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Energy & Fuels 2009, 23, 984–988
Mineral Accumulation by Perennial Grasses in a High-Rainfall Environment† G. M. Banowetz,*,‡ S. M. Griffith,‡ J. J. Steiner,§ and H. M. El-Nashaar‡ United States Department of Agriculture, Agriculture Research SerVice, National Forage Seed Production Research Center, 3450 SW Campus Way, CorVallis, Oregon 97331, and United States Department of Agriculture, Agriculture Research SerVice, National Program Staff, BeltsVille, Maryland 20705 ReceiVed June 20, 2008. ReVised Manuscript ReceiVed NoVember 12, 2008
Mineral content affects the suitability of biomass for thermochemical conversion to bioenergy and represents macro- and micronutrients whose loss from the production system can impact subsequent regrowth and ecosystem services provided by perennial grasses. Genotypic differences in mineral content among cool-season grasses grown for seed are not well documented, and, consequently, the potential for genetic improvement of this trait is not known. This study compared the concentrations of carbon, nitrogen, potassium, phosphorus, chlorine, silicon, aluminum, boron, calcium, cobalt, iron, magnesium, manganese, sulfur, and zinc in leaves and stems from perennial ryegrass (Lolium perenne L.), orchardgrass (Dactylis glomerata), tall fescue (Schedonorus phoenix (Scop.) Holub), and Kentucky bluegrass (Poa pratensis L.) grown in the high-rainfall area of western Oregon. The concentration of C was similar in all grasses and in leaves and stems, but orchardgrass contained the greatest quantities of N, P, and K. The concentration of N was greater in leaf tissue, and similar among these grasses. There were differences in Cl, K, P, and Ca concentrations among these species and between leaf and stem tissues. Genotypic differences in the concentration of some of the minerals occurred among three varieties of tall fescue and among varieties of perennial ryegrass grown at two locations. Amounts of N, P, and K removed by harvest of 2.4 Mg ha -1 of straw biomass of two perennial ryegrasses would range from 12 to 17, 3.4 to 3.8, and 40 to 47 kg ha-1. Location had significant impact on mineral content, although plant mineral concentrations were not strictly correlated with soil composition.
1. Introduction Perennial grasses have been proposed as sources of feedstock for bioenergy production because they offer environmental and economic improvements relative to currently utilized annual food crops,1,2 they sequester carbon in agricultural soils,3 and their production provides large net energy yield.4 The U.S. Department of Energy has selected switchgrass (Panicum Virgatum L.) as a model bioenergy crop because it is widely adapted to most regions of the U.S.,5 performs well under marginal production conditions,6 and produces large amounts of biomass with relatively small input.4 Grasslands in general also provide valuable ecosystem services.7 * To whom correspondence should be addressed. Telephone: (541) 7384125. Fax: (541) 738-4160. E-mail:
[email protected]. ‡ National Forage Seed Production Research Center. § National Program Staff. † The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the United States Department of Agriculture or the Agricultural Research Service of any product or service to the exclusion of others that may be suitable. (1) Tilman, D.; Hill, J.; Lehman, C. Science 2007, 314, 1598–1600. (2) Adler, P. R.; Del Grosso, S. J.; Parton, W. J. Ecol. Appl. 2007, 17, 675–691. (3) Purakayastha, T. J.; Huggins, D. R.; Smith, J. L. Soil Sci. Soc. Am. J. 2008, 72, 534–540. (4) Schmer, M. R.; Vogel, K. P.; Mitchell, R. B.; Perrin, R. K. Proc. Natl. Acad. Sci. U.S.A. 2008, 105, 464–469. (5) Parrish, D. J.; Fike, J. H. Crit. ReV. Plant Sci. 2005, 24, 423–459. (6) Hill, J.; Nelson, E.; Tilman, D.; Polasky, S.; Tiffany, D. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 11206–11210. (7) Paine, L. K.; Peterson, T. L.; Undersander, D. J.; Rineer, K. C.; Bartlelt, G. A.; Temple, S. A.; Sample, D. W.; Klemme, R. M. Biomass Bioenergy 1996, 10, 231–242.
