The effect of five years acid treatment on leaching,soil chemistry and weathering of a humo-ferric podzol

This paper describes the effect of treating a nutrient-poor forest soil in monolith lysimeters with H₂SO ₄, pH 3.0, for 4.75 yr. The lysimeters were instrumented with porous cup probes to distinguish processes occurring in each soil horizon. In the A horizon base cation exchange and sulphate absorption were the principal proton- consuming processes whereas lower down the profile Al³⁺ dissolution from hydrous oxides dominated. Acid treatment thus reduced the amount of amorphous Al in the lower horizons, but exchangeable Al was unaffected. Sulphate absorbtion was positively correlated with the distribution of Al hydrous oxides. High rates of nitrification reduced the differences between acid and control monoliths, but acid treatment significantly reduced soil pH down to 75 cm and reduced the levels of exchangeable base cations in the litter and A horizons. Acid treatment increased the leaching rates of base cations and Al. Consideration of the total base cation content shows that acid treatment increased the rate of weathering by 0.7–1.4 k eq ha^?1 yr^?1. The results should be useful in modelling more realistic rates of acid input to similar soils.     

Atmospheric deposition to grassland canopies: Lysimeter budgets discriminating between interception deposition,mineral weathering and mineralization

Lysimeter experiments were used to determine atmospheric input to grassland canopies. The combined effect of interception deposition + mineral weathering + mineralization was calculated from input/output budgets. Four types of lysimeters were used, either filled with very pure quartz sand or chalk grassland soil, and either without vegetation or planted with Brachypodium pinnatum (L.) Beauv., Combination of budgets for these four types of lysimeters yielded separate estimates of interception deposition and mineral weathering + mineralization. Ratios between total deposition and bulk deposition were 1.74 and 1.93 for N and S, respectively. Sources and sinks of H⁺ for lysimeters with chalk grassland soil and planted with Brachypodium (abbrev. CP-lysimeters) were about 10 times larger than for lysimeters without plants and filled with quartz sand. The contribution of atmospheric input to total H⁺-sources was 80% for bare lysimeters filled with quartz sand, and only 12% for CP-lysimeters. Bulk deposition and total atmospheric deposition of N was 1.25 and 2.18 kmol ha^?1 yr^?1, respectively, whereas N mineralization of chalk grassland soil yielded 1.62 kmol ha^?1 yr^?1, ‘Acid rain’ has only a minor influence on H⁺-transformations within a chalk grassland ecosystem, but N cycling is seriously affected by atmospheric input.     

Seasonal nitrification measurements with different species of forest litter applied to granite-sand-filled lysimeters in the field

Summary The biodegradation of litter from Festuca silvatica, Abies pectinata, Fagus silvatica, Calluna vulgaris, Picea abies associated with forest brown acid soils or with podzolic soils was studied in field lysimeters filled with granite sand. Analysis of the leachates collected during 2 years made it possible to determine NO _inf3 ^sup- , NH _inf4 ^sup+ , and soluble organic N production in order to investigate the specific influence of the different species of litter on the mineralization of organic N and the variations in nitrification. With Festuca silvatica (grass), active nitrification was observed after the addition of fresh litter in autumn (fall of leaves). Nitrification remained significant in winter, reached a maximum in spring until early summer, and then decreased after mineralization of the easily mineralizable organic N. Nitrification was the major N transformation process in this litter. The addition of fresh litter of Abies pectinata (fir), Fagus silvatica (beech), Calluna vulgaris (heather), and Picea abies (spruce) in autumn induced an inhibition of nitrification during winter and spring. With these litter species, nitrification started again by the end of spring and was at a maximum in summer and autumn until leaf fall. By comparison with Festuca, inhibition observed in winter and spring with the other litter species was definitely due to the chemical composition of the leaves. Simultaneously, a lower C mineralization of these plant material occured. These litter species, in particular Calluna and Picea released leachates containing significant amounts of soluble organic N that were only slightly decomposed. We conclude that NO _inf3 ^sup- production outside of the plant growth period can definitely be involved in soil acidification and weathering processes.     

