Switchgrass is a perennial, warmseason. Switchgrass is a promising, high-yielding crop for California biofuel

Transcription

1 Reserch Article Switchgrss is promising, high-yielding crop for Cliforni iofuel y Griel M. Pedroso, Christopher De Ben, Roert B. Hutmcher, Steve Orloff, Dn Putnm, John Six, Chris vn Kessel, Steven Wright nd Bruce A. Linquist Ethnol use in Cliforni is expected to rise to 1.62 illion gllons per yer in 2012, more thn 90% of which will e trucked or shipped into the stte. Switchgrss, nonntive grss common in other sttes, hs een identified s possile high-yielding iomss crop for the production of cellulosic ethnol. The productivity of the two min ecotypes of switchgrss, lowlnd nd uplnd, ws evluted under irrigted conditions cross four diverse Cliforni ecozones from Tulelke in the cool north to wrm Imperil Vlley in the south. In the first full yer of production, the lowlnd vrieties yielded up to 17 tons per cre of iomss, roughly doule the iomss yields of Cliforni rice or mize. The yield response to nitrogen fertiliztion ws sttisticlly insignificnt in the first yer of production, except for in the Centrl Vlley plots tht were hrvested twice yer. The iomss yields in our study indicte tht switchgrss is promising iofuel crop for Cliforni. Switchgrss is perennil, wrmseson (C4) grss ntive to North Americ. One of the dominnt species of the North Americn tllgrss pririe, switchgrss (Pnicum virgtum) grows nturlly in remnnt priries nd ntive grss pstures, nd long rodsides throughout the continentl United Sttes, except in Cliforni nd the Pcific Northwest (USDA 2006). Agriculturlly, it hs een used primrily s forge nd for grzing nd groundcover. Recently, however, it hs emerged s one of the most promising cellulosic iofuel crops for ethnol production. Cliforni consumes more ethnol thn ny other U.S. stte. Cliforni Switchgrss is grss ntive to North Americ tht hs een utilized primrily s forge crop nd groundcover. Becuse of its high iomss yields, switchgrss (ove, in El Centro, Imperil County) is considered good cndidte for dedicted energy crops (iofuels). gsoline contins out 6% ethnol y volume (since the sustitution of MTBE [methyl tert-utyl ether] in 2004), resulting in nnul ethnol consumption of nerly 1 illion gllons (3.78 million cuic meters). Of tht, out 80% is mize-sed ethnol trnsported y ril from the Midwest; 12% is sugrcne-sed ethnol shipped from Brzil; nd 8% is ethnol from mize grins produced in-stte (CEC 2010). The proportion of ethnol lended in Cliforni gsoline is expected to increse to 10% y 2012, resulting in ethnol demnd of 1.62 illion gllons (6.12 million cuic meters) per yer if no gsoline consumption chnges occur (CEC 2007). If in-stte production does not increse, Cliforni will need to import more thn 95% of its ethnol y Currently, most of the ethnol used in Cliforni is produced y fermenting the sugr in Brzilin sugrcne nd the strch in Midwestern grins (Mcedo et l. 2008). Technology is eing developed to produce ethnol from cellulose, the most undnt structurl crohydrte in plnts; the cellulose content of switchgrss, for exmple, is out 40% (Isci et l. 2008). Cellulose cnnot e directly fermented to produce ethnol; it needs to e roken down into more simple sugrs. There re different processes of lingo-cellulose conversion into ethnol, such s strong cid hydrolysis followed y fermenttion (SHF) nd simultneous scchrifiction nd fermenttion (SSF). Significnt chllenges remin nd need to e overcome efore the technology cn e commercilly used (CEC 2010). Compred to mize grin sed ethnol, which is the only ethnol currently produced in Cliforni, cellulosic ethnol hs higher productivity nd net energy vlue, nd lower net greenhouse-gs emissions (Adler et l. 2007). Cellulosic ethnol cn lso e produced from nonfood crops, wste nd forest products, diminishing the possile infltionry effects on food prices if lnd used to produce food were diverted to ethnol crops. Potentil of switchgrss There re mny possile crop sources for cellulosic ethnol production in Cliforni, including griculturl nd urn wstes, rice nd whet strw, wood Originlly pulished online only. lndingpge.cfm?rticle=c.e.v065n03p168&fulltext=yes DOI: /c.E.v065n03p CALIFORNIA AGRICULTURE VOLUME 65, NUMBER 3

