Published in Agron. J. 97:265-271 (2005).
© American Society of Agronomy
677 S. Segoe Rd., Madison, WI 53711 USA
Production Papers
Flue Gas Desulfurization Products as Sulfur Sources for Alfalfa and Soybean
Liming Chena,
Warren A. Dicka,* and
Sid Nelson, Jr.b
a School of Nat. Resour., The Ohio State Univ., Wooster, OH 44691
b Sorbent Technol. Corp., 1664 East Highland Rd., Twinsburg, OH 44087
* Corresponding author (dick.5{at}osu.edu)
Received for publication April 7, 2004.
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ABSTRACT
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Sulfur deficiencies in soil are expected to increase due to growth of high-yielding crop varieties, use of S-free fertilizers, and removal of S from industrial emissions. Flue gas desulfurization (FGD) products, created when coal is burned and SO2 is removed from the flue gases, may serve as efficient S sources. However, there are few reports on their use for the enhancement of crop growth. Agricultural gypsum and two types of FGD products, that contain either vermiculite or perlite, were applied at 0, 16, and 67 kg S ha–1 to an agricultural soil (Wooster silt loam, Typic Fragiudalf). Dry weight of a new planting of alfalfa (Medicago sativa L.) was increased up to 40% by the treatments of FGD products or gypsum compared with the untreated control. Gypsum and FGD products were also applied at 0, 8, 16, and 24 kg S ha–1 to five established alfalfa stands in different Ohio regions. Mean alfalfa yield was significantly (P 
0.05 ) increased by approximately 5.0% in 2001 and 6.0% in 2002 with the S treatments of FGD products or gypsum compared with the untreated control. Alfalfa yields for FGD products and gypsum treatments were similar. A slight positive yield response was observed for soybean (Glycine max L.) when soils were treated with S-containing materials. Soil and plant analyses were made to assess potential adverse environmental impacts and none were observed. Thus, these FGD products can be safely applied to agricultural soils as S sources and can improve alfalfa yields in S-deficient soils.
Abbreviations: FGD, flue gas desulfurization • ICP, inductively coupled plasma
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INTRODUCTION
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SULFUR IS AN ELEMENT essential for plant growth. It is a macronutrient and—like N, P, K, Ca, and Mg—must be available in relatively large amounts for good crop growth. Sulfur is a constituent of the amino acids cysteine and methionine and hence of protein. When deficient, it decreases the synthesis of proteins and the photosynthetic rate in plants (Marschner, 1986). Cysteine and methionine are also precursors of other S-containing compounds such as coenzymes and secondary plant products. Sulfur is a structural constituent of these compounds or acts as a functional group directly involved in metabolic reactions.
Deficiencies of S in crops are generally thought to be increasing (McGrath and Zhao, 1995). This is attributed to use of highly concentrated fertilizers containing little or no S, intensive cropping systems, increased crop yield that results in more S removal, less S deposition from the atmosphere, and less use of S-containing pesticides. Alfalfa has a relative high requirement for S and, when harvested yields are 15 Mg ha–1, removes approximately 40 kg of S from the soil each year (Troeh and Thompson, 1993, p. 262). Sulfur deficiencies of alfalfa have been reported in Ohio, Indiana, Michigan, Wisconsin, and Virginia during the 1960s and 1970s (Beaton and Fox, 1971). Alfalfa yields were increased by gypsum application in sandy loams but not in silt loams in Minnesota (O'Leary and Rehm, 1989). Waste S applied to alfalfa in the upper Midwest at agronomic rates did not affect yields but did increase the S content of alfalfa plants relative to alfalfa grown on untreated soil (Sloan et al., 1999). Alfalfa yields were not affected by elemental S or gypsum application in central Maryland and Prince Edward Island in Canada (Vough et al., 1986; Gupta and MacLeod, 1984).
Sulfur deficiencies not only decrease yield, but also influence the feeding value of soybean (Sexton et al., 1997). Yields of soybean, in S-deficient fields, were increased by almost 30% when supplemental S was added to soil (Agrawal and Mishra, 1994). Substantial amounts of farmland in western Canada have been reported to be S deficient, and yields of soybean were significantly increased by S fertilizer treatments (Beaton and Soper, 1986).