Chemical effects of pH 3 sulphuric acid on a soil profile

Cores of podzolic soil (monolith lysimeters) were treated for 4.8 yr with 1500 mm yr^?1 of either 0.5 mM H₂SO₄ at pH 3, equivalent to 24 g S m^?2 yr^?1 (acid treated) or distilled water (controls). The acid treatment was about 37 times greater than the average annual input of H₃O⁺ from rain at the site from which the monoliths were taken. Acid treatment acidified the litter (from pH(CaCl₂)3.4 to pH(CaCl₂)2.6) and the mineral soil to a depth of 80 cm (mean pH(CaCl₂) decrease of 0.2 unit). In the litter and upper A horizon, ion-exchange reactions provided the main neutralizing mechanism, resulting in a decrease in the reserves of extractable (in 2.5 % acetic acid) Ca, Mg, and Mn of about 70 to 80 %. Dissolution of solid phase Al from hydrous oxides provided most neutralization below this depth. Al3⁺ was the principal soluble Al species throughout the profile. In the litter and upper A horizon, some of the mobilized Al³⁺ was retained on cation exchange sites resulting in an increase in exchangeable Al. Deeper in the profile, where the exchange sites were effectively saturated with Al³⁺, no increase in exchangeable Al occurred, and Al³⁺ was, therefore, available for leaching. Some reversible adsorption of SO₄ ^2?, associated with hydrous Al oxides, occurred in the Bs and C horizons. The results are discussed in relation to possible effects of acid deposition over regions of Europe and N. America.     

Potassium-supplying power of some northern-Greece soils in relation to clay-mineral composition

The correlation between the content of the clay minerals, mica, montmorillonite or vermiculite, and the logarithmic form $\text{pK-}\text{1}\text{2}\text{p (Ca + Mg)}$ of the activity ratio (K)/√(Ca + Mg) was highly significant for 23 soils from northern Greece. The correlation was negative with mica and positive with montmorillonite and vermiculite. A free-energy term, ΔF¹, necessary to bring the activity ratio of each soil equal to the lowest value encountered, using the concentrations of soluble and exchangeable K and Ca + Mg in the equilibrium systems, was also calculated. The relationship between the content of the three clay minerals and ΔF¹ was the same as when $\text{pK-}\text{1}\text{2}\text{p (Ca + Mg)}$ was used except that the correlation coefficient was greater in all cases, being significant at P_0.001 with each of the clay minerals. The regression of ΔF¹ on each of the clay mineral contents was also much greater than the corresponding ones with $\text{pK-}\text{1}\text{2}\text{p (Ca + Mg)}$.     

Lysimeter study with a cambic arenosol exposed to artificial acid rain: II. Input-output budgets and soil chemical properties

The effects of artificial precipitation with different pH levels on soil chemical properties and element flux were studied in a lysimeter experiment. Cambic Arenosol (Typic Udipsamment) in monolith lysimeters was treated for 6 1/2 yr with 125 mm yr^?1 artificial rain in addition to natural precipitation. Artificial acid rain was produced from groundwater with H₂SO₄ added. pH levels of 6.1, 4 and 3 were used. ‘Rain’ acidity was buffered, mainly due to cation exchange with Ca²⁺ and Mg²⁺, which were increasingly leached due to the acid input. The H⁺ retention was not accompanied by a similar increase in the output of Al ions, but a slight increase in the leaching of Al ions was observed in the most acidic treatment. The net flux of SO₄ ^2? from the lysimeters increased with increasing input of H₂SO₄, but in the most acidified lysimeters significant sorption of SO₄ ^2? was observed. The sorption was, however, most likely a concentration effect. The ‘long-term’ acidification effects on soil were mainly seen in the upper O and Ah-horizons, where an impoverishment of exchangeable Ca²⁺ and Mg²⁺ was observed. An increased proportion of Al ions on exchange sites in the organic layer was observed in the pH 3-treated soil. By means of budget calculations the annual release of base cations due to weathering was estimated to be between 33 and 77 mmol_c m^?2.     