2 chips from tree pruning nd dedicted energy crops. Crops with high iomss yields, such s switchgrss, elephntgrss (Pennisetum purpureum) nd miscnthus (Miscnthus gignteus) re good cndidtes for dedicted energy crops. The dvntges of switchgrss re its high yield potentil, excellent soil conservtion ttriutes nd good comptiility with conventionl frming prctices (McLughlin et l. 1999). Like most field crops, for exmple, switchgrss is estlished from seeds, wheres elephntgrss nd miscnthus re estlished y trnsplnting illets nd rhizomes. Also, switchgrss is no longer on the Cliforni Deprtment of Food nd Agriculture list of noxious weeds (CDFA 2010). Under rin-fed conditions of the Midwest nd southern United Sttes, switchgrss iomss yields hve rnged from 2.5 to 11 tons per cre (5.5 to 25 metric tons per hectre) (Fike et l. 2006; Heton et l. 2004; McLughlin et l. 1999; Schmer et l. 2008). The responses of switchgrss crops to nitrogen fertilizer hve een vrile nd conflicting. Some studies report limited or no yield response (Christin et l. 2001; Thomson et l. 2004), while others hve found significnt yield increses due to nitrogen fertiliztion (Lemus et l. 2008; Muir et l. 2001; Stroup et l. 2003). Nitrogen response is n importnt re of study ecuse nitrogen fertilizer is the min energy input nd the min source of greenhouse-gs emissions during switchgrss cultivtion (Adler et l. 2007; Schmer et l. 2008). Understnding how switchgrss responds to nitrogen will help reserchers develop energy-efficient nd environmentlly enign production systems for iomss energy crops. Becuse it cn e used oth s forge nd s iofuel crop, switchgrss my e well suited to Cliforni, stte with lrge livestock industry nd higher ethnol consumption thn ny other. However, there is little informtion out switchgrss production in Cliforni, nor in other irrigted regions. Irrigted Western regions re significntly different in climte nd cropping ptterns thn the Midwest or southern United Sttes, where most switchgrss reserch hs een crried out. Cliforni s Mediterrnen climte suggests greter yield potentil ut lso higher wter nd nitrogen requirements. Switchgrss cn e seprted into two ecotype groups: lowlnd nd uplnd. Lowlnd ecotypes re found in floodplins nd re tller (round 6 feet), corser with more unch-type growth hit nd my e more rpid growing thn uplnd ecotypes. In contrst, uplnd ecotypes re found in drier uplnd sites nd re finer stemmed, rod sed nd often semi-decument (Porter 1996). Usully, lowlnd ecotypes flower nd mture lter thn uplnd ecotypes. Switchgrss is not ntive to Cliforni, nd no informtion hs een ville out the dptility of lowlnd nd uplnd ecotypes in Cliforni. In ddition, Cliforni hs different ecozones res defined y distinct climte ptterns, lndscpes nd plnt species. Therefore, it is possile tht one ecotype is etter dpted to one ecozone thn nother. The ojectives of our reserch were to identify (1) how well the lowlnd nd uplnd switchgrss ecotypes would dpt to the mjor ecozones in Cliforni, (2) the iomss yield potentil for ech ecozone nd (3) the response of uplnd switchgrss to vrious nitrogen fertilizer rtes. Switchgrss ecotype trils To identify the suitility of lowlnd nd uplnd switchgrss ecotypes for Cliforni, nd to test the dpttion of the crop itself, we estlished trils in July 2007 t four Cliforni loctions with different climte chrcteristics nd soil ttriutes (tles 1 nd 2). Tulelke (Siskiyou TABLE 1. Climtic chrcteristics of Cliforni ecozones used to evlute switchgrss production, Chrcteristics Tulelke Dvis Five Points El Centro Altitude (feet) 4, Ltitude ( N) Annul verge mx./ min. temp. ( F) 62/31 74/46 77/48 89/56 Annul precipittion (inches) Frost-free dys Source: ClClim