Nutrient Supply and Neutralizing Value of Alfalfa Stem Gasification Ash

Ash application influences availabilities of plant micronutrients either directly through addition of its miEnergy generation from biomass is an environmentally sound altercronutrients constituents or indirectly through the modinative to other energy producing technologies. Pilot studies have indicated that alfalfa (Medicago sativa L.) is a suitable feedstock for fication of soil pH. Increased availability of B and Mo energy generation via the gasification process. The resulting ash is a has been reported in soils amended with ash from power potential liming agent and a source of plant nutrients. A growth plants (Codling and Wright, 1998; Hammermeister et al., chamber study was conducted with three soils to evaluate the potential 1998). Clapham and Zibilske (1992) reported that wood use of this ash as a soil amendment. Corn (Zea mays L.) received 13 ash application increased acid-extractable (pH 3, 1 M treatments: control, K and/or P fertilizer, seven ash rates (0.6 to 14.6 g ammonium acetate [NH4OAc]) soil Fe, Zn, Cu, and Mn, ash kg 1 soil), and one ash rate with K or P fertilizer. Soil pH increased but in another study, wood ash decreased extractable with ash application on all soils. Ash application increased ammonium Fe and Al (Naylor and Schmidt, 1986). acetate-exchangeable K, Ca, and Mg, and Olsen P in soil and deModification of soil chemical properties by ash applicreased DTPA-extractable soil Fe, Mn, Ni, and Pb. Averaged across cation has resulted in altered elemental composition of the three soils, slopes of the cations recovered in plant and soil vs. cations applied in the ash were 0.48, 0.21, and 0.22 of total ash K, plants. Wood ash increased the K concentration in corn Ca, and Mg, respectively (r 2 0.97). Ash significantly increased plant and winter wheat (Triticum aestivum L.) in greenhouse K and Mo, and decreased Mg, Mn, and Zn concentration. Tissue P studies (Erich, 1991; Etiegni et al., 1991a) and alfalfa in concentrations were not affected by ash, but increased with P fertilizer. field studies (Meyers and Kopecky, 1998). Wood ash at Phosphorus fertilizer increased plant dry mass (DM), but K fertilizer rates below 20 g kg 1 increased P concentration in wheat did not, thus K did not limit yield. Alfalfa stem gasification ash is a (Etiegni et al., 1991a). Other studies have shown that P potential liming agent, a source of K, and would not lead to excessive availability can increase or decrease in ash-amended soils accumulation of trace elements in soil or plants when applied at rates (Erich, 1991; Voundinkana et al., 1998; Moliner and based on lime or K need. Street, 1982; Elseewi et al., 1980). Application of either coal fly ash or wood ash decreased tissue Zn, Fe, and Mn, and increased B and Mo (Elseewi et al., 1980; FranA has been recognized as an excellent soil amendcis et al., 1985; Naylor and Schmidt, 1989). Application ment since well before Jared Eliot wrote in 1748, of wood-fired boiler ash decreased the concentrations “Ashes is allowed on all hands to be some of the best of Mn and Cu in bean (Phaseolus vulgaris L.) plants dressing or manure for land; it enricheth much and lasts (Krejsl and Scanlon, 1996). These effects on plant microlong; but the misery is we can get but little” (Eliot, 1934; nutrient concentration may have implications for human Carman, 1934). Eliot was referring mainly to wood and or animal health. coal ash, which are available today in large amounts from Plant DM production has increased, decreased, or electricity generation. Effects of coal and wood ash on remained unchanged after coal or wood ash application, soil chemical properties, and on plant yield and eledepending on factors such as type and rate of ash applimental composition have been investigated, and recent cation, plant species, and soil properties. Oat (Avena reviews include Hammermeister et al. (1998) on coal sativa L.) grown in soil amended with 30 Mg ha 1 of ash and Mitchell and Black (1997) and Vance (1996) on wood-fired boiler ash produced significantly higher DM wood ash. than plants grown in nonamended soil, but DM declined The major effects of land application of ash are changes at 50 Mg ha 1 ash (Krejsl and Scanlon, 1996). Wood in soil pH and nutrient availability. Ash has been used ash application had no effect on production of spinach historically and primarily as a liming agent or K source. (Spinacia oleracea L.) in a greenhouse study (Clapham The liming potential or calcium carbonate equivalent and Zibliskie, 1992) nor on wheat yield in a field study (CCE) of ash is dependent both on the type of ash and (Huang et al., 1992). soil chemical properties (Clapham and Zibilske, 1992). In recent years, utilization of herbaceous species as Wood ash is generally rich in oxides, hydroxides, and biomass fuel for electricity generation has been viewed carbonates of Ca, K, and Mg, and contains small quantias an environmentally viable option. Preliminary studies ties of micronutrients (Erich and Ohno, 1992; Mitchell have indicated that alfalfa stems are suitable feedstock and Black, 1997). for energy generation via the gasification process (Wilbur et al., 1998). If the ash from alfalfa gasification can M. Mozaffari, C.J. Rosen, and E.A. Nater, Dep. of Soil, Water, and be utilized as a soil amendment, then economic viability Climate, 439 Borlaug Hall, 1991 Upper Buford Circle, Univ. of Minnesota. St. Paul, MN 55108; M.P. Russelle, USDA–ARS U.S. Dairy and public acceptance of this alternative energy source Forage Research Center (Minnesota Cluster) and Dep. of Soil, Water, may increase. Chemical characterization has indicated and Climate, 439 Borlaug Hall, Univ. of Minnesota. St. Paul, MN that alfalfa ash is a potential liming agent, its macronu55108; Joint contribution of the Minnesota Agric. Exp. Stn. and the trient content is equivalent to a 1-1-10 fertilizer, and it USDA-ARS. Received 8 Aug. 2000. *Corresponding author (crosen@ soils.umn.edu). Abbreviations: CCE, calcium carbonate equivalent; DM, dry matter; ICP-AES, inductively coupled plasma atomic emission spectroscopy. Published in Soil Sci. Soc. Am. J. 66:171–178 (2002).