Grass Seed Crops: Post Harvest Residue Management

Transcription

1 6 Grass Seed Crops: Post Harvest Residue Management 6.1 Introduction Field burning has been an important residue management practice in cool-season grass seed crops grown in the Pacific Northwest. Historically, residue burning has been justified on the basis of disease control (Hardison, 1976; Hardison, 198), weed control (Rolston et ai., 1997), and stimulation of seed yield (Chilcote and Young, 1991). Public concern over air quality has necessitated the identification of alternative residue management practices. Furthermore, research has established that agronomically feasible alternatives to field burning exist for all species grown in the region except for creeping red fescue (Chastain et ai., 1995; Chastain et ai., 1997a; Chastain et ai., 1997b; Garbacik et ai., 1997; Young et ai., 1998; Young et ai., 1999; Chastain and Young, 1999). Burton (1944) first reported that sod burning increased seed yield in warm-season grasses. Research by John Hardison in the early 194's examined field burning as a tool for the control of diseases that threatened the fledgling cool-season grass seed industry in Oregon (Hardison, 196). Musser (1947) showed that fall burning of creeping red fescue increased seed yields because of reduced disease and insect problems. Studies were initiated in the 196's to find alternatives to field burning for grass seed crops grown in the Pacific Northwest (Chilcote, 1968). Legislative action in Oregon in 1991 set in motion a plan to phase down the number of acres burned in the Willamette Valley by 1998, and in Washington, rules imposed by the State Department of Environmental Quality in 1996 had virtually eliminated burning of grass seed crop straw and stubble by Field burning in the Willamette Valley of Oregon is regulated by the Department of Agriculture and is restricted to 4, acres for all species, with another 25, acres set aside for steep terrain and species that have shown an economic response to field burning. Elsewhere in Oregon, field burning is locally regulated by special field burning districts. ill Idaho, field burning is regulated by the state, but the acreage allowed for burning is not restricted. Three major approaches to residue management of perennial grass seed crops have evolved in the Pacific Northwest; thermal, clean nonthermal, and full straw load. Following is the definition of each approach and examples of residue management practices: 1. Thermal - Fire-based residue removal and stubble management systems. a. Full straw load + Open field bum b. Full straw load + Open field bum + propane bum c. Bale + Open field bum d. Bale + Propane burner e. Mobile Field Burner

2 72 II. Clean Nonthermal - Primary straw removal by baling, various methods of secondary removal to achieve a clean field. Stubble management mayor may not be employed. a. Bale b. Bale + flail (various types) c. Bale + flail + rake (various types) + remove (various methods) d. Bale + reclip (with swather) + remove with loafer e. Bale + vacuum f. Bale + remove by rake, vacuum, loafer, etc. + compost (off field) III. Full Straw Load - No straw removal, straw composts in place on field. Stubble height is reduced by flail mower. a. Flail (1 to 3X) with various flails b. Flail (1 to 3X) with various flails + partial removal of straw on grass crowns by rake, drags (farm drags, chain-link fence, etc.) c. Flail (IX) after combine straw chopper 6.2 Thermal Management Open-field burning has been an effective, economical method of crop residue removal and pest control in Pacific Northwest grass seed crops for more than 5 years. Nevertheless, increased public concern about reduction in air quality caused by burning of grass seed crop straw and stubble has mandated that nonthermal residue management systems be identified. Why bum grass seed fields? Field burning provides disease control, especially diseases of the seed including blind seed and ergot but not foliar diseases. Weed control is aided by field burning as fire destroys volunteer crop seed, weed seed and weed plants. In creeping red fescue, field burning has a direct stimulative influence on seed yield, but this is not observed in other grass seed crops. Field burning also recycles several important nutrients to the soil including potassium and phosphorus but not nitrogen. Seed growers in the Willamette Valley have largely adopted field burning alternatives as burning has been on the decline for nearly two decades (Fig. 6.1). Note that grass seed producers had already began sizeable reductions in the acreage burned prior to the implementation of controlling legislation. This reduction in field burning acreage has taken place during a time of increased acreage and seed yield. Field burning is practiced in most parts ofthe Pacific Northwest with the full straw load, or in other words, no baling of the straw is done. However, in the central Oregon production region, field burning is widely practiced after the removal of most of the crop straw by baling. The thought here is to reduce some of the smoke from the field burning fire by removal of some of the straw load.