County), the northernmost site on the order with Oregon, is typicl of the intermountin regions of Cliforni nd other prts of the Pcific Northwest. Dvis (Yolo County) is situted in the Scrmento Vlley, nd Five Points (Fresno County) is in the Sn Joquin Vlley. El Centro (Imperil County) ws the southernmost site nd represents low desert griculturl region typicl of the Sonorn deserts of Cliforni, Mexico nd Arizon. In ech loction, we evluted five lowlnd nd five uplnd vrieties. However, the lowlnd vrieties slightly vried cross sites, so we tested six lowlnd vrieties totl, ut only five per site. Lowlnd ecotypes included two relesed vrieties (Almo nd Knlow) nd four experimentl vrieties. The uplnd ecotypes included four relesed vrieties (Trillzer, Cve in Rock, Blckwell nd Sunurst) nd one experimentl vriety. The trils were completely rndomized lock design with six replictions. At ll loctions, the seeded ws prepred to provide firm nd fine soil surfce. Switchgrss ws drill seeded in July 2007 t rte of 5 pounds per cre (5.6 kilogrms per hectre) of pure live seeds, t depth of TABLE 2. Soil properties of Cliforni ecozones used to evlute switchgrss production, Soil ttriutes* Tulelke Dvis Five Points El Centro Cly (%) Silt (%) Snd (%) ph CEC (meq/100 grms) Olsen-P (phosphorus) (ppm) Potssium (K) (ppm) Orgnic cron (%) Nitrtenitrogen (NO 3 -N) (ppm) Totl nitrogen (%) * Soil smples were tken efore plnting t verge depth of 4 inches (10 centimeters). CEC = ction exchnge cpcity. JULY SEPTEMBER

3 In the first full production yer, plots of lowlnd switchgrss in El Centro yielded 17.6 tons per cre. The crop s productivity tends to increse through the third nd fourth yers inch (0.6 centimeter) nd with 10 inches (25.4 centimeters) etween rows. Plot size ws 10 y 15 feet (3 y 5 meters). The plots were sprinkler irrigted fter seeding to ensure good germintion. No fertilizer ws pplied t plnting, ut t the three-lef stge nitrogen (N) ws pplied in the form of mmonium sulfte t rte of 50 pounds per cre (56 kilogrms per hectre). All fields were hrvested in Novemer 2007, fter which the crop entered winter dormncy (tle 3). The lst hrvests t Tulelke, Dvis nd Five Points were driven in prt y the onset of the winter rins or snow; lter hrvests would hve een imprcticl due to wet soils. Winter dormncy ws oserved t ll sites, including El Centro. El Centro ws the first site to rek dormncy in erly Ferury, followed y Five Points in lte Ferury, Dvis in erly Mrch nd Tulelke in erly My. In Tulelke, only one lowlnd ecotype vriety, Knlow, survived the winter. Lowlnd ecotypes developed in the southern United Sttes where winters re mild, lthough frost is not uncommon. Tulelke hs verge minimum tempertures of 22 F ( 5.5 C) during winter nd receives 21 inches (53.3 centimeters) of snow nnully (ClClim 2009). Therefore, lowlnd ecotype vrieties were generlly expected to e unsuitle t this loction, which ws confirmed y the winter mortlity of ll except one. In spring 2008, nitrogen, phosphorus (P) nd potssium (K) fertilizers were pplied. Nitrogen ws pplied in the form of mmonium sulfte t rte of 100 pounds per cre (112 kilogrms per hectre). Phosphorus (P 2 O 5 ) nd potssium (K 2 O) were ech pplied t rte of 50 pounds per cre (56 kilogrms per hectre). During the 2008 growing seson, the numer of switchgrss hrvests vried mong sites due to climtic differences. The plots were hrvested once t Tulelke (Octoer), twice t Dvis nd Five Points (July nd Octoer/Novemer) nd three times t El Centro (July, Septemer nd Novemer). After the first nd second hrvests, 100 pounds nitrogen per cre (112 kilogrms per hectre) ws pplied in the form of mmonium sulfte. Flowering differences In 2007, we recorded flowering differences mong ecotypes nd loctions t hrvest, ecuse erly flowering hs een ssocited with lower yields (Hopkins et l. 1995). The uplnd vrieties exhiited higher flowering percentges (percentge of flowering tillers) thn the lowlnd vrieties t ll loctions, nd flowering percentges