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Superintendent
David Davis
21262 Genoa Road
Linneus, MO 64653
Phone: 660 895-5121
FAX: 660 895=5122
Email: DavisDK@missouri.edu

Forage Systems Update
Vol 11, No. 1

Perennial ryegrass (PRG) is the predominant pasture grass in a good portion of the serious grazing world. It is touted for its productivity, palatability, and quality. Unfortunately, persistence in our strong continental climate has been an ongoing challenge. Most of the areas where PRG thrives are maritime or more temperate than the Midwest. Plant breeders have been trying to increase the winter hardiness of PRG for a number of years, as well as its drought tolerance. The challenge that we face in Missouri is that both extreme cold and extreme heat can be experienced and both in combination with extremely dry conditions or excessively humid conditions.

In the mid-1980's we seeded several PRG cultivars including varieties from western European, New Zealand, and the US The pastures were not intensively managed at that time and almost all the ryegrass disappeared in a matter of two growing seasons. It has more recently been proposed by some PRG advocates that increased sulfur, calcium, phosphorus, and micronutrient levels may enhance PRG survivability. Also, introduction of Eastern European germplasm, which was not available to Western breeders during the Cold War period could be used to increase winter hardiness. We began a study in 1999 to evaluate both increased levels of soil fertility and cultivar on performance of PRG in north Missouri. ‘Stargrazer' endophyte-free tall fescue was included in the study as a benchmark for pasture performance.

Research methods: The upland experimental site consisted of soils of the Armstrong-Lagonda association (fine, montmorillinitic, mesic) in north-central Missouri (W 93^o04':N 39^o50'). Cultivars in the study include ‘BG34' perennial ryegrass, ‘Mara' perennial ryegrass, and ‘Stargrazer' tall fescue. Grazing plots were established in a completely randomized design with four replications. Individual plots were 50 ft X 50 ft with a 10 ft buffer between each plot. Prior to seeding a uniform application of 36-92-62 was applied to the entire study area. Grass varieties were broadcast seeded at 30 pound/acre on a prepared seedbed on September 30, 1999. Plots were rolled with a cultipacker immediately after seeding. Soil conditions were extremely dry with less than 2 inches of precipitation falling in the 60 days after seeding and establishment was poor to fair. An additional 20 pounds/acre seed was broadcast March 7, 2000, and 4 pound/acre ‘Alice' white clover was broadcast March 10, 2000. It became apparent after the study began that the ‘Mara' seed lot used had a high level of annual ryegrass contamination.

In the discussion when references are made to ‘high' and ‘low' fertility, both treatments received equal amount of N/acre, but high treatment used ammonium sulfate (18-0-0-23) as the N source while low treatment used ammonium nitrate (34-0-0). Our concern is not with the source of N, but the provision of sulfur to the crop. Other differences in fertility treatments were in the levels of P, K, and micronutrients applied. Initial fertilizer treatments were applied May 19, 2000. Low fertility plots received 75 lbs N/acre as urea while the following materials were applied to the high fertility plots on a per acre basis:

In 2000, additional applications of 40 lbs N/acre were made on June 14, July 20, August 18, and September 29 as urea and ammonium sulfate for low and high fertility treatments, respectively, for a total of 235 lb N/acre. These four applications of ammonium sulfate added an additional 184 pounds of sulfur/acre. On September 8, 0-30-60 was applied to all plots. In 2001, 40 lb N/acre was applied on March 14, May 10, June 15, July 16, and August 15 for a total of 200 lb N/acre and 256 lb S/acre, in the high fertility treatment. On August 29, 0-60-250 was applied to all plots.

