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© 2008 Plant Management Network.
Accepted for publication 18 August 2008. Published 7 October 2008.

Winter Grazing can be Beneficial to Tall Fescue Seed Production in Oklahoma

J. Santillano-Cázares, D. D. Redfearn, and J. L. Caddel, Department of Plant and Soil Sciences, and C. L. Goad, Department of Statistics, Oklahoma State University, Stillwater, OK 74078; and A. A. Hopkins, Forage Improvement Division, Samuel Roberts Noble Foundation, Ardmore, OK 73401

Corresponding author: A. A. Hopkins. aahopkins@noble.org

Santillano-Cázares, J., Redfearn, D. D., Caddel, J. L., Goad, C. L., and Hopkins, A. A. 2008. Winter grazing can be beneficial to tall fescue seed production in Oklahoma. Online. Forage and Grazinglands doi:10.1094/FG-2008-1007-01-RS.

Abstract

There is little information available about the effects of winter grazing on tall fescue seed production in Oklahoma and north Texas. Our objective was to determine the effects of winter grazing on tall fescue seed yield, seed yield components, and seed germination in this region. Four tall fescue entries were either grazed or remained un-grazed during two growing seasons (2002-2003 and 2003-2004) near Burneyville, OK. Winter grazing lead to seed yield increases of as much as 380% under drought conditions in 2002-2003 but did not affect seed yield in 2003-2004. Winter grazing resulted in more seedheads/m² in both growing seasons, and greater seed weight, seeds/m², and germination in 2003-2004. Winter grazing could be a viable component of tall fescue seed production systems in Oklahoma and north Texas, although drought can severely limit yields in some years.

Introduction

An estimated 400,000 hectares of tall fescue [Festuca arundinacea Schreb. = Lolium arundinaceum (Schreb.) S.J.Darbyshire] are grown for pastures in Oklahoma (13), as well as a significant area grown in north Texas. In central states such as Missouri, Kansas, Arkansas, and Kentucky both forage and seed production of tall fescue was once common. Tall fescue seed was produced on 30,000 ha in Kentucky in the early 1950s versus only about 300 ha recently (8). Due to greater seed yields and extensive infrastructure, cool-season grass seed production has shifted to the Pacific Northwest of the USA (17). Changes in market and production conditions in the future may present an opportunity for tall fescue growers in the central and southern USA to implement (or re-implement) a multiple use management system.

Limited research has been conducted examining the effects of grazing (or defoliation) on seed production of tall fescue. In England, grazing prior to spring did not harm seed yields (3). Ward et al. (15) reported greater seed yield for tall fescue clipped in late fall (1 December) versus spring (March and April), although a non-clipped treatment was not included. Defoliation after stem elongation normally results in decreased seed yields (3,14). Brotemarkle and Kilgore (2) recommend removing cattle from tall fescue pastures intended for seed production by mid-March in southern Kansas.

Integrating forage and livestock into grass seed production systems may provide an alternative enterprise for farmers and ranchers in the southern Great Plains. The objectives of this research were to determine the effect of winter grazing on seed yield and seed yield components, as well as germination of tall fescue grown for forage and seed production in Oklahoma.

Pasture Management

This research was conducted at the Noble Foundation Red River Demonstration and Research Farm near Burneyville, OK (33°53’N, 97°15’W). Details regarding stand establishment, grazing management, fertilizer applications, and other management practices are provided by Hopkins and Alison (5). Paddocks 0.47 ha in size were grazed by two steers (Bos taurus L.) weighing approximately 300 kg each from 21 November 2002 to 5 February 2003 (76 days) and from 3 December 2003 to 25 February 2004 (85 days). Hereafter, the 2002-2003 and 2003-2004 growing seasons will be referred to as 2003 and 2004, respectively. Rainfall and temperature data were from a weather station approximately one mile from the research site.