were higher in the southern loctions due to the longer seson nd wrmer tempertures. In Tulelke, 5% to 10% of tillers on verge were flowering in the uplnd ecotypes cross ll vrieties, nd no flowering ws oserved in the lowlnd ecotypes. At Dvis nd Five Points, there ws 15% to 25% flowering for uplnd nd 0% to 10% for lowlnd ecotypes. The highest flowering percentges were found t El Centro, rnging from 50% to 75% for uplnd nd 10% to 40% for lowlnd ecotypes. In 2008, the uplnd ecotypes once gin exhiited higher flowering percentges t the first hrvest thn the lowlnd ecotypes t ll loctions: verge flowering percentges oserved in lowlnd nd uplnd ecotypes respectively were 2% nd 48% t Dvis, 4% nd 66% t Five Points, nd 6% nd 70% t El Centro. At Tulelke, the single-hrvest loction, the only surviving lowlnd vriety exhiited 30% flowering, while ll the uplnd TABLE 3. Mngement opertions in 2007 nd 2008, nd switchgrss dormncy rek in 2008 Yer Mngement Tulelke Dvis Five Points El Centro 2007 Plnting dte 7/24 7/5 7/17 7/19 N fertiliztion 3-lef stge 3-lef stge 3-lef stge 3-lef stge Hrvest 11/8 11/19 11/13 11/ Dormncy rek Erly My Erly Mrch Lte Ferury Erly Ferury N, P nd K fertiliztion* 5/5 4/9 7/21 Hrvest 10/1 7/18 10/30 * Nitrogen, phosphorus nd potssium. 3/25 7/25 7/23 11/19 3/27 7/14 9/8 7/11 9/5 11/6 170 CALIFORNIA AGRICULTURE VOLUME 65, NUMBER 3

4 Biomss yield (tons/cre) (A) Lowlnd Uplnd Lowlnd Uplnd Lowlnd Uplnd Lowlnd Uplnd Biomss yield (tons/cre) (B) Hrvest Third Second First Lowlnd Uplnd Lowlnd Uplnd Lowlnd Uplnd Lowlnd Uplnd Tulelke Dvis Five Points El Centro Tulelke Dvis Five Points El Centro Fig. 1. Switchgrss yields during (A) estlishment yer (2007) nd (B) first full production yer (2008) y ecotype nd ecozone. Ech r is men of five vrieties nd six replictions, except for the lowlnd ecotype t Tulelke, which represents one surviving vriety. All loctions were plnted in July The sme letter ove n ecotype indictes tht yields re not sttisticlly different (Tukey t P 0.05) within ech loction. ecotypes showed 100% flowering. Only smll differences in flowering mong ecotypes were seen t the second hrvest. Dvis showed 47% nd 35% flowering, Five Points 77% nd 71%, nd El Centro 29% nd 8% for lowlnd nd uplnd ecotypes, respectively. In our trils, erly flowering ws lso correlted with lower yields, in ccordnce with other studies (Hopkins et l. 1995). Biomss yields In the 2007 estlishment yer, the lowlnd ecotypes yielded significntly more iomss thn uplnd ecotypes t ll loctions, ut these differences were less evident t Tulelke (fig. 1A). The highest iomss production ws chieved y lowlnd ecotypes in Dvis t 5.2 tons per cre (11.6 metric tons per hectre). El Centro hd the lowest yield, with uplnd ecotypes producing only 0.8 ton per cre (1.7 metric tons per hectre). Biomss yields of switchgrss in the estlishment yer re expected to e lower thn in susequent yers. Our estlishment yields were similr to those reported in other U.S. studies (Muir et l. 2001) nd in Mediterrnen climtes of Europe (Alexopoulou et l. 2008). We plnted the switchgrss in July, nd it is likely tht n erlier plnting dte would hve resulted in higher yields. Vssey et l. (1985) compred erly, midnd lte-spring plnting dtes nd found tht the highest yields were chieved with the erliest plnting dtes. In 2008, the first full production yer, yields were generlly higher thn in 2007 (fig. 1B). The lowlnd ecotype yields were higher thn uplnd ecotypes t ll loctions except for Tulelke, where only one lowlnd ecotype survived the first winter. Yields of lowlnd ecotypes verged 8.7, 16.7 nd 17.6 tons per cre (19.4, 37.4 nd 39.4 metric tons per hectre) in Dvis, Five Points nd El Centro, respectively. The uplnd vrieties were not well suited to the wrmer loctions, ut in Tulelke ll the uplnd vrieties produced similr yields, which were higher thn yields of the single surviving lowlnd vriety. At loctions with multiple hrvests, the first hrvest produced significntly more iomss