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Published online 27 October 2005
Published in Crop Sci 45:2583-2590 (2005)
© 2005 Crop Science Society of America
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FORAGE & GRAZINGLANDS

Biomass Production of Switchgrass in Central South Dakota

D. K. Lee and A. Boe*

Plant Science Dep., South Dakota State University, NPB244, Box 2140-C, Brookings, SD 57007

* Corresponding author (arvid.boe{at}sdstate.edu)


   ABSTRACT
TOP
 NOTES
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Switchgrass (Panicum virgatum L.) has potential as feedstock for a cellulose-based biofuels industry in temperate steppe regions of the northern Great Plains. Therefore, our objectives were to determine: (i) patterns of biomass accumulation and optimum harvest times for an early maturing cultivar, Dacotah (origin 46° N, 100° W), and a later maturing cultivar, Cave-In-Rock (origin 37° N, 88° W), in central South Dakota (44° N, 100° W) and (ii) if variation in patterns of biomass accumulation were associated with variation in patterns of precipitation. Dacotah and Cave-In-Rock were no-till planted near Pierre, SD, on 6 Dec. 1999. Harvest dates were once per year during July, August, September, or October 2001 through 2004. Morphological development was determined in early, mid, and late summer 2004. Maximum biomass yields for Dacotah were obtained during July or August. Optimum harvest time for Cave-In-Rock was as late as September depending amount of summer precipitation. Biomass production of both cultivars was highly plastic, fluctuating > fivefold over a 4-yr period. Maximum annual biomass yields were from >9 Mg ha–1 to <2 Mg ha–1 for both cultivars. Variation in April through May precipitation explained >90% of variation in maximum annual biomass production. The superior biomass yield potential of the putatively unadapted Cave-In-Rock compared with the putatively adapted Dacotah was only expressed during years when precipitation was >75% of average.


   INTRODUCTION
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
SWITCHGRASS, a native, perennial, warm-season grass, is important for forage and conservation in the USA and southern Canada, primarily east of the 100th meridian. The use of switchgrass as a renewable bioenergy crop has many obvious environmental and economic benefits including improved soil conservation, improved energy gain, and improved reduction of greenhouse gas emission (McLaughlin and Walsh, 1998).

Over the past 10 or so years, switchgrass has been extensively evaluated for potential as a biomass–bioenergy crop in the Midwest (Vogel et al., 2002; Casler and Boe, 2003), southern Great Plains (Sanderson et al., 1999a; Muir et al., 2001), and southeastern Canada (Madakadze et al., 1998, 1999). A recent economic analysis identified parts of the northern Great Plains where net farm income would likely be increased by the introduction of a bioenergy crop, such as switchgrass (De La Torre Ugarte et al., 2003).

Proper management of genetically diverse cultivars for sustainable biomass production has recently been described for various regions of North America that receive average annual precipitation in excess of 500 mm. In Iowa and Nebraska, optimum biomass yields for Cave-In-Rock switchgrass were obtained when harvested at the stage of panicles fully emerged through postanthesis and fertilized with 120 kg N ha–1 (Vogel et al., 2002). Sanderson et al. (1999a) recommended that switchgrass be harvested once in the fall (about mid September) for maximum biomass yields in the southern Great Plains. Casler and Boe (2003) reported switchgrass biomass yields were unpredictable because of interactions among harvest date, site, year, and cultivar, but delaying harvest until at least late summer was advantageous for long-term sustainable biomass production in the Midwest.

Growing season precipitation has an important influence on switchgrass biomass production (Stout et al., 1988; Sanderson et al., 1999b; Muir et al., 2001; Heaton et al., 2004). Muir et al. (2001) reported switchgrass biomass yield was positively correlated with growing-season precipitation at various N fertilizations in north-central Texas, where average growing-season (March–August) precipitation is 458 mm. Sanderson et al. (1999b) reported the major factor affecting switchgrass biomass production seemed to be April to September rainfall in Texas. Precipitation pattern was important for affecting forage yield in semiarid regions in which average growing season precipitation is less than 300 mm (Smoliak, 1956; Currie and Peterson, 1966). However, little is known about biomass production patterns and harvest management of switchgrass in the mixed-grass prairie region [i.e., temperate steppe division (Bailey, 1998)] of the northern Great Plains. Such information is needed to determine if switchgrass has potential as a sustainable bioenergy crop west of the tallgrass prairie region.

