Use of flue gas desulfurization (FGD) by‐product gypsum on alfalfa

Abstract

Subsoil acidity in northeast United States has been associated with decreased yield and decreased water and fertilizer nitrogen (N) utilization by forages. Surface applications of gypsiferious products has been shown to reduce subsoil acidity largely caused by high levels of soluble aluminum (Al). Our objective was to test the effectiveness and safety of using FGD gypsum to increase dry matter (DM) yields of alfalfa (Medicago sativa L.). Four and one‐half, 9, and 18 mt/ha of either commercially available agricultural gypsum or two gypsum by‐products were applied to a Rayne soil (Fine‐loamy, mixed, mesic Typic Hapludult) with a strongly acid subsoil. Agricultural and FGD gypsum increased alfalfa DM yields by as much as 21 and 14%, respectively. Correspondingly, in the subsoil, soluble Al decreased and calcium (Ca) content and Ca:Al ratio increased. Heavy metal concentrations in either the alfalfa or soils were not increased by any treatment. However, S in the alfalfa grown at the highest treatments approached concentrations that are considered to be toxic to grazing animals.     

Effects of flue gas desulfurization gypsum by-products on microbial biomass and community structure in alkaline–saline soils

Purpose

For an alkaline?Csaline region in Northwest China, we examined the responses of soil microbial communities to flue gas desulfurization gypsum by-products (FGDB), a new ameliorant for alkaline?Csaline soils. In 2009 and 2010, we collected soils from 0?C20?cm and 20?C40?cm depths along an experimental FGDB gradient (0, 0.74, 1.49, 2.25, and 3.00?kg FGDB m^?2).

Materials and methods

As a measure of microbial community composition and biomass, we analyzed phospholipid fatty acids (PLFAs). We used real-time quantitative polymerase chain reaction (qPCR) to measure abundance of bacterial 16?S rRNA copy numbers. Additionally, physicochemical soil parameters were measured by common laboratory methods.

Results and discussion

Microbial community composition differed along the FGDB gradient; however, the microbial parameters did not follow a linear response. We found that, in 2009, total PLFA concentrations, and concentrations of total bacterial and Gram-negative bacterial PLFAs were slightly higher at intermediate FGDB concentrations. In 2010, total PLFA concentrations, and concentrations of total bacterial, Gram-positive bacterial, Gram-negative bacterial, and fungal PLFAs as well as the fungal:bacterial PLFA ratio were highest at 1.49?kg FGDB m^?2 and 3.00?kg FGDB m^?2. PLFA concentrations often differed between 2009 and 2010; however, the patterns varied across the gradient and across microbial groups. For both years, PLFA concentrations were generally higher at 0?C20?cm depth than at 20?C40?cm depth. Similar results were obtained for the 16?S rRNA copy numbers of bacteria at 0?C20?cm depth. FGDB addition resulted in an increase in soil Ca²⁺ and NO ₃ ^? ?CN and a decrease in pH and electrical conductivity (EC). Shifts in PLFA-based microbial community composition and biomass could partly be explained by pH, soil organic carbon, total nitrogen (TN), soil moisture, EC, inorganic nitrogen, C/N, and Ca²⁺. Indirect effects via shifts in abiotic soil properties, therefore, seem to be an important pathway through which FGDB affect soil microbial communities.

Conclusions

Our results demonstrate that addition of FGDB leads to significant changes in soil physicochemical and microbial parameters. As such, addition of FGDB can have large impacts on the functioning of soil ecosystems, such as carbon and nitrogen cycling processes.     

Maize growth and mineral acquisition on acid soil amended with flue gas desulfurization by‐products and magnesium