The treatment structure was a 2 × 4 factorial arranged as a split plot in a randomized complete block design.  The whole plot treatment was entry (with 4 levels), and the subplot treatment was grazing treatment which was replicated twice within each main unit (i.e., within each paddock). Entries included ‘Dovey’ and ‘Georgia 5’ free of an endophyte [Neotyphodium coenophialum (Morgan-Jones & Gams.) Glenn, Bacon, & Hanlin comb. nov.], as well as endophyte-infected Georgia 5 and ‘Kentucky 31’; entries were replicated three times. Georgia 5 endophyte free is identified as "Georgia 5 (E^-)". Grazing treatments were winter grazed (with fall grazing extended into winter) and winter non-grazed. Two exclosures (3 × 5 m) per paddock were constructed, prior to grazing, to impose the winter non-grazed treatment during winter 2002. An area adjacent to each exclosure was designated as winter grazed for seed yield sampling, resulting in six grazed/non-grazed pairs of exclosures for each entry. Exclosures were constructed around winter-grazed areas prior to spring grazing, so that none of the areas used to measure seed yield and seed yield components were grazed in spring. Exclosures were constructed as above in a different area of each paddock in winter 2003.

Determination of Seed Yield, Seed Yield Components, and Germination

Seed yield was determined by harvesting the 3 × 5-m exclosures with a Hege 140 combine (Wintersteiger Inc., Salt Lake City, UT), minus two areas consisting of frames of 0.09 m² each. Frames were placed randomly within exclosures. From these frames all seedheads were hand-clipped to determine seed yield components. The harvested seed was cleaned using a South Dakota blower with an opening set at 45° angle (16). The cleaned seed was weighed to calculate seed yield.

Seed yields are reported from the mechanical harvest and seed yield components from the manual process. Seed yield components (seedheads/m², seeds/m², number of seeds per seedhead, and individual seed weight) were determined for each exclosure by averaging data from the two 0.09-m² frames. Seedheads/m² was calculated by counting the seedheads in a frame. Seeds/m² was calculated by dividing total seed yield by individual seed weight (19). Number of seeds per seedhead was obtained by dividing the number of seeds/m² by the number of seedheads/m². Seed weight was determined by weighing and counting all seeds in an approximately 1-g sample of seed, and dividing seed weight by the number of seeds. Seed yields are reported from the mechanical harvest and seed yield components from the manual process.

Seed was harvested on 3 June 2003 and stored at 4°C with 30% humidity from harvest until mid-December 2003. After that, the seed was handled and stored at room conditions. Seed harvested on 18 May 2004 was always handled and stored at room temperature and humidity conditions. Germination tests were initiated on 24 September 2006, in accordance with the Association of Official Seed Analysis (1). Seed was pre-chilled for 7 days at 5 to 10°C, under light and imbibed with a 0.2% solution of potassium nitrate (KNO₃). After pre-chilling, seed was germinated at alternating temperatures from 15°to 25°C for 16 and 8 h, respectively. Seedlings were counted at 16 and 23 days after the beginning of the incubation treatment.

Statistics. For both seed yield and seed yield components, years were analyzed separately. Mixed models analyses of the data were performed where entry and grazing treatments were fixed effects with replications as random effects. All analyses were conducted using SAS version 9.1 (SAS Institute Inc., Cary, NC) and a nominal significance level of P = 0.05. Degrees of freedom were specified using the Kenward and Roger (7) method and means were compared using the LSMEANS PDIFF option.

Weather conditions. Precipitation varied greatly during the course of this study. Mean total annual precipitation from 1994 to 2004 was 857 mm but only 481 mm during 2003. From January through April precipitation totaled 87 mm in 2003 and 262 mm in 2004 compared to a mean of 251 mm from 1994 to 2004. January through April average temperatures were similar in 2003 (10.6°C) but slightly warmer in 2004 (11.1°C) compared to the 1994-2004 average (10.6°C).

Winter Grazing Effects on Seed yield

Winter grazing did not significantly affect seed yield of Kentucky 31 or Dovey in 2003 (Table 1). In contrast, seed yields of Georgia 5 (E^-) and Georgia 5 were almost five times greater for winter grazed versus non-grazed treatments (Table 1). Still, yields were so poor from fall 2002 to early spring 2003, averaging only 26 kg/ha across all treatments, that seed production would probably not have been economically viable. Similarly, in a study conducted in north Texas, Read and Hipp (12) reported a failure of tall fescue seed production in one of three years. Earlier maturity has been associated with greater shattering in cool season grasses (10), and probably was a major factor in low seed yields of Dovey, which is defined as a "very early entry" according to the Forage Information System of Oregon State University.

Table 1. Seed yield of four tall fescue entries subjected to winter grazing and winter non-grazing in pastures, near Burneyville, OK, during 2003 and 2004.

 ^× †SE, standard error for a given cultivar.

 ^y ‡For a given year within columns, means followed by the same lower case letter are not significantly different at the P = 0.05 level. For a given year within rows, means followed by the same upper case letter are not significantly different at the P = 0.05 level.