Therefore, the objectives of this study were to determine: (i) patterns of biomass accumulation and optimum harvest times for an early maturing cultivar, Dacotah (origin 46° N, 100° W), and a later maturing cultivar, Cave-In-Rock (origin 37° N, 88° W), in central South Dakota (44° N, 100° W) and (ii) if variation in patterns of biomass accumulation were associated with variation in patterns of precipitation.


   MATERIALS AND METHODS
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
This study was conducted at two sites on the South Dakota State University Dakota Lakes No-till Research Farm (44°15' N, 100° 00' W) 25 km east of Pierre, SD. Table 1 shows monthly mean temperature for 2000 through 2004 at the farm. Soil at Site 1 is a Lowry silt loam (coarse-silty, mixed, mesic Typic Haplustoll), and the previous crop was wheat (Triticum aestivum L.). Soil at Site 2 is a Canning loam (fine-loamy over sandy, mixed, mesic Typic Argiustolls), and previous vegetation was long-term Kentucky bluegrass (Poa pratensis L.) sod. Weather data were collected by an automatic-weather-station on the farm.


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  		Table 1. Mean monthly temperature (°C) for 2000 through 2004 at the Dakota Lakes Research Farm in central South Dakota.

 
Experimental designs were split-plots in randomized complete blocks with four replications. Harvest dates were whole plots and cultivars were subplots (3.7 by 3.7 m). Harvest date plots were separated by 3.7-m wide control plots, from which biomass allowed to stand over winter was removed during spring before greenup. The reason for control plots was to eliminate any differential border effects due to harvest date. Two cultivars, Cave-In-Rock [late maturing, origin southern Illinois (38° N 88° W)] and Dacotah [early maturing, origin southwestern North Dakota (46° N 102° W)] were planted into wheat stubble (Site 1) and herbicide-killed sod (Site 2) with a 750 John Deere No-till Drill on 6 Dec. 1999. The late autumn planting date was chosen to overcome any dormancy that would prevent rapid and uniform germination presumed necessary for successful stand establishment during the spring in this semiarid region. Seeding rate was 12 kg pure live seed ha–1. Bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) + MCPA (2-methyl-4-chlorophenoxyacetic acid) was applied at 0.42 kg ha–1 a.i. during spring 2001 through 2004 to control broadleaved weeds. No fertilizer was applied during the study. Harvest dates were generally during July, August, September, or October from 2001 through 2004 for Site 1 but only during 2003 and 2004 for Site 2. Site 2 was not harvested before 2003 because of slow stand development. Switchgrass biomass was harvested on only three dates during 2002 because of severe drought. In addition, uninterrupted growth from 2003 that was allowed to stand during the 2003–2004 winter was also harvested for biomass determination during March 2004. Switchgrass biomass was harvested from entire subplots with a sickle-bar mower at a cutting height of 10 cm, with the exception of March 2004 when harvest was at ground level, on the designated harvest dates (Table 2). Although harvest dates varied slightly from year to year, the order in which whole plots were harvested was the same (Table 2). Regrowth from the earliest harvest plots (i.e., 8 July) was harvested for biomass determination on the last harvest date (i.e., 24 Oct.) during 2004. This was the only year with machine harvestable regrowth from the earliest harvest treatment. Dry matter (DM) concentration determined for each cultivar by using about 0.5-kg grab-samples of harvested biomass dried at 60°C for 72 h was used to adjust plot wet yields to a DM basis. Biomass yield data were analyzed separately by site and year and subjected to analysis of variance for a split-plot design (Littell et al., 1996).


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  		Table 2. Harvest dates for biomass production of two switchgrass cultivars during 2001 through 2004 at the Dakota Lakes Research Farm in central South Dakota.

 
Estimates of plant stand were collected for all harvest date treatments at the last harvest (i.e., October) during 2004 using the frequency grid designed by Vogel and Masters (2001) for quantifying establishment success in grassland plantings. In each 3.7- x 3.7-m cultivar subplot within each harvest date plot and check plots at each site, the frequency grid (0.75 x 0.75 m) was randomly placed at two positions, and the number of 15- x 15-cm cells containing at least one tiller of switchgrass was determined. Since each tiller at the end of the growing season would be expected to have 3 to 4 axillary buds of variable size and rhizome development (Boe and Bortnem, 2003), the presence of at least one tiller within a 15- x 15-cm square represents meristematic potential for new tillers to develop in that cell during the subsequent growing season. Stand density data collected in October 2004 were analyzed separately by location as percentage of cells occupied by at least one tiller of switchgrass. Cultivars and harvest dates were considered fixed and replications were considered random.

