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Livestock Use as a Non-Thermal Residue Management Practice in Kentucky Bluegrass Seed Production Systems

^a Southwest Research and Extension Center, Kansas State Univ., Garden City, KS 67846
^b Dep. of Animal and Veterinary Science
^c Dep. of Plant, Soil and Entomological Sciences
^d Dep. of Agriculture Economics and Rural Sociology
^e Dep. of Plant, Soil and Entomological Sciences, Agricultural Science Building, Univ. of Idaho, Moscow, ID 83844

^* Corresponding author (jholman{at}ksu.edu)

Received for publication February 13, 2006.

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Kentucky bluegrass (Poa pratensis L.) postharvest residue has historically been burned to maintain stand productivity and profitability. Recent regulations were imposed that prohibit or restrict field burning since it negatively impacts air quality. Stand life is reduced from approximately 8 yr in a burn system to 3 yr in current nonburn systems, resulting in increased production costs and potential for soil erosion. Postharvest grazing might remove as much residue as burning, and maintain stand life longer than the current nonthermal practice of raking, baling, and mowing postharvest residue. This study determined treatment affect on seed production, cattle (Bos taurus) stocking density required to remove as much residue as burning, supplement requirements for cattle grazing Kentucky bluegrass residue, and value of Kentucky bluegrass residue utilized by cattle in bale + graze (BG) and graze-only (G) residue management treatments. Graze treatments yielded comparable to burning. The stocking density required to remove 80% of the residue in 30 d by G ranged from 17 to 23 animal units (AU) ha^–1 and BG ranged from 9 to 14 AU ha^–1. Nutritive value of Kentucky bluegrass residue ranged from 35 to 52 g kg^–1 crude protein (CP), 390 to 438 g kg^–1 acid detergent fiber (ADF), 716 to 763 g kg^–1 neutral detergent fiber (NDF), and 388 to 473 g kg^–1 48h in vitro true digestibility (IVTD). Daily requirement needed to be provided by supplement was less when fall plant regrowth was increased, and in G since dry matter (DM) intake tended to be greater in G than BG. The calculated value of baled Kentucky bluegrass residue on a DM basis averaged $33.27 Mg^–1. The calculated value of grazed Kentucky bluegrass residue on a DM basis ranged from $38 to $74 ha^–1 in BG, and $133 to $240 ha^–1 in G. Overall, BG required fewer cattle than G, but G was the most profitable grazing treatment.

Abbreviations: ADF, acid detergent fiber • AU, animal unit • BG, bale + graze • CP, crude protein • DM, dry matter • G, graze-only • IVTD, in vitro true digestibility • NDF, neutral detergent fiber

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
KENTUCKY BLUEGRASS seed producers have historically relied on burning residue after seed harvest to maintain stand productivity and profitability. However, field burning was associated with negative air quality and public health impacts, which has resulted in the State of Washington issuing a moratorium on burning Kentucky bluegrass fields since 1996, and Idaho and Oregon imposing restrictions on burning Kentucky bluegrass fields (Wulfhorst and Nielsen-Pincus, 2003). Profitable, environmentally sustainable, nonthermal and reduced thermal residue management practices must be developed; otherwise the viability of this important industry will be threatened severely.

Over 90% of the USA's Kentucky bluegrass seed is produced in the Pacific Northwest (ID, WA, OR), generating over $50 million annually in farm-gate seed sales (National Agricultural Statistics Service, 2005). Large areas of the Pacific Northwest landscape are classified as highly erodible because they receive over 50 cm of annual precipitation and are dominated by steep slopes. Including a perennial crop, like Kentucky bluegrass, in the crop rotation helps reduce nutrient runoff and soil erosion, protecting soil and surface water quality (McCool and Papendick, 1980).