Sulfur-deficient soils are often low in organic matter, coarse textured, well drained, and subject to leaching (Waddoups, 2003). The S status of Ohio's soils is not well defined, and S effects on the growth of crops have not been extensively researched. In Wooster, OH, USA, annual S deposition gradually decreased from 34.8 kg ha–1 in 1979 to 16.9 kg ha–1 in 1999 (Natl. Atmos. Deposition Progr., 2003). Based on the S status model created by McGrath and Zhao (1995) in England using soil characteristics, atmospheric S deposition, meteorological data, and S requirement of crops, many regions in Ohio, as well as other areas in North America, would be expected to require supplemental S for optimum growth of crops. Therefore, crop response to S application on agriculture soils will probably occur with greater frequency in the future.
In the United States, use of coal with high concentrations of S for energy often requires the SO2 produced during burning to be removed via some type of scrubbing technology to meet the clean-air regulations. The materials that are produced during scrubbing are given the generic name of flue gas desulfurization (FGD) products. Flue gas desulfurization products are typically composed of three components varying in proportion and composition, which depends on the coal, sorbent (which is generally highly alkaline), and scrubbing process used. These components are (i) the SO2 reaction products, which are primarily CaSO3 and CaSO4; (ii) unreacted sorbent; and (iii) coal combustion ash. Because of the unspent sorbent component, FGD products are usually alkaline and have significant neutralization potential. Several studies have shown that this property enables FGD products to be used as alkaline amendments for agricultural soils (Terman et al., 1978; Stout et al., 1979; Korcak, 1980; Stehouwer et al., 1995; Ritchey et al., 1996; Stehouwer et al., 1996; Chen et al., 2001).
A new type of dry FGD product that contains CaSO3 and CaSO4, Ca(OH)2, fly ash, and vermiculite or perlite is currently being produced. This FGD comes from the reaction of Ca(OH)2, on a vermiculite or perlite carrier, with sulfur dioxide (Nelson et al., 1998). Because plants take up S from soil primarily in the form of sulfate 
, and because the sulfite 
is also easily oxidized to SO42–, this new FGD product may be a good S source for crops. However, the fly ash in these FGD products also contains some trace elements of environmental concern (Chen et al., 2001).
In our work, we hypothesized that FGD products containing vermiculite or perlite have the potential to be effective sources of S and other nutrients for crops. The objectives of this research were, therefore, (i) to determine the suitability of using the new perlite- or vermiculite-containing FGD products as a fertilizer in S-deficient soils during production of alfalfa and soybean and (ii) to assess their potential environmental impacts on the chemical composition of plants and soils.
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MATERIALS AND METHODS
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2000 Experiments
Alfalfa and soybean were planted on an agricultural soil (Wooster silt loam, Typic Fragiudalf) located near Wooster, OH, USA. This had been a corn (Zea mays L.)–soybean rotation field where, before 2000, soybean was grown in 1998 and corn was grown in 1999. The field had not received S fertilizer in previous years. Before treatment, surface (0–20 cm) soil samples were collected, air-dried, and analyzed as described in Sparks et al. (1996) to determine their fertility status, pH, and soil organic matter content (Table 1).
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Table 1. Selected characteristics of the Wooster silt loam soil (0- to 20-cm depth) before application of S materials.
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Flue gas desulfurization products containing sulfate/sulfite, unused lime, and vermiculite or perlite were obtained from Sorbent Technologies Corporation (Twinsburg, OH). Agricultural gypsum (Nutrasoft Pelletized Gypsum) was produced by Rex International (Thomasville, NC). Chemical composition of the FGD products and the agricultural gypsum (Table 2) was determined by inductively coupled plasma (ICP) emission spectrometry after digestion with a mixture of HClO4–HNO3.
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Table 2. Concentrations of elements in the flue gas desulfurization (FGD) products and gypsum used as S sources. Data are means of two replicates.