Plot grazing began on April 7 and concluded November 5, 2000. Grazing in 2001 began on April 19 and concluded on October 11. Plots were individually grazed whenever mean sward height reached 6 to 8 inches. Mean sward height is defined as the height below which an estimated 90% of the forage biomass occurs. Prior to grazing, each plot was sampled individually. Data collected included clipped yield estimate from six 0.25m² quadrats in each plot with corresponding mean sward height at each quadrat. Clippings from all six quadrats were thoroughly mixed and a 100 g subsample was retained for forage quality analysis. Dry matter content of the forage sample was determined by oven drying at 130 F and forage dry matter yield calculated. Plots were grazed with 7 to 10 head of yearling heifers for four to seven hours to remove approximately 50% of the forage biomass. Grazing usually occurred between 6 AM to 3 PM but during the hottest part of the summer, cattle were placed on plots from 7 PM to 7 AM to encourage grazing.

Ground cover by the seeded species was visually estimated on April 2 and December 10, 2000. Basal cover by component species was determined using step-point method with 100 points/plot on April 17, May 27, and October 2, 2001. Final stand density is presented as the mean of all three 2001 sample dates.

All measured parameters were compared using the SAS GLM procedure and least square means calculated. Comparisons among treatment means was made using Fisher's protected least significant difference procedure.

Results and discussion: None of the measured parameters were significantly affected by fertility treatment. Soil test values at the beginning of the study were in the medium to high range according to MU recommendations. Based on this two year study, there is no indication that increasing P and K to high soil test values, applying sulfur, or any of several micronutrients contributed to the production or persistence of perennial ryegrass.

To evaluate uniformity of grazing treatment among all plots, pre- and post-grazing mean sward height and forage availability were compared (Figures 1 and 2). No significant differences in pre- and post-grazing mean sward height and forage availability existed in either year among the cultivars or fertility treatments indicating that plots had been managed uniformly through both grazing seasons. As would be expected based on similarity of pre- and post-grazing forage availabilities, temporal utilization rate was similar for all treatments and very close to our target of 50% (Figure 3), although utilization was somewhat higher in 2001. The forage dry matter yield per acre-inch was significantly greater for ‘Stargrazer' and ‘BG34' compared to ‘Mara' in 2000, but was similar for all cultivars in 2001(Figure 4). This may be due to the high level of annual ryegrass contamination in the ‘Mara' plots through June of 2000. Annual crops tend to be somewhat lower yielding per unit of height compared to perennial grass crops.

Stargrazer tall fescue required a shorter rest period to reach target grazing height that either PRG cultivar in 2001 (Figure 5). This was due to a significantly higher daily growth rate for Stargrazer(Figure 6). Midsummer temperatures in 2001 were higher than in 2000 which may have favored the somewhat more heat tolerant tall fescue over PRG. Shorter rest periods generally result in higher forage quality forage, which may help offset any potential quality advantage PRG has over fescue.

Total pasture yield for the grazing season was significantly greater for ‘Stargrazer' compared to either PRG cultivar (Figure 7). The total pasture yield includes yield contribution from the interseeded white clover, volunteer grasses and legumes, as well as weeds. Because the stand density of Stargrazer was significantly greater than PRG, the proportion of total yield which is attributable to the seeded species is proportionally greater. In the case of Mara, less than one-third of the yield was from PRG.

Stand persistence has been difficult to assess due to the unfavorable environmental conditions under which the trial was established. The annual ryegrass contamination in the ‘Mara' plots has also been a difficult factor to deal with in the analysis and interpretation of the data. Stand density at the end of the 2001 growing season was significantly different among species (Figure 8), but no effect of fertility treatment was observed. Stand density of ‘Stargrazer' increased through the two grazing seasons while both PRG cultivars declined.

After two grazing seasons, ‘BG34' PRG has persisted adequately well in several of the plots. It appears that where ‘BG34' initially established well it has been able to maintain its stand. Where stand density was initially poor, it has not improved, but has declined due to increased competition from invading, better adapted species. In contrast, Stargrazer tall fescue has improved in stand density over the two years of the study. Given the annual ryegrass contamination of the ‘Mara' seed lot, no meaningful conclusions can be drawn regarding the adaptation of ‘Mara' PRG in this environment. The application of micronutrient and higher levels of P and K had no benefit for production or persistence of either tall fescue or perennial ryegrass.

Quality analysis of the forage samples has not yet been completed, so no conclusions relative to forage quality can be made at this time.