thn susequent hrvests for ll vrieties. Of the totl iomss, 73%, 67% nd 57% ws otined in the first hrvest t Dvis, Five Points nd El Centro, respectively (fig. 1B). At El Centro, the third hrvest produced only 12% of the totl nnul iomss yield. The 2008 yields chieved in our trils were sustntilly higher thn those reported y Heton et l. (2004) from 21 studies of mture switchgrss stnds round the United Sttes (3 yers or older). In their studies, yields verged 4.6 tons per cre (10.3 metric tons per hectre) nd rnged from pproximtely 0.5 to 9.8 tons per cre (1.1 to 22 metric tons per hectre). Furthermore, we expect yields in our Cliforni plntings to increse in the following 1 to 2 yers. Productivity tends to increse until the switchgrss stnd reches mturity nd full yield potentil t 3 or 4 yers old (Shrm et l. 2003). Nitrogen trils Trils were conducted in the sme four loctions in 2008 to evlute the yield response of the uplnd ecotype vriety Trillzer to different levels of nitrogen fertilizer. Nitrogen fertilizer ws pplied t ech loction t nnul rtes of 0, 70, 140, 210 nd 280 pounds per cre (0, 75, 150, 225 nd 300 kilogrms per hectre) in Dvis, Five Points nd El Centro. In Tulelke, the nitrogen rtes were hlf tht of the other loctions (0, 35, 70, 105 nd 140 pounds per cre), due to the single hrvest nd shorter growing seson. Five Points nd El Centro received ll nitrogen fertilizer in Mrch nd April, in two pplictions spced 4 weeks prt. In Dvis, the first nitrogen fertilizer ppliction ws in April nd the second in July, fter the first hrvest. Tulelke received nitrogen fertilizer in one single ppliction in My. The plots were djcent to plots of the ecotype trils nd were estlished t the sme time in 2007 nd hrvested t the sme time. Overll yields were lowest t Tulelke nd El Centro, verging only 6.5 nd 7 tons per cre (14.5 nd 15.6 metric tons per hectre), respectively (fig. 2, pge 172). Trillzer is n uplnd vriety, nd in the ecotype vriety trils it usully hd lower yields thn the lowlnd vrieties (fig. 1B). Totl nnul iomss yields showed no response to nitrogen tretment t ny loction. This my e due to switchgrss s deep root system, reportedly up to 10 feet (3 meters), which is le to explore lrge mounts of soil for nitrogen (Prrish nd Fike 2005). While there ws no response to nitrogen fertilizer in the first hrvest yields t ny loction, the second hrvest t oth Dvis nd Five Points showed JULY SEPTEMBER

5 With the high yield potentil of switchgrss in Cliforni nd consequent high nitrogen removl, Cliforni growers would most likely need to pply nitrogen fertilizer (nd other nutrients) to sustin yields. Nitrogen fertilizer will likely e needed for switchgrss crops to chieve their full yield potentil. Aove, switchgrss is tested in Dvis in June, out 1 month efore the first hrvest. significnt yield response when the two highest nitrogen tretments were compred to the plots tht received no nitrogen. This suggests tht over time switchgrss depleted the ntive soil s nitrogen reserves nd required fertilizer nitrogen to chieve its yield potentil. Muir et l. (2001) reported just such sitution: switchgrss depleted ntive Biomss yield (tons/cre) Hrvest Third Second First soil nitrogen reserves when receiving no nitrogen fertilizer, nd over time yield differences etween unfertilized nd nitrogen-fertilized switchgrss incresed. Christin et l. (2001) found no yield response to nitrogen fertilizer during 5-yer study, ut tht ws minly ecuse soil supply nd deposition were dequte to support the low verge yields of 4 tons per cre (8.9 metric tons per hectre), nd the reserchers ffirmed tht long-term mngement strtegies would e necessry to void deficits in soil nitrogen. With the high yield potentil of switchgrss in Cliforni nd consequent high nitrogen removl, Cliforni growers would most likely need to pply nitrogen fertilizer (nd other nutrients) to sustin yields. Further reserch is still needed to improve nitrogen mngement, ut it is likely tht