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Acidic Soil Amendment with a Magnesium-Containing Fluidized Bed Combustion By-Product
Agronomy Journal
Abstract
Removal of SOâ from the emissions of coal-fired boilers produces by-products that often consist of CaSOâ, residual alkalinity, and coal ash. These by-products could be beneficial to acidic soils because of their alkalinity and the ability of gypsum (CaSOâ{center{underscore}dot}2HâO) to reduce Al toxicity in acidic subsoils. A 3-yr field experiment was conducted to determine the liming efficacy of a fluidized bed combustion boiler by-product (FBC) that contained 129 g Mg kgâ»Â¹ as CaMg(COâ)â and MgO and its effects on surface and subsurface soil chemistry. The FBC was mixed in the surface 10 cm of two acidic soils (Wooster silt loam, an Oxyaquic Fragiudalf, and Coshocton silt loam, an Aquultic Hapludalf) at rates of 0, 0.5, 1, and 2 times each soil's lime requirement (LR). Soils were sampled in 10-cm increments to depths ranging from 20 to 110 cm, and corn (Zea mays L.) and alfalfa (Medicago sativa L.) were grown. Application of Mg-FBC increased alfalfa yields in all six site-years, whereas it had no effect on corn grain yield in five site-years and decreased grain yield in one site-year. Plant tissue concentrations of Mg, S, and Mo were increased by Mg-FBC, while most trace elements were either unaffected or decreased. Application of Mg-FBC at one or two times LR increased surface soil pH to near 7 within 1 wk. Although surface soil pH remained near 7 for 2 yr, there was minimal effect on subjacent soil pH. Application of Mg-FBC increased surface soil concentrations of Ca, Mg, and S, which promoted downward movement of Mg and SOâ. This had different effects on subsoil chemistry in the two soils: in the high-Ca-status Wooster subsoil, exchangeable Ca was decreased and exchangeable Al was increased, whereas in the high-Al-status Coshocton subsoil, exchangeable Al was decreased and exchangeable Mg was increased. The Mg-FBC was an effective liming material and, because of the presence of both Mg and SOâ, may be more effective than gypsum in ameliorating subsoil Al phytotoxicity.
... The FBC ash is formed as a mixture of conventional coal combustion ash (either bed or fly ash), the SO 2 reaction product (primarily anhydrite, CaSO 4 ) and unspent sorbent (Stehouwer et al., 1999;Wang et al., 2006). Hence, the FBC ash is highly alkaline and has the potential to be used as liming material and S fertilizer. ...
... The maximum temperature and the rate of cooling influence the morphology and composition of CCPs (Kim, 2002). The trace elements present in CCPs include As, B, Ba, Cd, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, V and Zn (McDowell, 2005;Punshon et al., 2001;Sajwan et al., 2007;Stehouwer et al., 1999;Wang et al., 1995; Table 6.7). The partitioning of these elements is primarily determined by volatilization and condensation processes involved in the combustion of coal. ...
... In the case of FGD, CaCO 3 component is poorly soluble in soil and effective only on surface incorporation as they are not readily leached, but CaSO 4 present in FGD can effectively leach to subsurface and increase the Ca supply, thereby producing the neutralization effect (Clark et al., 2001). The best liming agent among the CCPs is FBC (CCE ranging from 31% to 105%), which is often utilized as a liming source to overcome the problems associated with soil acidity (Korcak, 1985(Korcak, , 1995Marsh and Grove, 1992;Stehouwer et al., 1999;Stout et al., 1998;Wang et al., 1995Wang et al., , 2006. Korcak and Kemper (1993) investigated the long-term effects of FBC applied at disposal levels on soil chemical properties. ...
Coal combustion products (CCPs), as the name suggests, are residues derived from the burning of coal in power generation industries. Traditionally, they have been dumped in large piles and/or ash-ponds mostly around the power stations. The CCPs are generally ash materials, mostly made of fine particles but some are also generated as coarse particles. Generation of these products poses serious threats to air, water and soil, and consequently to living organisms. The extent of the environmental effects caused by CCPs depends on (1) the coal source, (2) the combustion technology used and (3) the collection and segregation of the residues. Over the past two decades, there have been progressive research on the quality of power generation in terms of economic viability and environmental safety, and the effective usage of the waste products generated as a result of the power generation. This resulted in the emergence of clean coal technologies (CCTs), which aim at minimal environmental impacts, especially in curbing air pollution and ensuring more beneficial residues compared to conventional methods of combustion. In the global perspective, CCTs also reduce emission of several pollutants, decrease waste generation and increase the amount of energy gained per unit amount of coal combustion. This chapter will focus on the recent developments in CCTs and the applications of CCPs arising from those technologies, particularly agricultural and environmental applications. This chapter outlines the coal economy, their importance in power generation, latest technologies in the coal-fired power stations addressing emission control, the properties of CCPs generated, applications of CCPs and threats posed by the products. Each section will start with the products of conventional combustion technology (e.g. fly ash) and will later cover the applications pertaining to the products from CCTs (e.g. fluidized bed combustion ash). Future research should aim to focus more on the biological implications of CCPs addition to soil, long-term trials and a repository on ash information.
... Above that rate, plant growth was suppressed, likely due to cementing of the soil and increased salt concentration. Stehouwer et al. (1999) applied a CCP at rates up to 70 Mg ha -1 without negative effects on alfalfa yield. However, the authors did note dramatic differences in subsoil chemical parameters and plant response in the two Ohio soils they considered. ...
... Surface-applied gypsum achieved similar results in the same study. Stehouwer et al. (1999) found increases in extractable calcium and magnesium to a depth of 105 cm when a coal combustion byproduct was applied to the surface of two Ohio soils. However, water-soluble Al was decreased to that depth in only one soil. ...
... This indicates that S continued to move down in the profile. Downward movement of S, usually as SO 4 , from application of high-sulfate materials has been shown by other researchers (Farina, 1997;Farina et al., 2000b;Ritchey et al., 1995;Stehouwer et al., 1999). ...
Acid soils limit the growth of aluminum-(Al) sensitive crops such as alfalfa (Medicago sativa L.). Management of acid subsoils can be difficult due to physical and economic constraints. Field experiments were conducted at two locations to evaluate the effectiveness of surface-applied gypsum and a flue gas desulfurization by-product for reducing the toxic effects of acid subsoils on alfalfa. The materials were applied at rates of 0, 5, 10, and 15 Mg ha-1. In addition, a glasshouse experiment was conducted that used 0, 5, and 10 Mg ha-1 of gypsum only. Field studies were concluded 41 and 45 months after treatment application at the two locations. No effect of material on alfalfa yield or tissue mineral concentration was observed. Also, rate did not affect yield. However, there were differences in plant tissue mineral concentration in several harvests that were related to rate. Soil was sampled periodically to 120 cm and indicated movement of Ca and S into the soil profile to depths of 60 and 120 cm, respectively. Subsoil pHH2O and pHCaCl2 were not affected by treatment. Extractable and exchangeable Al were not reduced by movement of Ca and S into the soil. In the glasshouse study, alfalfa yields and root growth were not affected by gypsum rate. As gypsum rate increased, plant tissue S increased, but K and Mg decreased. Alfalfa roots did not grow below 60 cm, even though there was indication of material movement to 90 cm in the soil. Although sulfur moved to 75 cm, no effect on soil Al was observed. Leachate collected from the bottoms of columns indicated that soil cations were leached as a result of gypsum application. Gypsum and the flue gas desulfurization by-product did not significantly affect the acid soils used in these studies or improve alfalfa growth. "Major Subject: Agronomy." Title from author supplied metadata (automated record created on Apr. 30, 2004.). Vita. Abstract. Thesis (Ph. D.)--Texas A & M University, 2003. Includes bibliographical references. Text (Dissertation). Mode of access: World Wide Web. System requirements: World Wide Web access and Adobe Acrobat Reader.
