J.H. Cherney1 and D.J.R. Cherney2
1Soil and Crop Sciences Section, School of Integrative Plant Science; 2Animal Science Department; Cornell University
Over 90% of the alfalfa acreage in northern NY is seeded with a perennial grass. Meadow fescue is becoming increasingly popular for mixtures with alfalfa in New York. Most meadow fescue varieties were developed in northern Europe or at higher elevations in southern Europe. Meadow fescues are very winter hardy and tolerant of wet soils, they have been popular for both grazing and hay in Canada for decades. They have also been shown in NY and WI trials to be higher in fiber digestibility than other grasses more commonly used in mixture with alfalfa in the northern USA.
One concern in the Northeast has been the seeding rate for meadow fescue with alfalfa. This grass is very aggressive when grown with alfalfa, particularly if soil conditions are not optimal for alfalfa production. We evaluated one diploid (SW Minto) and one tetraploid (Tetrax) meadow fescue at 5 seeding rates with either a reduced-lignin alfalfa (HarvXtra) or a conventional high-quality alfalfa (Hi-Gest 360).
In May, 2018, we planted field trials on farms near Copenhagen in Jefferson County, NY (Site 1) and near Lowville in Lewis County, NY (Site 2). HarvXtra and Hi-Gest 360 were seeded at approximately 15 lbs/a, with the same number of pure live seeds per sq. ft. for both alfalfa varieties. Tetrax meadow fescue was seeded at 0.5, 1, 2, 3, and 4 lbs/a, with the same number of pure live seeds per sq. ft. for SW Minto. Tetraploid meadow fescue seed is up to three times greater in weight per seed compared to most diploid varieties.
Plots at both sites were mowed to control weeds during the seeding year, and no data was collected. In 2019, three photographs were taken per plot (covering >70% of the plot area) prior to each harvest and were visually evaluated for grass percentage. Site 1 was harvested four times in 2019, on 6 June, 10 July, 12 August, and 18 September. Site 2 was harvested three times on 31 May, 15 July, and 14 August. At each harvest, forage quality and dry matter samples were collected prior to harvest, and forage quality samples were separated into alfalfa and grass components for laboratory analysis.
Dry matter yield for Site 1 averaged 5.1 dry tons/acre and was 67% greater than Site 2. Site 2 had a soil pH of 6.4 at spring harvest in 2019 and had been adequately fertilized, but alfalfa never looked reasonably healthy and had a stunted appearance throughout the season. There was insufficient regrowth to justify a fourth harvest at Site 2. Yield at both sites was primarily attributed to spring growth. Site 1 yield distribution was 41%, 29%, 18%, and 12% for four cuts, while Site 2 yield distribution was 61%, 28%, and 10% for three cuts. Yield at both sites was influenced by grass seeding rate (Fig. 1).
Grass Percentage in Mixtures
Struggling alfalfa resulted in very high grass percentages at Site 2 (Fig. 2). Although alfalfa was normal in appearance at Site 1, grass percentage was also high for the year after seeding. SW Minto was considerably higher in grass percentage of mixtures than Tetrax at both sites (Fig. 3). Grass percentage consistently agreed with grass seeding rate, but plots with the 0.5 lb/acre grass seeding rate were less uniform than at higher seeding rates. Visual estimation of a majority of the plot area provided more consistent results than calculating a grass percentage estimation based on a small, separated sample of alfalfa-grass that may or may not be representative of the entire plot.
Grass crude protein (CP) was related to the proportion of alfalfa in the mixture, as alfalfa provides grass with nitrogen (Fig. 4). Grass quality was very similar between sites. Across sites and harvests, Tetrax averaged 51% NDF, while SW Minto averaged 55%. Tetrax averaged 2.5% greater fiber digestibility (NDFD48h) than SW Minto across sites. NDF, ADF, and lignin tended to increase with increased grass seeding rate, while in vitro digestibility and NDFD decreased with increasing grass seeding rate. Grasses were harvested prior to heading, so we lack relative maturity information, however, these two grasses had the same spring heading date in Ithaca, NY in 2019. Meadow fescue averaged 82% NDFD over variety, site and harvest, while alfalfa averaged 56%.
With less than ideal sites for alfalfa production, grass dominated stands at all but the lowest grass seeding rates. Typical forage quality differences between reduced-lignin alfalfa and conventional alfalfa were not observed at these sites. HarvXtra was significantly lower in lignin (but only 2.7% lower) than Hi-Gest 360 at Site 2, and varieties did not differ for lignin at Site 1. HarvXtra had 4.2% greater NDFD than Hi-Gest 360 at Site 1, while alfalfa varieties did not differ for NDFD at Site 2. Alfalfa composition was not affected by grass seeding rate.
Harvesting grass with reasonably good forage quality in mixtures in the spring in NY often results in alfalfa harvested at relatively immature stages. For example, mixtures were harvested on June 6, 2019 at Site 1, and alfalfa averaged 30% NDF, while grass averaged 58% NDF. A common rule of thumb for alfalfa is harvesting in the spring at approximately 40% NDF after accumulating 750 growing degree days (GDDbase41F). The two sites reached 750 GDD on June 15 and June 17.
Meadow fescue is well adapted to colder environments and to somewhat marginal soils. Meadow fescue also is generally high in fiber digestibility compared to other cool-season grasses typically sown with alfalfa in the Northeast. It is very competitive with alfalfa under such conditions. If the goal of a mixed seeding for dairy forage is to produce a stand with 20-30% grass on soil not ideally suited to alfalfa, meadow fescue seeding rate should probably not exceed 1 lb/acre. While seeding rates can be controlled, climatic conditions cannot. Grass percentage in alfalfa-grass mixtures can be greatly affected by soil moisture, particularly for the first month after seeding. Shallow-rooted young grass seedlings are much more susceptible to drought than alfalfa seedlings.
Reduced-lignin alfalfa may not perform as well on more marginal soils, as it generally does on good alfalfa soils. In these trials and other studies conducted in NY, Tetrax meadow fescue has been less aggressive with alfalfa than most meadow fescues evaluated and is often higher in fiber digestibility. There are over 120 meadow fescue varieties certified for sale in Europe; few are currently sold in North America. Optimum seeding rate for meadow fescue with alfalfa may vary for different cultivars and for different regions in the Northeast; more research on meadow fescue varieties is warranted.
This research was supported by the Northern New York Agricultural Development Program.