The fall postharvest growth period is a critical time for establishing the seed yield potential of the following season's Kentucky bluegrass crop. During this time, Kentucky bluegrass tillers must complete a juvenile growth requirement of at least 2 wk and be greater than 1.0 mm in basal diameter before fall floral induction is completed (Canode and Perkins, 1977; Holman and Thill, 2005b; Parker-Clark, 1997). Fall floral induction and vernalization are required for the tiller to produce seed the following year (Holman and Thill, 2005b; Peterson and Loomis, 1949). A tiller will not complete the juvenile growth requirement without adequate resources (nutrients, water, and growing degree days), and a tiller will not complete floral induction without adequate stimuli (daylength less than 13 h and temperatures less than 10°C) (Canode and Law, 1979; Carlson et al., 1995; Rhoads et al., 1992; Sylvester and Reynolds, 1999). Accumulation of postharvest residue reduces tiller floral induction by decreasing the extent of diurnal temperature fluctuation, increasing nighttime temperature, and decreasing the amount of light irradiance at the plant crown during the fall (Canode and Law, 1979; Chastain et al., 1995; Murray, 1996; Picha, 1976). Nonthermal Kentucky bluegrass residue management practices like rake + bale + mow remove less postharvest residue than burning and commonly yield less than thermal systems in stands older than 2 yr (Adams et al., 1976; Chastain et al., 1995; Ensign et al., 1983; Holman and Thill, 2005a), and usually are only profitable for 3 yr compared to 8 to 10 yr in a thermal system (Wolfley, 2006). Rake + bale + mow consists of raking and baling residue after seed harvest, removing the baled residue from the field, and mowing any remaining standing residue. Open field burning usually removes 78 to 85% of the Kentucky bluegrass postharvest residue (Holman and Thill, 2005a).

Postharvest residue removal and fertilizer application must be implemented early enough in the fall to provide sufficient plant regrowth for floral induction before winter (Chastain et al., 1997; Loeppky and Coulman, 2002). Delaying residue removal and fertilizer application can shorten the fall regrowth period resulting in fewer reproductive tillers and decreased seed production (Lamb and Murray, 1999). It is believed that Kentucky bluegrass postharvest residue needs to be removed by the first of October in the Pacific Northwest since burning later can result in reduced seed yield (Ensign and Hickey, 1980). The majority of Kentucky bluegrass seed is harvested between the end of July and the end of August in the Pacific Northwest. Thus, in order for nonthermal residue management systems to be successful, they must remove approximately 80% of the postharvest residue within 30 d after seed harvest.

The forage nutrient composition of Kentucky bluegrass residue and the effect of postharvest grazing on Kentucky bluegrass seed production are unknown. In New Zealand, grazing creeping red fescue (Festuca rubra L.) and Chewings fescue (Festuca rubra L. subsp. commutata) postharvest residue to 10 mm above the ground level immediately following seed harvest resulted in seed yields comparable to burning (Hare and Archie, 1990). The objective of this study was to: (i) determine the cattle stocking density required to remove 80% of the Kentucky bluegrass postharvest residue in a 30-d grazing period, (ii) determine the affect of postharvest residue management treatments on the following year's seed yield, (iii) determine the supplement requirement for cattle grazing Kentucky bluegrass postharvest residue, and (iv) determine the forage nutritive value of Kentucky bluegrass residue utilized by livestock in a nonthermal residue management practice.

	MATERIALS AND METHODS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Experimental Procedures
Field experiments were conducted on grower–cooperator farms in established Kentucky bluegrass stands that were previously burned every fall before initiation of the study. Postharvest residue management treatments were implemented during the late summer of 2003 in Lewis County, ID, and 2004 in Latah County, ID. Both sites were seeded during the spring of 1999 with the variety Palouse (Lewis County) and variety Kenblue (Latah County). Each year, 140 kg N ha^–1 was broadcast in mid-October as ammonium nitrate [(NH₄)₂SO₄ (21–0–0, N–P–K)]. The experimental design at both locations was a randomized complete block with four replicates. Two postharvest cattle grazing treatments: (i) bale + graze (BG), and (ii) graze-only (G), were evaluated as nonthermal residue management alternatives to a conventional open field burning treatment. Plots were 27.5 m wide and 122 m long at the Lewis County site, and 16.5 m wide and 122 m long at the Latah County site. Plot width was narrowed at the Latah County site to facilitate the incorporation of the study into the grower–cooperator's field, and stocking density was adjusted accordingly to prevent a plot size affect on the study results. Plots were fenced using high tensile electric wire, and water was provided in 3030-L poly tanks located in the corner of each plot. For the BG treatment, residue was baled the day following seed harvest on 18 July 2003 and 17 Aug. 2004 before grazing. Baled residue was weighed by plot.

