Acid Mineral Soils Research Articles

Prolonged leaching of mineral forest soils with dilute HCl solutions: the solubility of Al and soil organic matter

Long‐term acidification has been shown to result in a considerable decrease in the amount of organically bound soil Al and in a gradual decrease in the solubility of Al. We examined the solubility of soil organic matter (SOM) and Al in four acid mineral soils (one Arenosol Ah, two Podzol Bh, and one Podzol Bs) as they were leached sequentially using a solution containing 0.001 m HCl and 0.01 m KCl. The acid leaching resulted in relative decreases in Al that were 2–6 times greater than for organic C. The organic C and Al dissolved by the acid leaching originated mainly in the pyrophosphate‐extractable fraction of the elements. Protonation seems to be a major mechanism in stabilizing the residual SOM, as indicated by small changes in effective cation exchange capacity with the degree of acid leaching. In the samples of Podzol Bh and Arenosol Ah soils the solubility of Al (defined as log10{Al3+} + 1.5pH) in equilibrium suspensions (0.01 m KCl) was closely related to the ratio of pyrophosphate‐extractable Al to pyrophosphate‐extractable organic C. The Podzol Bs sample probably contained a small amount of a surface‐reactive Al(OH)3 phase, which rapidly became depleted by the acid leaching.

Acid‐Base Properties of a Limed Pyritic Overburden during Simulated Weathering

AbstractSurface‐mine reclamation is often hindered by the formation of acid minesoil and acid mine drainage from FeS2 oxidation. Surface soils containing FeS2 are often treated with crushed limestone (predominately CaCO3) to prevent acid minesoil formation. The main objective of this study was to evaluate the long‐term effectiveness of liming pyritic minesoil to prevent the formation of acid minesoil and acid mine drainage. Pyritic minesoils that did not receive lime became acidic very rapidly and produced acidic leachate. Almost all of the FeS2 in this treatment oxidized during the first 200 d. The addition of lime at a rate of 25% of the theoretical acid‐base account (ABA) significantly slowed FeS2 oxidation, but rapid oxidation ensued after the added lime was neutralized. Treatments receiving a liming rate of 50% ABA or greater remained neutral to alkaline throughout the study. Acid‐base values and residual FeS2‐CO3 data, however, indicate that the lime was dissolving from the system faster than the FeS2 was oxidizing, and all the treatments would eventually become acidic. The results indicate that the liming of a pyritic overburden to an ABA of 125% is not a sustainable solution to preventing acid minesoil and acid mine drainage.

Agronomic measures for better utilization of soil and fertilizer phosphates

Global known phosphate deposits are a finite resource which will run out in about four centuries at the present consumption rate. Since about 90% of the phosphate mined is used for fertilizer, soil and fertilizer phosphate should be efficiently used. Various agronomic measures are discussed relevant for saving phosphate and avoiding losses. Phosphate fertilizer rates should be adjusted to measured requirements for phosphate using soil tests. Particularly in areas with high livestock intensities soils frequently are much enriched in available phosphate and do not need further phosphate application whether in organic or in inorganic form. Excessively high levels of available soil phosphate, much higher than required for optimum crop production increase the hazard of phosphate loss by wind and water erosion and even leaching. Loss of plant available phosphate in soils occurs by phosphate fixation which is especially strong in acid mineral soils. Such losses can be dramatically reduced by liming soils to a pH of 6–7. In tropical areas where lime frequently is not available row placement of phosphate fertilizer is recommended. Oxisols with a very low pH liming, however, may promote phosphate fixation due to the formation of phosphate adsorbing Al complexes. Biological assimilation of phosphate may prevent inorganic phosphate from fixation by soil particles. Organic anions produced during the decomposition of organic matter in soils as well as the excretion of anions by plant roots depress phosphate adsorption by competing with phosphate for binding sites at the adsorbing surface. Hence farming systems and rotations which bring much organic matter into soils contribute to a better use of soil and fertilizer phosphate. Mycorrhization of plant roots with appropriate fungi ecotypes may essentially improve the exploitation of soil phosphates. The choice of the appropriate phosphate fertilizer type is crucial for its efficient use. This applies particularly for apatitic fertilizers of which the availability is poor in weakly acid to neutral and calcareous soils.