Lysimeter study with a cambic Arenosol exposed to artificial acid rain: I. Concentrations of ions in leachate

The effects of artificial acid rain on soil leachate composition were studied in a lysimeter experiment. Cambic Arenosol (Typic Udipsamment) in monolith lysimeters was treated for 6 1/2 yr with 125 mm yr^?1 artificial rain in addition to natural precipitation. Artificial acid rain was produced from groundwater with H₂SO₄ added. pH levels of 6.1, 4 and 3 were used. Increasing content of H₂SO₄ in the artificial rain increased the concentration of Ca²⁺ and Mg²⁺ in the leachate significantly. The pH of the leachate was slightly reduced only by the most acidic treatment (pH 3). The H^+? retention was not accompanied by a proportionate increase in the Al ion concentration. A slight increase in the Al ion concentration was only observed in the leachate from the pH 3-treated lysimeter. We conclud that cation exchange and/or weathering were the main buffer mechanisms in the soil. The study supports conclusions from other acidification studies, that acidic precipitation is likely to increase the leaching of Ca²⁺ and Mg²⁺ from soils.     

The analysis of isotherm data to describe polyfunctional exchangers and soils

The analysis of isotherms of cation ion-exchange adsorption in heterogeneous polyfunctional ion-exchangers and soils containing groups of adsorption centres non-equivalent in their preference for exchanging cations permits calculation on the basis of experimental data of the selectivity coefficients ($\text{K}{}_{\mathrm{<mtext>i</mtext>}}$) and maximum adsorption of cations ($\text{S}{}_{\mathrm{<mtext>i</mtext>}}$) for each individual group of heterogeneous centres and thus provides an expression for the exchange isotherm with stable values of $\text{K}{}_{\mathrm{<mtext>i</mtext>}}$ over a wide range of concentrations. A method based on a step-by-step breakdown of the experimental isotherm of ionexchange adsorption was used to describe Ca²⁺ and Pb²⁺ exchange in samples of a leached chernozemic soil. The data obtained demonstrated existence of two groups of non-equivalent adsorption centres. Theoretical and experimental data were found to be in sufficient agreement.     

Influence of polysaccharide structure on dextran adsorption by montmorillonite

Two dextrans of similar molecular weight (?2 × 10⁶) but containing different structural linkages (B-215F: 95% α-1→ 6 and 5% α-1→ 3 and Polytran: 75% β-1→ 3 and 25% β-1→ 6) were adsorbed on Na-montmorillonite. Adsorption isotherms showed strong, H-2-type (high-affinity. Langmuir mono-layer adsorption) clay-dextran interactions for both polymers. Maximum adsorption of the Polytran dextran (60 $\text{mg}\text{100mg}$ clay) was 33 per cent greater than that of the B-512F dextran (44.5 $\text{mg}\text{100mg}$ clay) for comparative equilibrium systems. Stable clay-Polytran complexes containing up to 47% dextran were prepared. Excess Na₂SO₄ (0.1 m) did not affect the quantity of dextran adsorption by montmorillonite at the 15% dextran concentration. Acid hydrolysis and modified Pregl method-C analyses did not quantitatively recover adsorbed dextran from complexes containing more than 13 mg of dextran adsorbed per 100 mg of clay. Loss on ignition determinations were in good agreement with the difference measurements of dextran adsorption, suggesting that part of the C was expelled as something other than CO₂ in the ignition determinations. The maximum adsorption segment for Polytran was much smaller than the individual molecule. In contrast, the maximum adsorption segment for the B-512F dextran appeared to be the same magnitude as the individual polymer molecule. Adsorption segment length was regarded as a manifestation of the relative proportions of primary and secondary alcohol groups of the molecules.     