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For the soybean experiment, the vermiculite-FGD product and gypsum were applied at rates equivalent to 16 and 67 kg S ha–1 (238 and 998 kg FGD ha–1 or 98 and 416 kg gypsum ha–1, respectively), and the perlite-FGD product was applied at a rate of 16 kg S ha–1 (240 kg FGD ha–1). For the alfalfa experiment, the vermiculite-FGD was applied at rates equivalent to 16 and 67 kg S ha–1, and the perlite-FGD and gypsum were applied at a rate of 16 kg S ha–1. Additional treatments included an untreated control. These treatments were surface-applied by broadcast to plots of 3 by 6 m (for alfalfa) or 6 by 6 m (for soybean) arranged in a randomized block with three replicates immediately after the alfalfa and soybean seeds were sown. Soybean was planted at a population of 350000 seeds ha–1 in row width of 30 cm on 12 June 2000. Alfalfa was planted at a seeding rate of 14 kg ha–1 in row width of 20 cm. Plots were supplied with P and K fertilizers based on soil test results and the Ohio Agronomy Guide (Ohio State Univ. Ext., 1995) recommendations at the beginning of the experiment.
Because alfalfa was planted late and it takes time for alfalfa to become fully established, alfalfa was harvested only one time in 2000 (on 8 Sept. 2000). Alfalfa samples, collected by clipping a randomly selected 1-m2 area from each plot, were dried at 60°C for 5 d, weighed, and ground to pass a 1-mm sieve. Concentrations of elements in the alfalfa were determined by ICP emission spectrometry after digestion with a mixture of HClO4–HNO3 (Isaac and Johnson, 1985). Soybean was harvested on 13 Oct. 2000 from a center 4.5- by 5.1-m2 area of each plot. Soybean seeds were ground to pass a 1-mm sieve, and concentrations of elements were also determined by ICP emission spectrometry.
Four months after applying treatments, five soil cores (2.5-cm diam.) from depth of 0 to 15 and 15 to 30 cm were collected from the plots in the soybean field, and the samples from each layer were combined. Soil samples were air-dried, crushed, passed through a 2-mm sieve, and extracted with Mehlich-III extractant (Mehlich, 1984). Extracted elements were determined by the ICP emission spectrometry.
2001 and 2002 Experiments
Alfalfa field studies in 2001 and 2002 were conducted in six fields in different regions of Ohio. At the Wooster field site where alfalfa had been grown in 2000, treatments using the same materials and amounts were applied again to the same plots each year. In addition, we selected five established stands of alfalfa in different regions of Ohio. They were located in Wayne County (two stands called OARDC and Baker), Pike County, Hancock County, and Sandusky County. Sites selected did not have a history of S fertilizer application. Gypsum and FGD products were applied to plots of 3 by 6 m at the rates of 0, 8, 16, and 24 kg S ha–1 (119, 238, and 357 kg FGD ha–1 or 49, 98, and 146 kg gypsum ha–1) on these established stands by broadcast in early April 2001 and 2002. No vermiculite-FGD was applied in 2002. Experimental design was a randomized complete block with four replications. Before treatment application, soil samples from the 0- to 20-cm soil layer were collected and analyzed (Table 3). Alfalfa was harvested three to four times between the late-bud and early-bloom stage of maturity in each field from May to September during the growing season in 2001 and 2002. This was done by clipping a randomly selected 1-m2 area from each plot.
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Table 3. Selected characteristics of soils collected in 2001 from five established alfalfa field sites and from one soybean field site before application of S materials.
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In August 2002 at the OARDC, Baker, Pike County, Hancock County, and Sandusky sites, five soil cores (0- to 20-cm soil layers) were removed from each control plot and the plots treated with 24 kg S ha–1 (as FGD) and then mixed to form a single sample. Similarly, samples from the control and the 16 kg S ha–1 FGD treatment plots were collected from the Wooster site. Soil samples were air-dried, crushed, passed through a 2-mm sieve, and extracted with Mehlich-III solution (Mehlich, 1984), and the concentration of selected elements in the extracts was measured by ICP emission spectrometry.