10.1021/ef800488j
Perennial grass crops grown for seed production offer many of these same advantages, but the primary economic return from the crop is provided by seed sales.8 As a consequence, utilization of residues from these seed-producing systems represents a potential value-added enterprise that could contribute to renewable energy production9 and enhance opportunities in rural communities. The Pacific Northwest produces much of the world’s supply of cool-season grass seed,10 and most of that production occurs in the humid temperate marine environment of the Willamette Valley of western Oregon where seedproducing operations produce 3 to 5 Mg ha-1 of straw as a coproduct.11 Historically, the straw remaining after seed harvest was burned due to a lack of local markets and the high cost of transporting straw to distant markets. Regional legislation reduced or banned the use of field burning due to citizen concerns about air quality and safety.12,13 As a result of this legislation, significant quantities of straw are available for alternative uses. These straws as well as clippings from (8) Ehlke, N. J.; Undersander, D. J. AlternatiVe Field Crops Manual; University of Wisconsin-Extension: Cooperative Extension University of Minnesota, Center for Alternative Plant & Animal Products, Minnesota Extension Service; 1990; http://www.hort.purdue.edu/NEWCROP/AFCM/ grassseed.html, verified April 2008. (9) Lal, R. EnViron. Intl. 2005, 31, 575–584. (10) Oregon Department of Agriculture. Oregon Agriculture: Facts and Figures. 2007.http://www.nass.usda.gov/Statistics_by_State/Oregon/ Publications/facts_and_figures/ facts_and_figures.pdf, verified Dec 2007. (11) Steiner, J. J.; Griffith, S. M.; Mueller-Warrant, G. W.; Whittaker, G. W.; Banowetz, G. M.; Elliott, L. F. Agron. J. 2006, 98, 177–186. (12) Oregon Department of Agriculture. 2005. http://egov.oregon.gov/ ODA/NRD/smokehistory.shtml, verified Dec 2007. (13) Hinnman, H. R.; Schreiber, A. Farm Business Management Rep.; Washington State Univ.:Pullman, 2001, EB1922E.
This article not subject to U.S. Copyright. Published 2009 by the American Chemical Society Published on Web 12/24/2008
Mineral Accumulation by Perennial Grasses
residential and municipal turfs represent an abundant and potentially sustainable feedstock from which biopower, liquid fuels, and other bioproducts could be produced. Approximately 2.24 Mt of grass straw are produced in excess of that required for conservation purposes in the Pacific Northwest, much of that within the high-rainfall area of western Oregon.14 Removal of crop residue from the agroecosystem represents a potential reduction in soil quality and fertility and a loss of soil carbon and other mineral nutrients that need to be replaced with purchased inputs.15 Cycling of carbon and other nutrients within grassland agroecosystems is impacted by rainfall and agronomic practices,16 and, consequently, residue requirements are closely related to local weather conditions. Mineral constituents of crop residues also impact their suitability as feedstock for thermochemical conversion technologies17,18 and affect tar formation and the sulfur and ammonia content of syngas produced during gasification.19 Thermochemical approaches like gasification offer the potential to utilize these feedstocks in scalable distributed systems.20 Gasification of straw requires temperatures in excess of 750 °C to produce highquality syngas, a mixture of carbon monoxide and hydrogen gases suitable for catalytic conversion to liquid fuels or for the production of electricity by powering internal combustion engines or turbines.21 Syngas quality and yield depends greatly on the temperature at which the gasifier is operated. At higher operational temperatures where carbon conversion efficiency is high, calcium, chloride, potassium, silica, and other alkalis present in crop residue feedstocks vaporize and react with other mineral components in straw to form a sticky glasslike substance