Biochemical activities in peat sterilized by gamma-irradiation

Peat is effectively sterilized by 4 Mrad of γ-irradiation and microbial sulphate-reducing activity is abolished by this dose. Enzymatic activities persist to a variable extent, but have higher inactivation coefficients than are usually encountered with soil enzymes. Inactivation coefficients (Mrad^?1) in surface peat, and in peat from 25–30 cm depth were as follows: β-d-glucosidase 0.144, 0.176: β-d-galactosidase 0.409, 0.458; $\text{β-N-}\text{acetyl-}\text{d}\text{-glucosaminidase}$ 0.201, 0.284; exo-l,4-β-d-xylosidase 0.268, 0.178: arylsulphatase 0.168, 0.174; 4-nitrophenylphosphatase 0.102, 0.118; “dehydrogenase” 0.094. 0.050; thiosulphate: cyanide sulphur transferase 0.079, 0.021. The greater radiosensitivity of the peat enzymes may be because of the absence of protection afforded by adsorption onto clay minerals, the nature of humic-colloid enzyme complex, or as a result of greater indirect damage caused by the products of radiolysis of water.     

Dissolved components in precipitation water percolated through forest litter

Leaves lying on the forest floor are a major source of dissolved organic substances in soil and surface waters, and these substances have important effects in those environments. We used zero‐tension lysimeters to study the chemical characteristics of water percolating through litter from various species of forest trees. The leaching rates were greatest in the autumn and declined rapidly thereafter, especially for deciduous litter. During an annual cycle, 2.5–17% of the initial contents of the carbon in the litter was recovered as dissolved organic carbon in percolates. Humus‐like substances, hydrophilic acids and hydrophilic neutral compounds constituted the major fractions of dissolved C. Leachates from deciduous leaf litter were only partly biodegradable, and those from spruce needles were scarcely biodegradable. Low molecular weight organic acids constituted 0–12% of the dissolved organic carbon in the percolates of the first autumn sampling and decreased over time. Acetic and formic acids were present at the largest concentrations, up to 30 μmol l^?1 per g litter, and gluconic, pyruvic, fumaric, oxalic and citric acids were also frequent in significant concentrations. Among the aromatic acids, p‐hydroxybenzoic acid was identified in four out of five autumn samples. The organic components in litter leachates are important for the microbial activity in soil and surface waters. The organic acids enhance weathering and translocation of metals by their ability to form complexes. Litter is also a source of inorganic ions in soil solutions. The dominant cations in the percolates were K⁺, Ca²⁺ and Mg²⁺, and spruce litter also yielded large quantities of Al and Fe.     

Effects of liming,fertilization and acidification on pH,soil moisture,and ATP content of soil from a spruce forest in Southern Germany

Short-term and medíum-term effects of liming (CaCO₃), fertilization [5Ca(NO)₃)₂·NH₄NO₃], and acidification on soil bioactivity were measured in a spruce stand in Southern Germany. The experiment was set up in a randomized block design. Acid precipitation lowered the pH, liming increased the pH, while fertilization caused only small alterations in pH values. Significant differences in soil moisture occurred only in the mineral horizons. The soil ATP content of the humus layers decreased in all plots (control included) up to day 100. On all sampling dates, a pronounced decrease in ATP content followed the acidification. Minor decreases in ATP were observed after fertilization, while liming produced no defined effects. Similar trends, but less pronounced, were observed in the mineral horizons. Only a few significant correlations were found between pH values and ATP or between moisture and ATP within a treatment and sampling date. Present address: Institut für Biologie II (Zoologie), RWTH Aachen, Kopernikusstrasse 16, D-52056 Aachen, Germany     

Nutrient changes in decomposing beech leaf litter assessed using a solution flux approach

The decomposition of beech (Fagus sylvatiea L.) leaf litter was examined in lysimeters. The experiment allowed comparison of data from mass changes of bioelements in leaf litter and the solution flux balance of through fall input and lysimeter output over a two-year period (1983 and 1984). The annual C loss from the leaf litter was 19%. Na and K concentrations in this leaf litter decreased in the first year and remained constant in the second, while those of Ca and Mg showed no significant changes. N and S amounts per ha increased during the first year by about 7 kg N ha^?1 and 0.5 kg S ha^?1. Ash, Fe, Mn and Al amounts per ha increased to 470, 130 and 240% of their initial levels. These net increases in the first year of decomposition are discussed. The mean annual water and element input by through fall during the experiment corresponded approximately to the long-term average. Thirty to 40 mm more water was evaporated from the litter layer in the drier year (1983) than in 1984. Total N, NO, Na and C1 flux rates of through fall inputs and lysimeter outputs were equal. NH, input rates were greater and organic N smaller than the output rates of the lysimeters. Water balance data indicated that the lysimeter output of K, Mg, Ca and SO, exceeded through fall input. Probable reasons for these differences are discussed.     