In 2004 seed yield responded favorably to improved distribution and amounts of rainfall. Mean seed yield was 231 kg/ha across all entries. Winter grazing did not affect seed yield (Table 1). Mean seed yield in 2004 compared favorably to a two year average of 178 kg/ha in north Texas during the early 1990’s obtained by Read and Hipp (12) and to the mean of 252 kg/ha reported for tall fescue seed production in nine states during the late 1970s (20). More recently, fescue seed yields in Arkansas averaged approximately 200 kg/ha, with experienced growers consistently producing 400 to 600 kg/ha (6).

Winter Grazing Effects on Seed Yield Components and Germination

Seedheads/m². In 2003, winter grazing was associated with an increase in seedheads/m² (Table 2), though an entry × treatment interaction occurred. Winter grazing had no effect on seedheads/m² for Dovey or Kentucky 31,which produced 26 and 125 seedheads/m², respectively, averaged across treatments. Seedheads/m² averaged 206 and 93 for GA-5 (E^-) and 238 and 93 for GA-5 in the winter grazed versus non-grazed treatments, respectively. In 2004, winter grazing resulted in more seedheads/m² (P = 0.025) than the winter non-grazing treatment (Table 2). Seedheads/m² averaged 117 and 475 in 2003 and 2004, respectively. This compares to a range of 300 to 600 in France (9), 388 for ‘Fawn’ grown in Oregon (19), and 180 seedheads/m² for winter clipped ‘AU Triumph’ in Alabama (15).

Table 2. Seed yield components for four tall fescue entries subjected to winter grazing and winter non-grazing in pastures, near Burneyville, OK, during 2003 and 2004.

 * For a given row, least square means followed by a different letter are significantly different at the P = 0.05 level.

Defoliation can lead to increased light interception by developing tillers at the base of grass plants during periods of heavy forage accumulation and tiller initiation. Young et al. (18) indicated that grazing in annual ryegrass seed production systems increased the number of both vegetative and reproductive tillers. Although not determined in the current research, it is likely that fall grazing lead to an increased number of tillers, which subsequently resulted in the observed increase in seedheads/m².

Seeds/m² and seeds per seedhead. Winter grazing was associated with a 25% increase in seeds/m² in 2004, with a similar trend (P = 0.075) in 2003 (Table 2). The number of seeds per seedhead did not differ between grazing treatments. Young et al. (19) reported an average of 46,500 seeds/m² and 130 seeds per seedhead in Oregon, about twice or more than the corresponding numbers for these seed yield components in the present research (Table 2). Dovey produced significantly fewer seeds/m² and seeds per seedhead than any other entry in 2003 and 2004 (data not shown), which may be a reflection of greater shattering prior to or at harvest.

Seed weight. Seed weight was not affected by grazing treatment in 2003 (Table 2); seed of Dovey was significantly smaller (P = 0.02) than that of the other entries (0.77 vs. 1.79 mg/seed, respectively). In 2004 winter grazing resulted in heavier seed compared to winter non-grazing with Kentucky 31 producing lighter seed (1.86 mg/seed) than the other entries (2.09 mg/seed) (P = 0.01). The number of tall fescue seeds/kg normally ranges from 387,000 to 574,000 (4), equivalent to a range of approximately 2.6 to 1.7 mg/seed, respectively. Except for Dovey in 2003, seed weight in this research fell within the range of normal seed size for tall fescue.

The positive effects on seed yield and seed yield components associated with winter grazing were most noticeable during 2003, a drought year. Rather than a drought related response, though, this may have been because grazing removed a greater accumulation of forage in 2003, as herbage mass before and after winter grazing, in kg/ha, averaged 2958 and 693 in 2003, respectively, and 1537 and 468 in 2004, respectively.

Germination. In 2003, seed germination averaged approximately 81% and did not differ between entries or grazing treatments (data not shown). In 2004, germination ranged from about 83 to 91% (data not shown) and winter grazing resulted in significantly greater germination (89%) than winter non-grazing (86%). All of these germination percentages exceed the minimum standard of 80% for Foundation, Registered, and Certified classes of tall fescue seed in Oklahoma (11).