The soybean experiment in 2001 was conducted on a silt loam soil located in Clark County, OH. This is a no-tillage corn–soybean rotation field where soybean was grown in 1999 and corn was grown in 2000. No S fertilizer had been applied in this field over the past several years. Before application, soil samples were collected and analyzed (Table 3). Gypsum and vermiculite-FGD product were applied to plots of 6 by 6 m at 0, 5.6, and 17 kg S ha–1 (0, 83, and 253 kg FGD ha–1 or 0, 35, and 105 kg gypsum ha–1). Experimental design was a randomized complete block with four replications. Materials were applied on 25 Apr. 2001 by broadcast. Soybean was planted at a density of 300000 seeds ha–1 in row width of 38 cm on 30 Apr. 2001. Harvest yields were obtained from the center 2- by 6-m2 area of each plot on 3 Oct. 2001. Soybean data from 2002 will be not reported because dry weather in 2002 caused a severe drought stress and significantly reduced the yield of soybean.
Data Analyses
Data were subjected to analysis of variance (ANOVA) using the PROC GLM statement of the SAS statistics program (SAS Inst., 2001). When ANOVA generated a significant F value for treatment (P 0.05), means were compared by the LSD test.
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RESULTS AND DISCUSSION
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Alfalfa
Total dry weight yields of a newly established alfalfa field at the Wooster site for the 2000 through 2002 harvests are presented (Fig. 1). Growth of alfalfa in the Wooster silt loam soil was increased by all FGD products or by gypsum applied at a rate of 16 kg S ha–1. Alfalfa yields for the vermiculite-FGD, perlite-FGD, or gypsum treatments were similar. Increasing application rates of the FGD products did not increased alfalfa yields. This indicated the low rate of applied S to this soil was sufficient for the growth of alfalfa. These results are in agreement with the studies of O'Leary and Rehm (1989), who applied gypsum at the rates of 28 to 112 kg S ha–1 to two alfalfa stands in sandy loam soils in Wisconsin. They found that alfalfa yields were significantly (P 0.10) increased by S additions, but there were no differences in yield among rates. At the application rate of 16 kg S ha–1 used in our study, mean alfalfa yields were increased l0 to 40% by the FGD products or the gypsum treatments compared with the unamended control in 2000. The increases in total alfalfa yields associated with the FGD products or gypsum treatments were greater than for the control plots by 15 to 25% in 2001 and by 2 to 10% in 2002.
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Fig. 1. Cumulative yields of alfalfa at the Wooster site as affected by application of 16 kg S ha–1 as flue gas desulfurization (FGD) products or gypsum from 2000 through 2002. Different letters over each bar represent a significant difference at P 0.05.
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Mean alfalfa yields were also increased by applying FGD products or gypsum to established alfalfa fields (Table 4). Mean alfalfa yields were increased by an average of approximately 5.0% when S was applied to five alfalfa fields in 2001 and 6.0% in 2002. These results contrast with those in Wisconsin on silt loam soils (O'Leary and Rehm, 1989) where dry weights of alfalfa were not affected by gypsum application. At the Sandusky site, alfalfa did not respond to S applications, probably because this site contains the highest concentration of organic matter among those we tested. It seems that sufficient S was mineralized and released for alfalfa growth. Alfalfa grown in the fields, where the original soil S concentrations extracted by the Mehlich-III solution were less 40 mg kg–1 soil, responded more positively to S treatments than when the Mehlich-III S concentration value was greater than 40 mg kg–1 soil (Fig. 2). We also found that at an application rate of 16 or 24 kg S ha–1, the concentration of available S in the treated soils compared with the control soils was increased 14% to 37% by the FGD product treatments.
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Table 4. Cumulative dry weight of alfalfa from five established alfalfa field sites treated with flue gas desulfurization (FGD) products or gypsum in 2001 and 2002. Results are averages across all application rates.
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Fig. 2. Relationship between yield increase (% of alfalfa growing in soil treated with S compared with control soil) and S concentration in Mehlich-III soil extracts.