Abstract

The large amounts of coal combustion by‐products (CCBs) generated by coal burning power plants must be utilized or discarded, and beneficial use of these materials are desired. One beneficial use of CCBs could be application to agricultural land. Information about the use of one kind of CCB (flue gas desulfurization by‐product, FGD‐BP) on soil is limited. Maize (Zea mays L.) was grown (greenhouse) on an acid soil [Umbric Dystrochrept, pH_Ca (1:1, soil: 10 mM CaCl₂) 4.2] amended with two high CaSO₄ FGD‐BPs (5 and 15 g#lbkg^‐1 soil) and CaCQ₃ (2.5 and 5.0 g#lbkg^‐1 soil) at varied calcium/magnesium (Ca/Mg) equivalency ratios (0/0, 1/0, 1/0.01, 1/0.05, 1/0.1, and 1/0.5) to determine treatment effects on growth traits [shoot and root dry matter (DM) and total and specific root length (RL)], mineral concentrations in leaves, and soil pH and electrical conductivity [(EC) 1:1, soil:water]. Magnesium deficiency symptoms were induced on leaves of plants grown with and without low Mg, and the Mg to Ca ratio in each amendment needed to be about 1 to 20 to alleviate Mg deficiency. Shoot and root DM and total RL of plants grown with FGD‐BPs became higher as Mg increased. Specific RL (total RL/root DM, root fineness) was not affected by FGD‐BP and only slightly by Ca/Mg ratio. Shoot concentrations of Mg increased; Ca, phosphorus (P), and manganese (Mn) decreased; and potassium (K), sulfur (S), iron (Fe), zinc (Zn), and copper (Cu) remained relatively constant as amendment and Mg increased. On unamended soil, aluminum (A1) and Mn concentrations in shoots were above normal. Enhancement of growth was closely related to increased soil pH compared to added Mg for CaCO₃ amended soil and to increased Mg compared to increased soil pH for FGD‐BP amended soil. Except at the highest level of Mg where soil pH increased, added FGD‐BPs and Mg had only limited effect on increasing soil pH. Soil EC increased from added FGD‐BPs but not from added Mg, and EC was not sufficiently high to be detrimental to plants. Maize grown on this acid soil amended with FGD‐BPs received benefits when caution was used to alleviate mineral deficiencies/toxicities inherent in the soil.     

Extraction of phosphorus,potassium, calcium,and magnesium from soils by an ion‐exchange resin procedure

Abstract

A procedure for the simultaneous extraction of phosphorus, potassium, calcium and magnesium from soils, by an ion‐exchange resin procedure applicable to large‐scale advisory soil testing, is described. The important steps are the disaggregation of soil by shaking in water during 15 minutes with a glass marble, the transference of the elements from the soil to a sodium bicarbonate treated mixture of anion and cation exchange resins during a 16‐hour shaking period, the separation of the resin from the soil by sieving and extraction of the elements from the resin.

The results of resin extractable calcium, magnesium and potassium were comparable to the results of these elements extracted with 1M NH₄OAc, to calcium and magnesium extracted with 1M KCl, and to potassium extracted with 0.025M H₂SO₄.

For phosphorus the resin extractable values were not comparable to the results obtained by the former routine method, based on the extraction with 0.025M H₂SO₄. The results of resin extractable P presented closer correlation with cotton response to phosphorus application in 28 field experiments (r = 0.85**) as compared with 0.025M H₂SO₄ extractable P (r = 0.68**), and also with P uptake by flooded rice in a pot experiment with eight lowland soil samples (r = 0.98**), as compared with extraction with 0.0125M H₂SO₄ in 0.050M HCl, for which the correlation was not significant. The reasons for the superiority of the extraction of P with the described procedure are discussed.     

Initial and residual utilization by alfalfa and bromegrass of sulphur from 35S‐labelled gypsum

Abstract

An experiment designed to measure the utilization of sulphur from gypsum by forage species and to determine the residual effect in the year following application failed to show a dry matter yield response to S. From 15 to 57% of the total S in the herbage, however, was obtained from the surface application; the proportion was lower in the legume than in the grass, was increased by increasing the rate of gypsum application, was increased by N fertilization of the grass but not the legume and was generally higher in the first two harvests than in the third. 9.4 to 27.4% of the applied S was recovered by three harvests in the first year, the recovery decreasing with increasing rate of application and increasing with N fertilization. Only 1.1% was recovered by the first harvest of the second year when 2.5 to 15% of the S in the herbage was derived from the previous season's application. Evidence of significant downward movement of S in the soil profile is presented to account in part for the low residual effect of gypsum.     

