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FORAGES AND PASTURE MANAGEMENT

Effects of Nitrogen Fertilization Rate, Stockpiling Initiation Date, and Harvest Date on Canopy Height and Dry Matter Yield of Autumn-Stockpiled Bermudagrass

^a Dep. of Anim. Sci., Univ. of Arkansas, Fayetteville, AR 72701
^b III, Livestock and Forestry Branch Stn., Batesville, AR 72501

^* Corresponding author (coblentz{at}comp.uark.edu).

Received for publication May 5, 2003.

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Autumn stockpiling is a management technique in which forage is allowed to accumulate throughout the late summer and early fall for subsequent grazing throughout the late fall and winter. Well-established stands of common and ‘Tifton 44’ bermudagrass [Cynodon dactylon (L.) Pers.] located at Fayetteville and Batesville, AR, respectively, were chosen to evaluate the effects of stockpiling initiation date (August or September) and N fertilization rate (0, 37, 74, or 111 kg N ha^–1) on the canopy height and dry matter (DM) yield potential of autumn-stockpiled bermudagrass forage. Within year, DM yield increased linearly (P 0.008) with N fertilization rate at Fayetteville in 2001 and in Batesville during both years. For August initiation dates, DM yield declined linearly (P 0.007) with harvest date at both sites during both years; however, cubic responses (P 0.024) also were observed at both sites in 2000 but not (P 0.076) in 2001. For September initiation dates, DM yield exhibited less consistent patterns over harvest dates, but responses were cubic (P 0.053) over time for all four site-years. Tests of homogeneity for regressions of DM yield on canopy height for individual site-years indicated there were differences for the intercepts (P < 0.001) and linear coefficients (P < 0.001) and a tendency for the quadratic coefficients (P = 0.063) to differ. Quadratic equations are not suitable for producer use; therefore, a combined linear model for all data (N = 512) was determined, Y = 146X – 838 (P < 0.001; r² = 0.762), which may address the need for a quick estimator of available forage.

Abbreviations: DM, dry matter

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
BEEF CATTLE PRODUCERS in Arkansas and throughout the southeastern USA face many economic obstacles, including the maintenance of cows throughout the winter months. Many producers in this region rely on bermudagrass as the primary warm-season forage during the growing season. Bermudagrass has the potential to produce high forage yields in response to fertilization with N (Doss et al., 1966; Hill et al., 1993). This growth has been used traditionally to support grazing livestock, but large quantities are also harvested as hay that is fed during the late autumn and early winter when bermudagrass is dormant. In contrast, autumn stockpiling is a management technique in which forage is allowed to accumulate throughout the late summer and early fall for subsequent grazing throughout the late fall and winter. Recently, there has been increased interest in the utilization of autumn-stockpiled standing bermudagrass for this purpose (Lalman et al., 2000; Scarbrough et al., 2001). Stockpiled forages can provide winter pasture for grazing livestock, thereby reducing the need for supplemental hay and its associated costs (Adams et al., 1994; D'Souza et al., 1990; Hitz and Russell, 1998).

Previously, Lalman et al. (2000) suggested that the digestibility and concentrations of crude protein in stockpiled bermudagrass are generally adequate to meet the nutritional requirements of spring-calving cows during the first few weeks after frost. Scarbrough et al. (2001) suggested that this forage should be used in northern Arkansas during a relatively short (60-d) window between mid-October and mid-December; after that time, the nutritive value becomes very poor. However, autumn-stockpiled bermudagrass potentially could fill an important niche in the upper South by providing forage in mid- to late autumn when many producers in the region are allowing tall fescue (Festuca arundinacea Schreb.) to accumulate before use throughout the winter months. This system offers considerable potential for reducing reliance on harvested forages.

Traditionally, agronomic research has not focused on measuring the DM yield potential of bermudagrass during the late summer and early autumn. Relatively little information is available that describes the DM yield potential of autumn-stockpiled bermudagrass forages, or how agronomic practices may be best managed to maximize yield. Therefore, the objectives of this study were to evaluate the effects of N fertilization rate, stockpiling initiation date, and harvest date on the DM yield potential of stockpiled common and ‘Tifton 44’ bermudagrass forages throughout late autumn and early winter. A secondary objective was related to management. It is generally recommended that autumn-stockpiled forages should be strip-grazed to improve utilization. A quick method to estimate available forage would be a useful tool for producers using strip-grazing techniques that need to allocate forage on a regular basis. Therefore, our secondary objective was to assess the relationship between DM yield and plant canopy height to determine if canopy height could be used as a quick estimator of available forage.