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Concentrations in alfalfa of Ca, a major element in the FGD and gypsum, were slightly decreased by the vermiculite-FGD products applied at a rate of 16 kg S ha–1. There was no significant affect when soil was treated at the rate of 67 kg S ha–1 as perlite-FGD or gypsum compared with the untreated control (Table 5). Concentrations of S in alfalfa were not affected by FGD products or gypsum treatments. This does not agree with other results where S concentration in the crop tissue generally increased with S supplement (O'Leary and Rehm, 1989; Goodroad et al., 1989). Concentrations in alfalfa of Mg decreased when soil was treated with FGD at the rate of 16 kg S ha–1 compared with the untreated control and were not affected by the treatments of FGD products at the rate of 67 kg S ha–1 or gypsum. These results are similar to the response of rabbiteye blueberry (Vaccinium ashei R.) to S treatments, which reduced Ca and Mg concentrations in the leaves (Spiers and Braswell, 1989). Goodroad et al. (1989) found that the concentrations of Ca decreased with the increase of S treatment in soft red winter wheat (Triticum aestivum L.). All the other major elements were not affected by the treatments of FGD or gypsum.
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Table 5. Mean concentrations of essential elements in alfalfa grown in soil treated with flue gas desulfurization (FGD) products or gypsum at Wooster in 2000.
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Plant essential trace elements such as Fe, B, Zn, Cu, Ni, and Mo in alfalfa tissue were not affected by the FGD treatments or gypsum (Table 5). Concentrations of Mn were greatly decreased, compared with the untreated control, by the vermiculite-FGD product at the rate of 16 kg S ha–1. This is in agreement with the results of Goodroad et al. (1989), for soft red winter wheat, where concentrations of Mn decreased with an increase of S application rate.
Comparison of concentrations of the regulated elements, measured using the Toxicity Characteristic Leaching Procedure (TCLP) and regulated by the Resource Conservation and Recovery Act (RCRA), indicated no potential problems associated with the use of these FGD products (Chen et al., 2001). Plant tissue analyses reported in this study confirmed there were no potential environmental effects (Table 6). Concentration of Se was significantly decreased in the alfalfa growing in plots treated with FGD or gypsum. Concentrations of Al, As, Ba, Cd, and Cr were not affected by the FGD products or gypsum treatments. The reason why the lowest rate of vermiculite-FGD increased the Pb concentration while the high rate did not is unclear. In a previous study, concentrations of environmental-regulated elements in alfalfa tissue grown in soil treated at a very high rate (75 Mg ha–1) of FGD product were determined and showed that these elements in the alfalfa were not significantly increased (Chen et al., 2001). In this study, the concentrations of plant nutrients in Mehlich-III extracts (except for S) in the 0- to 20-cm soil layer of alfalfa fields after 2 or 3 yr of applying FGD products did not change compared with the no-S-treatment control (data not shown). For S, however, the concentrations in the Mehlich-III soil extracts increased 25.9% from 35.9 mg kg–1 in the control to 45.2 mg kg–1 after S application.
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Table 6. Mean concentrations of selected nonessential and potentially toxic elements in alfalfa grown in soil treated with flue gas desulfurization (FGD) products or gypsum at Wooster in 2000.
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Soybean
Application of FGD products or gypsum at the rates of 16 and 67 kg S ha–1 to the Wooster silt loam soil in 2000 increased yields of soybean over the control by 3.3 to 11.6% (Table 7). The increases were significant at the P 0.10 level for several treatments. For the 2001 experiment, however, which was conducted at the Clark site, there were no significant differences in the yields of soybean between (i) the control and S application treatments, (ii) the FGD product and gypsum treatments, or (iii) the application rates of S treatments. The 2001 experiment was conducted at a different site than the experiment in 2000. We attribute the nonresponse at this site, compared with the Wooster site, to the fact that it receives greater amounts of S (annual 23 kg SO4 ha–1 in 2000) from precipitation and air pollution (Natl. Atmos. Deposition Progr., 2003), and the soil contains a higher concentration of organic matter (3.15%) (Table 3), which releases sufficient S for soybean growth.