On three harvest dates during 2004, tillers in randomly selected 0.1-m2 plots in each of two replications of the control (i.e., biomass removed during March before resumption of growth) plots at each site were excised at ground level with rice knives. Tillers were bulked across replications before randomly selecting 30 tillers for morphological analysis. Tillers were dried at 60°C for 72 h and partitioned into stem, leaf sheath, leaf blade, and inflorescence (if present) components. Components were weighed on an electronic balance with milligram readability. Tiller component DM weights and their DM partitioning coefficients (Sanderson, 1992) were subjected to analyses of variance for which site, cultivar, and harvest date were considered fixed. Least significance differences were used to separate means when F tests were statistically significant (P = 0.05).


   RESULTS AND DISCUSSION
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS
 REFERENCES
 
Biomass Yield—Harvest Dates and Cultivars
Analysis of variance indicated highly significant differences among harvest dates for biomass yield for both cultivars in all years, with the exception of 2002 (Table 3), which was by far the driest growing season and lowest biomass production year (Fig. 1b) . In 2002, biomass production reached maximum by early July and was only about 25% of the maximum during the most productive years of 2001 and 2003 (Fig. 1a, c).


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  		Table 3. Mean squares for sources of variation for biomass yields of two switchgrass cultivars in response to harvest dates and years at the Dakota Lakes Research Farm in central South Dakota.

 


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  		Fig. 1. Pattern of precipitation and cultivar and harvest date effects on biomass production of two switchgrass cultivars for 4 yr at Site 1 on the Dakota Lakes Research Farm in central South Dakota. Means with same letter are not significantly different at the 0.05 level (a: 2001, significant cultivar x harvest date interaction; b: 2002; c: 2003, significant harvest date main effect; d: 2004, significant cultivar x harvest date interaction).

 
For Dacotah, the general trend was highest biomass production in early July to early August when the cultivar was in early anthesis to seed development stages. Substantial declines in biomass yield occurred between then and September and October when plants were in senescence–seed shattering stages (Fig. 1 and 2) . The large difference between biomass yields of early July and early August harvests in 2004 at Site 1 suggested a negative effect on spring vigor from harvests in three previous years of Cave-In-Rock and Dacotah similar to what was described for mid summer harvests in Wisconsin and eastern South Dakota (Casler and Boe, 2003). This premise is also supported by data from Site 2, where harvesting did not begin until 2003, and there was no difference between early July and early August harvests for Dacotah in 2004 (Fig. 2b). There was a difference between July and August harvests for Cave-In-Rock at Site 2, but it was much smaller than at Site 1 (Fig. 1d and 2b).



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  		Fig. 2. Pattern of precipitation and cultivar and harvest date effects on biomass production of two switchgrass cultivars for 2 yr at Site 2 on the Dakota Lakes Research Farm in central South Dakota. Means with same letter are not significantly different at the 0.05 level (a: 2003, significant harvest date main effect; b: 2004, significant cultivar x harvest date interaction).

 
For Cave-In-Rock, the pattern of biomass accumulation was similar to Dacotah during 2003, with both cultivars producing their greatest standing crop at the late July harvest. During the severe drought of 2002, biomass production was stymied similarly for both cultivars during early July (Fig. 1b). In 2001 and 2004, Cave-In-Rock produced its highest biomass yields later in the growing season than Dacotah (Fig. 1a, d and 2b).

Averaged across harvest dates, Cave-In-Rock produced more biomass than Dacotah in 2001 and 2004 (Table 3; Fig. 1a, d and 2b), with the biggest difference between cultivars occurring in the latter part of the growing season. In contrast, there were no differences between cultivars for biomass production at Site 1 in 2002 and at both sites in 2003 (Table 3; Fig. 1b, c and 2a).

The harvest date x cultivar interaction was significant for biomass in 2001 and 2004 (Table 3; Fig. 1a, d and 2b). At Site 1 in 2001, biomass yields were comparable for Cave-In-Rock and Dacotah through early July, but standing crop for Cave-In-Rock was about 40% higher than that of Dacotah in mid August and late September (Fig. 1a). In 2004, Dacotah had greater standing crop than Cave-In-Rock in early July at Site 1, but biomass yields of the two cultivars were similar on that date at Site 2. However, by early August, Cave-In-Rock had accumulated more biomass than Dacotah at both sites (Fig. 1d and 2b).