3 ~ Acres Grown -6- Acres Burned 4 en Q) t3 3 «2 Figure 6.1. Grass seed production acreage and field burning acreage in the Willamette Valley Year There is no "physiological shock" associated with field burning that stimulates seed yield as had been widely thought in the lay community (Meints et ai., 21). Field burning simply removes stubble and straw that inhibit regrowth characteristics, which otherwise would improve the chances for successful induction of flowering. Propane burning of straw and stubble was used primarily by perennial ryegrass and tall fescue producers in the Willamette Valley as a replacement for field burning, but the practice was an expensive and highly regulated management alternative. Consequently, interest in propane burning has waned and few acres are now managed by this method in the Willamette Valley. Some propane burning continues in the Grande Ronde Valley of northeastern Oregon, where it is used as a field burning substitute for Kentucky bluegrass and Chewings fescue seed crops. Propane burners are also used in this region for removal of any unburned stubble that might remain in fields that have been previously open-burned. 5.3 Clean Nonthermal Management Economical clean nonthermal management in Oregon has been made possible by the development of an off-farm straw removal and handling industry. 'Straw farmers' are independent operators that bale and remove straw after harvest of grass seed fields. Some grass seed producers bale their own straw after harvest. The straw is stored or is shipped directly to bale compressor facilities where the bulk is reduced for export to international straw markets, especially Japan. Some straw is also used for animal feed within the region. Baling removed on average about 75% ofthe straw remaining after harvest (by weight). Stubble management by flail mowers or rotary mowers is also a major component of clean nonthermal management.

4 74 Several investigators have studied nonthermal residue management in grass seed crops. Pumphrey (1965) demonstrated that seed yield in Oregon's Grande Ronde Valley was not reduced when residue was mowed and removed by raking in Kentucky bluegrass. Canode (1972) reported that field burning reduced seed yield of Kentucky bluegrass in eastern Washington in the second and third seed crops compared with clipping and raking. Nevertheless, burning produced higher seed yield than mechanical removal in the fourth and fifth seed crops. Young et ai. (1984) found that close-clipping straw and stubble produced Kentucky bluegrass yields greater than burning in the second seed crop, equal to burning in the third seed crop, and lower than burning in the fourth seed crop in Oregon's Willamette Valley. Research on nonthermal residue management practices indicated that seed yields of Manhattan perennial ryegrass were best maintained by burning over a four-year period (Young et ai., 1984). Seed yields in Oregon residue management trials were dependent on residue management technique and stand age, and varied among species (Chastain et ai., 1997a; Chastain et ai., 1997b; Garbacik et ai., 1997; Young et ai., 1998; Young et ai., 1999; Chastain and Young, 1999). Species with a bunch-type growth habit (tall fescue, orchardgrass, perennial ryegrass) are more tolerant of residue management without straw removal (Table 6.1 ) Perennial ryegrass and tall fescue seed yields are best maintained over the life of the stand by nonthermal management practices that remove more than 6% of the straw. Field burning is not required to maintain seed yield of tall fescue and perennial ryegrass under Oregon conditions (Young et ai., 1999). Orchardgrass seed yield is equally responsive to any of the residue management possibilities. Perennial ryegrass, tall fescue, and orchardgrass seed yield was independent of fall regrowth and plant development. Table 6.1. Residue management technique effects on seed yield in orchardgrass, tall fescue, and perennial ryegrass. Seed yield is expressed as a percentage of the vacuum treatment in each triai. Seed yield for each species is averaged over all sites, cultivars, and years during the study period (Chastain and Young, 1999). Treatment Orchardgrass Tall fescue Perennial ryegrass Full straw load % of vacuum treatment Bale only Bale + flail Bale + flail + rake Bale + vacuum Bale + propane Site years