Concentrations of K, Mg, and S in soybean seeds were slightly decreased by some of the FGD product treatments or gypsum compared with the control treatment (Table 8). Other major elements and all the plant essential trace elements in soybean seeds were not affected by FGD products or gypsum treatments.
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Table 8. Mean concentrations of essential elements in soybean seeds harvested from plots treated with flue gas desulfurization (FGD) products or gypsum at Wooster in 2000.
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Inspection of concentrations of selected elements in soybean seeds potentially toxic to plants or regulated by the Resource Conservation and Recovery Act (i.e., Al, As, Ba, Cd, Cr, Pb, and Se) revealed Ba was significantly decreased in soybean seeds harvested from plots treated with vermiculite-FGD at the rate of 67 kg S ha–1 or gypsum at the rate of 16 kg S ha–1 compared with the control treatment (data not shown). Concentration of Cr was significantly increased (to 0.423 mg kg–1) by the vermiculite-FGD at the rate of 67 kg S ha–1, and Pb concentrations were significantly increased (to 4.11 mg kg–1) by the 16 kg S ha–1 vermiculite-FGD treatment. However, these concentrations are still well below toxic levels. Concentrations of Al, As, Cd, Pb, and Se were not affected by the FGD products or gypsum treatments compared with the control treatment.
Four months after S application and soybean growth, soluble Ca concentrations in the surface soil layer (0–15 cm) increased approximately 10 to 20% by the FGD products treatments and 3% by the gypsum treatment compared with the untreated control (Table 9). Sulfur concentrations in the soil were increased 10 to 50% by the treatments of FGD products or gypsum compared with the untreated control. Plant essential trace elements such as Fe, B, Zn, and Cu were much less affected by application of FGD products. An increase of S concentration in the subsoil layer (15–30 cm) was detected in soil treated with perlite-FGD or gypsum.
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Table 9. Mean concentrations of essential elements in Mehlich-III extracts obtained from the 0- to 15- and 15- to 30-cm soil layer of the soybean field four months after treating the soil with flue gas desulfurization (FGD) products or gypsum.
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The concentration of B in the surface soil layer (0–15 cm) of the soybean field was increased significantly by the application of the vermiculite-FGD product at the rate of 67 kg S ha–1 (Table 9). Concentrations of B in soil treated with some fly ashes can reach phytotoxic levels (Sutton and Dick, 1987), but the results from this study indicate that the alfalfa tissue and soybean seeds did not accumulate B. Many reports indicate foliar B applications improve soybean yield (Gascho and McPherson, 1997; Reinbott and Blevins, 1995; Schon and Blevins, 1990). Also, B applied to a silty clay loam soil at 2.8 kg ha–1 increased soybean yield by 11 to 13% (Reinbott and Blevins, 1995). Broadcast fertilizer applications of FGD (applied at rates of 0.28 to 1.12 kg B ha–1) to a loamy sand with a low test level of B in Georgia increased soybean yield by 4% (Touchton and Boswell, 1975). A study by Sloan et al. (1999), also using FGD products, demonstrated that FGD can serve as an excellent B source for alfalfa production, particularly late in the growing season, when native soil B availability decreases.
In soil samples extracted with Mehlich-III (for Al, As, Ba, Cd, Cr, Pb, and Se), only As was affected by any treatment (increased by gypsum) in the 0- to 15-cm soil layer compared with the control (data not shown). In the 15- to 30-cm soil layer, only Pb was affected and was increased when S was applied at a rate 16 kg S ha–1 using vermiculite-FGD. However, there was no difference, compared with the control plot, when S was applied at the higher rate of 67 kg S ha–1 using the same vermiculite-FGD product.
