Month: May 2020

Meadow Fescue-Alfalfa Mixtures in Northern New York

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).

Procedure

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.

Forage Yield

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).

Graph 1
Fig. 1. Yield of alfalfa-meadow fescue as related to grass seeding rate.

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.

Graph 2
Fig. 2. Grass percentage in mixtures for Tetrax meadow fescue in 2019 at two sites, averaged over harvests, weighted for dry matter yield.
Graph 3
Fig. 3. Grass percentage in mixtures in 2019 for two meadow fescues averaged over two sites, and averaged over harvests, weighted for dry matter yield.

Grass Quality

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%.

Graph 4
Fig. 4. Crude protein in meadow fescue as influenced by grass seeding rate in alfalfa-grass mixtures in 2019. Average of two meadow fescue varieties and two sites. Harvests were also averaged, weighted for yield.

Alfalfa Quality

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.

Summary

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.

Wheat spindle streak mosaic in spring: A reminder to plant a resistant wheat variety in fall

Gary C. Bergstrom, Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell University

The Disease

Wheat spindle streak mosaic (WSSM), caused by wheat spindle streak mosaic virus (WSSMV), is a disease that attracts little attention today because most of our widely grown, winter wheat varieties have significant levels of resistance to it.  Yet WSSMV persists in New York soils in its protozoan vector ready to infect the roots of susceptible winter wheat varieties soon after planting.  Swimming spores (zoospores) of the vector move through films of water in the soil and thus root infection is favored by moist conditions in fall. Plants remain infected over the winter dormant period but do not develop typical leaf symptoms until spring following a number of weeks of cool weather which favors virus replication and virus movement from roots into shoots. Temperature, not moisture, is what drives symptom development in spring since plants were already infected in the fall. Only winter wheats, not spring wheats, are affected by WSSMV because of the time it takes to build up virus levels in the roots and then the shoots.

Symptoms

Symptoms of WSSM first appear in late April or early May and are characterized by long, light green, spindle-shaped streaks with dark centers (Fig. 1). As leaves age, these streaks can become necrotic and resemble lesions of Septoria tritici blotch but without dark fruiting bodies, i.e., pycnidia of Zymoseptoria, in evidence under a hand lens. Symptoms of WSSM fail to develop on new leaves that emerge when average daily temperatures exceed 60 F, though symptoms can reinitiate at later growth stages if persistent cool conditions occur during stem elongation, head emergence, and even grain-filling. Conditions have been ideal in April and May 2020 for development of WSSM.  Symptom development is extremely sensitive to warm temperatures such that we have seen very little WSSM in years with high temperatures in early spring.

wheat leaves
Figure 1. Characteristic symptoms of wheat spindle streak mosaic on wheat flag leaves at boot stage (A) and close-up of spindle streaks (B).

Management

What should a wheat producer do if she/he observes characteristic symptoms of WSSM this spring?  There is no action that can be taken to mitigate WSSM in a growing crop – the yield damage, which can exceed 30% of the crop’s potential, has already occurred. However, diagnosis of the disease is a sure reminder that the variety they are currently growing is susceptible to WSSMV, and they need to choose a variety with at least moderate resistance for planting in the coming fall.  This should elicit a conversation with your seed supplier about varieties resistant to WSSMV; some companies include that information on their website and in their seed catalogs but others do not.  While the majority of available varieties express resistance to WSSMV, susceptible varieties appear in the seed market from time to time. Scores for WSSM also are included in winter wheat variety trial tabular results (https://blogs.cornell.edu/varietytrials/small-grains-wheat-oats-barley-triticale/small-grains-cultivar-trial-results/) from Cornell’s Small Grains Breeding Program in years when symptoms are observed.

If you find more pronounced mosaic and fewer distinct streak symptoms in a variety designated to be WSSMV-resistant, your wheat could be infected by another soilborne, protozoan-transmitted virus called soilborne wheat mosaic virus (SBWMV), which we have diagnosed occasionally in isolated fields in southern areas of the Finger Lakes Region.  Resistance to SBWMV is independent from resistance to WSSMV, though it is also available from wheat seed suppliers in a choice of adapted varieties.