... ) minerals, and limestone sludge with alkaline components in the form of carbonates, hydroxides , and oxides (Stehouwer et al. 1999). In the United States, electricity-generating plants must adopt methods to remove SO 2 from exhaust gas to comply with air-quality standards set by the U.S. Environmental Protection Agency (USEPA). ...
... Mixing FGD by-products with manure could solve some problems [Treating manure with CCBs, such as FGD by-products, before field application has been shown to stabilize soluble P in some studies (Stout et al. 1998; Dou et al. 2003; Zhang et al. 2004). In other studies, these CCBs have been used as soil amendments and have demonstrated agronomic benefits, such as reduced subsoil acidity, improved root growth, and better crop yields (Stout et al. 1979; Stehouwer et al. 1999). One less studied aspect is the possibility of CCBs adding detrimental trace elements, such as arsenic (As) and selenium (Se), to the environment. ...
... For example, rates less than 1 ton acre À 1 have been applied in some cases and over 5 tons acre À 1 in others when FGDs have been used to supply fertilizer mineral nutrients like Ca, S, and B to plants (Alva et al., 1999c;Dorsett et al., 1995;Fisher et al., 1997;Sloan et al., 1997). Rates of FGD as high as 10-30 tons acre À 1 have been used as soil liming agents and/or as gypsum amendments Stehouwer et al., 1999;Toma et al., 1999). Application rates greater than 200 tons acre À 1 have been used when FGDs were added to mine reclamation sites to increase pH of coal/refuse materials to fairly high values (Stehouwer et al., 1998). ...
... In the past, when concentrations of trace elements were reported in soils or plants grown in soil amended with FGDs, they usually were at or below established standards and often were below detection limits (Alva et al., 1999a,b;Clark et al., 1999c;Punshon et al., 1999;Stehouwer et al., 1999). Accumulation of trace elements over time might be of concern if amendments are added frequently or at sufficiently high levels over a considerable length of time. ...
Combustion of coal produces over half of the electricity used in the United States and generates 123.5mmtyear−1 of coal combustion products (CCPs). Only about 45% of CCPs are beneficially utilized and the rest are discarded, mainly in landfills. One class of CCPs, called flue gas desulfurization (FGD) products, generated by removal of SO2 from the exhaust gas of power plants, has physical and chemical properties that make them suitable for beneficial uses in agriculture. FGDs can be used as a soil amendment to provide a nutrient source for crops; ameliorate acidic soils; remediate sodic soils; improve soil structure to increase infiltration and water storage; reduce soil erosion and movement of sediments, nutrients, and pesticides to surface water; and stabilize and enrich organic composts and manures. FGD gypsum produced by a forced oxidation step following wet scrubbing of SO2, is the most promising of the FGD materials for agricultural uses. FGD gypsum is comparable to commercially available mined gypsum. When applied to soil at agronomic rates, FGD gypsum appears to pose little environmental risk. However, more information is needed on risks associated with the introduction of trace elements such as Hg and As to the environment. Management practices for specific uses of FGDs also need to be developed across a range of soils, cropping systems, and climate regimes.
... dry matter. [19] Enhanced alfalfa (Medicago sativa L.) and tall fescue (Festuca arundinacea Schreb.) growth in glasshouse studies were noted when dry FGDs [fluidized bed combustion (FBC) products] were applied, and alfalfa produced greater yields than tall fescue. [20] In field studies, a FBC þ Mg product enhanced growth of alfalfa, but not maize. [21] The objective of our studies was to determine effects of different levels of three FGDs added to acidic soil on growth of six forage species. These plants were also grown in acidic soil amended with different levels of the ). See data tables for levels of each material added to soil mixes. Levels of control substances and FGDs added to ...
... Relatively high soil EC from added CaSO 3 may have been because of HSO 3 2 formation in acidic soil, as this ion should be prominent in solution at low soil pH with added CaSO 3 . [25] The increase in EC with added FGD-27 may have been due to formation of MgSO 4 ·7H 2 O. [21] Only FGD-27 at its highest level increased soil pH Ca and EC sufficiently to potentially induce detrimental effects to plants. Soil at pH 7 to 8 may induce deficiencies of P, Fe, Zn, and/or Mn because solubilities of these minerals are reduced as soil pH increases. ...
Large amounts of flue gas desulfurization products (FGDs) are produced when SO2 emissions are trapped in the coal burning process for generation of electricity. FGDs are normally discarded instead of being reused, and reuse on soils could be important in overall management of these products. Glasshouse experiments were conducted to determine effects of various levels of three FGDs (a FGD gypsum, an oxidized FGD+Mg, and a stabilized FGD) and the control compounds CaCO3, CaSO3, and CaSO4 on growth of alfalfa (Medicago sativa), white clover (Trifolium repens), orchardgrass (Dactylis glomerata), tall fescue (Festuca arundinacea), switchgrass (Panicum virgatum), and eastern gamagrass (Tripsacum dactyloides) in acidic (pH 4) soil (Typic Hapludult). The FGDs enhanced growth of each plant species, with alfalfa, white clover, and tall fescue receiving greater increases than the other species, especially when grown in soil amended with FGD+Mg. FGD gypsum did not often enhance growth unless high amounts were added. FGDs containing high B and low levels of CaSO3 were detrimental to growth. Overall, FGDs improved growth responses of these forage plants grown in an infertile low pH soil.
... Magnesium-containing fluidized bed combustion by-products have proved to be effective liming materials with a high effectiveness to ameliorate subsoil Al phytotoxicity (Stehouwer et al., 1999). ...