5 Several clean nonthermal management methods produce seed yield that are equivalent to field burning in Kentucky bluegrass, Chewings fescue, and dryland bentgrass, but not in creeping red fescue (Table 6.2). Clean nonthermal management is more difficult in species with a creeping-type growth habit. Rhizome forming grass seed crops are perhaps the most difficult to manage crop residues without the use of fire. Hickey and Ensign (1983) reported increased number of rhizomes when Kentucky bluegrass seed crops were managed without fire. Chastain et al. (1997a) noted that Kentucky bluegrass tillers were etiolated at the cessation of fall regrowth when full-straw managed fields or baled. Consequently, fertile tiller number was lower in the following spring with these residue management treatments compared to burning. Seed yield averaged across a three-year period was reduced 38% when managed with full straw loads and 1% when managed by baling compared to burning. Crop regrowth, fertile tiller production, and seed yield resulting from rake and vacuum treatments were equivalent to burning. Rake and vacuum treatments reduced stubble height and removed at least 9% of the straw. High seed yield and quality can be maintained in Kentucky bluegrass without open-field burning when straw removal is thorough and stubble height is reduced prior to crop regrowth. Table 6.2. Residue management technique effects on seed yield in Kentucky bluegrass, Chewings fescue, creeping red fescue, and dryland bentgrass. Seed yield is expressed as a percentage of the bum treatment in each trial. Seed yield for each species is averaged over all sites, cultivars, and years during the study period (Chastain and Young, 1999). Treatment Kentucky Chewings Creeping red Dryland bluegrass fescue fescue bentgrass Full straw load Bale only % of bum treatment Bale + flail Bale + flail + rake Bale + vacuum Bale + propane Site years The potential for nonthermal production of Kentucky bluegrass seed has been demonstrated elsewhere in the Pacific Northwest with different cultivars and production conditions (Murray and Swensen, 1994; Coats et ai., 1994). Lamb and Murray (1999) indicated that seed yield of Kentucky bluegrass were not affected in 2ndyear stands by non-thermal management (Vacuum, Rake) in the Rathdrum Prairie region of northern Idaho. However, seed yield of three ofthe six cultivars in their study experienced major yield losses in the 3rdharvest year. Crowe (unpublished) reported that bale + flail (99%) 75

6 76 and bale + flail + rake (1%) were not different from the central Oregon field bum treatment (bale + bum) in Kentucky bluegrass. Low stubble height may be an important aspect of post-harvest management in rhizome forming grass seed crops (Table 6.3). Results show that highest seed yields with nonthermal management of Kentucky bluegrass and creeping red fescue will generally be obtained by reducing stubble height to less than 1.5 inches (Chastain and Young, 1999). Stubble removal tended to imporve seed yield in Kentucky bluegrass more in young stands than in old stands. Thompson and Clark (1989) reported that fertile tiller production and seed yield in Kentucky bluegrass was greater when straw was removed and stubble height was reduced to 2.5 cm than with only straw removal. Kentucky bluegrass seed yields with nonthermal management are equivalent to burning when stubble and straw removal is thorough, but may not be as economical as open-field burning. Nonthermal management is not a reliable method for seed production of creeping red fescue regardless of stubble height. Table 6.3. Stubble height effects on seed yield in Kentucky bluegrass and creeping red fescue in Oregon. Seed yield is expressed as a percentage of the bum treatment in each trial. Seed yield for each species is averaged over all sites, cultivars, and years during the study period (Chastain and Young, 1999). Stubble height Kentucky bluegrass Creeping red fescue % of burn treatment Low 11 High Bum Full Straw Management Management of crop residue without removal by baling has become a common practice in grass seed production in Oregon's Willamette Valley. This form of residue management is commonly known as full straw management. Several forms of chopping a full straw load in place have evolved as seed growers seek low cost residue management alternatives. Full straw management is a reasonable alternative tool that allows producers to forego baling when straw might not meet quality standards. Moreover, some growers object to the potential loss of important plant nutrients when straw is removed by baling and instead desire the benefits of nutrient cycling associated with the decomposition of the straw. Other growers have used the full straw load as a mulch to aid in the suppression of troublesome weeds. Despite the growing acceptance of full straw management, several potential risks have been identified. The quantity of straw remaining on the field after harvest differ among the species. Full straw loads often exceed 6 lbs. per acre in perennial ryegrass, tall fescue, and orchardgrass. In Chewings fescue and Kentucky bluegrass, the full straw load usually