Recovery of 15N labelled ammonium nitrate by flue‐cured tobacco growing on a sandy loam

Abstract

An experiment was conducted to investigate the possible leaching of fertiliser N in flue‐cured tobacco growing on a sandy loam with two irrigation treatments using ^I5N as a tracer. No significant difference in ¹⁵N accumulation in the tobacco plant could be detected between the two irrigation treatments, recommended and conventional. Minimal soil leaching of the ^I5N was observed for both treatments at 60–90 cm depth. In four of the six experimental plots, recoveries were approximately 100% of the ¹⁵N applied, with 70% of the ¹⁵N being accumulated by the tobacco plant.     

Reactions of copper sulfate with wetland‐taro soils in Hawaii

Abstract

The environmental impact of copper sulfate (CuSO₄#lb5H₂O) must be evaluated before the chemical can be registered as a pesticide to control the apple snail (Pomacea canaliculata) in Hawaii's wetlands. To help achieve this goal, we investigated the sorption‐desorption reactions of CuSO₄#lb5H₂O with six wetland‐taro soils (Tropaquepts) of Hawaii. Our results indicated that: (i) copper (Cu) was sorbed rapidly: 98.0–99.9% of the added Cu was removed from solution within one hour when the loading rate was less than or equal to 300 mg Cu kg^‐1 [initial Cu concentration = 30.0 mg Cu L^‐1 or 12 kg (ha‐cm)^‐1 as CuSO₄#lb5H₂O which is 10 times the maximum recommended rate of pesticide applications, (ii) Cu sorption increased as soil pH increased from 5.0 to 8.0, and (iii) sorption capacity varied from 210 mg Cu kg^‐1 in a Tropaquept from Kauai Island to 500 mg Cu kg^‐1 in another Tropaquept from Maui Island, after seven days of incubation at soil‐solution pH 6.0 and total solution Cu concentration of 0.10 mg Cu L^‐1, a Cu level deemed toxic to some living organisms. It appears that more Cu was sorbed (less Cu remained in solution) if the soil contained high organic carbon (C) and low indigenous Cu. Also, there was an inverse relationship between Cu sorption and desorption by the soils tested: the more Cu a soil can sorb, the tighter it holds Cu, and the less Cu it releases. Since soil pH increases by 1 to 1.5 units upon flooding and Cu sorption increases with increasing pH, the recommended practice of flooding the soil for at least 48 hours between CuSO₄#lb5H₂O application and crop planting should be followed.     

Limestone and gypsum effects on calcium nutrition of ‘Florunner’ and ‘NC‐7’ Peanuts

Abstract

Minimum sufficiency levels of hull and seed Ca for maximum yield and grade of runner or Virginia type peanuts (Arachis hypogaea L.) have not been established and there is limited information on single and combined effects of limestone and gypsum on production and quality of peanuts. Field experiments were conducted on runner and Virginia type peanuts to study single and combined effects of limestone and gypsum on yield and grade, and to attempt to establish minimum sufficiency levels of hull and seed Ca for maximum yield and grade of each type. Gypsum treatments, O, low, medium, and high rates, were superimposed on residual limestone rates on three sites with ‘Florunner’ (runner type) and on one site with ‘NC‐7’ (Virginia type) peanuts. Yield and grade of Florunner peanuts were not increased by limestone or gypsum treatments on any site even though soil Ca concentrations (Mehlich 1) ranged from 152 to 200 mg/kg among the sites. These levels were lower than the Georgia recommended minimum sufficiency value of 250 mg/kg. However, yield and grade of ‘NC‐7’ peanuts were increased by limestone or gypsum, but maximum yield occurred only where gypsum was applied even with soil Ca levels of 682 mg/kg. The minimum hull Ca level of 1.2 g/kg and seed Ca of 0.42 g/kg were sufficient for Florunner peanuts since yields and quality were not increased by limestone or gypsum application. Maximim yield and grade were achieved with Florunner at leaf, hull, and seed Ca concentrations of 13.2, 1.2, and 0.42 g/kg as compared with 26.0, 1.9, and 0.58 g/kg for NC‐7, respectively. These data show that NC‐7 has a higher Ca requirement than Florunner.     