	MATERIALS AND METHODS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Forage Management
In August of 2000 and 2001, well-established stands of common and Tifton 44 bermudagrass were divided into four field blocks consisting of eight 3.7- by 6.1-m plots at the Forage Research Area in Fayetteville (36°06' N, 94°10' W) and the Livestock and Forestry Substation near Batesville (35°50' N, 91°48' W), AR, respectively. Soil types were a Captina silt loam (fine-silty, mixed Typic Fragiudults) at Fayetteville and a Secesh silt loam (fine-loamy, siliceous, mesic Ultic Hapludults) at Batesville. The bermudagrass grown at the Fayetteville site was a locally adapted common type of unknown origin while Tifton 44 was grown at the Batesville site. Tifton 44 bermudagrass has been described as a vegetatively propagated F₁ hybrid that has finer stems, more rhizomes, and denser sod characteristics than its ‘Coastal’ bermudagrass parent (Burton and Monson, 1978). By comparison, the common bermudagrass found at the Fayetteville site had finer stems and leaves than Tifton 44, and extremely dense sod characteristics, but also exhibited considerable upright growth. It has been utilized regularly for hay production. From an experimental viewpoint, it would have been best to use the same type of bermudagrass at both locations; however, many popular hybrids, including Tifton 44, are not commonly grown in the Fayetteville area, in part because of potential for winterkill. Producers in the Fayetteville area most frequently utilize ‘Greenfield’ or common bermudagrass of unknown origin that is well adapted to the colder climate in northwest Arkansas. For this reason, we selected bermudagrass that was consistent with the hay types used by producers in each area.

Plot areas at both sites were located in areas that were managed strictly for hay production. Before initiating the study each year, a final harvest as hay was taken as close to the trial initiation date as possible. To initiate the trial, any forage that remained in the plot area following the final hay harvest was clipped to a 5-cm stubble height with a rotary mower (Model HRB215 K4HXA, Honda Power Equipment Manufacturing., Swepsonville, NC) equipped with a bagging attachment. Any clipped forage was removed from the site and discarded. Immediately thereafter, N fertilizer treatments (0, 37, 74, or 111 kg N ha^–1) were applied as ammonium nitrate to half of the plots. Early initiation dates were on 8 Aug. 2000 and 7 Aug. 2001 at Fayetteville and 10 Aug. 2000 and 9 Aug. 2001 at Batesville. A second (late) initiation date was also evaluated. These treatments were established on 6 Sept. 2000 and 4 Sept. 2001 at Fayetteville and 6 Sept. 2000 and 6 Sept. 2001 at Batesville. Establishment techniques for the second initiation date were identical to those used in August. For treatments initiated in September, any bermudagrass growth that accumulated between the August and September initiation dates was clipped to a 5-cm height as described previously and removed before fertilization. This approach is consistent with normal haying practices because recommendations for 4- to 6-wk harvest intervals are common (Ball et al., 2002).

At Fayetteville, the site had a long history of dairy waste application, and soil tests indicated that no additional fertilization with P and K were required (Chapman, 2001). At the Batesville site, early summer or late spring (12 July 2000 and 13 June 2001, respectively) applications of P and K were made via a commercially blended fertilizer, which delivered 59, 26, and 75 kg ha^–1 of actual N, P, and K, respectively, in 2000. In 2001, this supplemental application included 45, 39, and 74 kg ha^–1 of actual N, P, and K, respectively. During 2000, there was an outbreak of fall armyworms (Spodoptera frugiperda J.E. Smith) at both locations. These were controlled before significant damage occurred with an application of tebufenozide [3,5-dimethylbenzoic acid 1-(1,1-dimethylethyl)-2-(4-ethylbenzoyl)hydrazide] at a rate of 0.13 kg active ingredient ha^–1 on 12 August in Fayetteville and 5 September in Batesville.