Mining drastically alters the physico-chemical and biological environment of the landscape. Low organic matter content, unfavourable pH, low water holding capacity, salinity, coarse texture, compaction, siltation of water bodies due to wash off of mineral overburden dumps, inadequate supply of plant nutrients, accelerated erosion, acid generating materials, and mobilization of contaminated sediments into the aquatic environment are the principal constraints experienced in mining contaminated sites. A variety of approaches have been considered for reclaiming mine wastes including direct revegetation of amended waste materials, top soiling, and the use of capillary barriers. The simplest technology to improve crop productivity is the addition of organic amendments. Biosolids and animal manure can support revegetation, but its rapid decomposition especially in the wet tropics, necessitates repeated applications. Recalcitrant materials such as “biochars”, which improve soil properties on a long term basis as well as promote soil carbon sequestration, hold enormous promise. An eco-friendly and cost-effective Microbe Assisted Phytoremediation system has been proposed to increase biological productivity and fertility of mine spoil dumps. Agroforestry practices may enhance the nutrient status of degraded mine spoil lands (facilitation). N-fixing trees are important in this respect. Metal tolerant ecotypes of grasses and calcium-loving plants help restore lead, zinc, and copper mine tailings and gypsum mine spoils, respectively. Overall, an integrated strategy of introduction of metal tolerant plants, genetic engineering for enhanced synthesis and exudation of natural chelators into the rhizosphere, improvement of rhizosphere, and integrated management including agroforestry will be appropriate for reclaiming mining contaminated lands.
... To date, this reclamation practice led by Tsinghua University has been conducted in over 10 Chinese provinces with a total area exceeding 6,000 hectares. Moreover, there have been some studies on the use of FGD gypsum for acidic soil remediation to reduce the soluble phosphorus in soils or as sulfur sources for crops (Stehouwer et al., 1999;Chen et al., 2008;Watts and Torbert, 2010). ...
Although flue gas desulfurization (FGD) gypsum has become an effective soil amendment for sodic soil reclamation, it carries extra heavy metal contamination into the soil environment. The fate of heavy metals introduced by FGD gypsum in sodic or saline-alkali soils is still unclear. This work aims to investigate the effects of FGD gypsum addition on the heavy metal distributions in a sodic soil. Original soil samples were collected from typical sodic land in north China. Soil column leaching tests were conducted to investigate the influence of FGD gypsum addition on the soil properties, especially on distribution profiles of the heavy metals (Pb, Cd, Cr, As, and Hg) in the soil layers. Results showed that pH, electrical conductivity, and exchangeable sodium percentage in amended soils were significantly reduced from 10.2 to 8.46, 1.8 to 0.2 dS/m, and 18.14% to 1.28%, respectively. As and Hg concentrations in the soils were found to be positively correlated with FGD gypsum added. The amount of Hg in the leachate was positively correlated with FGD gypsum application ratio, whereas a negative correlation was observed between the Pb concentration in the leachate and the FGD gypsum ratio. Results revealed that heavy metal concentrations in soils complied well with Environmental Quality Standard for Soils in China (GB15618-1995). This work helps to understand the fate of FGD gypsum-introduced heavy metals in sodic soils and provides a baseline for further environmental risk assessment associated with applying FGD gypsum for sodic soil remediation.
... The fly ash was a product of a fluidized bed combustion process at a coal-fired power plant, possessed relatively high Ca and Al concentrations, and was similar in composition to fly ash characterized in previous studies (Stout, Sharpley, and Pionke 1998;Laperche and Bigham 2002;Dou et al. 2003). Fly ashes are often mixtures of various minerals with coal ash, limestone residues, and hydroxide/oxides (Stehouwer, Dick, and Sutton 1999;Laperche and Bigham 2002). The bauxite residual was produced by treating bauxite ore with NaOH to separate Fe from the desired Al, resulting in a very high pH (9.8) and considerable Al concentrations (77.8 g kg −1 ) because of process inefficiencies. ...
The potential of six industrial by-products for use as phosphorus-sorbing materials (PSMs) in solutions was evaluated. These included two different acid mine drainage treatment residuals (AMDR1 and AMDR2), water treatment residual (WTR), fly ash, bauxite mining residual, and flue gas desulfurization product (FGD). Characterization of the by-products and their mechanisms for sorption and retention of inorganic phosphorus (P) from solution identified those PSMs that sorbed primarily by an iron and aluminum (Fe/Al) mechanism, those that sorbed primarily by a calcium and magnesium (Ca/Mg) mechanism, and those that sorbed by both mechanisms. Degree of P sorption and associated mechanisms were strongly influenced by the pH, buffer capacity, ionic strength, and common ion effects.
... The use of ash from the gasifi cation of biomass has been examined in a limited number of trials (Mozaff ari et al., 2002;Stehouwer et al., 1999). Mozaff ari et al. (2000) found that ash generated from gasifi cation of alfalfa (Medicago sativa L.) stems was a valuable nutrient and soil amendment for corn grown in a greenhouse. ...
Emerging markets for fuels and energy from crop biomass are creating new opportunities for redesigning agricultural systems for improved ecological function and energy-use efficiency. Innovative bioconversion processes configured to recover key plant nutrients from biomass will allow recycling nutrients to crop fields, thereby closing nutrient cycles and reducing the energetic and economic costs of fertiliz,ation. Such advanced bioconversion matched With complementary biomass production,may promote the i development of highly productive agricultural-industrial systems that protect environmental quality. A generally representative example of nutrient recovery from an-integrated biological and thermochemical conversion process designed to produce ethanol and synthetic 1 fuels from switchgrass (Panicum virgatum L.) indicates that approximately 111 kg ha(-1) yr(-1) of N can be recovered. This is equivalent to 78% of the N-fertilizer input required. This example illustrates that N recovery and cycling could significantly improve the sustainability of biomass production as well as the overall energy balance of ethanol production from lignocellulosic biomass. Demand for lignocellulosic biomass as an industrial feedstock may also allow the introduction of new crops and cropping systems. In addition to perennial grasses, double-crop sequences and systems incorporating greater I use of legumes, cover crops, and living mulch I may be able to produce large amounts of bioi mass while improving resource use efficiency I and reducing environmental impact.
... Therefore, FBA can be utilized for controlling soil erosion on agricultural land and construction sites, especially those with permanently charged clays."". 7 Reichert & ort ton" measured the steadystate infiltration rates (I,) for five soils, with and without addition of 5000 kg ha-' surface applied FBA (74% CaS04,23% CaO, total dissolved salts 4700 mg litre-'). They found that surface sealing and erosion were significantly reduced by the surface applied FBA on all studied soils, but with a lesser effectiveness on the illitic and smectitic soils. ...
To meet the Clean Air standard, many North American and European power plants have adopted fluidized bed combustion techniques. These systems require lower capital investment, to reduce the sulfur-dioxide (SO2) emissions in flue gases, than the wet flue gas desulfurization process. In the former system, limestone chip mixed with the fine coal is burnt in a bed suspended by compressed air. Sulfur dioxide released as the coal is burnt, reacts with CaO generated in the furnace therefore minimizing SO2 emissions from the stack. The resulting ash from the boiler bed and trapped fly ash, known as fluidized bed boiler ash (FBA), contains CaSO4 and unreacted CaO. Mixing this ash with water, to overcome dust problems, subsequently converts CaO to Ca(OH)2. The chemical composition of FBA is highly dependent on the efficiency of the boilers and the nature of the fuel and limestone sources.