The involvement of iron and aluminum in the bonding of phosphorus to soil humic acid

With a peat soil similar amounts of phosphorus (P) were coprecipitated with humic acid from alkali extracts over a limited range of strongly acidic pH, whereas with a mineral soil the amount was pH dependent. The difference between the two soils relates to the much greater total amounts of inorganic P and aluminum (Al) present in the extract of the mineral soil. In this acid mineral soil, Al rather than iron (Fe) may be involved in the formation of metal bridges in humic acid‐metal‐inorganic P complexes. Neither Al or Fe were implicated in binding of organic P to humic acid. The P species observed in humic acids was dependent on the pH at which they were precipitated from the alkali extracts. In the peat soil the inorganic P was an order of magnitude lower than the organic P.

Survival of Three Tree Species on Old Reclaimed Surface Mines in Ohio

Early studies of mine reclamation emphasized trees for revegetating minesoils. Scientists of the USDA Forest Service transplanted four tree species in 1946 into leveled or unleveled overburden near Georgetown, OH, and into unleveled overburden near Dundee, OH. Black locust (Robinia pseudoacacia L.) had good initial survival on both sites but died in later years due to locust borers (Megacyllene robiniae). Survival and growth of remaining white ash (Fraxinus americana L.), white pine (Pinus strobus L.), and yellow-poplar (Liriodendron tulipifera L.) were determined and soil properties examined on both sites in 1992. Minesoil bulk density in Georgetown leveled areas was similar (1.1 to 1.2 Mg/m3) to unleveled areas in 1992. Minesoil pH was 7.7 and no nutrient deficiencies were found. Bulk density at Dundee was 1.1 Mg/m3 and minesoil pH was 4.2 with high exchangeable acidity, Al, and Fe concentrations. White ash had the best survival after 46 yr, averaging 43% in both leveling treatments at Georgetown and 33% at Dundee. White pine survival averaged 22% at Georgetown and 14% at Dundee. Yellow-poplar had poor survival (3%) on Georgetown leveled areas, 21% survival on Georgetown unleveled areas, and 17% survival at Dundee. White pine and yellow-poplar trees were 4 to 6 m shorter on Georgetown leveled areas vs. unleveled areas. White ash height was similar between leveling treatments and no height differences were seen for any species between Georgetown unleveled and Dundee. Volume for yellow-poplar ranged from 39 m3/ha on the Georgetown leveled area to 350 m3/ha on unleveled areas. Volumes roughly paralleled survival for white pine and yellow-poplar. Thirteen volunteer tree species were identified and they averaged 20% total tree basal area across the three areas. Maple (Acer sp.) and elm (Ulmus sp.) were two common volunteer trees. After 46 yr, these areas support a closed canopy of commercially valuable trees, providing soil stabilization, potential economic returns, and wildlife habitat. Eastern U.S. surface mine reclamation should emphasize tree planting and forests as postmining land uses. White ash is recommended on leveled or unleveled sites with alkaline or acidic minesoils.

A simple model of soil organic matter complexation to predict the solubility of aluminium in acid forest soils

SummaryA simple equilibrium model for competitive binding of Al and protons to soil organic matter shows that Al activities in soil solutions of acid mineral soils are controlled by complexation reactions with soil organic matter. The model successfully explains the relation between pH and the activity of dissolved Al in several forest soils. Furthermore, we found evidence that pools of organically bound Al may be depleted fairly quickly. Kinetically controlled dissolution of inorganic soil Al compounds, which may be considerable, is the main cause for the re‐supply of the organically bound Al in the soil. The previously reported decrease in Al solubility that accompanies measured decline in organically bound Al in three Dutch soils was found quantitatively consistent with the model for organically bound Al proposed here.

Causes of changes in pH in acidic mineral soils

Seasonal variation in soil pH and long-term decreases in pH have been observed for the soils of the south-western slopes of New South Wales. We have determined and measured some processes which are likely to contribute to pH changes within these acidic, mineral soils. The studies were undertaken on closed systems in the absence of plants. Changes in soil pH, in the absence of plants, were controlled by the relative rates of alkali-producing (acid-consuming) reactions and of acid-producing (alkali-consuming) reactions. The alkali-producing reactions studied were ammonification, reduction of Mn-oxides, oxidation of organic anions and SO 4 2− adsorption. The acid-producing reactions were nitrification, oxidation of Mn 2+ and oxidation of organic S. Measurements of changes in the concentration of the chemical species involved in these reactions were converted to the corresponding changes in μmol H + or OH − g −1 soil. The sum of the H + budget for each soil was transformed to change in pH by using the soil's titration curve. With this procedure 96% of the variance of the observed changes in soil pH was explained. On the basis of our results we propose that changes in temperature and water potential determine changes in microbiological activity which in turn determine changes in the H + budget and its physicochemical consequences.

