cows in field

Evaluating Perennial Ryegrass Blends for Improving Pasture Productivity and Extending the Grazing Season

By Sid Bosworth, Extension Forage Specialist, University of Vermont

Added April 3, 2013. A 2010 needs assessment of organic dairy producers in the Northeast region revealed that extending the grazing season, complying with the new pasture rules, and implementing strategies to facilitate value-added marketing of milk are major challenges to the industry. To address these issues, a multi-state team of university and USDA researchers and extension specialists, collaborating with several organic dairy farms, were successful in obtaining a USDA-Organic Agriculture Research and Extension Initiative grant titled, “Assessing Organic Dairy Producers to Meet the Demands of New and Emerging Milk Markets.” This is a large grant involving five states and is coordinated by Dr. Andre Brito of the University of New Hampshire.

This multi-year grant has many objectives including 1) the assessment of multi-cultivar mixtures for optimizing pasture resources while extending the grazing season, 2) identification of annual forages to enhance and extend the grazing season while improving nutritional quality, and 3) evaluating the utility of supplemental organic flaxseed to further bolster health beneficial fatty acid components and enhance the marketability of organic milk. This article will focus on the first objective but I’m sure that you will be hearing more on the other objectives in future articles.

There have been numerous studies to show that complex mixtures of pasture species can be beneficial for improving pasture yield, seasonal distribution and stability, but we know less about complex blends of cultivars of the same species. The theory is that complex blends that vary in their ability to utilize soil resources will have greater yields, a longer grazing season, greater stand stability and a lesser chance of stand failure. Also, the variation in levels of host resistance and susceptibility between different cultivars should decrease the overall severity caused by diseases and insect pests.

As part of this project, we proposed evaluating blends of perennial ryegrass. Why did we choose perennial ryegrass and not other grass species? First, perennial ryegrass is generally more digestible and has higher energy content than most other cool season grasses. A high total non-structural carbohydrate forage like perennial ryegrass will tend to increase the supply of readily fermentable energy, thus enhancing the capacity of the rumen microbes to better capture the ammonia from forage soluble proteins. In addition, limited research in the Northeast and elsewhere has shown perennial ryegrass to have higher levels of alpha-linolenic acid; therefore, it may have potential to improve beneficial fatty acid components of the milk.

Perennial ryegrass germinates quickly and is relatively easy to establish. I think this is a very important benefit. There is nothing more frustrating than a promising new forage specie that looks great but is near impossible and, therefore expensive, to get established.

Historically, universities in the Northeast have not recommended perennial ryegrass for forage because it is less winter hardy compared to other grasses. This is still generally true; however, more recently, seed companies have produced improved cultivars that appear to be more winter hardy. Our study is an opportunity to see just how well some of these newer cultivars will perform under a wide range of locations and conditions.

So, in August of 2012, research trials were planted in four states including Vermont, New Hampshire, Maine and Pennsylvania. Collaborators include researchers from University of New Hampshire, University of Maine, USDA-ARS at Penn State, and the University of Vermont. All the sites are being managed organically and, although the focus is on perennial ryegrass blends, all the plots also include white clover since most well managed pasture include a grass-legume mixture.

The field experiments are looking at six different types of perennial ryegrass treatments including a single cultivar of our “most adapted” variety, a three-way blend, three five-way blends and one commercial blend. Our criteria for formulating specific cultivars into a blend was based on relative heading date (early, medium, or late), winter hardiness rating, and ploidity level. Perennial ryegrass can be either a diploid (two sets of chromosomes – 2N) or tetraploid (four sets of chromosomes – 4N) and they do differ in size, growth rate and winter hardiness.
We will begin collecting data starting this season. These are small plot trials but we will be simulating a rotation grazing system in which we’ll harvest when the sward reaches about 10 inches and clip it down to 3 o 4 inches. We plan to collect yield at each grazing as well as forage nutrient content. Three times a year, we will do botanical separations to determine the levels of grass, clover and weeds as well as visual ratings for disease.

Our desired outcome of this project is to develop a rational basis for formulating blends that results in higher yield, a longer grazing season and greater forage quality. As we collect data over the next three years, we will make sure to share the results with you. Also, if you have any suggestions for this study, please contact me at

Collaborators in the perennial ryegrass project include Rich Smith and Kirk Broders of The University of New Hampshire, Rick Kersbergen of The University of Maine, Sid Bosworth of The University of Vermont, and Howard Skinner and Sarah Goslee of the USDA- Pasture Systems and Watershed Management Research Laboratory at Penn State.