Chemical changes in decomposing forest litter in response to atmospheric sulphur dioxide

Decomposing needle and leaf litter, from a pine (Pinus sylvestris L.) stand and a mixed deciduous woodland, respectively, were exposed to arithmetic mean SO, concentrations of up to 50 nl l^?3 (mm³ m^?3) in controlled field-based experiments lasting up to 215 d. The objectives of the study were: (1) to evaluate whether SO, concentrations, known to occur in parts of Europe, could alter the chemical composition of forest litter and leachates, and (2) to use such information to complement results obtained during microbiological studies (Wookey et al., 1991). Dry deposition of SO, on the litter resulted in the production of sulphate during damp conditions or when the litter was moist. The formation of SO^2?₄ and associated H+ ions led to cation exchange processes whereby Mg²⁺ and Ca²⁺ in particular were leached from the litter. This resulted in significant (P<0.01) depletion of magnesium and calcium in both litter types, even at the lowest SO₂ concentrations tested (15 nl l^?1). Incomplete buffering by base cations resulted in acidification of leachates. The magnitude of cation leaching and depletion within the litter was not always linearly related to SO, or leachate SO^2?₄ concentrations, and the role of microbial processes and litter quality as modifiers of such responses is considered.     

An empirical model for stomatal resistance of field-grown wheat

From concurrent data of stomatal conductance of sunlit leaves (C_i; mm s^?1), leaf water potential (ψ; m), and net radiation (R_n; W m^?2) we derive the empirical relationship:

$\text{C}{}_{\mathrm{l}}\text{=(0.986+0.025R}{}_{\mathrm{<mtext>n</mtext>}}\text{)}\text{1}\text{1+(}\text{ψ}\text{?230.8}\text{)}{}_{5.51}$

Stomatal conductances calculated using the above equation are compared with an independent data set. Canopy resistance derived from the above equation is used in a plant water balance equation to simulate diurnal evaporation fluxes for three days, and we compare the calculated fluxes with lysimeter observations for well-watered and water-stressed wheat. Canopy temperatures are additionally obtained from an energy balance equation and compared with infrared radiometer observations. Regression analysis of simulated and observed evaporation fluxes yields a correlation coefficient of 0.98 and a standard error of estimate of about 37 W m^?2; while for the canopy temperatures the correlation coefficient is 0.98 and the standard error of estimates 1.04°C. Variation of canopy net photosynthesis with insolation, and leaf area index are also simulated and compared with observations.     

Effects of nitrite toxicity on soil bacteria under aerobic and anaerobic conditions

Isolates of a soil Pseudoimonas, as well as other soil bacteria, showed a different sensitivity towards NO^?₂ when grown under aerobic or anaerobic conditions. The tolerance to NO^?₂ was increased in the presence of O₂: for instance, a concentration of $\text{200parts}\text{10}{}^6$ of NO^?₂-N proved to be toxic to a Pseudomonas sp. under anaerobic conditions, whereas over $\text{400 parts}\text{10}{}^6$ were needed aerobically to suppress its growth completely. The addition of NO^?₃ as an electron acceptor for anaerobic respiration did not overcome the inhibitive effect of NO^?₃. The pH range, at which NO^?₂ was utilized anaerobically, was narrowed with increasing NO^?₂ concentration (pH 6.8–8.8 at $\text{70 parts}\text{10}{}^6$ of NO^?₂-N and 7.4–8.5 and $\text{140 parts}\text{10}{}^6$ of NO^?₂-N).Tolerance to nitrite varied considerably among the bacteria tested. Each species was able to overcome the inhibitory effect of NO^?₂ up to a certain concentration, while the length of the lag phase was related to NO^?₂ concentration.     