7 ranged from 4 to 5 lbs. per acre. Partial removal by needle-nose rake accounted for 35 to 4% ofthe total straw load, regardless of flail type. Full straw loads averaged 24% and 1% more soil water in summer than complete removal of straw at the 3-inch and 9-inch soil depths, respectively. No increases in soil water content were observed under full straw loads during fall or spring. The straw acted as a mulch and soil water was conserved during the dry summer months. However, increased late summer soil water under the straw mulch did not improve fall regrowth. Full straw management often increased the height of tillers and reduced tiller numbers at the end of fall regrowth. These negative impacts on crop regrowth in fall sometimes caused reductions in fertile tiller number in the following spring. Three types of crop yield responses to full straw management have been among the species tested (Fig. 6.2). In the first response type, orchardgrass seed yields were never affected by full straw management. A second response type was characteristic of tall fescue and perennial ryegrass. Seed yields in tall fescue and perennial ryegrass are dependent on stand age. Full straw loads tend to reduce seed yield in tall fescue during the 4thyear and during the 3rdand 4thyear in perennial ryegrass. The third response type is observed in Chewings fescue and Kentucky bluegrass. Chewings fescue and Kentucky bluegrass will not tolerate full straw load management as seed yield is consistently low regardless of stand age. 77? 12 ::::: ~ 1 bi) ;1 ::::: ;1 8 ~ ::::: ;1 ~ 6 U ~'-' 4 "' ) ;;:: 2 "' izj. ChewingsFescue - TallFescue '" PerennialRyegrass v Orchardgrass. KentuckyBluegrass 2nd 3rd 4th Stand Age (Year) Figure 6.2. Effect of full straw load and stand age on seed yield in perennial grass seed crops. Crop cultivar also affects seed yield responses to full straw management. Some cultivars of tall fescue and perennial ryegrass are tolerant of full straw management over the entire stand life. Other cultivars of both species exhibit reduced seed yield in old stands managed with a full straw load but not in young stands. Flail mower type (conventionalj-blade vs. straight blade) did not have any effect on seed yield in tall fescue and perennial ryegrass. However, seed yield is marginally better with

8 78 partial removal of the straw load than with a full straw load (Table 6.4). It is not known whether this partial removal is an economic practice. Table 6.4. Straw removal effects on seed yield in perennial ryegrass, tall fescue, Kentucky bluegrass, and Chewings fescue in Oregon. Seed yield is expressed as a percentage of the vacuum treatment in each trial. Seed yield for each species is averaged over all sites, cultivars, and years during the study period (Chastain and Young, 1999). Straw Removal Perennial Tall fescue Kentucky Chewings ryegrass bluegrass fescue Full Straw Load 94 Partial Straw Loadt 99 % of clean nonthermal management Complete Straw Removal tpartial straw removal was accomplished by using a needle-nose rake following straw chopping. Partial straw removal averaged 39%. Full straw management can be a profitable practice for grass seed production, but this practice is not without risks. Careful consideration of these risks must be weighted before adoption of full straw management. The following factors are known to affect seed yield of grasses grown under full straw management: Species Cultivar. Stand Age Some pest problems may be increased by full straw management. There is a potential for increased costs in cleaning the seed when the crop is managed with a full straw load. Given these considerations, seed growers must tailor full straw load management to fit the site-specific financial requirements of their farming operation. 5.5 Pest and Fertility Management Considerations Chilcote and Young (1991) contemplated potential changes that grass seed growers might need to make to facilitate successful grass seed crop management without the aid of field burning. They listed the following potential changes and modifications in crop management in the absence of open-field burning: (i) stand establishment practices, (ii) pest management, (iii) fertility management, and (iv) residue removal practices. Considerable research work has been done to address each item on this list since that time with the notable exception of stand establishment. Growers have noted that premature losses in stand have been widespread and have been accompaniedby herbicide-inducedcropdamage.restrictionson herbicideavailability and use, and reductions in open-field burning have resulted in increased volunteer crop