As many countries including Australia and USA are rich in coal resources, coal plays a significant role in supplying energy. But, some of the coal resources are rich in sulfur (S) and with increasing concern for environmental pollution, low cost techniques, such as fluidized bed combustion, are required to reduce SO2 emission from the burning of such high S coal. Consequently, large quantities of FBA or similar by-products would be expected. Although the resulting large volumes of FBA materials are generally disposed of in landfills, limited landfill space and increased costs, however, have stimulated investigations in many countries to develop and demonstrate agricultural and environmentally safe uses for FBAs, thereby reducing the cost of SO2 scrubbing.
Agricultural utilization of FBA overcomes a waste problem and at the same time provides a liming material and an inexpensive form of S source. Furthermore, FBA also has potential as a micro-nutrient fertilizer, providing elements such as boron and selenium. In this chapter the chemical characteristics of FBA and its potential uses as a liming material, soil conditioner and S fertilizer are reviewed.
... Because of these concerns, limits for trace elements have been established in leachates (TCLP), drinking water, and land loading (Table 10; [27]). When concentrations of trace elements have been reported in soils amended with FGDs or in plants grown in soil amended with FGDs, they have usually been below established standards and are often below detectable limits [4,5,22,49]. For example, mean leaf concentrations of Ni, Pb, Cd, and Cr varied somewhat depending on type and level of FGD added to acidic soil (Table 11), and meanTable 9 Calcium and S concentrations in leaves of maize grown in acidic soil amended with different levels of FGDs (from Clark et al. [21]Table 11 Mean leaf concentrations of Ni, Pb, Cd, and Cr of maize grown in acidic soil amended with different levels of FGDs (from Clark et al. [22]) concentrations (mg kg 21 ) over all levels and FGDs used were 1.22 for Ni, 1.28 for Pb, 0.31 for Cd, and 0.62 for Cr, which were below established standards and at concentrations considered normal for plant tissue (Table 10; [13]). ...
Considerable amounts of coal combustion products (CCPs) are generated when coal is burned for generation of electricity. To meet Clean Air standards, large amounts of S must not be emitted into the atmosphere, which means considerable amounts of flue gas desulfurization products (FGDs) are and will be produced. Beneficial uses of FGDs are continually being sought to reduce waste, decrease cost of disposal, and provide value-added products. Beneficial agricultural uses of FGDs include application as amendment to acidic soil to mitigate low pH problems (Al and Mn toxicities); provide plant nutrients (i.e. Ca, S, and Mg); improve soil physical properties (e.g. water infiltration and soil aggregation); help alleviate soil compaction and improve aggregate stability of sodic soils; and inactivate P under high P-soil conditions to reduce P runoff. Co-utilization of FGDs with organic materials (manures, composts, biosolids) should also provide many benefits when used on land. Constraints for use of FGDs on agricultural land could be both insufficient or excessive amounts of CaCO3, CaO, and/or Ca(OH)2 in raising soil pH insufficiently or too much; excessive Ca to cause imbalanced Mg, P, and K in soils/plants; Ca displacement of Al from soil exchange sites to induce Al toxicity in plants; high B to induce B toxicity in plants; excessive sulfite which is toxic to plants; and excessive amounts of undesirable trace elements (e.g. As, Cd, Cr, Ni, Pb, and Se) which could potentially contaminate water and pose toxicity to plants/animals/microorganisms. Most constraints should not impose problems for FGD use on land.
... Ni concentrations the second year after surface application of various levels of a dry FBC þ Mg product. [27] In both of these studies, concentrations of most mineral elements in tissue did not change significantly when plants were grown in amended soil. However, the highest level of FBC added was only 2- fold higher than the lime requirement for soil, which meant that relatively low levels (e.g., , 1.0– 1.5% in soil) were added. The objective ...
Considerable quantities of flue gas desulfurization products (FGDs) are generated when coal is burned for production of electricity, and these products have the potential to be reused rather than discarded. Use of FGDs as soil amendments could be important in overall management of these products, especially on acidic soils. Glasshouse studies were conducted to determine shoot concentrations of calcium (Ca), sulfur (S), potassium (K), magnesium (Mg), phosphorus (P), boron (B), zinc (Zn), copper (Cu), manganese (Mn), iron (Fe), aluminum (Al), sodium (Na), molybdenum (Mo), nickel (Ni), cadmium (Cd), chromium (Cr), and lead (Pb) in alfalfa (Medicago sativa), white clover (Trifolium repens), orchardgrass (Dactylis glomerata), tall fescue (Festuca arundinacea), switchgrass (Panicum virgatum), and eastern gamagrass (Tripsacum dactyloides) grown in acidic (pH 4) soil (Typic Hapludult) amended with various levels of three FGDs and the control compounds CaCO3, CaSO3, and CaSO4. Shoot concentrations of Ca, S, Mg, and B generally increased as levels of soil applied FGD increased. Concentrations of Mn, Fe, Zn, Cu were lower in shoots, especially when soil pH was high (.7). Shoot concentrations of the trace elements Mo, Ni, Cd, Cr, and Pb were not above those reported as normal for foliage. Overall concentrations of most minerals remained near normal for shoots when plants were grown in FGD amended acidic soil.
... Some of these chemicals, such as ferrous sulphate, are often found in FA and therefore the chemistry of unamended FA itself may contribute to reducing the bioavailability of co-occurring trace metals. The agronomic benefits of FBC byproducts consisting of coal ash and anhydrite (CaSO 4 ), with residual alkalinity due to carbonates, hydroxides and oxides, include reduction of Al phytotoxicity in acidic subsoils and improved plant growth and crop yield (Stehouwer et al., 1999). Applying FA with sewage sludge has been proposed as a means of reducing the bioavailability of heavy metals and augmenting ambient levels of B, Ca, K and S (Sajwan et al., 2003;Lau et al., 2001;Su and Wong, 2004). ...
Growing dependence on coal-fired power plants for electrical generation in many countries presents ongoing environmental challenges. Burning pulverized coal in thermal power plants (TPPs) generates large amounts of fly ash (FA) that must be disposed of or otherwise handled, in an environmentally-sound manner. A possible option for dealing with fly ash is to use it as an amendment for mine spoil or other damaged soil. It has been demonstrated through studies in India and other countries that FA alone or in combination with organic or inorganic materials can be used in a productive manner for reclamation of mine spoil. The characteristics of FA, including silt-sized particles, lighter materials with low bulk density (BD), higher water holding capacity, favorable pH and significant concentrations of many essential plant nutrients, make it a potentially favorable amendment for mine spoil reclamation. Studies have indicated that the application of FA has improved the physical, chemical and biological qualities of soil to which it is applied. The release of trace metals and soluble salts from FA could be a major limitation to its application. This is particularly true of fresh, un-weathered FA or acidic FA, although perhaps not a concern for weathered/pond ash or alkaline FA. Some potential contaminants, especially metals and other salt ions, could be immobilized and rendered biologically inert by the addition of certain inorganic and organic amendments. However, in view of the variability in the characteristics of FAs that are associated with location, feed coal, combustion conditions and other factors, the suitability of a particular FA for a specific soil/mine spoil needs to be critically evaluated before it is applied in order to maximize favorable results and eliminate unexpected consequences. FA generated in India tends to be mostly alkaline, with lower levels of trace elements than are often found in FAs from other countries. The concentrations of potential chemical stressors, predominantly metals, in Indian FAs are often less than established or proposed permissible limits and are thus better suited for soil application. A major logistic limitation to the use of FA could be the cost involved in transport of ash from production to utilization sites.