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CONCLUSIONS
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The FGD products are good S sources for improving the growth of alfalfa and soybean in Ohio soils. Gypsum caused similar yield increases of alfalfa and soybean. However, FGD products may have additional beneficial effects on crop growth due to their ability to supply other essential plant nutrients such as B. The FGD products did not increase the concentrations of potentially toxic metals such as As, Ba, Cd, Cr, and Se in plant tissues. This study indicates that more attention should be paid to potential S requirements of agronomic crops in various parts of the United States where S deficiencies may be occurring because of growth of high-yielding crop varieties, use of S-free fertilizers, less input of S from industrial emissions, and soil leaching of S. The new vermiculite- or perlite-containing FGD products can supply needed S to plants and have potential benefits for increasing alfalfa and soybean yields when applied to agricultural soils.
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ACKNOWLEDGMENTS
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Salaries and research support were provided by Sorbent Technologies Corporation (Twinsburg, OH, USA), the Ohio Coal Development Office (Columbus, OH, USA), and by state and federal funds appropriated to The Ohio State University and The Ohio Agricultural Research and Development Center (Wooster, OH, USA).
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REFERENCES
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- Agrawal, H.P., and A.K. Mishra. 1994. Sulphur nutrition of soybean. Commun. Soil Sci. Plant Anal. 25:1303–1312.
- Beaton, J.D., and R.L. Fox. 1971. Production, marketing, and use of sulfur products. p. 335–379 In Olson et al. (ed.) Fertilizer technology & use. 2nd ed. SSSA, Madison, WI.
- Beaton, J.D., and R.J. Soper. 1986. Plant response to sulfur in western Canada. p. 375–403. In Sulfur in agriculture. Agron. Monogr. 27. ASA, CSSA, and SSSA, Madison, WI.
- Chen, L., W.A. Dick, and S. Nelson. 2001. Flue gas desulfurization by-products additions to acid soil: Alfalfa productivity and environmental quality. Environ. Pollut. 114:161–168.[Medline]
- Gascho, G.J., and R.M. McPherson. 1997. A foliar boron nutrition and insecticide-program for soybean. p. 11–15. In R.W. Bell et al. (ed.) Developments in plant and soil sciences: Boron in soils and plants. Vol. 76. Proc. Int. Symp. on Boron in Soils and Plants, Chiang Mai, Thailand. 7–11 Sept. 1997. Kluwer Academic Publ., Dordrecht, the Netherlands.
- Goodroad, L.L., K. Ohki, and D.O. Wilson. 1989. Influence of sulfur on growth and nutrient composition of soft red winter wheat. J. Plant Nutr. 12:1029–1039.
- Gupta, U.C., and J.A. MacLeod. 1984. Effect of various sources of sulfur on yield and sulfur concentration of cereals and forages. Can. J. Soil Sci. 64:403–409.
- Isaac, J.B., and W.A. Johnson. 1985. Elemental analysis of plant tissue by plasma emission spectroscopy: Collaborative study. J. Assoc. Off. Anal. Chem. 68:499–505.
- Korcak, R.F. 1980. Fluidized bed material as a lime substitute and calcium source for apple seedling. J. Environ. Qual. 9:147–151.[Abstract/Free Full Text]
- Marschner, H. 1986. Mineral nutrition of higher plants. Academic Press, London.
- McGrath, S.P., and F.J. Zhao. 1995. A risk assessment of sulphur deficiency in cereals using soil and atmospheric deposition data. Soil Use Manage. 11:110–114.
- Mehlich, A. 1984. Mehlich III soil test extract: A modification of Mehlich II extractant. Commun. Soil Sci. Plant Anal. 15:1409–1419.
- National Atmospheric Deposition Program. 2003. Annual data summary for site OH 71 [Online]. Available at http://nadp.sws.uiuc.edu/sites/ntnmap.asp (verified 30 Sept. 2004). Natl. Atmos. Deposition Progr. Office, Illinois State Water Survey, Champaign.
- Nelson, S., Jr., W.A. Dick, and L. Chen. 1998. Agricultural use of a flue gas desulfurization by-product. In Proc. Int. Tech. Conf. on Coal Utilization & Fuel Syst., 23rd, Clearwater, FL. 9–13 Mar. 1998. Coal and Slurry Technol. Assoc., Washington, DC.
- Ohio State University Extension. 1995. Ohio agronomy guide. Bull. 472. Ohio State Univ. Ext., Columbus.