9 contamination of seed fields and some increases in weedy grass species have been reported. Furthermore, the development of resistant weed species further complicates this serious situation. Reductions in open-field burning have resulted in increased volunteer crop contamination of seed fields and some increases in weedy grass species have been noted (Chastain and Kiemnec, 1994; Chastain et ai., 1995). Control of volunteer perennial ryegrass plants (Mueller-Warrant et ai., 1994a; Mueller-Warrant et ai., 1994b) and tall fescue plants (Mueller-Warrant et ai., 1995a; Mueller-Warrant et ai., 1995b) is essential for maintaining seed yield in the absence of field burning. Failure to control volunteer plants often results in reduced seed yield when seed fields are not burned. Full straw loads may increase the incidence of some weeds and volunteer crops in fields, but the mulch effect may reduce the incidence of other weeds (Mueller-Warrant, 1999). Full straw loads have been observed to reduce annual bluegrass infestations; this weed is one of the hardest to control in grass seed production (Table 6.5). Crop damage by herbicides may reduce the effectiveness of the mulch as a weed control agent. Table 6.5. Herbicide and straw load effects on percentage weed ground cover in perennial ryegrass seed crops in Oregon (Mueller-Warrant, 1999). Residue Technique Weed No herbicide Goal + diuron 79 Full Straw Clean nonthermal PuInualbluegrass Volunteer crop PuInualbluegrass Volunteer crop % ground cover Foliar diseases have not been observed to be increased in incidence or severity by full straw management in grass seed fields. There seems to be somewhat more slugs found in full straw management than in clean nonthermal management (Table 6.6). The straw cover may be a better habitat for slug survival. Rodents, including the gray tailed vole seem to make a comfortable home in grass seed crops managed by with a full straw load.

10 8 Table 6.6. Effect of full straw load management on slug populations in perennial ryegrass and tall fescue seed fields (Fisher, unpublished). Species Cultivar Full Straw Clean Nonthermal Perennial ryegrass slugs per plot Prelude II 37 1 Sherwood 14 4 Cutter Tall fescue Barlexus 11 1 Decomposition of the straw layer over time from full straw loads caused marked improvement of several important soil characteristics (Chastain and Young, 1999). Soil ph was increased by full straw management in 29% of soil samples taken from the root zone each fall. Organic matter was similarly improved in 21% of soil samples, suggesting the possible benefit of returning straw on soil tilth. Nutrient levels increased by full straw management included: potassium, magnesium, and phosphorus were increased in 57%, 21%, and 14% of soil samples, respectively \7 Crewcut -FullStraw Crewcut - Vacuum Rebel" - Full Straw Rebel" - Vacuum. Ē 2 c.. -- c.. ~ 15.- (f) 1 Figure 6.3. Full straw management and stand age effects in soil potassium (K) in Crewcut and Rebel II tall fescue. 5 1st 2nd 3rd Stand Age

11 cf c: 4 :.;:; ro!... C 3 (]) () c: () 2 Z (]) ~ 1 (j) ~. First-year Vacuum First-year Full Straw T Third-year Vacuum "V Third-year Full Straw Figure 6.4. Full straw management and stand age effects on plant tissue potassium (K) in tall fescue. Day of Year Concentration of soil potassium was increased by full straw management as stands aged in two cultivars of tall fescue (Fig. 6.3). The return of potassium to the soil from the decomposition of straw resulted in rather large increases of soil K in comparison to the Vacuum removal of straw. Potassium concentration in tall fescue plants was better maintained during rapid spring growth in older stands when the crop was managed with a full straw load rather than with straw removal by Vacuum (Fig. 6.4). Residue management had no effect on tissue N concentration in tall fescue (Fig. 6.5). 3 Figure 6.5. Full straw management and stand age effects on plant tissue nitrogen (N) in tall fescue "#. -- c: :.;:; -~ 2 c: (]) () c: ~1 (]) ::J C/) C/) ~. First-year Vacuum First-year Full Straw T Third-year Vacuum "V Third-year Full Straw Day of Year

12 Seed Quality Seed growers in Oregon have largely adopted field burning alternatives but some still believe that these practices may reduce seed quality. One concern has been that seed quality will progressively decline as crop stands age in the absence of field burning (Chilcote and Young, 1991). Kim (1973) found that seed germination and seed purity in creeping red fescue was similar regardless of how the residue was managed in Oregon. But field burning produced the highest percentage of pure seed and the lowest amount of weed seed in perennial ryegrass (Young et ai., 1984). Young et ai. (1998) reported that maximum pure seed percentage and minimum weed seed contamination were attained with open-field burning in fine-leaf fescue seed crops. Chastain et ai. (1997a) reported that without straw removal, pure seed percentage was reduced and inert matter increased in Abbey Kentucky bluegrass. Non-burning residue management practices produced Kentucky bluegrass seed with germination percentages similar to field burning. Chastain et ai. (2) found that growing cool-season perennial grass seed crops without open-field burning did not reduce seed purity or germination in trials conducted over a six-year period in Oregon (Table 6.7). There were no interactions between stand age and residue management technique for seed quality evident for perennial ryegrass, tall fescue, Kentucky bluegrass, creeping red fescue, Chewings fescue, orchardgrass, and dryland bentgrass. This finding refutes one of the major concerns of seed producers that field burning alternatives would not only lower seed quality but that this problem would be exacerbated in aging stands. The incidence and severity of ergot and blind seed diseases in 1164 harvested seed samples also were not related to residue management or stand age. Control of ergot and blind seed has been attributed to field burning in grass seed crops (Hardison, 198), and has long been used as ajustification for the use offield burning as a management practice in grass seed production.