The role of organic matter in controlling aluminum solubility in acidic mineral soil horizons

Despite the ecological importance of potentially phytotoxic Al, its solubility control in acidic mineral soils remains unresolved. We examined the solubility of Al in mineral horizons of two acidic forest soils (Inceptisol and Spodosol) in southern Sweden using a series of batch experiments. Dissolution of Al was found to consist of a rapid solubilization of reactive solid phase Al, which quickly reached an equilibrium state, superimposed on a slow dissolution of less reactive Al-containing phases (e.g., primary Al-silicates). Titration experiments in the pH range 3.2–4.7 using an equilibration time of 5 days showed that at pH < 4.1, all suspensions were undersaturated with respect to gibbsite (Al(OH) 3; log ∗K SO = 8.85 at 8° C) . Under such conditions, the Al solubility could be explained qualitatively by equilibrium complexation reactions with soil organic matter. Quantitatively, our results could be reproduced reasonably well using the mechanistic model WHAM, which describes the binding of Al by humic substances in organic soils. This suggests that the pool of organically bound soil Al controls the Al solubility in suspensions of strongly acidic soils. Due to the kinetically constrained release of Al from primary and secondary minerals, the amount of organically bound Al, and therefore the Al solubility in the suspensions, gradually increases with time. Consequently, a quantitative evaluation of Al solubility data from long-term batch experiments should consider both equilibrium and kinetic processes.

Atmospheric deposition in maritime environments and its impact on terrestrial ecosystems

Seasalts are the dominant chemical constituents of precipitation in maritime regions. Dry deposition of these salts is also an important process and consequently, canopy interception by forest ecosystems greatly augments wet deposition. The separation of seasalt from non-seasalt sulphur is usually accomplished by reference to the concentration ratio of other major component ions of seawater, such as sodium-, chloride-, or magnesium-to sulphate. Biogenic sulphur, from the oceans or from terrestrial ecosystems is sometimes of importance in maritime regions. Seasalts, which dominate atmospheric deposition in maritime regions can induce short-term acidification in surface waters as a result of ion-exchange reactions following storm events. The results of one large storm in western Ireland in 1991 and the recovery process in a peat soil were clearly discernible in soil water analysis. The seasalt impact on acid mineral soils can be seen in the exchangeable sodium levels and the degree of base saturation of these soils.

The role of the apoplast in aluminium toxicity and resistance of higher plants: A review

AbstractIn acid mineral soils excess of aluminium ions (AI) is one of the most important factors determining plant species and ecotype distribution, and limiting growth and yield of crops. Aluminium preferentially accumulates in the root tips as sites of cell division and cell elongation. Whether inhibition of cell‐division rate is due to direct interaction of Al with the chromatin in the nuclei is rather questionable because of the low radial mobility of Al in the root and the rapidity of cessation of root elongation after Al addition to the growth medium. Externally applied Al instantaneously binds to binding sites in the apoplast. Cross binding of pectates by Al may affect extensibility and water permeability of the cell wall. Interaction of Al with other cell‐wall constituents is most likely but needs clarification.Aluminium also affects plasma‐membrane characteristics. Ca2+ influx and K+ efflux are inhibited, and synthesis of callose is induced. Induction of callose suggests an increase rather than a decrease in cytosolic Ca2+ as initial response to Al.There is little evidence suggesting major disruption of plasma membrane and cytoplasmic functions by AI. K+ uptake, H+ extrusion, Fe(III) reducing capacity and lipid peroxidation are hardly affected even in roots severely inhibited in elongation by Al. Al uptake and physiological/biochemical effects of Al on intact plant roots can be mimicked even more sensitively using cell suspension cultures which, therefore, represent a powerful tool for the study of Al toxicity.Large differences in Al resistance exist between plant species and cultivars of a species. Root elongation‐rate and callose formation can be used as indicators for Al injury. Since short term Al injury is mainly expressed in the apoplast. Al resistance requires exclusion of Al from or/and inactivation of Al in the apoplast. Generally, Al‐resistant genotypes are characterized by lower Al accumulation of the root apical meristems. This is achieved by a lower cation‐exchange capacity/surface negativity or complexation of Al through root exudates (mucilage, organic acids).Long term exposure of plants to Al also inhibits shoot growth via induction of nutrient (Mg, Ca, P) deficiencies, drought stress and phytohormone imbalances. Such longer term effects have to be taken into consideration when selecting genotypes for high yielding capacity on acid soils high in available Al.