The grazed component of the residue management treatments were stocked at densities aimed at removing 80% of the postharvest residue within 30 d after seed harvest. Grazing was terminated based on a visual estimation of 80% residue removal. A commercial crossbred cowherd of Angus x Hereford x Shorthorn cow/calf pairs were used to graze the postharvest residue both years and were weighed immediately before grazing. Cows ranged from 3 to 10 yr in age. An AU was defined as 454 kg of body weight, and calves and cows received an AU measurement based on their weight. For example, a 227-kg calf received an AU of 0.5. In 2003, the BG treatment was stocked at 10 AU ha^–1, and the G treatment was stocked at 15 AU ha^–1. Stocking density was increased to 21 AU ha^–1 in BG, and to 55 AU ha^–1 in G in 2004 in an attempt to end the grazing period at similar dates both years. Differences in stocking density did not affect residue removal since grazing was ended based on a visual determination of 80% residue removal. Postharvest grazing was initiated on 22 July 2003 and 12 Sept. 2004. Postharvest grazing was ended on 25 Aug. 2003 and 25 Sept. 2004. The open field burning treatments were implemented on 15 Sept. 2003 and 29 Sept. 2004.

Each animal unit was fed 0.68 kg d^–1 of a supplement with 28% CP and 86% digestible DM in 2003, and 1.36 kg d^–1 of a 25% CP and 86% digestible DM supplement in 2004. Cattle were watered regularly and water consumption was measured by plot.

Aboveground postharvest residue was collected and weighed from three 0.25-m² quadrats per plot before and after grazing from different random locations. Residue dry weight was adjusted to ash-free weight using a Fischer Scientific Isotemp muffle furnace (Fischer Scientific International, Inc., Liberty Lane, Hampton, NH) at 500°C for 6 h. Kentucky bluegrass regrowth during the grazing period was estimated from an additional aboveground plant material subsample collected from three 0.25-m² quadrats per BG plot excluded from grazing before and after the grazing period. Kentucky bluegrass regrowth is not postharvest residue, but is DM accumulated during the grazing period. Regrowth must be removed by grazing in order for the postharvest residue to be removed, thus regrowth was measured to determine AU DM intake.

Forage Nutritive Value
Forage nutritive value (DM, CP, ADF, NDF, ash, lignin, and 48-h IVTD) of the postharvest grazed residue was determined by plot from a composite sample of the residue collected from the same three 0.25-m² quadrats per plot used to determine initial residue level. The forage nutritive value of the baled residue was determined from a composite sample of 50 bale cores taken at random per plot using a hay probe.

Forage nutritive value was determined using a 300-g forage subsample after it was dried at 60°C in a forced-air oven for 48 h, weighed and ground sequentially in Wiley (Thomas-Wiley Laboratory Mill, Model 4, Thomas Scientific U.S.A.) and UDY (Cyclone Sample Mill, Model 310-030, UDY Corporation, Fort Collins, CO) mills with 2- then 1-mm screens, respectively. Dry matter was used to correct forage yield to a DM basis. Neutral detergent fiber and ADF were determined using an ANKOM Fiber Analyzer (Model no. ANKOM 200, Ankom Technology, Fairport, NY) (Goering and Van Soest, 1970; Vogel et al., 1999). In vitro true digestibility was determined using an ANKOM Rumen Fermenter (Model no. Daisy II, Ankom Technology, Fairport, NY) (Goering and Van Soest, 1970). Total N was measured using the macro Kjeldahl procedure (Association of Official Analytical Chemists, 1999) with a BUCHI Nitrogen Analyzer (Model no. B-324, Buchi Labortechnik AG, Switzerland). Total N was multiplied by 6.25 to estimate CP. Lignin was determined according to procedures described by Goering and Van Soest (1970).

Dry matter intake, excluding supplement, was determined by the difference in the amount of ash-free residue per plot before and after grazing plus plant regrowth during the grazing period. Animal unit DM intake d^–1 was estimated by the amount of residue removed divided by the number of AU grazing. Protein and digestible DM intake were determined by AU DM intake d^–1 x the concentration of CP and IVTD in the residue. The ability of Kentucky bluegrass residue to meet the minimum daily energy and protein intake requirements for cattle grazing postharvest residue was estimated quantitatively from protein and digestible DM intake (National Research Council, 1996).