13 83 Table 6.7 Residue management practices and seed quality in perennial grass seed crops. Purity Residue Species Management Pure Inert seed Other crop matter Weed seed Germination % Perennial Straw 93.8 a 2.a 3.9 a.1 a 91.6 a ryegrass Bale 94.2 a 1.9 a 3.8 a.1 a 92.4 a Propane 94.1 a 1.6 a 4.1 a.1 a 91.3 a Tall fescue Straw 95.9 a.4 a 3.7 a.1 a 91.4 a Bale 96.1 a.3 a 3.5 a.1 a 91.4 a Chewings Straw 83.9 a. a 17.1 b. a 76. a fescue Bale 9.4 b. a 9.4 a.1 a 86.4 b Propane 91.4 b. a 8.5 a.1 a 88.5 b Bum 89.9b. a 1. a. a 86.6 b Kentucky Straw 87.3 a. a 12.7 a. a 83.7 a bluegrass Bale 9.6 a. a 9.4 a. a 85.7 a Bum 91.3 a. a 8.8 a. a 86. a Orchardgrass Straw 94.2 a.4 a 5.4 a. a 95.3 a Bale 94.2 a.5 a 5.3 a. a 95. a Creeping red Bale 93.5 a. a 6.4 a.1 a 88. a fescue Propane 91.6 a. a 8.5 a. a 87.7 a Bum 93. a. a 7.1 a. a 86. a tmeans in colunms within species and residue management followed by the same letter are not different. 5.7 References Burton, G.W Seed production of several southern grasses as influenced by burning and fertilization. J. Amer. Soc. of Agronomy. 36: Canode, C. L Grass seed production as influenced by cultivation, gapping, and post-harvest residue management. Agron. J. 64: Canode, C. L., and A. G. Law Influence of fertilizer and residue management on grass seed production. Agron. J. 7:

14 84 Canode, e. L., and A. G. Law Thatch and tiller size as influenced by residue management in Kentucky bluegrass seed production. Agron. J. 71: Chastain, T. G., and G. L. Kiemnec Residue management strategies for Kentucky bluegrass seed production. Agron. Abstr., Madison, WI, p Chastain, T.G., W.e., Young, III, and B.M. Quebbeman Post-harvest residue management for perennial ryegrass seed crops. Agronomy Abstracts, American Society of Agronomy, Madison, WI. p Chastain, T.G., G.L. Kiemnec, G.H. Cook, C.J. Garbacik, RM. Quebbeman, and F.J. Crowe. 1997a. Residue management strategies for Kentucky bluegrass seed production. Crop Science 37: Chastain, T.G., W.C. Young III, G.L. Kiemnec, C.J. Garbacik, G.A. Gingrich, and G.H. Cook. 1997b. Post-harvest residue mangement for fine fescue seed crops in Oregon. Proc. 18th IntI. Grassland Congress. 25: Chastain, T.G., and W.e. Young III Post-harvest residue management: species, stand age, and technique affects grass seed yield. Proc. 4thInternational Herbage Seed Conference. 4: Chastain, T.G., W.C. Young III, C.J. Garbacik, P.D. Meints, and T.R Silberstein. 2. Alternative residue management and stand age effects on seed quality in cool-season perennial grasses. Seed Technology 22: Chilcote, D.O Field burning research. Proc. Oregon Seed Growers League. 28: Chilcote, D.O., and W.C. Young III Grass seed production in the absence of open-field burning. Journal of Applied Seed Production 9:33-37 (supplement). Coats, D. D., W. e. Young III, and F. 1. Crowe Evaluation of post-harvest residue removal equipment on Kentucky bluegrass grown for seed in Central Oregon. p In Agronomy abstracts. ASA, Madison, WI. Garbacik, C.J, T.G. Chastain, W.C. Young, III, and T.B. Silberstein Residue management techniques for dryland bentgrass seed fields in Oregon. Western Society of Crop Science Abstracts, American Society of Agronomy, Madison, WI, p. 6. Hardison, J.R Disease control in forage seed production. Advances in Agronomy 12: Hardison, J. R Fire and flame for plant disease control. Ann. Rev. Phytopathology. 14: Hardison, J.R Role of fire for disease control in grass seed production. Plant Disease 64: Hickey, V. G., and R. D. Ensign Kentucky bluegrass seed production characteristics as affected by residue management. Agron. J. 75: Kim, S.C Influence of post-harvest burning, thinning, shading, and residue management on the subsequent growth and seed yield of Festuca rubra L. Ph.D. Dissertation. Oregon State University. pp Lamb, P.F., and G.A. Murray Kentucky bluegrass seed and vegetative response to residue management and fall nitrogen. Crop Sci. 39: Meints, P. D., Chastain, T.G., W.C. Young III, G.M. Banowetz, and C. J. Garbacik. 21. Stubble management effects on three creeping red fescue cultivars grown for seed production. Agron. J. 93: Mueller-Warrant, G. W., W. C. Young III, and M. E. Mellbye. 1994a. Influence of