switchgrss vriety with higher yielding potentil thn Trillzer would show greter response to nitrogen fertilizer. We found tht the plnts were green t the first hrvest, with high nitrogen content, resulting in high rtes of nitrogen (nd possily other nutrients) removl from the soil, which in production Tulelke Dvis Five Points Nitrogen fertilizer (l. N/cre) El Centro Fig. 2. Response of switchgrss vriety Trillzer (uplnd ecotype) to nitrogen fertiliztion in Letters ove yield rs refer to totl iomss for the full yer, nd letters inside rs refer to tht hrvest. The sme letter indictes tht yields were not sttisticlly significnt (Tukey t P 0.05) within ech loction nd hrvest. No differences were seen in Tulelke or El Centro for ech hrvest or totl iomss. fields would need to e replenished. Likewise, multiple-hrvest systems re likely to require more fertilizers thn single-hrvest systems. In multiplehrvest situtions, the crop s nutrient content is high t the first hrvest, generlly in midsummer. The lst hrvest (or the one hrvest of single-hrvest systems) tkes plce in the fll fter the plnts hve senesced. During senescence, most nutrients, including nitrogen, likely retrnslocte to the roots, ecoming ville for next yer s growth. Retrnsloction to the roots cn increse nitrogen conservtion within the plnt-soil system nd my reduce nitrogen fertilizer requirements in susequent yers. Further reserch is necessry to quntify nitrogen removl nd develop nitrogen mngement strtegies for single- nd multiple-hrvest crops. Promising iofuel crop Our results suggest tht switchgrss hs high yield potentil in Cliforni. Although its productivity in the stte s cooler mountin regions is limited, productivity is considered good in the Sn Joquin nd Imperil vlleys. Switchgrss hd moderte yields in the estlishment yer nd up to 17 tons per cre (38 metric tons per hectre) in the second yer. By comprison, Cliforni mize nd rice produce pproximtely 9 tons per cre (20.1 metric tons per hectre) of totl iomss (grin plus stover), nd lflf produces 7 to 8 tons per cre (15.6 to 18 metric tons per hectre). Therefore, the switchgrss yields reported here re promising oth for forge nd use s iofuel crop. Our results show tht switchgrss requires little or no nitrogen in the estlishment yer, suggesting tht it cn efficiently use the ntive soil nitrogen pool; ut switchgrss my require nitrogen fertilizers in multiple-hrvest systems in the second nd susequent yers in order to sustin high yields. In ddition to the 172 CALIFORNIA AGRICULTURE VOLUME 65, NUMBER 3

6 effect of multiple hrvests on nitrogen removl, the hrvesting nd trnsporttion costs (mchinery, fuel nd lor) of multiple hrvests should e considered when evluting the production nd economic fesiility of switchgrss s iofuel crop. Wter use lso elicits concern in Cliforni. Switchgrss is C4 plnt, nd it is expected to show high rtes of trnspirtion efficiency due to its more efficient photosynthesis pthwy. Although not determined in these trils, we re currently reserching wter use in switchgrss production. Productivity is dependent on ecotype vrietl selection nd proper fertility mngement. Uplnd vrieties were est suited for Tulelke nd the cooler mountin regions; most lowlnd vrieties did not survive the first winter. For ll other loctions, where winter survivl ws not concern, the lowlnd vrieties were etter While productivity in the cooler regions of Cliforni ws limited, switchgrss did well in the wrm Sn Joquin nd Imperil vlleys. Averge iomss yields were nerly doule tht of mize, rice nd lflf. Aove, Frncisco Mciel shows the height of switchgrss t the El Centro field tril. dpted nd chieved higher yields thn the uplnd vrieties. G.M. Pedroso is Ph.D. Student, Deprtment of Plnt Sciences, UC Dvis; C. De Ben is Reserch Associte, Deprtment of Plnt Sciences, UC Dvis; R.B. Hutmcher is Director, West Side Reserch nd Extension Center, UC Dvis; S. Orloff is Coopertive Extension Advisor, ANR North Cost nd Mountin