The forage value of Kentucky bluegrass was determined by comparing the forage nutritive value of Kentucky bluegrass to a referenced grass hay with 90% DM, 6.4% CP, 51% digestible DM, and the 20-yr historical monthly average price of $70.99 Mg^–1 for grass hay sales in Idaho (Goering and Van Soest, 1970; National Agricultural Statistics Service, 2005; USDA, 2005). Kentucky bluegrass residue and the referenced grass hay were adjusted to 100% DM basis before assigning an economic value to the Kentucky bluegrass residue. This analysis assumed the economic value of protein and digestible DM energy was comparable.

Data were analyzed with a mixed model ANOVA using the general linear model procedure of SAS software (SAS Institute, 2001) with blocks as a random effect, and years and treatments as fixed effects. Main and interaction effects were tested for in the model. Treatment effects were determined significant at P 0.05, and when ANOVA indicated significance, significant effects means were compared using the protected Least Significant Difference test at P 0.05.

	RESULTS AND DISCUSSION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Post-Harvest Residue and Seed Yield
The amount of residue remaining after seed harvest and before treatment (hereafter referred to simply as initial postharvest residue) was comparable across years and treatments, averaging 6830 kg ha^–1 (Table 1). Aboveground biomass production can vary greatly depending on Kentucky bluegrass variety (Holman, 2005; Lamb and Murray, 1999). The varieties in this study, Palouse and Kenblue, were selected in part due to their high biomass production. Since postharvest residue must be removed for seed production to be sustained, varieties that produce a large amount of biomass can pose a greater challenge in nonthermal production systems. Palouse produced an average of 6890 kg ha^–1 of postharvest residue in 2003 and Kenblue produced an average of 6770 kg ha^–1 of postharvest residue in 2004.

Increased precipitation and lower average daily temperature during the 2004 grazing period resulted in more plant regrowth in 2004 (897 kg ha^–1) than 2003 (163 kg ha^–1) (P 0.05). The average daily temperature during the grazing period was 23°C in 2003 and 17°C in 2004. Precipitation during the grazing period was 38 mm in 2003 and 104 mm in 2004. Kentucky bluegrass regrowth was not affected by block, and the average regrowth across years was 530 kg ha^–1 (Table 1). Since regrowth was not affected by block, the mean of block within year was used to calculate AU DM intake. Grazing must remove plant regrowth in order for postharvest residue to be removed. Thus, grazing had to remove more total biomass (postharvest residue + regrowth) in 2004 than 2003 due to increased plant regrowth in 2004.

The amount of postharvest residue consumed through grazing was estimated by the difference in the amount of initial postharvest residue for G and amount of residue remaining after baling in BG, less the amount of residue remaining after the treatments were implemented, plus plant regrowth during the grazing period. The grazing component of BG removed 27% of the initial postharvest residue, and grazing the G treatment removed 82% of the initial postharvest residue (Table 1). Less postharvest residue was removed by grazing in BG primarily due to baling removing between 45 and 64% of the postharvest residue before grazing. Grazing was ended prematurely in 2004 to facilitate residue burning in the adjacent open field burn treatment. The G treatment was stocked at a greater density than BG, and grazing would have been completed sooner in G than BG if grazing would have not been terminated early. Thus, terminating grazing early in 2004 resulted in less residue removed in BG than G.

A significant treatment x year interaction occurred among the amount of postharvest residue remaining after treatment (Table 2). The amount of postharvest residue remaining in 2003 was not different across treatments, averaging 1140 kg ha^–1. In 2004, 45% less residue remained in open field burn (1360 kg ha^–1) than BG (2470 kg ha^–1), and the amount of residue remaining in G (2080 kg ha^–1) was not different than the other treatments. Open field burn removed 85% of the initial postharvest residue in 2003 and 78% in 2004. The BG treatment was assumed to removal all of the regrowth during the grazing period and 86% of the initial postharvest residue in 2003 and 64% in 2004. The G treatment was assumed to remove all of the regrowth during the grazing period and 79% of the initial postharvest residue in 2003 and 71% in 2004. Bale and graze and G removed less postharvest residue in 2004 than 2003 due to terminating grazing prematurely in 2004, and for the reasons explained earlier, these adverse affects on residue removal were greatest in the BG treatment.