Switchgrass that stood over winter and was harvested near ground level during March 2004 had biomass yields not different from biomass harvested at 10-cm stubble height in October 2003 at Site 2. However, at Site 1, 15% less biomass was harvested in March 2004 compared with October 2003. No difference occurred between cultivars at either site (Table 4). It appeared that loss of biomass due to weathering during the winter could, in some situations, be compensated for by harvesting near ground level to include the basal, which would normally be expected to be the heaviest (Boe et al., 2000), internodes.


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  		Table 4. Biomass yields of uninterrupted growth of two switchgrass cultivars produced during 2003 and harvested in October 2003 or March 2004 at the Dakota Lakes Research Farm in central South Dakota.

 
During the 4-yr study, 2004 was the only year that produced machine harvestable amounts of regrowth from the early July harvest (data not shown). This may have been due to above average precipitation during the latter half of the growing season (123% of average during June through September). The later maturing Cave-In-Rock produced 1.7 Mg ha–1 of regrowth, which was comparable to the first harvest (1.5 Mg ha–1). However, regrowth yield for Dacotah (0.9 Mg ha–1) was lower than the first harvest (2.8 Mg ha–1) at Site 1. In comparison, regrowth yields for Cave-In-Rock (1.4 Mg ha–1) and Dacotah (0.6 Mg ha–1) were lower than the first harvest yields of 3.6 and 4.1 Mg ha–1, respectively at Site 2, where harvesting was not initiated until 2003.

Biomass Yield—Precipitation
Monthly precipitation amounts are presented in Fig. 1 for 2001 through 2004 and in Fig. 2 for 2003 and 2004. Growing season (April–September) precipitation ranged from 46% of the 30-yr average in 2002 to 101% of the 30-yr average in 2004. During 2000, the establishment year, growing season precipitation was 56% of the 30-yr average. From December 1999 through completion of data collection in October 2004, the only months for which precipitation exceeded the 30-yr average were February and April 2001, April and June 2003, and March, August, and September 2004 (Fig. 1 and 2). The only 2- and 3-mo intervals for which the precipitation exceeded the 30-yr average were April through May 2001 (113%), April through May 2003 (107%), and April through June 2003 (113%). In comparison, April through May totals for 2000, 2002, and 2004 were 53, 26, and 60% of the 30-yr average, respectively. The April through July precipitation fractions of the 30-yr averages were 91% in 2001 and 97% in 2003 compared with 60, 34, and 68% for 2000, 2002, and 2004, respectively.

In 2001, both cultivars produced large quantities of biomass presumably associated with the precipitation spike during April (175% of average) and near average precipitation during July even though August was extremely dry and May through September precipitation was 30% below average (Fig. 1a). Biomass production in 2002 (~2 Mg ha–1) was severely depressed by drought during the entire growing season (precipitation was 46% of average) with large moisture deficiency during mid spring (April–May precipitation was 74% below average) (Fig. 1b). Switchgrass appeared to respond to spikes of precipitation during April and June (April–May precipitation was 107% of average) in 2003, even though the drought persisted through the winter of 2002–2003 (Fig. 1b, c). However, shortage of moisture during July through September 2003 resulted in maximum biomass production being obtained at the late July harvest. Biomass yields in 2004 were lower than in 2003, presumably because of extremely low precipitation during April (5% of average) (Fig. 1d and 2b).

Significant harvest date x cultivar interactions occurred for biomass yield in 2001 and 2004 (Table 3). In both years, July precipitation was near average. However, no precipitation fell during August 2001, whereas greater than 60 mm fell during August 2004. There was no harvest date x cultivar interaction for biomass yield in 2003, in which July through August precipitation was 38.9 mm (36% of average). Thus, it appeared spikes of precipitation during July through August enabled Cave-In-Rock, which reached anthesis in late August, to advance development and increase biomass in the latter part of the growing season. However, precipitation during July through August was too late for Dacotah, which reached anthesis in early July and matured seed in August.