Cadmium sulfate application to sludge‐amended soils: II. Extraction of Cd,Zn and Mn from solid phases

Abstract

Cadmium, Zn and Mn in eleven paired soils (one which had a history of sludge application and a control from adjacent land where sludge had not been used) were partitioned into five fractions: exchangeable, adsorbed, organically bound, carbonate bound and sulfide, by the use of KNO₃, H₂0, NaOH, EDTA and HNO₃, respect‐ively. The data indicate that the major portion of the total metals was found in the carbonate, sulfide and organic fractions. Addition of CaCO₃caused an increase in the exchangeable + soluble fractions of added Cd in the soils, but had little effect on native or sludge derived Cd.     

Total analysis of soils by ICP‐AES and ICP‐MS (Mass spectrometry)

Abstract

Total contents of the major and several minor constituents in soils were determined by the titled methods and compared with those obtained by X‐ray fluorescence or atomic absorption spectrometry, which have been successfully used in the authors’ laboratory as the most reliable method in recent years.

ICP‐AES: Excellent agreement was observed for Mg, Ca and Mn. Although agreement was somewhat lower in Fe, Al and Ti, there seemed to be little problem for routine analysis. Sodium, K, Zn and other minor elements, however, showed only poor agreement, and it was considered to be not acceptable even for routine analysis.

ICP‐MS: Much higher dilution ratios must be used in ICP‐MS to avoid the destruction of the detector due to a high strong signal. Agreement between ICP‐ MS and the reference methods is acceptable for all the elements examined, though precision seems to be somewhat poorer than that of ICP‐AES. Besides Ni, Cu, Zn, and Pb, more than about 30 other elements, including all of the rare earth elements, plus Th and U, are positively identified in the diluted acid digests. Due to a lack of the appropriate methods for determining such low level elements, the full evaluation of ICP‐MS for the analysis of these elements, however, remains to be examined.     

Influence of air drying and soil gas‐phase carbon dioxide on DTPA‐extractable iron in calcareous soils

Abstract

The extraction of a field‐moist soil with DTPA will result in a level of extractable iron (Fe) lower than that of the air‐dried soil. Soil gas‐phase carbon dioxide (CO₂) levels may be considerably higher than ambient atmospheric levels, especially in wet soils in the field. This study was undertaken to determine whether gas‐phase CO₂ level influences the quantity of Fe extracted by DTPA. Three moist calcareous soils were incubated for 21 days, each at three different partial pressures of CO₂, after which the moist soils were extracted with DTPA. A sample of each soil was also air dried, and was subsequently extracted with DTPA. In each case, DTPA‐extractable Fe from the moist sample was lower than that from the air‐dried sample; however, DTPA‐extractable Fe increased with increasing CO₂ partial pressure of in the moist soils. DTPA‐extractable Fe concentration for a given soil following air drying was not significantly influenced by the CO₂ partial pressure during incubation of the originally field‐moist soil. DTPA‐extract pH of the moist soils followed the same trend as soil‐solution pH (i.e., as CO₂ concentration of the soil gas‐phase increased, soil solution pH and DTPA extract pH both decreased); however, the slope of the pH versus log P_CO2 curve was less pronounced in the DTPA extract due to the buffering capacity of the triethanolamine. From this study, it is concluded that elevated soil gas‐phase CO₂ partial pressure does not contribute to the lower level of DTPA‐extractable Fe observed when the extraction is performed on a field‐moist versus an air‐dried soil; increased CO₂ partial pressure actually resulted in a slight increase in concentration of DTPA‐extractable Fe obtained from a field‐moist soil.     

Variation in extraction of calcium from dry‐ashed embryos of cucurbits and other lipid‐rich seeds

Abstract

All cucurbit embryos analyzed showed a decrease in the ease with which calcium could be extracted from the ash as the ashing temperature increased beyond 600°C. After ashing at 500°C, the Ca in the cucurbit ash was fully extracted by 5% o HC1. After 650°C ashing, lower than expected Ca levels were obtained unless additional ash treatment with HNO₃ and HC1 was applied. Castor bean embryos plus endosperm showed the same effect but other oily embryos tested did not need ash treatment to fully extract Ca from either the 500 or 650°C ash. Neutron activation analysis indicated that the differences in ash characteristics were related to the differences in concentrations of K and P in the embryo tissues.     