referred to as slag.22 Slag formation and corrosive alkalis reduce the lifespan and utility of the gasifier hardware and diminish the economic feasibility of converting straw to energy. Differences in the accumulation of silica by selected native grasses have been documented,23 but little is known about mineral accumulation by cultivated grasses produced in the high-rainfall area of western Oregon. The objective of this research was to evaluate genotypic variability in the content of minerals that impact the suitability of straws from grasses produced for seed in the high-rainfall area of western Oregon for thermochemical conversion processes and to quantify micro- and macronutrient loss associated with straw harvest in this high-rainfall region. The mineral content of grasses grown for seed in the low-rainfall region of the Pacific Northwest will be described in a separate report. The mineral concentrations in straw from four species of grasses (14) Banowetz, G. M.; Boateng, A.; Steiner, J. J.; Sethi, V.; El-Nashaar, H. M. Biomass Bioenergy 2008, 32, 629–634. (15) Wilhelm, W. W.; Johnson, J. M. F.; Karlen, D. L.; Lightle, D. T. Agron. J. 2007, 99, 1665–1667. (16) Knapp, A. K.; Fay, P. A.; Blair, J. M.; Collins, S. L.; Smith, M. D.; Carlisle, J. D.; Harper, C. W.; Danner, B. T.; Lett, M. S.; McCarron, J. K. Science 2002, 298, 2202–2205. (17) Miles, T. R.; Miles, T. R., Jr.; Baxter, L. L.; Bryers, R. W.; Jenkins, B. M.; Oden, L. L. Biomass Bioenergy 1996, 10, 125–138. (18) Thompson, D. N.; Shaw, P. G.; Lacey, J. A. Appl. Biochem. Biotechnol. 2003, 105-108, 205–218. (19) Elliott, D. C.; Baker, E. G. Biomass 1986, 9, 195–203. (20) Boateng, A. A.; Banowetz, G. M.; Steiner, J. J.; Barton, T. F.; Taylor, D. G.; Hicks, K. B.; El-Nashaar, H.; Sethi, V. K. Biomass Bioenergy 2007, 31, 153–161. (21) Boateng, A. A.; Hicks, K. B.; Vogel, K. P. J. Anal. Appl. Pyrolysis 2006, 75, 55–64. (22) Jenkins, B. M.; Baxter, L. L., Jr.; Miles, T. R. Fuel Process. Technol. 1998, 54, 17–46. (23) Shewmaker, G. E.; Mayland, H. F.; Rosenau, R. C.; Asay, K. H. J. Range Manage. 1989, 42, 122–127.
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were characterized at one location along with that of three grasses grown at two different locations within the Willamette Valley. 2. Experimental Section 2.1. Straw Collection. Above-ground plant biomass of tall fescue (Schedonorus phoenix (Scop.) Holub), experimental line TFA4, perennial ryegrass (Lolium perenne L.), cv ‘Manhattan’, Kentucky bluegrass (Poa pratensis L.), and orchardgrass (Dactylis glomerata L.) was collected from the Oregon State University Hyslop Experimental farm located in north Benton County (44° 38′ 05.91” N, 123°12′ 09.36” W; 69 m elevation). The straw biomass from these four species was utilized in a study to quantify the partitioning of minerals in plant tissues. The soil at the site was a Woodburn silt loam (fine-silty, mixed, superactive, mesic Aquultic Argixerolls). Above-ground biomass of selected varieties of perennial ryegrass (“Linn”, “Manhattan”, “Palmer II”, and “Pennfine”) also were collected at a farm in Linn County, OR (44° 34′ 46.14” N, 122° 53′ 15.32” W; 97 m elevation) from a Malabon silty clay loam (fine, mixed, superactive, mesic Pachic Ultic Argixerolls). Varieties (Linn, Manhattan, and “SR-4600”) of perennial ryegrass also were collected at a farm in south Benton County OR (44° 31′ 10.25” N, 123° 16′ 32.82” W, 73 m elevation) from a Woodburn silt loam soil. Only Linn and Manhattan perennial ryegrasses were available from Linn and south Benton counties. Three cultivars of tall fescue (“Grand II”, “Harrier”, and “Titan LTD” were collected from the farm in south Benton County. The tall fescue cultivars were not available from the Linn County site. The straw biomass collected from Linn and south Benton counties were used for genotypic comparisons of mineral concentrations in whole plants. All three sites were located in the high-rainfall area (average annual