Harvest Management
Forage growth was allowed to accumulate from respective stockpiling initiation dates until mid-October, which coincides approximately with the expected first frost date for northern Arkansas. Plots were harvested by cutting a single swath (0.9 by 3.7 m) across each plot with a self-propelled sickle-bar mower (Model Monarch, Year-A-Round Cab Corp., Mankato, MN). A swath from each plot was harvested a total of four times at 3-wk intervals over a 9-wk period ending in December. Swaths were chosen from random locations within each plot, and no area within each plot was clipped more than once. During 2000, the final sampling date was delayed until early January of 2001 due to poor weather conditions that included substantial snowfall and prolonged ground cover by snow and ice. Harvest dates in Fayetteville for 2000 were 18 October, 9 November, 29 November, and 8 January while in Batesville, the corresponding dates were 19 October, 10 November, 30 November, and 9 January. The January harvest dates at Fayetteville and Batesville were the first possible opportunities to harvest the plots after the snow cover melted. For 2001, harvest dates were 17 October, 6 November, 27 November, and 18 December at Fayetteville and 18 October, 7 November, 29 November, and 19 December at Batesville. Approximately 1000 g of each forage was dried to a constant weight in a forced-air oven (55°C) to determine the concentration of DM in the harvested forages. This value was used to calculate the total DM yield from each plot. Immediately after harvesting each plot, canopy height was measured from the ground at three random locations along the border between the freshly mowed swath and the adjacent unharvested forage. These values were then averaged to provide an estimate of canopy height for the entire plot. This method was used to estimate forage height because it provided a good contrast between harvested and unharvested forage and made measurement easy. Measurement of forage height was made on an as is basis; no adjustment to height was made when the forage was lodged due to snow cover or other environmental factors.

Statistical Analysis
Because the growth characteristics of the bermudagrass varieties used in this study were not the same, data for each location were analyzed independently. Data within each site-year were analyzed as a split-plot design (PROC GLM; SAS Inst., 1990). Whole plots were arranged in a 2 x 4 factorial arrangement of treatments that included two initiation dates (August or September) and four fertilization rates (0, 37, 74, or 111 kg N ha^–1). The subplot treatment factor was autumn harvest date. Initially, the effects of year were included in the model, but there were numerous interactions (P < 0.05) of other treatment factors with year at both locations; therefore, each year was analyzed independently. Single degree-of-freedom orthogonal contrasts (PROC GLM; SAS Inst., 1990) were used to describe the effects of N fertilization rate and harvest date on DM yield and canopy height.

Because stockpiled forages are often strip-grazed to limit waste, a quick estimator of available forage would be an extremely useful management tool. Therefore, the relationship between DM yield and canopy height was evaluated for each of four site-years using PROC REG (SAS Inst., 1990) to determine if canopy height could serve as an acceptable predictor variable for estimating available forage. Both linear and quadratic terms were included in the regression model, but the quadratic term was dropped if it was not significant at P = 0.05. An independent test of homogeneity (PROC GLM; SAS Inst., 1990) was included to determine if a common line could be used to combine the data from both locations and years.

	RESULTS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Precipitation
Weather conditions were extremely dry in August 2000 at both locations; there was no measurable rainfall in Fayetteville (Fig. 1) , and only 3.3 mm of precipitation fell at Batesville (Fig. 2) during this time period. Between July and December 2000, cumulative precipitation was only 89 and 63% of the 30-yr average (NOAA, 2002) for the Fayetteville and Batesville sites, respectively. At Fayetteville in 2001, monthly precipitation exceeded the 30-yr average during four of the six months between July and December. In August and November, months in which precipitation was less than the 30-yr average, cumulative precipitation was at least 90% of expected levels. Similarly, precipitation at Batesville met or exceeded the 30-yr average during five of the six months comprising this same time period. The lone exception to this trend was in August when only 10.9 mm of precipitation fell; this was only 14% of the 30-yr average.

View larger version (29K): [in this window] [in a new window]   Fig. 1. The 30-yr average and total monthly precipitation from July through December in 2000 and 2001 at Fayetteville, AR.

View larger version (26K): [in this window] [in a new window]   Fig. 2. The 30-yr average and total monthly precipitation from July through December in 2000 and 2001 at Batesville, AR.

Canopy Height
For both August and September initiation dates, canopy height changed in linear, quadratic, and cubic (P 0.001) patterns over harvest dates (Table 4). Generally, substantial increases in canopy height were observed between the first and second harvest dates, followed by a rapid decline by the third harvest date.