Conclusions

Winter grazing in Oklahoma had positive effects or was neutral for tall fescue seed yield, seed yield components, and germination. Winter grazing resulted in greater seed yields in one of two years and a generally greater number of seedheads/m². Neither seed size nor germination percentage was adversely affected by winter grazing. Winter grazing can be a viable component of tall fescue seed production systems where tall fescue is adapted in the southern Great Plains. However, drought can severely limit tall fescue seed production in this region.

Literature Cited

1. AOSA. 1998. Rules for testing seeds. Assoc. of Official Seed Analysts (AOSA), Lincoln, NE.

2. Brotemarkle, J., and Kilgore, G. 1989. Seed production management for bromegrass and tall fescue. Coop. Ext. Serv. Pub. MF-924, Kansas State Univ., Manhattan, KS.

3. Green, J. O., and Evans, T. A. 1957. Grazing management for seed production in leafy strains of grasses. J. Br. Grassl. Soc. 12:4–9.

4. Hannaway, D., Fransen, S., Cooper, J., Teel, M., Chaney, M., Griggs, T., Halse, R., Hart, J., Cheeke, P., Hansen, D., Klinger, R., and Lane, W. 1999. Tall fescue (Festuca arundinacea Schreb.). PNW Ext. Ser. Circ. 504., Oregon State Univ., Corvallis, OR.

5. Hopkins, A. A., and Alison, M. W. 2006. Stand persistence and animal performance for tall fescue endophyte combinations in the south central USA. Agron. J. 98:1221-1226.

6. Jennings, J. 2005. Seed production of tall fescue. Cooperative extension service, University of Arkansas, Little Rock, AR.

7. Kenward, M. G., and Roger, J. H. 1997. Small sample inference for fixed effects from restricted maximum likelihood. Biometrics. 53:983-997.

8. Lacefield, G. D., Henning, J. C., and Phillips, T. D. 2003. Tall fescue. Ext. Pub. AGR-59, Kentucky Agric. Exp. Stn., Univ. of Kentucky, Lexington, KY.

9. Lafarge, M. 2006. Reproductive tillers in cut tall fescue swards: differences according to sward age and fertilizer nitrogen application, and relationships with the local dynamics of the sward. Grass Forage Sci. 61:182-191.

10. Lewis, E. J. 1969. Fertile tiller production and seed yield in meadow fescue (Festuca pratensis L.). J. Br. Grassl. Soc. 24:50-58.

11. OCIA. n.d. Grass seed certification standards. Online. Oklahoma Crop Improvement Association (OCIA), Stillwater OK.

12. Read, J. C., and Hipp, B. W. 1998. Nitrogen and phosphorus fertilizer requirements of tall fescue grown on blackland prairie soils. J. Plant Nutr. 21:2329-2334.

13. Redfearn, D., and Caddel, J. 2006. Role of forages in Oklahoma. Online. Oklahoma Forages, Oklahoma State Univ., Stillwater, OK.

14. Rolston, M. P., Rowarth, J. S., Young, W. C., III, and Mueller-Warrant, G. W. 1997. Grass seed crop management. Pages 105-126 in: Forage Seed Production. D. T. Fairey, and J. G. Hampton, ed. CAB International, New York, NY.

15. Ward, C. Y., Pedersen, J. F., and Kee, D. 1984. Effect of defoliation and nitrogen on seed production of ‘AU Triumph’ tall fescue. Pages 162-169 in: Proc. of the Forage and Grassl. Conf., Houston, TX. 23-26 Jan. 1984. Am. Forage Grassl. Council, Georgetown, TX.

16. Watson, C. E., and Watson, V. H. 1982. Nitrogen and date of defoliation effects on seed yield and seed quality of tall fescue. Agron. J. 74:891-893.

17. Young, W. C. III. 1997. Festuca arundinacea Scheb. (tall fescue) in the USA. Pages 287-310 in: Forage Seed Production. D. T. Fairey, and J. G. Hampton, ed. CAB International, New York, NY.

18. Young, W. C. III, Chilcote, D. O., and Youngberg, H. W. 1996. Annual ryegrass seed yield response to grazing during early stem elongation. Agron. J. 88:211-215.

19. Young, W. C., III, Youngberg, H. W., and Silverstein, T. B. 1998. Management studies on seed production of turf-type tall fescue: II. Seed yield components. Agron. J. 90:478-483.

20. Youngberg, H., and Wheaton, H. N. 1979. Seed production. Pages 141-153 in: Tall Fescue. Agron. Monogr. 20. R. C. Buckner, and L. P. Bush, ed. ASA, CSSA, SSSA, Madison, WI.