The yield decline between years was greatest in BG that is likely due to terminating grazing prematurely in 2004, resulting in more postharvest residue remaining in BG than the other treatments. Nonthermal production systems consistently yield less than thermal production systems in stands older than 2 yr when nonthermal residue management systems remove less postharvest residue than burning (Adams et al., 1976; Chastain et al., 1995; Ensign et al., 1983; Holman and Thill, 2005a). Grazing treatments removed at least 79% of the postharvest residue in 2003, and would have removed a comparable amount in 2004 if grazing was not terminated prematurely. Despite removing less residue in 2004, grazing treatments had seed yields comparable to open field burn in 2005 (Holman and Thill, 2005b). Our interpretation suggests that grazing 70% of the postharvest residue might be adequate to maintain yields comparable to open field burn. To ensure the following year's yield potential is maximized, grazing should be managed so that no more than about 20% or 1370 kg ha^–1 of postharvest residue remains after grazing, and that grazing is completed within 30 to 45 d postharvest.

Dry matter intake was measured to estimate the time and stocking density required to remove postharvest residue (Table 1). The weight of the cows used to graze the residue ranged from 400 to 700 kg in 2003 and 440 to 653 kg in 2004. The weight of the calves used to graze the residue ranged from 104 to 317 kg in 2003 and 122 to 299 kg in 2004. Residue DM intake AU^–1 was not different between treatments or years (Table 2), and averaged 6.5 kg d^–1 AU^–1 in BG and 10.2 kg d^–1 AU^–1 in G (Table 1). In this study, the high DM intake error (CV = 52% and RMSE = 4.03 in 2003, and CV = 36% and RMSE = 3.24 in 2004) prevented mean separation of the graze treatments. Dry matter intake variability can be attributed to variation in forage biomass measurements, variation among the cattle used in the study, and stand regrowth during the grazing period. Other studies have also reported high variability in forage yield when small plots were clipped before and after grazing (Shewmaker et al., 1997). The DM intake requirement of an AU in this study was 9.7 kg d^–1, indicating that supplement requirements were higher in BG than G (National Research Council, 1996). Greater DM intake in G might have been due to easier consumption of the loose residue early in the grazing period compared with grazing short stubble following baling in the BG treatment. The amount of supplement provided might need to be increased at the end of the grazing period, since DM intake would be lowest at the end of the grazing period when little postharvest residue remains.

The required stocking density was greater in G than in BG due to less residue following the pregraze baling operation in the BG treatment (Table 1). The grazing requirement for one AU to remove 80% of the postharvest residue was higher in 2004 than 2003, and ranged from 267 to 408 d in BG and 510 to 675 d in G. The stocking density required to remove 80% of the postharvest residue in 30 d was higher in 2004 than 2003, and ranged from 8.9 to 13.6 AU ha^–1 in BG and 17 to 22.5 AU ha^–1 in G. The required stocking density was greater in 2004 than 2003 due to more regrowth in 2004. The lesser stocking density requirement in the BG system might enable more Kentucky bluegrass hectares to be grazed if the number of cattle available in an area is limited.

Forage Nutritive Value
The forage nutritive value of Kentucky bluegrass residue was measured in the baled fraction of the BG treatment and the grazed fraction of the BG and G treatments. Differences in forage nutritive value can influence the supplement requirements and the monetary value of forage. Differences in ash, CP, and IVTD concentration occurred among treatments (Tables 3 and 4). The ash concentration of bales ranged from 51 to 65 g kg^–1, and was less than BG (97–106 g kg^–1) and G (88–101 g kg^–1) (Table 4). The lower ash concentration in the bales was suggestive of less soil contamination in the bale samples (Kellems and Church, 2003). Ash concentration was not correlated to CP, NDF, ADF, lignin, or IVTD concentration. In 2003, CP concentration ranged from 35 to 37 g kg^–1 and was not different among treatments. In 2004, G residue was greater in CP concentration (52 g kg^–1) than BG residue (44 g kg^–1) and baled residue (36 g kg^–1), and the CP concentration of BG residue and baled residue were not different from each other. The greater August and September precipitation in 2004 increased plant regrowth, and the regrowth was greater in CP concentration than postharvest residue. Acid detergent fiber, NDF, and lignin were not significantly different among treatments (Tables 3 and 4). In 2003, IVTD concentration was greater in bales (463 g kg^–1) than G (395 g kg^–1) and BG (388 g kg^–1), which were not different from each other. In 2004, IVTD concentration did not differ among treatments. In vitro true digestibility concentration was greater in the bales than the grazed residue in 2003 because the baled residue contained only the upper portion of the Kentucky bluegrass plant. The upper portion of plants have a greater leaf/stem ratio and lower lignin content than the lower portion of plants, resulting in the upper portion of plants being more digestible (Barnes et al., 2003; Holman, 2005). The increased postharvest regrowth in 2004 likely mitigated any differences in IVTD concentration among treatments since new plant growth is greater in CP, lower in NDF and ADF, and greater in IVTD concentration than mature plant residue (Barnes et al., 2003; Holman, 2005).