Batesville 2001
Dry Matter Yield
Yields of DM increased linearly (P < 0.001; Table 2) with N fertilization rate; plots fertilized at the highest rate accumulated more than three times as much DM as unfertilized controls, but all yields of DM were poor, and the only treatment mean to exceed 1000 kg ha^–1 was associated with the highest fertilization rate. For treatments initiated in August, yield of DM declined linearly (P = 0.007; Table 3) from 1334 to 823 kg ha^–1 over the 9-wk sampling period. Yields of DM for all treatments initiated in September were low (350–520 kg ha^–1) and exhibited a cubic (P = 0.053) response over harvest dates. At best, plots initiated in September yielded only about 50% of comparable treatments initiated in August.

Canopy Height
Canopy height increased linearly (P < 0.001; Table 2) with N fertilization rate. There was a 5.5-cm advantage in canopy height for plots fertilized at the highest rate relative to unfertilized controls. Regardless of initiation date, canopy height declined linearly (P 0.001; Table 4) over harvest dates, decreasing by 6.5 cm in plots initiated in August and by 2.5 cm for plots initiated in September. However, the maximum height for plots initiated in August was 18.1 cm compared with only 11.7 cm for plots established in September.

Fayetteville 2001
Dry Matter Yield
Yields of DM increased linearly (P = 0.002) with N fertilization rate and were 25% greater in plots fertilized at the highest rate compared with unfertilized controls (Table 2). A quadratic trend (P = 0.060) also was observed; this occurred because there was no yield response in plots fertilized with 37 kg N ha^–1 relative to unfertilized controls. For both August and September initiation dates, DM yield changed in linear (P < 0.001) and cubic patterns (P 0.076) over harvest dates (Table 3); however, yields decreased over harvest dates in plots initiated in August but increased in plots initiated in September. As was observed at both sites in 2000, yields from plots initiated in September were only 16 to 55% of those from comparable treatments initiated in August.

Canopy Height
The height of the forage canopy (Table 4) decreased linearly (P < 0.001) from 35.0 to 21.0 cm between the first and last harvest date for plots initiated in August. In contrast, canopy height increased linearly (P < 0.001) over harvest dates for plots initiated in September but reached a maximum of only 18.1 cm.

Regressions of Dry Matter Yield on Canopy Height
Tests of homogeneity indicated that there were differences among the four site-years in regressions of DM yield on canopy height for intercepts (P < 0.001) and linear coefficients (P < 0.001). There also was a tendency (P = 0.063) for quadratic coefficients to differ over site-years. The best regression model included a quadratic term (Table 5) for each site-year except Fayetteville in 2000 where a linear model best described the relationship. The R² statistics were 0.626 for all site-years except Fayetteville in 2000 where the model explained only 44% of the variability in the data.

	DISCUSSION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

Another climatic factor that warrants discussion is the snow and ice cover that occurred during the winter of 2000–2001. This condition delayed the final harvests at both Fayetteville and Batesville during the 2000 growing season until early January 2001, which was the first possible opportunity for harvest after the snow and ice melted. In addition, temperatures remained well below the expected 30-yr average (NOAA, 2002) at both sites throughout both November and December of 2000 (Fig. 3 and 4) . Mean daily temperatures remained well below freezing (0°C) for much of December 2000 at both sites. These effects, coupled with droughty conditions throughout the late summer at both sites, and well into the autumn at Batesville, may have weakened stands of bermudagrass. During 2001, stands of bermudagrass in Arkansas were generally characterized as poorly productive and uncompetitive. These characteristics were observed at our experimental sites during the early-season hay harvests in 2001; however, there was no evidence of winterkill at either site, and bermudagrass covered both plot areas in solid stands.

View larger version (24K): [in this window] [in a new window]   Fig. 3. Mean daily temperatures at Fayetteville, AR, from July through December in 2000 and 2001. The 30-yr average temperature for each month is represented by a large filled circle (•).

View larger version (24K): [in this window] [in a new window]   Fig. 4. Mean daily temperatures at Batesville, AR, from July through December in 2000 and 2001. The 30-yr average temperature for each month is represented by a large filled circle (•).