Region; D. Putnm is Extension Specilist in Crop Ecology, UC Dvis; J. Six is Professor, Deprtment of Plnt Sciences, UC Dvis; C. vn Kessel is Professor, Deprtment of Plnt Sciences, UC Dvis; S. Wright is Coopertive Extension Advisor, ANR Centrl Vlley Region; nd B.A. Linquist is Professionl Resercher, Deprtment of Plnt Sciences, UC Dvis. The uthors thnk Chevron Technology Ventures nd Ceres Inc. for funding nd provision of seeds. We lso thnk stff of the Intermountin, West Side nd Desert reserch nd extension centers, whose ssistnce with field nd lortory work ws essentil: Crig Ginnini, Ed Scott, Jmes Jckson, Fred Stewrt, Don Kiry, Frncisco Mciel, Mri Crolin Andre, Filipe Sd, Jose Crlos Gv Jr., Cristino Jorge, Leonrdo Bordin, Joo Schmidt Jr. nd Dniel Pereir. References Adler PR, Del Grosso SJ, Prton WJ Life-cycle ssessment of net greenhouse-gs flux for ioenergy cropping systems. Ecol Applic 17: Alexopoulou E, Shrm N, Pptheohri Y, et l Biomss yields for uplnd nd lowlnd switchgrss vrieties grown in the Mediterrnen region. Biomss Bioenergy 32: [ClClim] Cliforni Climte Dt Archive www. clclim.dri.edu/ (ccessed My 29, 2009). [CDFA] Cliforni Deprtment of Food nd Agriculture Encycloweedi, Noxious Weed List Section 4500 Food nd Agriculture (pdf ). encycloweedi/encycloweedi_hp.htm (ccessed My 12, 2010). [CEC] Cliforni Energy Commission Trnsporttion Energy Forecsts for the 2007 Integrted Energy Policy Report. CEC /CEC SF.PDF (ccessed Jn. 8, 2010). CEC Sttistics nd Dt on Ethnol nd E85 s Trnsporttion Fuels. trnsporttion/ethnol.html (ccessed Jn. 8, 2010). Christin DG, Riche AB, Ytes NE The yield nd composition of switchgrss nd costl pnic grss grown s iofuel in southern Englnd. Biores Technol 83: Fike JH, Prrish DJ, Wolf DD, et l Long-term yield potentil for switchgrss for iofuel systems. Biomss Bioenergy 30: Heton E, Voigt T, Long SP A quntittive review compring the yields of two cndidte C4 perennil iomss crops in reltion to N, temperture nd wter. Biomss Bioenergy 27: Hopkins AA, Vogel KP, Moore KJ, et l Genotypic vriility nd genotype X environment interctions mong switchgrss ccessions from the Midwestern USA. Crop Sci 35: Isci A, Himmelsch JN, Pommeto AL III, et l Aqueous mmoni soking of switchgrss followed y simultneous scchrifiction nd fermenttion. Appl Biochem Biotechnol 144: Lemus R, Brummer EC, Burrs CL, et l Effects of N fertiliztion on iomss yield nd qulity in lrge fields of estlished switchgrss in southern Iow, USA. Biomss Bioenergy 32: Mcedo IC, Ser JE, Silv JE Greenhouse gses emissions in the production nd use of ethnol from sugrcne in Brzil: The 2005/2006 verges nd prediction for Biomss Bioenergy 32: McLughlin S, Bouton J, Brnsy D, et l Developing switchgrss s ioenergy crop. In: Jnick J (ed.). Perspectives on New Crops nd Uses. Alexndri, VA: ASHS Pr. Muir JP, Snderson MA, Ocumpugh WR, et l Biomss productions of Almo switchgrss vriety in response to N, phosphorus nd row spcing. Agron J 93: Prrish DJ, Fike JH The iology nd gronomy of switchgrss for iofuels. Criticl Rev Plnt Sci 24: Porter CL An nlysis of vrition etween uplnd nd lowlnd switchgrss, Pnicum virgtum L., in centrl Oklhom. Ecology 47: Schmer MR, Vogel KP, Mitchell RB, et l Net energy of cellulosic ethnol from switchgrss. Proc Nt Acd Sci 105: Shrm N, Piscioneri I, Pigntelli V An evlution of iomss yield stility of switchgrss (Pnicum virgtum L.) cultivrs. Energy Conver Mng 44: Stroup JA, Snderson MA, Muir JP, et l Comprison of growth nd performnce in uplnd nd lowlnd switchgrss types to wter nd N stress. Biores Technol 86: Thomson WE, Run WR, Johnson GV, et l Switchgrss response to hrvest frequency nd time nd rte of pplied N. J Plnt Nutri 27: [USDA] U.S. Deprtment of Agriculture Plnt Mteril Progrm. Plnt Fct Sheet, Pnicum virgtum (switchgrss). Nturl Resources Conservtion Service. Wshington, DC. fs_pvi2.pdf. Vssey TL, George JR, Mullen RE Erly-spring, midspring nd lte-spring estlishment of switchgrss t severl seeding rtes. Agron J 77: JULY SEPTEMBER