nirsconsortium.org/).

Results

Establishment year DMY ranked from perennial ryegrass (2.96 Ton acre^-1), tall fescue, orchardgrass, species mixture, tall wheatgrass, meadow bromegrass, and intermediate wheatgrass (1.60) were observed (Table 1). In 2018, orchardgrass had the greatest (P < 0.05) total DMY at 5.33 ton acre^-1 compared to intermediate wheatgrass (4.52), tall wheatgrass (4.41), perennial ryegrass (4.32), meadow bromegrass (3.87), species mixture (3.79), and tall fescue (3.60) (Table 2).  No significant differences were observed in the 2018 2^nd harvest DMY between orchardgrass, intermediate and tall wheatgrass (Table 2).  Meadow bromegrass and tall fescue had the least DMY regrowth at the 2018 2^nd harvest (Table 2).  Overall, 2019 DMY was less than 2018.  Attributing to this decline might be a cooler than normal spring resulting in a delayed 1^st harvest when phonologically the grasses were still actively growing. No significant differences in 1^st harvest DMY were observed on the first 2019 harvest between meadow brome, tall fescue, orchard grass and intermediate wheatgrass. Tall wheatgrass produced significantly less DMY than other species, and the perennial ryegrass yielded the lowest of all the species on the first cutting. The second cutting showed more growth than the first cutting, but yields were overall lower than the 2018 year. There was no significant difference between tall fescue, tall wheatgrass, meadow brome, or orchardgrass in the second cutting. Perennial ryegrass continued to be the low yielding species.

Establishment year crude protein (CP) values ranged from 13.1% in perennial ryegrass and the species mix to 17.7% in intermediate wheatgrass (Table 4). The first harvest of 2018 ranged from 7.3% (perennial ryegrass) to 10.3% (tall wheatgrass). Crude protein percentage in DMY regrowth in 2018 ranged from 11.1 to 15.1% in tall wheatgrass and perennial ryegrass, respectively (Table 6). The first harvest of 2019 was the lowest crude protein recorded, with a mean of 6.48%. The second harvest of 2019 showed higher protein levels with a mean of 14.3%.

                Perennial ryegrass consistently had among the highest RFQ value. The higher yielding varieties tended to be toward the bottom of the RFQ value scale, with tall wheatgrass being consistently lower. The exception of that is tall fescue in the 2^nd harvest of 2018, where tall fescue yielded toward the higher end.(Table 6)

DM = Dry matter concentration. CP = Crude protein. ADF = Acid detergent fiber. aNDF= Neutral detergent fiber (with amylase).  IVTDMD 30H = In vitro dry matter digestibility at 30 hours in rumen. Ash = An estimate of the total mineral content. FAT= An energy source within plants, usually measure with ether extract. Lignin = Indigestible plant component.  ESC = Ethanol-soluble carbohydrates. WSC = Water-soluble carbohydrates. NDFD 48 = The proportion of NDF potentially digestible as determined by an in vitro incubation. TDN = Total Digestible Nutrients. RFV = Relative feed value. RFQ = Relative forage quality. 

Terms and definitions for tables 4-8:

DM = Dry matter concentration. CP = Crude protein. Higher protein levels indicate less need for more expensive supplements in the ration. ADF = Acid detergent fiber. A measure of the less digestible components in the forage. Lower ADF is more desirable. Higher ADF is generally related to more mature plants. aNDF= Neutral detergent fiber (performed with amylase).  A measure of the total fiber content. Relates to feed intake level in livestock. Lower aNDF is more desirable. IVTDMD 30H = In vitro dry matter digestibility. A measure of digestibility at 30 hours in the rumen. Higher digestibility is more desirable. Ash = An estimate of the total mineral content.  The residue remaining after burning a sample.  Levels below 10% are desirable. FAT= An energy source within plants, usually measured using Ether Extract. Lignin = Indigestible plant component, giving the plant cell wall its strength and water impermeability.  It increases as plant matures and reduces NDF digestibility. Higher temperatures during the growing season tend to increase lignin. ESC = Ethanol-soluble carbohydrates. Carbohydrates that are soluble in 80% ethanol. WSC = Water-soluble carbohydrates. Carbohydrates that are soluble in water. NDFD 48 = The proportion of NDF potentially digestible as determined by an in vitro incubation. NDFD is expressed as a percentage of the NDF. The NDFD can be used to rank forages on potential fiber digestibility.  Higher values indicate higher intake and animal performance. RFV = Relative feed value. An index for ranking cool season grasses and legume forages based on intake of digestible energy.  RFV is calculated from ADF and NDF.  Feeder quality hay is <160 and dairy quality hay is >160.  Hay with RFV >180 should be fed with a total mixed ration or blended with lower quality hay. TDN = Total Digestible Nutrients. This is calculated as a sum of the fiber, protein, as well as the lipids and carbohydrates. It is a measure of the energy within a given feed. RFQ = Relative forage quality.  An index for ranking all forages based on intake of TDN calculated by estimating digestible portions of protein, fatty acids, fiber (NDF), and non-fibrous carbohydrates.  RFQ is based on a more comprehensive analysis than RFV and it should be more reflective of the feeding value of the forage, especially grasses. RFQ is based on the same scoring system as RFV.  The higher the RFQ, the better the quality.