Spore Germination and Hyphal Growth of Arbuscular Mycorrhizal Fungi in Relation to Soil Aluminum Saturation

Several arbuscular mycorrhizal fungi were evaluated for aluminum tolerance based on spore germination and hyphal growth in soils with 6%, 27%, and 100% aluminum saturation. There were interspecific as well as intraspecific variations in aluminum tolerance. Most species of Gigaspora showed high tolerance. Often, spore germination was not affected by aluminum saturation as in Gi. margarita (International Culture Collection of VA Mycorrhizal Fungi isolate GMRG 444) or was even increased as in Gi. albida (GABD 185). Similarly, hyphal growth of Gi. margarita (GMRG 444) and Gi. gigantea (GGGT 663) was not affected, while that of Gi. gigantea (GGGT 109) was increased by increasing aluminum saturation. Aluminum did not affect the spore germination of most Scutellospora species but did reduce their hyphal growth. Glomus species proved extremely sensitive to aluminum except Gl. manihot (LMNH 980) which showed consistently high germination in all the aluminum-saturated soils. Aluminum tolerance may be an important factor in the selection of arbuscular mycorrhizal fungi for acid mineral soils.

Spore germination and hyphal growth of arbuscular mycorrhizal fungi in relation to soil aluminum saturation

Several arbuscular mycorrhizal fungi were evaluated for aluminum tolerance based on spore ger? mination and hyphal growth in soils with 6%, 27%, and 100% aluminum saturation. There were interspe? cific as well as intraspecific variations in aluminum tolerance. Most species of Gigaspora showed high tol? erance. Often, spore germination was not affected by aluminum saturation as in Gi. margarita (International Culture Collection of VA Mycorrhizal Fungi isolate GMRG 444) or was even increased as in Gi. albida (GABD 185). Similarly, hyphal growth of Gi. margarita (GMRG 444) and Gi. gigantea (GGGT 663) was not affected, while that of Gi. gigantea (GGGT 109) was increased by increasing aluminum saturation. Alumi? num did not affect the spore germination of most Scutellospora species but did reduce their hyphal growth. Glomus species proved extremely sensitive to alumi? num except GI. manihot (LMNH 980) which showed consistently high germination in all the aluminum-sat- urated soils. Aluminum tolerance may be an important factor in the selection of arbuscular mycorrhizal fungi for acid mineral soils.

Inhibitory effects of acidic minesoil on the sericea lespedeza/Bradyrhizobiumsymbiotic relationship1

Abstract Effects of acidic minesoil on sericea lespedeza [Lespedeza juncea (L.F.) var. sericea (Mig.)] and its nitrogen (N2)‐fixing symbiotic relationship with Bradyrhizobium spp. were examined. Sericea lespedeza was grown in pots with N fertilization, without N fertilization, or with commercial Bradyrhizobium as a seed inoculant. Minesoil (pH 5.2) was fertilized with calcium (Ca), phosphorus (P), molybdenum (Mo), and potassium (K), and the pH level was adjusted to 4.8 or 4.5 with aluminum or iron sulfate [Al2(SO4)3; Fe2(SO4)3]. Minesoil was also limed to pH 6.1. Shoot dry weights, shoot N concentrations, nodule dry weights, and nodule numbers were significantly lower (P < 0.05) when inoculated plants were grown in soil at pH 4.5 and 4.8 compared to limed soil. Thus, the N2 fixation process was adversely affected below pH 5.0. Nitrogen‐fertilized plants grew well in acidified soil, and there were no significant differences in shoot dry weights of such plants among the soil acidification treatments includi...