precipitation ) 1060 mm) of the Willamette Valley of western Oregon where mean monthly temperatures range from -4 °C (January) to 19 °C (August). Monthly minimum temperatures range from 1 °C (January) to 11 °C (August). Monthly maximum temperatures range from 7 °C (January) to 27 °C (August). Plants were harvested in July while the above-ground biomass was still green. Harvest was conducted by hand 4 cm above the soil surface from four replicated 30 × 30 cm2 quadrants. Sufficient quantities of whole plants were retained for mineral analyses, and the remainder of the biomass was separated into leaves and stems. Plant material was dried at 80 °C for 24 h and ground. Three 1 inch diameter soil cores were collected to a depth of 30 cm from each location. 2.2. Mineral Analysis. Minerals were extracted from plant tissue utilizing microwave-assisted acid digestion (EPA method 3052) with an Ethos D microwave station (Milestone, Monroe, CT) and analyzed for a panel of minerals by Inductive Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (PerkinElmer Life and Analytical Sciences, Shelton, CT). A quality control check standard (QCCS) representing the approximate midpoint of the calibration range for each mineral was included as the first sample in each set and was repeated following every 10th sample. All QCCS value determinations were within 10% of the actual concentration. Plant Cl content was quantified on tissue samples (25 g) that were extracted with 100 mL of deionized water, shaken for 30 min at 350 rpm, and filtered through Whatman Qualitative No. 42 filters (Florham Park, NJ) that had been washed three times with 1% H2SO4 (v/v) and deionized water. The filtrate was analyzed colorimetrically for Cl (QuickChem method 10-117-07-1-C) on a Lachat flow injection autoanalyzer (Hach Co., Loveland, CO). Soil pH was determined on a slurry consisting of 1:2 double distilled H2O/soil. Soil organic matter was determined by loss on ignition at 500 °C, after 4 h. 2.3. Quantification of Available N, P, K, and S in Soil. Available quantities of soil N, P, K, and S were determined by the Oregon state University Soil Testing Laboratory. Prior to analysis, soils were air-dried, ground, and sieved (40 mesh). Soils were
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Table 1. Partitioning of Minerals in Tall Fescue (TF; Schedonorus phoenix (Scop.) Holub, Experimental Line TFA4), Perennial Ryegrass (PR; Lolium perenne L., cv Manhattan), Kentucky Bluegrass (KBG; Poa pratensis L.), and Orchardgrass (OG; Dactylis glomerata L.) Plants Grown at Oregon State University Hyslop Research Farm, Corvallis, Oregona Leaf mineral
TF
PR
Stem KBG
OG
TF
PR
Whole Plant KBG
Al B Ca Cl Co Fe K Mg Mn P S Si Zn
196ab 27.8b 4764c 2628a 149ab 180a 18573b 1288b 99.2a 415c 900b 9495a 49.1c
282a 58.8a 9918a 1958b 188a 213a 17475b 1756a 60.7b 1065b 980a 7203a 62.2bc
187ab 49.1a 5245c 2392a 184a 218a 17323b 1092b 79.0ab 1284b 910b 8343a 83.1a
56b 25.5b 7488b 1514b 110b 114b 26503a 1832a 63.4b 1754a 840b 9789a 71.8ab
58a 19.7ab 1354b 4376a 46.2ab 34.8b 17979a 846a 41.4ab 365b 900b 1594b 41.5ab
mg kg-1 63a 53a 12.8b 24.9a 1476b 1421b 2756c 3441b 64.3a 36.8ab 70.2a 45.7ab 14095a 20073a 712b 530c 51.4a 30.3b 831a 756a 910a 910a 1916ab 2113ab 37.3ab 48.5a
C N
426b 6.9c
434a 11.3b
432ab 14.1ab
430ab 15.7a
432a 5.2a
435a 5.3a
g kg-1 431a 4.7a
OG
TF
PR
KBG
OG
60a 13.2b 2124a 1688d 25.3b 38.6b 19433a 868a 39.5ab 711a 910a 2450a 31.3b
197a 23.0b 4006bc 3712a 142a 172a 20740b 1419b 87.7a 667d 900ab 6895a 38.9a
118ab 25.9b 4743b 2113c 85.8b 106b 17233b 1186b 55.5b 1381b 840b 3733b 44.4a
94ab 36.3a 3003c 2859b 107ab 130b 18140b 801c 50.2b 938c 760b 4354b 46.4a
70b 23.2b 6482a 1393d 100ab 104b 28855a 1756a 54.7b 1661a 910ab 7046a 48.8a
435a 3.4a
429a 7.2b
401a 8.8b
436a 10.1b
432a 14.8a
a Mean (n ) 4) values within a row of four values corresponding to each tissue followed by the same letter are not significantly different at P ) 0.05 using Fisher’s LSD mean comparison test.