Data collected during the 4-yr period of below-normal precipitation indicated switchgrass biomass production fluctuated widely with variation in annual patterns of precipitation. Cassida et al. (2005) concluded that water availability from April to July was critical for switchgrass biomass production in South Central USA. However, the most critical month differed among locations and genotype groups differed in their response to moisture availability. Similarly, Muir et al. (2001) reported switchgrass biomass yield was positively correlated with precipitation during the growing season in Texas. April and May precipitation accounted for 97% of the variation in forage yields of crested wheatgrass [Agropyron cristatum (L.) Gaertn.] grazed in the spring where average precipitation during the growing season was 274 mm (Currie and Peterson, 1966). Smoliak (1956) reported that May-plus-June precipitation was a predominant factor affecting forage productivity in short-grass prairie in southeastern Alberta, where average precipitation during the growing season was 147 mm.

Smart et al. (2005) described rainfall patterns for the past 95 yr at Cottonwood, SD, which is located about 170 km west of our study site, and concluded that drought, defined as 75% of average annual precipitation, occurred 14 out of 95 yr. During the duration of our study, average annual precipitation was much less than 75% of average in 2000 and 2002, slightly less than 75% of average in 2003 and near average in 2004. Smart et al. (2005) also pointed out that it is generally accepted that the amount of April through June precipitation is highly variable and a particularly strong indicator of the current year's forage production in the northern mixed-grass prairie. During the duration of our study, April through July cumulative precipitation was 60, 34, and 68% for 2000, 2002, and 2004, respectively.

A strong linear relationship occurred between total April through May precipitation and biomass production during the 4 yr of this study (Fig. 3) . Switchgrass produced high biomass (10 Mg ha–1) with 125 mm or more rainfall during April and May even though the remainder of the growing season may have produced substantially less precipitation than normal. Annual maximum biomass yield for Dacotah was highly predictable from precipitation during April through May (Fig. 3). Precipitation during April through May was also a good predictor of biomass production for Cave-In-Rock (Fig. 3). However, since Cave-In-Rock did not reach anthesis until late August, it was able to respond to favorable growing conditions during mid summer (Fig. 1a, d). Our results indicated April through May precipitation was an important factor affecting biomass production of two switchgrass cultivars of differing maturities and biomass yield potentials in central South Dakota. However, difference in maturity between the two cultivars also determined whether or not growth in biomass occurred in response to precipitation during the latter half of the growing season.



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  		Fig. 3. Relationships between maximum annual biomass production of two switchgrass cultivars and April and May precipitation for 2001 through 2004 at Site 1 on the Dakota Lakes Research Farm in central South Dakota. Each point is the mean of four observations.

 
Maximum annual biomass yields ranged from 2.1 to 10.6 Mg ha–1 for Cave-In-Rock and from 2.0 to 9.3 Mg ha–1 for Dacotah during the 4 yr. The highest annual yields were comparable to the 4-yr average of 9.0 Mg ha–1 for 20 switchgrass populations reported by Lemus et al. (2002) in southern Iowa. Annual biomass production patterns of Dacotah, with origin about 250 km north of the study sites, were similar during the 4-yr study. However, biomass production patterns of Cave-In-Rock, with origin in southern Illinois about 1000 km east and 850 km south of the study sites, varied with patterns of precipitation during the middle of the growing season. Superior biomass potential of Cave-In-Rock compared with Dacotah in areas that average 500 mm or more rainfall during the growing season (Madakadze et al., 1998; Casler and Boe, 2003) was not consistently demonstrated under below average precipitation in this semiarid environment.

Stand Density and Developmental Morphology
On the basis of frequency of occupation of frequency grid subunits by switchgrass tillers, stand density of Cave-In-Rock (56.5% of subunits contained at least one tiller) was less than that of Dacotah (71.1%) at Site 1. However, stand densities were similar (70%) for the two cultivars at Site 2. No differences were found among harvest date treatments for stand density at either site. Stand densities of both cultivars and all harvest treatments at both sites exceeded the frequency grid value of 50%. On the basis of their research and that of others, Vogel and Masters (2001) concluded that stands with frequency grid values ≥50% in the Great Plains were fully successful.

In general, 2- and 3-factor interactions involving site, cultivar, and harvest date were highly significant (P < 0.01) for tiller and tiller component DM weights (Table 5) and DM partitioning coefficients. Given Dacotah was already in early anthesis on the first harvest date (8 July), it showed only a slight increase in tiller, stem, and inflorescence component weights between July and August harvests, presumably related to seed development, followed by slight declines from August to September likely associated with seed shatter and deterioration of vegetative organs due to senescence (Fig. 4a, b, c) . This pattern was similar at both sites. The proportion of tillers that were reproductive was about 80% for Dacotah on each harvest date.