... This indicates that CaSO 4 in the perlite-FGD, was more rapidly released to the soil than that in the vermiculite-FGD. Our results are consistent with those of Stehouwer et al. (1999) where FGD increased the concentrations in soil of soluble Ca and S and also increased plant uptake and downward transport in the soil pro®le. Application of perlite-FGD (1Â rate) also signi®cantly increased soluble Mg concentrations but application of vermiculite-FGD, which contains high concentrations of Mg, only slightly increased soluble Mg concentrations in soil. ...
Flue gas desulfurization (FGD) by-products are created when coal is burned and SO2 is removed from the flue gases. These FGD by-products are often alkaline and contain many plant nutrients. Land application of FGD by-products is encouraged but little information is available related to plant responses and environmental impacts concerning such use. Agricultural lime (ag-lime) and several new types of FGD by-products which contain either vermiculite or perlite were applied at 0, 0.5, 1.0, and 2.0 times the soil's lime requirement (LR) rate to an acidic soil (Wooster silt loam). The highest FGD by-products application rate was equivalent to 75.2 Mg ha(-1). Growth of alfalfa (Medicago sativa L.) was significantly increased compared to the untreated control in the second year after treatment with yields for the 1 x LR rate of FGD approximately 7-8 times greater compared to the untreated control and 30% greater than for the commercial ag-lime. Concentrations of Mo in alfalfa were significantly increased by FGD by-products application, compared to the untreated control, while compared to the ag-lime treatment, concentrations of B increased and Ba decreased. No soil contamination problems were observed, even at the 2xLR rate, indicating these materials can be safely applied to agricultural soils.
Pot experiment was used to study the effect of increased doses of fly ash, obtained from coal combustion in the EC Rzeszów heat and power generating plant, on chemical properties of sandy soil. The experiment comprised ten fertilizer combinations in 4 replications. Polyethylene pots were filled with soil and then fertilized with increased doses of fly ash, set according to 0.5, 0.75, 1, 2, 3, 4, hydrolytic acidity (Hh) (objects I–VI), with dolomite (containing 25.4% CaO and 20.7% MgO), according to 1 and 3 Hh, (objects VII–VIII), as well as an 1:1 mixture of ash and dolomite, according to 1 and 3 Hh, (objects IX–X). Application of the highest dose of ash (i.e. 134.4 t·ha-1) caused a marked increase in total content of magnesium by 633%, phosphorus – by 361%, and a slight increase in potassium content-by 38% (compared to reference), a using the growth of the content of heavy metals to the level of increased content (IIº) simultaneously, the Cd to 0.22 mg·kg-1 and Pb to 36.6 mg·kg-1. Availability forms Mg i K of in the soil improved under effect of fertilization with ash. It was observed that, combined application of ash and dolomite had favorable effect on chemical properties of soil. Higher ash doses significantly decreased yield of oats. A positive effect on yielding of oat has been proved on sandy soil with 16.8 t·ha-1 fly ash.
Combustion of fossil fuels for energy production releases sulfur dioxide (SO2) at a rate proportional to the S concentration in the fuel. Industrialized nations have adopted flue gas desulfurization (FGD) technologies to reduce SO2 emissions. FGD technologies will generate increased amounts of product in the future as more utilities install scrubbers for SO 2 control. These FGD products raise economic and environmental issues for which satisfactory solutions still need to be found. The type of coal and desulfurization process used influences the chemical composition and properties of an FGD product. The properties of the FGD material have a direct impact on potential land application uses. FGD properties most commonly captured for beneficial purposes are (1) ability to neutralize acid, (2) high amounts of soluble calcium and sulfate, (3) source of plant nutrients, and (4) uniform particle size. Land application uses of FGD materials are identified by matching the properties of the FGD material with improvement in some ecosystem function (or functions). For beneficial use, the change in ecosystem function is assumed to be positive. FGD use must be considered in terms of recommended application rates, environmental impact and economic return. Beneficial land application implies the applied FGD material will improve the soil (primarily) and also the total environment. Often, the intended benefit relates to plant growth, but there may be other benefits to soil or water such as reduction of erosion, improved quality of runoff and/or leachate water, or improved internal drainage. The application rate must be sufficient to cause soil improvement, but not so great as to constitute disposal of the FGD material. Although there is recognition of the potential of using FGD materials in agriculture, there is also uncertainty whether this use is sustainable. Currently, there is a general lack of acceptance in the agricultural community for using FGD materials. This barrier can only be overcome by research and sound knowledge that sometimes already exists in the scientific and technical literature. To promote use of FGD products, especially FGD gypsum, a national network of agricultural demonstration and research sites has been established. Network sites, strategically located in the United States, are available to producers, users and marketers of FGD products to provide places where observations can be made as to the benefits of FGD product use under regional agricultural conditions. In addition, data on crop yields, environmental impacts and economic benefits will aid in the marketing of the FGD products.
Coal combustion in traditional powder-fed boilers produces two types of residues: (1) fly ash, which is a fine fraction dispersed in the flue gas and (2) bottom ash collected in the boiler. Fly ash is separated from flue gas by electrostatic precipitators or a variety of mechanical methods. Large emissions of sulfur dioxide (SO2) from coal combustion are one of the major atmospheric pollutants. To minimize these emissions, fluidized bed combustion (FBC) and wet scrubbing technologies are used. The effect of fly ash application on soil water content depends on fly ash rate and soil texture. In contrast to agricultural land, potting mixtures and artificial soils create a market for fly ash that can be used to improve their texture and water-holding capacity. Because fly ash contains almost all elements and their concentrations depend on coal source, periodic monitoring of the chemical composition should be undertaken to ensure safe utilization. Gypsum is applied to soils to supply S and Ca for crops, ameliorate subsoil acidity, and improve soil physical condition and is recognized as a valuable soil amendment, being used on a commercial scale in many countries.