Discussion

Differences in yield varied widely from year to year. It should be noted that the 2019 growing season was delayed in the spring for all hay and pasture producers in eastern Idaho, especially in the higher elevations. This trial also experienced a delay. Growing degree days were lacking compared to past years, and grasses were slower to emerge, establish and put out green growth. Years with reduced growing degree days are not uncommon for hay and pasture producers above 6000 ft in elevation.

The harvested plots that yielded more tonnage per acre tended to have higher ADF, aNDF, and ash, as well as have an inverse relationship with TDN, RFV and RFQ, with exceptions. Two examples of this are perennial ryegrass and tall wheatgrass. Perennial ryegrass, which consistently yielded low in relation to the other species, always had high quality in terms of RFQ. Tall wheatgrass did not consistently have high RFQ, but yielded high in relation to the other species in tons/acre. This is similar to the findings of Jensen et al. (2006).

The RFQ index has on average 47% higher values than RFV.  This is because RFQ uses NDF digestibility in the calculation in contrast to RFV which uses ADF and NDF concentrations.  This confirms the recommendation to market grass hays based on RFQ over RFV. (Undersander et al., 2014).

More research is needed for hay and pasture producers who grow cool season perennial grasses in higher elevations. This study focused primarily on the effectiveness of a monoculture system of cool season grass at high elevation. This study did not calculate the longevity of species within a mix, establishment effectiveness of mixed grass species, or effectiveness of a mixed grass system. This study lays the groundwork for future studies to establish the relationships of cool season perennial grasses in higher elevations.

Acknowledgements

The seed donated for this trial was provided by Grimm Growers in Blackfoot, Idaho. The planting equipment was provided by the USDA-ARS Forage and Range Research Lab in Logan Utah. The Plant, Soil, and Entomological Science Department of the University of Idaho also contributed salary and equipment.

Literature Cited

Jensen, K., Horton, H., Reed, R., Whitesides, R., Intermountain Planting Guide. Utah State University. Retrieved on December 16, 2019 from: https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=2332&context=extension_curall

Jensen, K. B., Waldron, B., and Robins, J. (2006). Cool Season Perennial Grasses for Hay. UC Davis. Retrieved on January 10, 2020 from: https://alfalfa.ucdavis.edu/+symposium/proceedings/2006/06-137.Pdf

National Agricultural Statistics Service. Retrieved on December 16, 2019 from: https://www.nass.usda.gov/Quick_Stats/Ag_Overview/stateOverview.php?state=IDAHO

NIRS Forage and Feed Testing Consortium (NIRSC), E17995 Western Rd, Hillsboro, WI 54634, USA. Retrieved on March 18, 2020 from: https://www.nirsconsortium.org/

Robins, J. R., Jensen, K., Jones, T., Waldron, B., and Peel, M. (2013). Stand Establishment and Persistence of Perennial Cool-Season Grasses in the Intermountain West and the Central and Northern Great Plains.

Shewmaker et al. (2010). Pasture Management and Grazing in the Pacific Northwest. Retrieved on December 16, 2019 from: https://www.extension.uidaho.edu/publishing/pdf/pnw/pnw0614.pdf

Undersander, D., Moore, J.E., and Schneider, N. (2014). Relative Forage Quality. University of Wisconsin. Retrieved on March 18, 2020from https://fyi.extension.wisc.edu/forage/files/2014/01/RFQ-FOF.pdf