Initiation Date
These results indicate that the best technique for stockpiling bermudagrass should include an early August initiation date. Although initiation could occur earlier, this would also result in excessively mature forage by mid-October. Lalman et al. (2000) has suggested that the stage of maturity at the onset of dormancy is an important factor affecting nutritional value. Despite the stressful growing conditions throughout much of the study, plots initiated in August yielded 1.5 to 6.4 times the forage DM as comparable treatments initiated in September (Table 3). When August rainfall approached expected levels at Fayetteville in 2001, yields reached 4740 kg ha^–1 in mid-October for plots averaged over all fertilization rates. However, these yields were nearly 2000 kg ha^–1 lower than those reported on other highly fertile producer sites in northwestern Arkansas that were harvested in mid-October (Coblentz et al., 1998).

Clearly, the suitability of stockpiling bermudagrass as a method of extending the grazing season is highly dependent on August rainfall. Delaying initiation until September, when rainfall events are more likely in northern Arkansas, apparently does not allow adequate time for accumulation of DM before the targeted 60-d grazing window beginning in mid-October.

Other Considerations
Previously, Scarbrough et al. (2001) has suggested that stockpiled bermudagrass should be utilized throughout a 60-d window from mid-October through mid-December in northern Arkansas. After that time, the nutritive value becomes very poor. This recommendation is supported by the declining yields observed in six of eight combinations of site, year, and initiation date over this time period (Table 3). Yields declined due to weathering and senescence in primarily linear patterns in all four combinations of site and year for plots initiated in August. For plots initiated in September, responses were less consistent, but reductions in DM yield were observed at Batesville in both years. At Fayetteville, DM yield doubled between the first and second harvest dates in 2000. This can largely be explained because rainfall levels were at, or above, expected averages for September and October (Fig. 1) and ambient temperatures were above normal throughout much of October (Fig. 3). This allowed growth to continue between the first and second harvest dates.

Based on visual assessment, contaminating species made up very minor proportions of the DM harvested in seven of the eight combinations of site, year, and initiation date. However, DM yield increased with harvest date for plots initiated in September 2001 at Fayetteville (Table 3); this occurred in part because of contamination by other species, particularly annual ryegrass (Lolium multiflorum Lam.), with lesser proportions of other winter–annual grasses and broadleaf weeds. This was not observed in companion plots initiated in August and suggests that the shading created with an August initiation date may have suppressed growth of winter–annual contaminants. Currently, legal herbicide options for controlling this type of contaminant vegetation in growing bermudagrass in Arkansas are extremely limited. Because the goals of this study were production oriented, and because this problem occurred in only one of eight combinations of site, year, and initiation date, no attempt was made to control this contaminant vegetation with herbicides that are unavailable to the public.

Regression of Dry Matter Yield on Canopy Height
Unfortunately, tests of homogeneity indicated that the relationship between canopy height and DM yield was not consistent across site-years, and combining the data from all four site-years into a single regression model was not appropriate statistically. Furthermore, the inclusion of quadratic terms in the regression model improved the regression relationship in three of four site-years (Table 5), but the use of a quadratic model as a quick estimator of forage availability for producers is undesirable because of its complexity. However, a quick field test to estimate available forage does not necessarily need to meet the statistical standards required for scientific work. Based on this premise, a linear model combining forage canopy height and DM yield data from all site-years (N = 512) also was evaluated. The combined linear model for all data was Y = 146X – 838 (P < 0.001; r² = 0.762), where X = height in cm and Y = DM yield in kg ha^–1. The relatively high r² statistic suggests that a simple linear approach may be useful to producers as a quick field estimator of forage availability.

	CONCLUSIONS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Acceptable accumulation of bermudagrass for use in grazing systems during the late autumn and early winter is highly dependent on receiving adequate precipitation in August. Yields of DM in excess of 4000 kg ha^–1 were obtained in mid-October when rainfall in August approached the 30-yr norm, but DM yields were far less for the other three site-years that were very droughty. In all cases, an August initiation date resulted in more DM yield than companion plots initiated in September; averaged over all site-years, plots initiated in September yielded only about 40% of the DM harvested from plots initiated in August. Fertilization with N improved DM yield linearly in three of four site-years, but this clearly is not cost effective in the absence of August rains. The use of autumn-stockpiled bermudagrass may be best adapted to less droughty sites or where irrigation is available to ensure adequate growth in dry years. Although the relationship between forage height and DM yield was often best explained with a quadratic model for individual combinations of site and year, a linear model based on all data may be adequate for a producer friendly, quick estimator of forage availability.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Contribution of the Arkansas Agricultural Experiment Station.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 