Land application of sewage biosolids is a cheap disposal method that permits recycling of plant nutrients, but there are concerns about its long-term agronomic value and environmental effects. This study investigated the fertilizer value of alkaline-stabilized biosolids applied annually to spring barley (Hordeum vulgare L.). Dewatered biosolids [320-350 g kg-1 dry matter (DM)] were alkaline stabilized by mixing them with cement kiln dust and composting aerobically. The product had some liming value (300 g kg-1 DM CaCO3 equivalent on average) and contained an average of 7.2, 2.3, and 19.5 g kg-1 DM of N, P, and K. Two field experiments compared the P or K value of the biosolids with inorganic fertilizer P or K for seven consecutive annual spring barley crops on two contrasting soils. All biosolid and fertilizer treatments gave higher yields than the controls. Biosolids gave higher grain and straw yields than fertilizer P, similar grain and straw yields to fertilizer K, and higher grain weights and more grains per ear than fertilizer P or K. These effects may have been due to, inter alia, higher soil pH and S inputs. An increasing soil pH from biosolid application was associated with lower shoot Mn concentrations, but no Mn deficiency symptoms were observed. Alkaline biosolids acted as a slow-release P fertilizer, and biosolid P was at least as available to the crops as inorganic fertilizer P. Biosolid K was also as available as fertilizer K. A calculation of nutrient balances indicated that current fertilizer P recommendations could be lowered.
The combustion of petroleum coke with limestone in a circulating fluidized bed (CFB) to remove SO2 from flue gas creates a product that may be used in agriculture. However, there are no reports on changes of soil chemical properties by application of petroleum coke CFB product. Two field experiments were conducted to determine elements in topsoil, subsoil, and soil water after CFB product application at 67.2 Mg/ha. Sulfur in the 0- to 60-cm and Ca, Mo, Ni, Sb, Sr, and V in the 0- to 15-cm soil layers were all increased 7 and 30 months after application. Concentrations of Ca, Mg, Ni, S, and Sr in soil water at the 60-cm depth were 2 to 4 times greater than control levels 6 months after treatment and 8 to 31 times greater 27 months after treatment. Concentrations of Al, As, Cd, Cr, Mn, and Sb were also increased in soil water 6 months after treatment at the 30-cm depth and 27 months after treatment at the 60-cm depth. Subsoil chemical properties and vadose water quality in this study were significantly changed by the surface application of petroleum coke CFB product, but the changes would not preclude the use of CFB product as a beneficial soil amendment.
The flue gas desulfurization process employing forced oxidation technology generates an almost pure gypsum (FGD), which may substitute for mined gypsum used as a soil amendment in the southeastern United States. Under specific conditions, a mixture of FGD and fly ash (FA) may be produced by an electric power plant. A field experiment was conducted to study the effect of FGD applied both singly and as a 1:1 mixture with fly ash (AFGD) on the distribution of the exchangeable cations Ca, Mg, K, and Al and the trace elements B, As, and Pb in the profiles of soils having various textures. Lime was not applied in this study. The experiment was conducted at three different locations near Tifton, Athens, and Calhoun, Georgia. The total amount of rainfall plus irrigation at these locations during the experimental period was 1385, 1418, and 1406 mm, respectively. Soil cores were collected to a depth of 70 or 80 cm about 13 months after by-product application. FGD application increased exchangeable Ca levels in the subsoil. Exchangeable K levels were significantly decreased by FGD application only in a sandy soil. FGD promoted release of Mg from the soil sorptive complex and increased leaching of this element. Cations were transported most effectively in the profiles of a sandy soil. FA application increased plant available As in the surface layer of a sandy soil and plant available B in the zone of incorporation in the soils containing more clay, but it only partially alleviated deficiencies of this element. FA did not sufficiently supplement K and Mg losses induced by FGD application. The results of this study demonstrate that the FGD material had greater agronomic value than the mixed AFGD by-product.
Large amounts of coal combustion products (CCPs) are produced when coal is burned for generation of electricity. Some of these CCPs could potentially be used as soil amendments, and information about their effects on plant mineral nutrition is needed. Glasshouse experiments were conducted to test the effects of different levels of 15 CCPs and chemical grade CaCO3, CaSO4, and CaSO3 added to acidic soil (Umbric Dystrochrept) on shoot calcium (Ca), sulfur (S), phosphorus (P), potassium (K), magnesium (Mg), manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), and aluminum (Al) concentrations of maize (Zea mays L.). The CCPs consisted of two fly ashes (FAs), one CaO material, three fluidized bed combustion products (FBCs), three "non-stabilized" flue gas desulfurization products (FGDs), three "stabilized" FGDs, and three "oxidized" (FGD gypsum) FGDs. Level of CCP added to soil ranged from beneficial to detrimental effects on plants. Differences in shoot mineral element concentrations were related to kind and amount of CCP added and soil pH. Plants grown in unamended (pH 4) soil had symptoms of P and Mg deficiencies and Al toxicity. High concentrations of Ca, S, Mg, and Mn accumulated when plants were grown with some CCPs, but most mineral nutrients were at concentrations considered normal for maize. Shoot concentrations of P, K, Zn, Mn, Fe, and Al decreased when soil pH became high (>7). Even though detrimental mineral element acquisition effects were imposed on plants at high levels of CCP application, shoot element concentrations were usually normal when applied at levels near those commonly used as soil amendments.
Calcium-rich soil amendments can improve plant growth by supplying Ca and reducing detrimental effects of soil acidity, but solubility and neutralizing capacity of Ca sources vary. Our objectives were to evaluate effects of calcitic dolomite and several coal combustion by-products on soil properties at various depths 6 yr after surface application and their influence on grass-clover herbage accumulation. Calcium and Mg soil amendments were surface-applied to an acidic grassland in 1993, and orchardgrass (Dactylis glomerata L.) and tall fescue Lolium arundinaceum (Schreb.) Darbyshire were oversown in 1994. In 1998, amendment treatment plots were split to accommodate sod seeding with red clover (Trifolium pratense L.) or white clover (T. repens L.) as well as a nonseeded control. No N fertilizer was applied after sod seeding. Six years after amendment application, reductions in soil Al and Mn and increases in Ca and pH from 4654 kg ha(-1) calcitic dolomite, 15 000 kg ha(-1) fluidized bed combustion residue, or 526 kg ha(-1) MgO amendment were greatest in the surface 2.5 cm while rates of gypsum as high as 32 000 kg ha(-1) left little residual effect except for decreases in Mg. Percentage clover in the sward tripled as pH increased from 4.3 to 5.0 while herbage mass increased 75% as clover percentage increased. Herbage mass was generally more closely correlated with properties of soil samples collected from the surface 2.5 cm than from deeper samples.
Acid soils limit the growth of aluminum-(Al) sensitive crops such as alfalfa (Medicago sativa L.). Management of acid subsoils can be difficult due to physical and economic constraints. Field experiments were conducted at two locations to evaluate the effectiveness of surface-applied gypsum and a flue gas desulfurization by-product for reducing the toxic effects of acid subsoils on alfalfa. The materials were applied at rates of 0, 5, 10, and 15 Mg ha-1. In addition, a glasshouse experiment was conducted that used 0, 5, and 10 Mg ha-1 of gypsum only. Field studies were concluded 41 and 45 months after treatment application at the two locations. No effect of material on alfalfa yield or tissue mineral concentration was observed. Also, rate did not affect yield. However, there were differences in plant tissue mineral concentration in several harvests that were related to rate. Soil was sampled periodically to 120 cm and indicated movement of Ca and S into the soil profile to depths of 60 and 120 cm, respectively. Subsoil pHH2O and pHCaCl2 were not affected by treatment. Extractable and exchangeable Al were not reduced by movement of Ca and S into the soil. In the glasshouse study, alfalfa yields and root growth were not affected by gypsum rate. As gypsum rate increased, plant tissue S increased, but K and Mg decreased. Alfalfa roots did not grow below 60 cm, even though there was indication of material movement to 90 cm in the soil. Although sulfur moved to 75 cm, no effect on soil Al was observed. Leachate collected from the bottoms of columns indicated that soil cations were leached as a result of gypsum application. Gypsum and the flue gas desulfurization by-product did not significantly affect the acid soils used in these studies or improve alfalfa growth.