Performance of Trees and Shrubs on Sludge-Amended Acidic Minesoils

Performance of Trees and Shrubs on Sludge-Amended Acidic Minesoils

Natural Revegetation of an Unreclaimed Lignite Surface Mine in East-Central Texas

Evaluating plants and soils on unreclaimed surface mines helps land managers un- derstand the effects of minesoil properties on plant growth and community development and may aid in the development of current reclamation plans. Eight unreclaimed surface mined sites in east-central Texas, ranging in age from 3 months to 50 years, were sampled to evaluate vegetation and minesoil changes over time and for comparison to an adjacent unmined area. Three- and 6-month-old unre- claimed areas had about 1% plant cover composed of pioneer grass and forb genera, including Di- chanthelium, Aster, Chenopodium, and Polygonum. Herbaceous plant cover increased from 12% on the 5-year-old site to a peak of 25% on the 20-year-old site. Dominant genera on 10- to 20-year-old sites were Andropogon, Bothriochloa, Cynodon, Dichanthelium, Paspalum, Aster, and Rumex. Woody species established as early as 5 years after mining (predominantly Baccharis salicina T. et G.), and canopy cover reached 14 and 35% on the 20- and 30-year-old sites, respectively. On the 50-year-old site, 17 woody species formed a multilayered vegetation structure with > 100% cover. Bulk density of minesoils in the surface 12 cm declined with time from 1.30 to <1.00 Mg/m3 as vegetation and litter increased. Undisturbed soils had an average pH of 5.9. Minesoil pH decreased from 6.9 on 3- and 6-month- old sites to 3.8 on 5- to 30-year-old sites (due to pyrite oxidation) and increased to 6.8 on the 50- year-old site. Several grass and forb species found on acidic minesoils in this study may be good candidates for low input revegetation programs for other postmining land uses.

Effect of pH and nitrogen source on aluminium tolerance of rye (Secale cereale L.) and yellow lupin (Lupinus luteus L.)

Soluble aluminium (Al) is a major factor limiting plant growth in acid mineral soils. Aluminium concentrations in soil solutions are mainly determined by soil pH. However, pH also affects the ratio between activities of protons and cationic Al species and the equilibrium between mono-and polynuclear hydroxy-Al species. The phytotoxicity of these species is not yet clear. The objective of the present study was to clarify the role of minor changes of pH in the rhizosphere on Al phytotoxicity in two Al-tolerant plant species by direct control of the pH in the nutrient solution (4.1, 4.3, 4.5) and in addition by varying the pH in the root apoplast using either nitrate or ammonium as N source. The plants were grown in solution culture at constant external pH. Whereas the Al-sensitive plant species barley and horse bean were damaged at very low Al supplies (1.85 μM and 9.3 μM respectively), 222 μM had to be applied to rye and yellw lupin for a comparable inhibition of root elongation. Yellow lupin was initially severely inhibited in root growth by Al, but then gradually recovered from this ‘Al shock’ within 3 days. In contrast to lupin, rye was hardly affected by Al initially, and it took about 16 h until maximum inhibition of root elongation. In the presence of nitrate, raising the pH from 4.1 to 4.5 aggravated root-growth depression by Al in rye and lupin. Whereas rye roots were severely damaged by ammonium especially at low pH, lupin was rather indifferent to the N source. Aluminium toxicity was less severe in presence of ammonium compared to nitrate N. This effect was less clear with rye at lower pH, because of it's higher proton sensitivity compared to lupin. Less Al injury at lower pH and in presence of ammonium was related to lower Al concentrations in the 1 cm root tips. The results are compatible with data showing high phytotoxicity of mononuclear and polynuclear hydroxy-Al species. However, they could also be interpreted in the light of proton amelioration of Al toxicity owing to competition for Al-sensitive binding sites in the root apoplast.

Inorganic leaf phosphorus and soil tests as indicators of phosphorus nutrition in cereals

Abstract A plant extraction method, which measures the inorganic phosphorus (Pi) in leaves, and four different soil testing methods were studied as indicators of phosphorus availability. Analytical values were compared with the yield responses and P uptakes of pot‐grown barley and oats. The inorganic leaf phosporus test was a sensitive indicator for P availability. This simple plant extraction method appeared to be at least as reliable as the best soil tests. Of the four soil tests studied, the water extraction test (Pw) was the most accurate method for mineral soils, but the water method as well as its modification with CaCl‐ addition (P‐Cl) gave overly high relative values for acid organic soils. The acid ammonium acetate test (P‐AAc) which is currently used in Finland, indicated excessively high P availabilities in strongly acid mineral soils, and gave erroneously low relative values in clay soils. The acid ammonium acetate EDTA method (P‐EDTA), which is used for micronutrients and could possibly serve as a universal extraction method, was found to be inferior to the other tests studied.