Differences in CP and digestible DM intake and animal nutrient requirement affect the amount of supplement required for cattle-fed Kentucky bluegrass residue (National Research Council, 1996). A 500-kg beef cow in the middle third of pregnancy (nonlactating) requires 570 g d^–1 of CP and 4 kg d^–1 of digestible DM, and 12 to 16 wk postpartum (lactating) requires 911 g d^–1 of CP and 5.29 kg d^–1 of digestible DM (National Research Council, 1996). Kentucky bluegrass residue is classified as "low quality" forage (USDA, 2005) and is better suited for nonlactating cattle that have a lower nutrient requirement than lactating cattle. Kentucky bluegrass postharvest residue plus regrowth provided sufficient digestible DM for nonlactating cattle across all treatments except BG in 2003 because of lower DM intake in BG relative to G and lower forage nutritive value in 2003 relative to 2004. Crude protein supplement was required for both lactating and nonlactating cattle across treatments and years. Supplement requirements were less in 2004 than 2003 because forage nutritive value was greater in 2004, greater for lactating cattle than nonlactating cattle because lactating cattle have a greater nutrient requirement, and less in G than BG because DM intake tended to be greater in G.

Forage Economic Value
The forage economic value of Kentucky bluegrass was derived by comparing the forage nutritive value of Kentucky bluegrass to grass hay with 90% DM, 6.4% CP, 51% digestible DM, and valued at $70.99 Mg^–1 (Downing and Gamroth, 1999) (Table 5). The value assigned to the grass hay was derived from the average monthly grass hay price received in Idaho over the past 20 yr (National Agricultural Statistics Service, 2005). Kentucky bluegrass baled and grazed residue averaged 93% DM, and did not significantly differ across treatments or years. Kentucky bluegrass residue was adjusted to a 100% DM basis to assign an economic value. Kentucky bluegrass baled DM and economic value were 4.1 Mg ha^–1 and $137 ha^–1 in 2003, and 3.0 Mg ha^–1 and $99 ha^–1 in 2004 (Table 6). Kentucky bluegrass baled DM was worth $33.27 Mg^–1 when averaged across years (Table 6). It costs between $24.75 and $34.42 Mg^–1 to rake, bale and stack Kentucky bluegrass DM at the edge of the field (Hinman and Schreiber, 2001; Van Tassell, 2002). Thus, the margin available for profit and trucking is between $1.15 and $8.52 Mg^–1 of DM. It is uncertain, but preliminary data suggest that fertilizer densities might need to be increased in systems where the postharvest residue is baled and removed from the field since macro- (N, P, K, S, Ca, Mg) and micro- (B, Fe, Mn, Cu, and Zn) nutrients are removed with the baled residue (Holman and Thill, 2005a). An increase in the amount of fertilizer required will increase the cost of fertilizing and reduce the margin gained from selling the baled residue.

The value of the Kentucky bluegrass forage will be offset by the need to provide feed supplement, fencing, labor, and water. Water consumption was 78 and 23 L d^–1 AU^–1 in 2003 and 2004, respectively. The greater water consumption in 2003 was due to warmer and drier summer conditions.

	CONCLUSIONS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Postharvest grazing can remove 80%, or as much residue as burning, when the stocking density and grazing duration are adequate. Seed yield in postharvest graze treatments were comparable with those in the open field burn treatment for both years, indicating postharvest grazing is a potential nonthermal alternative for managing Kentucky bluegrass residue and sustaining seed production when at least 70% of the postharvest residue is removed. However, the long-term impact of grazing on stand productivity and profitability needs to be evaluated.