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  		Table 5. Mean squares for sources of variation for tiller weight and stem, sheath, blade, and inflorescence components of tillers of two switchgrass cultivars at two locations at the Dakota Lakes Research Farm in central South Dakota.

 


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  		Fig. 4. Individual tiller weight (a) and weight of stem (b) and inflorescence (c) fractions of tillers from two switchgrass cultivars (CIR = Cave-In-Rock, DAC = Dacotah) at three harvest dates during 2004 at two sites on the Dakota Lakes Research Farm in central South Dakota.

 
The large difference between sites for tiller weight (Fig. 4a) for Cave-In-Rock may have been related to more available space per tiller at Site 1, resulting in similar biomass production at the two sites in 2004 (Fig. 1d and 2b). For Cave-In-Rock, patterns of increase in tiller and tiller component weights varied between sites. Tiller (Fig. 4a) and tiller component (Fig. 4b, c) weights were greater at Site 1 than Site 2 on each of the three harvest dates, with the greatest difference on the September harvest (Fig. 1a, b, c). The proportion of reproductive tillers increased from 67 to 89% between the August and September harvests at Site 1, compared with an increase of 54 to 63% at Site 2. The difference between the two sites for tiller and tiller component weights suggested the gross morphology of the stands of Cave-In-Rock, as indicated by reproductive-to-vegetative tiller ratio and tiller and tiller component weights, was more sensitive to environmental variation than Dacotah. The difference in tiller weight at the two sites (Fig. 4a) was likely a reflection of differences in tiller densities, with weight per tiller inversely related to tiller density (Berg et al., 2005; Boe, unpublished data).

As expected, partitioning coefficients for stem revealed increases in stem proportions with increased biomass accumulation for Cave-In-Rock or with disproportionate decreases in leaf and inflorescence fractions compared with stem fractions during senescence for Dacotah (Fig. 5a) . The partitioning coefficient for Dacotah for inflorescence reached a maximum in August but declined with seed shatter during the interval between August and September harvests. The inflorescence component of tiller weight for Cave-In-Rock increased linearly from July to September and comprised about 12% of tiller biomass at the end of the growing season (Fig. 5b).



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  		Fig. 5. Dry matter partitioning coefficients for stem (STPRC, a) and inflorescence (INPRC, b) components of tillers from two switchgrass cultivars (CIR = Cave-In-Rock, DAC = Dacotah) at three harvest dates during 2004 at two sites on the Dakota Lakes Research Farm in central South Dakota.

 

   CONCLUSIONS
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
REFERENCES
 
Switchgrass has potential for bioenergy feedstock production 250 km west of the tallgrass prairie region in temperate steppe in central South Dakota, but biomass yields varied more than fivefold among years. The optimal harvest time for biomass production was mid July to early August for Dacotah. For Cave-In-Rock, which matured later and thus exhibited greater variation in peak standing crop in response to variation in precipitation during July through September, the optimal harvest time ranged from August to September. Biomass production from over-wintered stands harvested near ground level in March 2004 was 85 to 99% of biomass production of stands harvested at a 10-cm stubble height at the end of the growing season in 2003, suggesting stands could be stockpiled over winter for conservation (e.g., snow catch) and wildlife habitat without significant loss in biomass.

A strong linear relationship was found between April through May precipitation and annual maximum biomass production for both cultivars. However, since this study was conducted during a 4-yr period of below normal average precipitation, such a strong relationship may not exist under normal or above normal precipitation patterns.


   NOTES
TOP
 NOTES
ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
This research was supported by the South Dakota Agricultural Experiment Station, the U.S. Department of Energy through contract DE-FC36-02G012028, A000 with Great Plains Institute for Sustainable Development, Minneapolis, MN, and U.S. Department of Energy's Biomass program through contract DE-A105-900R2194 with Oak Ridge National Laboratory (ORNL). ORNL is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. South Dakota State Agric. Expt. Stn. Journal Series No.

Received for publication May 23, 2005.


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




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Journal of Natural Resources
and Life Sciences Education		 Soil Science Society of America Journal
Journal of Plant Registrations Journal of
Environmental Quality		 The Plant Genome