• Adams, D.C., R.T. Clark, S.A. Coady, J.B. Lamb, and M.K. Kielson. 1994. Extended grazing systems for improving economic returns from Nebraska sandhills cow/calf operations. J. Range Manage. 47:258–263.
• Ball, D.M., C.S. Hoveland, and G.D. Lacefield. 2002. Southern forages. 3rd ed. Potash and Phosphate Inst. and the Foundation for Agron. Res., Norcross, GA.
• Burton, G.W., and W.G. Monson. 1978. Registration of Tifton 44 bermudagrass. Crop Sci. 18:911.[Free Full Text]
• Chapman, S.L. 2001. Soil test recommendations guide. Publ. AGR 9. Coop. Ext. Serv. and Agric. Exp. Stn., Univ. of Arkansas, Little Rock.
• Coblentz, W.K., K.P. Coffey, G.V. Davis, and J.E. Turner. 1998. Evaluation of stockpiled bermudagrass after hay and pasture summer management. p. 43–45. In Arkansas Animal Science Department Report. Res. Ser. 464. Arkansas Agric. Exp. Stn., Fayetteville.
• Doss, B.D., D.A. Ashley, O.L. Bennett, and R.M. Patterson. 1966. Interactions of soil moisture, nitrogen, and clipping frequency on yield and nitrogen content of coastal bermudagrass. Agron. J. 58:510–512.[Abstract/Free Full Text]
• D'Souza, G.E., E.W. Maxwell, W.B. Bryan, and E.C. Prigge. 1990. Economic impacts of extended grazing systems. Am. J. Alternative Agric. 5:120–125.
• Hart, R.H., W.G. Monson, and R.S. Lowrey. 1969. Autumn-saved Coastal bermudagrass (Cynodon dactylon (L.) Pers.): Effects of age and fertilization on quality. Agron. J. 61:940–941.[Abstract/Free Full Text]
• Hill, G.M., R.N. Gates, and G.W. Burton. 1993. Forage quality and grazing steer performance from Tifton 85 and Tifton 78 bermudagrass pastures. J. Anim. Sci. 71:3219–3225.[Abstract]
• Hitz, A.C., and J.R. Russell. 1998. Potential of stockpiled perennial forages in winter grazing systems for pregnant beef cows. J. Anim. Sci. 76:404–415.[Abstract/Free Full Text]
• Lalman, D.L., C.M. Taliaferro, F.M. Epplin, C.R. Johnson, and J.S. Wheeler. 2000. Review: Grazing stockpiled bermudagrass as an alternative to feeding harvested forage. In Proc. Am. Soc. Anim. Sci. Symp., Lexington, KY [Online]. 29 Jan.–2 Feb. 2000. Available at http://www.asas.org/symposia/0621.pdf. Am. Soc. Anim. Sci., Savoy, IL.
• [NOAA] National Oceanic and Atmospheric Administration. 2002. Monthly station normals of temperature, precipitation, and heating and cooling degree days 1971–2000. Climatography of the United States 81. 03 Arkansas. Natl. Clim. Data Cent., NESDIS, NOAA, Asheville, NC.
• SAS Institute. 1990. SAS/STAT: User's guide. Version 6. 4th ed. SAS Inst., Cary, NC.
• Scarbrough, D.A., W.K. Coblentz, K.P. Coffey, J.E. Turner, G.V. Davis, D.W. Kellogg, and D.H. Hellwig. 2001. Effects of calendar date and summer management on the in situ dry matter and fiber degradation of stockpiled forage from bermudagrass pasture. J. Anim. Sci. 79:3158–3169.[Abstract/Free Full Text]

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This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Scarbrough, D. A. Articles by Turner, J. E. Search for Related Content PubMed Articles by Scarbrough, D. A. Articles by Turner, J. E. Agricola Articles by Scarbrough, D. A. Articles by Turner, J. E. Related Collections Other Forage Crops Production Agriculture