Sequential fractionation of chromium and nickel from some serpentinite‐derived soils from the eastern Transvaal

Abstract

Soils derived from ultramafic serpentinitic rocks are inherently infertile. These soils support plant species that are able to hyperaccumulate both chromium (Cr) and nickel (Ni). This study was conducted to determine the efficacy of a sequential extraction technique in explaining sources of Cr and Ni that are taken up by plant species growing on these soils. The sequential extraction of soil samples obtained from the eastern Transvaal involved the following reagents: H₂O and 0.5M KNO₃, 0.5M NaOH, 0.05M Na₂EDTA, and 4M HNO₃. More than 95% of the total Cr was extracted by HNO₃ while the remaining extractants fell into the order NaOH > EDTA ? KNO₃ + H₂O. There would appear to be a loose correlation between easily soluble Cr (KNO₃ + H₂O) and the uptake of Cr by the plant. A somewhat higher proportion of Ni was extracted prior to the HNO₃ treatment although amounts removed by KNO₃ + H₂O were all less than 1% of the total. It would appear that plant species growing on these soils are able to accumulate these elements from sources other than those considered easily available. A highly significant coefficient of determination was obtained between Ni extracted by oxalate and EDTA extractable. The fraction extracted by the steps in the sequential procedure can be related to exchangeable and sorbed (KNO₃ and H₂O) and an easily acid soluble inorganic fraction (HNO₃). The NaOH and EDTA fractions are probably related to the Cr and Ni bound in the form of organic complexes and associated with iron oxides.     

Humic matter isolated from soils and water by the XAD‐8 resin and conventional NaOH methods

Abstract

Differences were studied in humic (HA) and fulvic acid (FA) extracted from soils and streams in South Georgia by the Amberlite XAD‐8 resin and conventional NaOH method. Characterization analysis was performed by liquid ¹³C NMR, infrared (IR) spectroscopy, scanning electron microscopy (SEM), and chemical analysis. The NMR spectra indicated that the resin method yielded black water HA and FA with spectroscopic, chemical and elemental characteristics different from those isolated by the conventional NaOH method. Humic acids from both the resin and conventional NaOH methods were composed of aliphatic, aromatics and carboxyl groups, but the “resin”; HA contained more aliphatic groups. These differences were also noticed between the FA fractions obtained by the two methods. The differences corresponded to differences in IR spectra. The IR spectrum of “resin”; FA exhibited only a weak shoulder at 1625/cm for the COO”; stretching vibration, in contrast to that of FA isolated by the conventional NaOH procedure. Apparently, the high aliphatic‐CH₃ group content has blocked the vibration above, as evidenced by methylation of HA. Fulvic acid extracted by the resin method was also higher in total acidity, but considerably lower in N content than FA obtained by the conventional NaOH method. Both methods yielded black water FA which was less aromatic in nature than black water HA, or soil FA.     

Surface charge characteristics of volcanic‐ash‐soils from Spain. Effect of organic matter and mineralogical composition

Abstract

Surface charge characteristics of several Spanish Andosols were investigated. The relationship between these characteristics and the mineralogical composition and organic matter content of the soils were also taken into account.

The electro‐chemical behaviour of the soils was similar to that of many metallic oxides, in which the surface charge is determined exclusively by the activity of potential determining H and OH^‐ ions in the bulk solution.

The ZPC of the soils varies between 3.7 and 5.1 and always remains below the zero point of titration (between 0.6 and 10 meq/100g). These low ZPC values seem to be related to the high content of organic matter in the soils, but no clear correlation between both values has been found.

The mineralogical composition and the percentage of amorphous oxides in the soils, on the other hand, had an effect on the charge characteristics’. A correlation coefficient (r=0.801) was found between the Al₂O₃% and ZPC value of the soils.     

Effects of extraction period and soil.‐solution ratio on the amount of zinc extracted from soils by different extractants

Abstract

Investigations have examined the effects of extraction period and soil:solution ratio on the extraction of zinc from some New Zealand soils by EDTA, DTPA, HCl, Ca(NO₃)₂ and CH₃COONH₄. A high proportion of the zinc extracted by EDTA, DTPA, HCl, and Ca(NO₃)₂ was extracted rapidly, within the first 0.5 h, followed by small increases over the next 15 h. An exception occurred with a soil containing iron/manganese concretionary material. In this soil, with both EDTA and DTPA, there were significant increases in the amount of zinc extracted between 1 and 8 h. The amounts of zinc extracted by CH₃COONH₄ increased gradually with the time of extraction up to approximately 4 h.