Agricultural utilization of biosolids poses a potential risk to ruminant animals due to transfer of Mo from biosolids to forage to the animal in amounts large enough to suppress Cu uptake by the animal. Alkaline-stabilized biosolids (ASB) must be given particular consideration in assessment of Mo risk because the high pH of these biosolids could increase Mo and decrease Cu uptake by forage legumes. In this 3-yr field experiment, ASB and ground agricultural limestone (AL) were applied based on their alkalinity at rates equivalent to 0, 0.5, 1.0, and 2.0 times the lime requirement of the soil and alfalfa (Medicago sativa L.) was grown. Alfalfa yield was similar with AL and ASB except in the second year when ASB produced larger yields, apparently due to increased B availability with ASB. Application of ASB did not detectably increase extractable soil Mo (0- to 15-cm depth), but increased alfalfa Mo uptake in all cuttings with yield-weighted uptake coefficients (UCs) of 8.07 and 7.11 following the first and second ASB applications, respectively. Although ASB increased extractable soil Cu, and alfalfa Cu content was greater with ASB than with AL, yield-weighted alfalfa Cu to Mo ratio was decreased by ASB to levels near 3. These results suggest that ASB may have a greater effect on Mo uptake and Cu to Mo ratio of forage legumes than do other biosolids. Additional research is needed to determine implications of larger Mo cumulative loading with ASB for Mo risk, particularly in the soil pH range of 7 to 8.
Coal combustion power plant flyash materials have been reported as useful soil amendments with agronomic and environmental benefits. This paper reports the efficacy of fluidized bed combustion (FBC) and flue gas desulfurization (FGD) byproducts, when amended with dairy, swine, and broiler litter manures, in reducing phosphorus (P) solubility and potential impact on water quality. At a rate of 400 g/kg, FBC reduced water soluble P by 60% for dairy and swine and 50% for broiler litter, as compared to un-treated control samples. Byproduct FGD had little effect when amended into dairy manure, but reduced water soluble P by nearly 80% when amended into swine and broiler manure at a rate of 250 g/kg. The amount of Ca added in the amendments together with pH of the mixture is the major contributing factor in soluble P reduction. Sequential extraction results showed that the flyash treatments shifted water soluble P into mainly bicarbonate extractable P. The latter is still considered available for crop uptake but less vulnerable for environmental losses. Coal combustion byproducts, when amended into manure and used properly, can provide a useful and viable option for improving nutrient management on animal farms.
To reduce S emissions, petroleum coke with a high concentration of S was combusted with limestone in a circulating fluidized bed (CFB) boiler. The combustion process creates a bed product that has potential for agricultural uses. This CFB product is often alkaline and enriched in S and other essential plant nutrients, but also contains high concentrations of Ni and V. Agricultural land application of CFB product is encouraged, but little information is available related to plant responses and environmental impacts. CFB product and agricultural lime (ag-lime) were applied at rates of 0, 0.5, 1.0, and 2.0 times the soil's lime requirement (LR) to an acidic soil (Wooster silt loam). The 2.0x LR application rate of CFB product was equivalent to 67.2 Mg ha(-1). Alfalfa yield was increased 4.6 times by CFB product and 3.8 times by ag-lime compared to untreated control. Application of CFB product increased the concentration of V in soil and alfalfa tissue, but not in soil water, and increased the concentration of Ni in soil and soil water, but not in alfalfa tissue. However, these concentrations did not reach levels that might cause environmental problems.
Animal manures contain large amounts of soluble phosphorus (P), which is prone to runoff losses when manure is surface-applied. Here we report the efficacy of alum and three coal combustion by-products in reducing P solubility when added to dairy, swine, or broiler litter manures in a laboratory incubation study. Compared with unamended controls, alum effectively reduced readily soluble P, determined in water extracts of moist manure samples with 1 h of shaking, for all three manures. The reduction ranged from 80 to 99% at treatment rates of 100 to 250 g alum kg(-1) manure dry matter. The fluidized bed combustion fly ash (FBC) reduced readily soluble P by 50 to 60% at a rate of 400 g kg(-1) for all three manures. Flue gas desulfurization by-product (FGD) reduced readily soluble P by nearly 80% when added to swine manure and broiler litter at 150 and 250 g kg(-1). Another by-product, anthracite refuse fly ash (ANT), was ineffective for all three manures. In all cases, reduction in readily soluble P is primarily associated with inorganic phosphorus (P(i)) with little change in organic phosphorus (P(o)). Sequential extraction results indicate that the by-product treatments shifted manure P from H2O-P into a less vulnerable fraction, NaHCO3 - P, while the alum treatment shifted the P into even more stable forms, mostly NaOH-P. Such shifts in P fractions would have little influence on P availability for crops over the long-term but would retard and reduce potential losses of P following manure applications.
Removal of sulfur dioxide from flue gas produced by coal-burning power plants has increased the availability of by-products that may be useful as soil amendments for agriculture. We studied the effects of surface layers (caps) of fluidized bed combustion residue-fly ash mixture (FBCR-FA) or calcium sulfate on reduction of evaporative water losses and improvements in subsurface acid soil chemical characteristics. Caps 3.8 cm thick of porous FBCR-FA, hydrated commercial calcium sulfate (CCS), or soil (check) were placed on columns of coarse-loamy, mixed, mesic Umbric Dystrochrept soil of pH 4.2. After the addition of 40 cm of water during a 16-week period, mean daily water loss from the column with the FBCR-FA cap was 0.51 mm compared to 0.98 mm in the check. Mean increase in soil exchangeable Ca in the 5- to 40-cm depth for the CCS treatment was 0.83 cmolc kg–1 and mean pH (H2O) increase was 0.21 units. Mean KCl-extractable Al decreased from 6.08 to 5.52 cmolc kg–1. Roots of sudangrass (Sorghum bicolor (L.) Moench) planted in the columns after removal of the caps reached 2 cm depth in the control, 18 cm in the FBCR-FA and 38 cm in the CCS treated columns after 47 days of growth. The gypsum cap was effective in improving deep rooting in acid soils and the FBCR-FA cap reduced evaporative water losses.