Long-term, G might be more profitable than BG since the profit margin of baled Kentucky bluegrass is small, and the capital outlay to implement grazing (fence, water, etc.) on a per hectare basis can be allocated over more AU in the G treatment compared to the BG treatment. In addition, it is generally accepted that harvesting forage through grazing is less expensive than baling. However, 43% fewer cattle are required with the BG treatment compared to the G treatment. The resources (fence, water, supplement, stocking density, and management) required to graze Kentucky bluegrass residue are important to consider since they might not be readily available or easily implemented in all situations. In particular, the high stocking density required to remove the postharvest residue will likely limit the implementation of postharvest grazing because of the limited number of cattle available in many bluegrass production areas. A cooperative grazing agreement between grass seed producers and livestock producers might improve the successful implementation of postharvest grazing practices.

	ACKNOWLEDGMENTS

 
This research was funded in part by the Idaho State Department of Agriculture, Sustainable Agriculture Research and Education; the Washington Turfgrass Seed Commission; and the Idaho Agricultural Experiment Station. Authors thank Paul Williams, John Pearson, Andy Cochrane, Andrew Steinkamp, Brandon Davis, Katherine Beavers, and Tianna Fife for their assistance.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Contrib. 07-72-J from the Kansas Agric. Exp. Stn. Mention of a trade name is for identification only and does not imply endorsement or preference to other products not mentioned.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 