analyzed for extractable P,25 N, and S were analyzed by combustion on a LECO Model CNS 200 (Fisons Instruments, Beverly MA), and K was analyzed by ICP-OEC ammonium acetate extraction.26 2.4. Statistical Analyses. Statistical analyses of mean differences between species and plant tissue were calculated by analysis of variance (ANOVA; PROC GLM, SAS, Statistical Analysis System Institute, Cary, NC). In the ANOVA, location was considered random and varieties were considered fixed. Species was considered a factor in the analyses of mineral partitioning but not in analyses of cultivar or location differences because all species were not available at each location. Means of all minerals were evaluated for main effects, and interaction of the locations and varieties were compared utilizing Tukey’s Studentized Range (HSD) Test (PROC GLM, SAS). Mean differences among tissues within each species were also subject to ANOVA. All differences reported are significant at P e 0.05, unless otherwise stated. The Tukey’s test was used for the multiple comparisons of the observed means.
Table 2. ANOVA of Species x Tissue Partitioning Interactions with Mineral Concentration
3. Results and Discussion
more N, P, and K, three fertilizer components important to soil fertility. There were significant interactions between species of grasses and how minerals were partitioned among stems and leaves (Table 2), but the partitioning of Si and K, two minerals that impact thermochemical conversion process, had minimal interaction with species.
The concentration of most minerals in green biomass collected just prior to seed harvest was greater in leaves than in stems from tall fescue, perennial ryegrass, Kentucky bluegrass, and orchardgrass (Table 1). One exception was Cl, which was generally greater in stem tissue. The concentrations of K and S were similar in leaves and stems. Whole-plant concentrations of Ca, Cl, and Si varied more than 2-fold among these grasses. Perennial ryegrass generally contained the least amount of K, the most plentiful mineral detected in this study, and one that varied significantly between these species. Whole-plant concentrations of Si also were generally lower in perennial ryegrass. In contrast, orchardgrass contained the least amount of Cl. Chloride is important in thermochemical conversion because it contributes to corrosion within reactors.22 Whole-plant concentrations of Si and Cl were relatively low in Kentucky bluegrass straw. Relative to the other species, orchardgrass straw contained (24) Olsen, S. R.; Sommers, L. E. In Methods of Soil Analysis. Part 2. Chemical and Microbiological Properties; Page, A. L., Miller, R. H., Keeney, D. R., Eds.; American Society of Agronomy: Madison, WI, 1982; pp 404-406. (25) Thomas, G. W. In Methods of Soil Analysis. Part 2. Chemical and Microbiological Properties; Page, A. L., Miller, R. H., Keeney, D. R., Eds.; American Society of Agronomy: Madison, WI, 1982; pp 159-166. (26) Waters, B. M.; Grusak, M. A. New Phytol. 2008, 177, 389–405.
mineral
mean square species x tissue df ) 6
F value
Pr > F
Al B Ca Cl Co Fe K Mg Mn P S Si Zn C N
12 460 333 7 107 488 481 346 2686 4154 335 613 642 169 101 619 265770 0.2017 3 153 727 281 439 27.45
2.90 8.03 21.22 5.24 3.82 6.04 1.32 7.01 2.56 10.43 2.57 1.95 1.95 1.54 8.70
0.022