- O'Leary, M.J., and G.W. Rehm. 1989. Effect of sulfur on forage yield and quality of alfalfa. J. Fert. Issues 6:6–11.
- Reinbott, T.M., and D.G. Blevins. 1995. Response of soybean to foliar-applied boron and magnesium and soil-applied boron. J. Plant Nutr. 18:179–200.
- Ritchey, K.D., R.F. Korcak, C.M. Feldhake, V.C. Baligar, and R.B. Clark. 1996. Calcium sulfate or coal combustion by-product spread on the soil surface to reduce evaporation, mitigate subsoil acidity and improve plant growth. Plant Soil 182:209–219.
- SAS Institute. 2001. SAS/STAT user's guide. Release 8.2. SAS Inst., Cary, NC.
- Schon, M.K., and D.G. Blevins. 1990. Foliar boron applications increase the final number of branches and pods on branches of field-grown soybeans. Plant Physiol. 92:602–607.[Abstract/Free Full Text]
- Sexton, P.J., W.D. Batchelor, and R. Shibles. 1997. Sulfur availability, rubisco content, and photosynthetic rate of soybean. Crop Sci. 37:1801–1806.[Abstract/Free Full Text]
- Sloan, J.J., R.H. Dowdy, M.S. Dolan, and G.W. Rehm. 1999. Plant and soil responses to field-applied flue gas desulfurization residue. Fuel 78:169–174.
- Sparks, D.L., A.L. Page, P.A. Helmke, R.H. Loeppert, P.N. Soltanpour, M.A. Tabatabai, C.T. Johnston, and M.E. Sumner. (ed.) 1996. Methods of soil analysis. Part 3. Chemical methods. SSSA Book Ser. 5. SSSA and ASA, Madison, WI.
- Spiers, J.M., and J.H. Braswell. 1989. Effects of sulfur and micronutrients on growth and elemental leaf content of rabbiteye blueberrie. Acta Hortic. 241:151–156.
- Stehouwer, R.C., W.A. Dick, J.M. Bigham, D.L. Forster, F. Hitzhusen, E.L. McCoy, S.J. Traina, W. Wolf, and R. Heafner. 1995. Land application uses for dry flue gas desulfurization by-products. Project 2796–02. EPRI TR-105264. Electric Power Res. Inst., Palo Alto, CA.
- Stehouwer, R.C., P. Sutton, and W.A. Dick. 1996. Transport and plant uptake of soil-applied dry flue gas desulfurization by-products. Soil Sci. 161:562–574.
- Stout, W.L., R.C. Siddle, J.L. Hern, and O.L. Bennett. 1979. Effects of fluidized bed combustion waste on the Ca, Mg, S and Zn levels in red clove, tall fescue, oats, and buckwheat. Agron. J. 71:662–665.[Abstract/Free Full Text]
- Sutton, P., and W.A. Dick. 1987. Reclamation of acidic mined lands in humic areas. Adv. Agron. 41:377–405.
- Terman, G.L., V.J. Kilmer, C.M. Hunt, and W. Buchanan. 1978. Fluidized bed boiler waste as a source of nutrients and lime. J. Environ. Qual. 7:147–150.[Abstract/Free Full Text]
- Touchton, J.T., and F.C. Boswell. 1975. Effects of boron application on soybean yield, chemical composition, and related characteristics. Agron. J. 67:417–420.[Abstract/Free Full Text]
- Troeh, F.R., and L.M. Thompson. 1993. Soils and soil fertility. 5th ed. Oxford Univ. Press, New York.
- Vough, L.R., R.R. Weil, and A.M. Decker. 1986. Fertilizing alfalfa for higher yields. p. 230–234. In Proc. Forage Grassl. Conf., Lexington, KY. Univ. of Kentucky, Lexington.
- Waddoups, M. 2003. Interpreting soil & plant tissue tests [Online]. Available at http://www.nwag.com/interpre.html (verified 30 Sept. 2004). Northwest Agric. Consultants, Kennewick, WA.
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