Nitrogen and Carbon accretion on Ohio coal minesoils: Influence of soil-forming factors

Plantations of white pine ( Pinus strobus L.), tuliptree ( Liriodendron tulipifera L.), white ash ( Fraxinus americana L.) and black locust ( Robinia pseudoacacia L.), established in 1946 on ungraded calcareous, neutral or acid coal spoils, were sampled in 1976 for weight, carbon and nitrogen content of the forest floor, and for total N concentration in 4 depth increments of the underlying mineral soil. Minesoil characteristics were related to the following soil-forming factors: parent material (overburden), organisms (tree species) and relief (aspect and slope position). Forest floor weight was high under white pine on all parent materials and under black locust on acid parent material. Nitrogen content of the forest floor was highest on acid minesoil, as was total weight of N in the forest floor under all species except tuliptree. Although concentration of N in the forest floor was highest under black locust, total weight of forest floor N under pine exceeded that under locust on calcareous and neutral minesoils because of the much greater weight of forest floor under pine. C/N ration of forest floor was lowest under locust and on the acid minesoil. Total N concentration was highest at all depths in soils that formed under black locust: rate of decrease in total N concentration between the 0–5 and 5–15 cm depth increments was also greatest under black locust. Soils formed on calcareous parent material had higher total N concentrations at all depths than those formed on neutral or acid parent materials. We estimate that concentration of total N in the 0–5 cm horizon of calcareous minesoils has increased from 0.04 to 0.23% in the 30 years since tree establishment. The corresponding increase in the acid minesoils has been from 0.03 to 0.18%. Our results show that accretion of carbon and nitrogen on minesoils will be influenced both by overburden strata placed at the surface as parent material of the new soil and by tree species chosen for planting.

Effects of phosphatic amendments on yield and elemental composition of corn grown on acid minesoils

Effects of phosphatic amendments on yield and elemental composition of corn grown on acid minesoils

Evaluation of respiration-based methods for measuring microbial biomass in metal-contaminated acidic mineral and organic soils

To select the most suitable method for determining microbial biomass in metal-polluted acidic soils both the chloroform fumigation-incubation (FI) method and the substrate-induced response (SIR) method were used on four acidic (pH 2.9–4.4) mineral and four organic soils from sites situated 1–42 km from a copper smelter. The FI biomass was calculated with or without nonfumigated controls by using either the general 0.41 or individual soil k c values, and through the kinetic model of Chaussod and Nicolardot ( Revue d'Écologie et de Biologie du Sol 19, 501–512, 1982) which does not use a nonfumigatedcontrol (because it may have a microbial population different to that of the fumigated sample). As SIRbiomass calculated by the standard procedure was found not to correlate with the FI biomass in the soils, a new calibration was derived on the basis of the respiration rate during the first hour after glucose addition. Somewhat at variance with the few other reports on FI biomass in soils of pH below 4.5: (a) only one of the eight soils showed a negative “flush”; (b) the k c values for 14C-labelled fungal biomass were > 0.41 in six soils, and > 0.45 in five; (c) the k c values were not dependent solely on the soil metal content or pH; and (d) the FI biomass-C estimated by the usual methods was up to 2.6% of the total C in the mineral soils, and the biomass did not seem to be influenced by the concentrations of toxic metals in the organic soils. The FI biomass-C values determined by the kinetic model of Chaussod and Nicolardot were, on an average, 0.32 and 0.71% of the total C in the organic and mineral soils, respectively. The method also discerned the effect of a high level of Cu pollution. The single organic and mineral soils containing biocidal concentrations of Cu had biomass-C values, as percentages of total soil organic C, that were 44 and 36% less than the mean values for other soils within their respective groups. Also, the FI biomass values determined by the use of the model correlated significantly ( P > 0.01) with total C in both the organic and mineral soils groups.