Fluidized bed material (FBM), a dry, high‐Ca, alkaline waste product from the combustion of coal and limestone, was used as a lime substitute/Ca source for ‘York Imperial’ apple seedlings ( Malus domestica ) grown on three acidic soil materials in the greenhouse. Application rates were based on the lime requirement (LR) for each soil material determined by the BaCl 2 triethanolamine procedure. The LR values were 4.57, 12.54, and 11.65 mt CaCO 3 /ha for the Galestown Ap, Arendtsville Ap, and Tatum subsoil soil materials, respectively. Actual rates of FBM were one, two, four, and eight times the LR on a weight basis. A CaCO 3 treatment at the LR and a non‐Ca amended fertilized control were used as comparisons.
Fluidized bed material applied at the LR significantly increased leaf and stem dry weights and linear growth after 17 weeks, while the CaCO 3 treatment was not significantly different from the control. However, the highest FBM rate significantly reduced growth. The reason for this reduced growth was not evident from tissue elemental analyses or measurements of various soil properties.
Applied FBM significantly increased leaf and stem Ca levels and decreased Zn and Mn concentrations. Soil pH and electrical conductivities were elevated as were neutral 1 N NH 4 OAc extractable Ca levels with increasing FBM rates. Extractable soil Al, Zn, and Mn were reduced with increasing FBM. Approximately four times as much FBM was required to achieve final soil pH values equivalent to the CaCO 3 treatment applied at the LR.
Surface and subsurface acidity are of agronomic concern in the southeastern USA. The limits to crop production imposed by subsoil acidity need to be further defined for this region. Gypsum is being applied to ameliorate subsoil acidity and to overcome the problem of very slow lime movement from surface lime applications. Reduced crude conversion spent lime (RCCSL) containing anhydrite (CaSO 4 ) was evaluated for use as a liming material with specific consideration given to the movement of SO 2‐ 4 into the acid subsoil. Agricultural lime and RCCSL were applied at 0, 3.36, 6.72, and 10.08 Mg ha ⁻¹ to an acid Trappist silt loam (clayey, mixed, mesic Typic Hapludult). Soybean [ Glycine max (L.) Merr.] was grown in the second year following lime application. Soil cores to 0.90 m were taken at growth stage R5 for root length measurement and soil chemical analyses. Yields were increased by the soil amendments and were well correlated with total root length ( R ² = 0.84). Root growth below the surface limed layer was positively related to increased soil solution base cation (especially Ca) concentrations and SO 2‐ 4 movement into the subsoil. Previously described solution Ca plus Al species activity models were not well related to field rooting responses. There remains a need for soil test procedures that predict the need for, and the amount of, subsurface acidity amelioration.
Reduced crude conversion spent lime (RCCSL) containing mostly CaO, CaSO4, and MgO, was evaluated as an alternative lime source in greenhouse studies with tobacco and corn. Equivalent amounts (CaCO3 basis) of RCCSL, reagent-grade Ca(OH)2, and agricultural-grade dolomitic limestone were applied at different rates to an acid Maury silt loam (Typic Paleudalf). The RCCSL and Ca(OH)2 were equivalent in raising the soil pH and reducing active Al3+, H+, and Mn2+. Agricultural line was less effective. The overliming response could not be ascribed to impaired P, Mg or Zn nutrition in either species and was speculatively attributed to Al toxicity at near-neutral pH. -from Authors
Fluidized bed boilers for steam electric power plants have been developed recently to improve efficiency and to utilize coal and a wide range of other fuels. The fluidized bed waste (FBW) generated by these boilers is expected to reach large volumes as new plants are built. It is an anhydrous waste containing substantial amounts of CaSO 4 and unreacted CaO. Since no previous agronomic evaluation of FBW has been reported, greenhouse pot experiments were carried out.
At moderate rates of application, FBW is satisfactory as a source of sulfur for crops and as a soil liming material. High disposal rates of new waste initially restrict crop growth, apparently because of high alkalinity resulting from the high oxide content of the FBW. On acid Mountview sil, fine (< 0.1 mm) FBW was 47% as effective as fine CaCO 3 over a 5‐week period for increasing soil pH. Coarse (< 3.4 mm) FBW was only 8% as effective as fine CaCO 3 , because of less reactivity apparently resulting from its granular nature and CaSO 4 coatings on the granules. On pyritic coal mine spoil, lower liming rates did not affect spoil pH, but at higher rates coarse FBW was 44% as effective as fine CaCO 3 for increasing spoil pH over a 10‐month period.
Fluidized bed combustion, a desulfurization process for coal-fired power plants, produces a waste that contains large amounts of calcium oxide and calcium sulfate. Since approximately 200 kg of fluidized bed combustion waste (FBCW) is generated per metric ton of coal burned, it represents a significant potential source of lime that must be evaluated before it can be properly utilized. In this study, FBCW was compared with calcium hydroxide as a lime source in a greenhouse study with red clover, tall fescue, oat, and buckwheat. The FBCW and calcium hydroxide were applied at rates calculated to adjust the pH of Westmoreland silt loam (Ultic Hapludalf, mixed, mesic) to 5.0, 5.5, 6.0, and 6.5. Though the loading rates from FBCW were higher than those from calcium hydroxide, FBCW treatments increased Ca levels more than did calcium hydroxide only in red clover. Only dry matter yields of buckwheat were higher for FBCW than for calcium hydroxide applications. All species showed higher FBCW-induced Mg and S increases than hydrated lime. In spite of the Zn loading, Zn levels in herbage decreased as the pH levels increased as a result of FBCW application. Soil pH increases in FBCW and Calcium hydroxide treatments were comparable when the materials were applied in equivalent amounts. It was concluded that FBCW may be valuable as a lime, Mg, or S source when the effects of heavy metals in the material are evaluated.
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Clean air legislation has resulted in increased production of flue gas desulfurization (FGD) by-products by coal-fired boilers. Use of FGD by-products as substitutes for agricultural limestone represents a potential beneficial use alternative to landfill disposal of these materials. To determine the efficacy and potential for environmental impact of such use, an 8-month greenhouse study was conducted in which three dry FGD by-products were mixed with Wooster silt loam at rates of 0, 3.5, 7, 14, and 28 g kg-1. Separate pots were planted with alfalfa (Medicago sativa, L) and tall fescue (Festuca arundinacea, Schreb). Following a 3-month growth period, plants were harvested monthly for a total of six harvests. Pots were leached at the beginning and end of the experiment. All three FGD by-products increased soil pH from 4.5 to approximately 7.5. Leachate concentrations of Ca, Mg, and S were increased by FGD, indicating a potential for transport of these solutes to subjacent soil. Leachate Mn and Zn concentrations were decreased by FGD amendment of alfalfa, and leachate Al was decreased with both crops. Leachate trace element concentrations were not increased by FGD with the exceptions of B and Cu. Alfalfa yield was increased by FGD, although the largest amendments suppressed yields of the first two harvests. Fescue yield was also increased by FGD amendment although the response was less than with alfalfa. Plant tissue contents of Ca, Mg, and S were increased by FGD. There were no increases in tissue concentrations of any trace elements except B and Mo. Dry FGD by-products appear to be effective substitutes for agricultural limestone with little potential for adverse environmental impacts.