• Adams, D., A.G. Law, C.L. Canode, M. Jensen, D.K. McCool, R.I. Papendick, W. Bruehl, R.D. Oetting, C. Anderson, M.E. Wirth, and C. Burt. 1976. Alternatives to open field burning of grass seed field residues. Progress Rep. Washington State Univ. and ARS, Pullman, WA.
• Association of Official Analytical Chemists. 1999. Official methods of analysis of the Association of Official Analytical Chemists. 14th ed. AOAC, Arlington, VA.
• Barnes, R.F., J.C. Nelson, M. Collins, and K.J. Moore. 2003. Forages: An introduction to grassland agriculture. 6th ed. Iowa State Press, Ames, IA.
• Canode, C.L., and M. Perkins. 1977. Floral induction and initiation in Kentucky bluegrass cultivars. Crop Sci. 17:278–282.[Abstract/Free Full Text]
• Canode, C.L., and A.G. Law. 1979. Thatch and tiller size as influenced by residue management in Kentucky bluegrass seed production. Agron. J. 71:289–291.
• Carlson, J.M., N.J. Ehlke, and D. Wyse. 1995. Environmental control of floral induction and development in Kentucky bluegrass. Crop Sci. 35:1127–1132.[Abstract/Free Full Text]
• Chastain, T.G., G.L. Kiemnec, G.H. Cook, C.J. Garbacik, and B.M. Quebbeman. 1995. Potential alternatives to field burning in the Grande Ronde valley. Seed Prod. Res. Rep. Oregon State Univ. and USDA-ARS, Corvallis, OR.
• Chastain, T.G., G.L. Kiemnec, G.H. Cook, C.J. Garbacik, B.M. Quebbeman, and F.J. Crowe. 1997. Residue management strategies for Kentucky bluegrass seed production. Crop Sci. 37:1836–1840.[Abstract/Free Full Text]
• Downing, T., and M. Gamroth. 1999. Valuing forages based on moisture and nutrient content. Pacific Northwest Ext. Publ. 259. Oregon State Univ., Corvallis, OR.
• Ensign, R.D., and V.G. Hickey. 1980. Effects of post-harvest residue removal on Kentucky bluegrass growth and development: Highlights of 8 years of research. Progress Rep. 216. Univ. of Idaho, Moscow.
• Ensign, R.D., V.G. Hickey, and M.D. Bernardo. 1983. Seed yield of Kentucky bluegrass as affected by post-harvest residue removal. Agron. J. 75:549–551.[Abstract/Free Full Text]
• Goering, H.K., and P.J. Van Soest. 1970. Forage fiber analyses. Apparatus, reagents, procedures, and some applications. USDA Agric. Handb. 379. U.S. Gov. Print. Office, Washington, DC.
• Hare, M.D., and W.J. Archie. 1990. Red fescue seed production: Post-harvest management, nitrogen and closing date. N.Z. Grassl. Assoc. 52:81–85.
• Hinman, H.R., and A. Schreiber. 2001. The effect of the "no-burn ban" on the economic viability of producing bluegrass seed in select areas of Washington State. Farm Business Manage. Rep. (Econ. Rep.) EB1922E. Washington State Univ., Pullman.
• Holman, J.D. 2005. Kentucky bluegrass (Poa pratensis L.) non-thermal and reduced-thermal residue management and forage utilization. Ph.D. diss. Univ. of Idaho, Moscow.
• Holman, J.D., and D.C. Thill. 2005a. Kentucky bluegrass seed production. Univ. of Idaho Ext. Publ. 842. Univ. of Idaho, Moscow, ID.
• Holman, J.D., and D.C. Thill. 2005b. Kentucky bluegrass growth, development and seed production. Univ. of Idaho Ext. Publ. 843. Univ. of Idaho, Moscow, ID.
• Kellems, R.O., and D.C. Church. 2003. Livestock feeds and feeding. 5th ed. Pearson Education, New Jersey.
• Lamb, P.F., and G.A. Murray. 1999. Kentucky bluegrass seed and vegetative responses to residue management and fall nitrogen. Crop Sci. 39:1416–1423.[Abstract/Free Full Text]
• Loeppky, H.A., and B.E. Coulman. 2002. Crop residue removal and nitrogen fertilization affects seed production in meadow bromegrass. Agron. J. 94:450–454.[Abstract/Free Full Text]
• McCool, D.K., and R.I. Papendick. 1980. Runoff, soil erosion, and quality of runoff water as affected by bluegrass seed production in the rotation. Progress Rep. 0227. Washington State Univ. and ARS, Pullman, WA.
• Murray, G.A. 1996. Bluegrass seed production without open field burning. STEEP Progress Rep. Univ. of Idaho, Moscow.
• National Agricultural Statistics Service. 2005. Historical data. Available at www.nass.usda.gov/index.asp (accessed 20 July 2005; verified 20 July 2005). USDA-NASS, Washington, DC.
• National Research Council. 1996. Nutrient requirements of beef cattle. 7th ed. Natl. Acad. Press.
• Parker-Clark, V.J. 1997. Growth stage model for seedling Kentucky bluegrass (Poa pratensis L.) and leaf anatomical/morphological features associated with transition from juvenile to adult vegetative plants. Ph.D. diss. Univ. of Idaho, Moscow.
• Peterson, M.L., and W.E. Loomis. 1949. Effects of photoperiod and temperature on growth and flowering of Kentucky bluegrass. Plant Physiol. 24:31–43.[Free Full Text]
• Picha, G.M. 1976. Shoot development in Kentucky bluegrass (Poa pratensis L.) as influenced by post-harvest residue management. M.S. thesis. Washington State Univ., Pullman.
• Rhoads, J.L., J.H. Dunn, D.D. Minner, and K.L. Hunt. 1992. Reproductive morphology of five Kentucky bluegrass cultivars. Agron. J. 84:144–147.[Abstract/Free Full Text]
• SAS Institute. 2001. SAS/STAT user's guide. Version 9.3. SAS Inst., Cary, NC.
• Shewmaker, G.E., H.F. Mayland, and S.B. Hansen. 1997. Grazing preference among eight endophyte-free tall fescue cultivars. Agron. J. 89:695–701.[Abstract/Free Full Text]
• Sylvester, A.W., and J.O. Reynolds. 1999. Annual and biennial flowering habit of Kentucky bluegrass tillers. Crop Sci. 39:500–508.[Abstract/Free Full Text]
• USDA. 2005. Alfalfa hay. Washington, Oregon and Idaho market summary. Available at www.ams.usda.gov/lsmnpubs/PDF_MonthlyWOIHay2002.pdf (accessed 20 July 2005). USDA.
• Van Tassell, L.W. 2002. Assessment of non-thermal bluegrass seed production. Univ. of Idaho Res. Bull. 161. Univ. of Idaho, Moscow.
• Vogel, K.P., J.F. Pedersen, S.D. Materson, and J.J. Toy. 1999. Evaluation of a filter bag system for NDF, ADF, and IVDMD forage analysis. Crop Sci. 39:276–279.[Abstract/Free Full Text]
• Wolfley, J.L. 2006. Economic evaluation of thermal and non-thermal residue removal techniques in Kentucky bluegrass. M.S. thesis. Univ. of Idaho, Moscow.
• Wulfhorst, J.D., and M. Nielsen-Pincus. 2003. Negotiating public health: A theoretical perspective on agricultural burning and community conflict in northern Idaho. Appl. Environ. Sci. Public Health 1:33–43.

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