15 residue removal method and herbicides on perennial ryegrass seed production. I. Weed control. Agron. J. 86: Mueller-Warrant, G. W., W. e. Young III, and M. E. Mellbye. 1994b. Influence of residue removal method and herbicides on perennial ryegrass seed production. II. Crop tolerance. Agron. J. 86: Mueller-Warrant, G.W., W.C. Young III, and M.E. Mellbye. 1995a. Residue removal method and herbicides for tall fescue seed production. I. Weed control. Agron. J. 87: Mueller-Warrant, G.W., W.e. Young III, and M.E. Mellbye. 1995b. Residue removal method and herbicides for tall fescue seed production. II. Crop tolerance. Agron. J. 87: Mueller-Warrant, G.W Stand loss and weed encroachment in perennial grass seed crops. Proc. 4thInternational Herbage Seed Conference. 4: Murray, G. A., and J. B. Swensen Panicle expression and seed yield of Kentucky bluegrass with mechanical residue removal. p.138. In Agronomy abstracts. ASA Madison, WI. Musser, H.B The effect of burning and various fertilizer treatments on seed production of red fescue. J. Am. Soc. of Agronomy 39: Pumphrey, F. V Residue management in Kentucky bluegrass (Paapratensis L.) and red fescue (Festuca rubra L.) seed fields. Agron. J. 57: Rolston, M.P., J.S. Rowarth, W.C. Young III, and G.W. Mueller-Warrant Grass seed crop management. In D.T. Fairey and J.G. Hampton (ed.) Forage seed production 1. Temperate species. CAB International. p Thompson, D. J., and K. W. Clark Influence of nitrogen fertilization and mechanical stubble removal on seed production of Kentucky bluegrass in Manitoba. Can. J. Plant Sci. 69: Young, W.C., III, H.W. Youngberg, and D.O. Chilcote Post-harvest residue management effects on seed yield in perennial grass seed production. I. The longterm effect from non-burning techniques of grass seed residue removal. Journal of Applied Seed Production. 2:36-4. Young, W.e. III, and R.E. Barker Ryegrass seed production in Oregon. In F.M. Roquette Jr. and L.R. Nelson (ed.) Ecology, production, and management of Latium for forage in the USA. Crop Science Society of America, Special Publication. 24: Young, W.C., III, G.A. Gingrich, T.B. Silberstein, and B.M. Quebbeman Postharvest residue management of creeping red fescue and Chewings fescue seed crops. Agronomy Journal 9: Young, W.C., III, M.E. Mellbye, and T.B. Silberstein Residue management of perennial ryegrass and tall fescue seed crops. Agron. J. 91: Youngberg, H Techniques of seed production in Oregon. In P. D. Hebblethwaite (ed.). Seed Production. Butterworths, London. 85