Substantial increases in the amounts of zinc extracted with HCl, Ca(NO₃)₂ and CH₃COONH₄ were obtained by increasing the soil:solution ratio from 1:2.5 to 1:10. However, soil:solution ratio has little effect on the amounts of zinc extracted by EDTA or DTPA.     

Estimation of sulfate and amino acid sulfur in plant material by X‐ray spectrometry

Abstract

The SKα shift between the valences of sulfur has been used to determine by X‐ray spectrometry the two main forms of sulfur present in plant material, viz: oxidised S (S⁶⁺) and covalently bonded sulfur (S^c). S⁶⁺ and S^c were shown to correlate closely with sulfate, as determined by reduction with hydriodic acid, and cysteine+methionine S, respectively. The method is rapid and reliable provided the X‐ray spectrometer is stable and has high reproducibility in goniometer setting. The use of S⁶⁺ and S^c is recommended as an alternative to chemical methods for assessing the sulfur status of crops and the sulfur amino acid content of diets.     

Moisture stress and calcium absorption from immersions during the seed‐filling stage of soybean

Abstract

Calcium (Ca) uptake was studied by immersing the central tip of a trifoliate leaf in various concentrations of ⁴⁵CaCl₂ solutions and under moisture stress conditions during the seed‐filling period of soybean. Beta‐ray gauging and the diurnal leaf temperature variation showed similar characteristics for leaf water status. The activities of ⁴⁵Ca were significantly higher (p < 0.0001) at 5, 10, 20, and 30 mM concentrations for water stressed and non‐stressed leaves compared with the control. Calcium (⁴⁵Ca) activities at 5, 10, and 20 mM Ca concentrations between stressed and non‐stressed leaves were not significant, but the difference in their mean values at 30 mM Ca concentration was significant (p = 0.0159). The relationship between ⁴⁵Ca uptake and Ca concentration was parabolic for both stressed (R² = 0.77) and non‐stressed (R² = 0.81) leaves. Autoradiographs indicated Ca movement through the mid‐rib and veins of the tip‐immersed trifoliate leaf but showed no activity in other plant parts. An activity gradient developed between seeds when a pod‐tip was immersed in the radioactive solution.     

Nitric acid dissolution and multi‐element analysis of soils and sediments by inductively coupled plasma spectrometry

Abstract

A method was developed for the simultaneous analysis of P, K, Cu, Cd, Zn, Fe, Mn and Pb in soils and sediments by inductively coupled plasma spectrometry (ICP) after digestion in nitric acid. The procedure extracted 82 to 94% of the totals of the heavy metals, 78% of total P and 34% of total K. Inter‐element interference correction data are given for the ICP method. The method gave results similar to those obtained by other analytical procedures. The precision of the method was satisfactory but was lowest for Cd which had the lowest concentrations (<2.7 mg/kg) of the elements determined.     

Orthophosphate and organic phosphate in the soil solution of four sandy soils in relation to pH‐evidence for humic‐FE‐(AL‐) phosphate complexes

Abstract

Soil from the Ap‐horizon of four acid sandy soils differing mainly in Corg content was adjusted to pH values between 3 and 7.5 with NaOH and HCl respectively and incubated for two weeks. Afterwards, displaced soil solution was obtained and analyzed.

The concentrations of Fe, Al, and P showed a broad minimum in the pH range from 4 to 6. The concentration of these elements strongly increased with the increase of pH to 7.5. Acidification below pH values of 4 led to a slight increase.

Separation of dissolved organic carbon by ultrafiltration before the photometric orthophosphate determination decreased measured concentrations in comparison to direct determination in two of the four soils. This decrease was more pronounced for soil solutions with higher concentrations of organic carbon. The effect of acid hydrolysis of organic phosphorus during orthophosphate determination can be explained by existence of humic‐Fe‐(Al phosphate complexes in the soil solution. These complexes can account for more than 50% of the total organic P in solution.