Chemical equilibria and quantity—Intensity relationship of zinc in some acid soils of India

Laboratory studies were conducted to investigate the nature of chemical equilibria of zinc in some acid soils of Himachal Pradesh (India). The results indicated that one of the chemical reactions controlling zinc ion activity in the ambient soil solution may be represented by the equation:

$\text{Si(OH)}{}_4\text{+ 2H}{}_2\text{O ? Zn(OH)}{}_2\text{(}\text{crys.}\text{) + SiO}{}_2\text{(}\text{amorph.}\text{) + 2H}{}_3\text{O}{}^{\mathrm{+}}$

Sequential extraction of ⁶⁵Zn-equilibrated soils provided a measure of the intensity of its different forms and their relative contribution to the pool of potentially available zinc in such soils. Adsorption-desorption parameters have been derived from a quattitative treatment of these phenomena as defined by the Langmuir equation. A supply parameter, $\text{√}\text{cq}\text{√K}{}_1\text{K}{}_2$, integrating the combined effects of quantity, intensity and buffering capacity has been derived from the adsorption studies. A linear relationship between the supply parameter and cumulative desorption of applied zind in these soils has been noted. The desorption of zinc from these soils is an exponential process. The solubility relationship of zinc is expressed in terms of the theory of simultaneous equilibria of competitive chemical reactions which obviates the necessity of assuming a single physico-chemical model in predicting and relating the activity of zinc in the ambient soil solution and its surface reactivity on solid phases in the immediate vicinity of plant roots to its ultimate transport and uptake by plants.     

Sediment acid neutralization in softwater lakes

Acid neutralizing capacities (ANC) of sediments from McCloud Lake, Florida and seven other lakes in Wisconsin and Florida were as high as 10 meq 100 g^?1 over the pH range 4.5 to 5.5 in well-mixed batch experiments. Exchange of Ca²⁺ and Mg²⁺ accounted for over 50% of the neutralizing capacity; Al solubilization and sulfate adsorption were unimportant in neutralizing H⁺ additions. ANC was correlated with sediment volatile solids content. Sulfate reduction occurred in microcosms that simulated lake-water interactions and subsurface seepage;in situ pore water profiles and a whole-lake mass balance confirm the occurrence of this process in McCloud Lake. Sediment neutralization is important for lakes that receive most of their water from precipitation and thus are particularly susceptible to acidification.     

Evaluation of selected medicinal plant materials and dicyandiamide on nitrification of urea‐derived ammonium under laboratory conditions

Background : Poor utilization of urea fertilizer and N losses from agriculture lands demands alternate fertilization practices to reduce N losses and improve utilization, i.e., application of nitrification inhibitors. Aims : This study was aimed to evaluate and compare the influence of dicyandiamide (DCD) and selected medicinal plant materials and on N transformations, nitrification inhibition and recovery of applied N. Methods : Treatments included: urea nitrogen (UN), UN + DCD, UN + Gingiber officinale, UN + Viola odorata, UN + Sewertia chirata, UN + Azadirachta indica, UN + Sphaenathus indicus, UN + Allium sativus, UN + Artemisia absenthium, UN + Fumaria indicus, UN + Caesalpinea bondusella, UN + Barberis lyceum, and an un‐amended control. Urea was applied at 200 mg N kg^?1 soil, while DCD and medicinal plant materials were applied at of 1% and 20% of applied urea, respectively. Results : Medicinal plant materials inhibited nitrification of urea‐derived ${\mathrm{NH}}_4^{+}\text{-}N$. On an average of medicinal plant materials treatments, 51% of ${\mathrm{NH}}_4^{+}\text{-}N$ was still present in soil compared to 17% ${\mathrm{NH}}_4^{+}\text{-}N$ in UN treatment without medicinal plant materials after 28 days. Similarly, ${\mathrm{NO}}_3^{-}\text{-}N$ was 76.54 mg kg^?1 in UN treatment compared to 34.40 mg kg^?1 in UN + medicinal plant materials treatments, indicating 55% reduction in nitrification. Apparent nitrogen recovery (ANR) in UN treatment was 65% compared to 74% in UN + DCD treatment. ANR in treatments, where UN was amended with medicinal plant materials, varied between 58 to 70%. Conclusions : The use of DCD and medicinal plant materials with UN significantly reduced ${\mathrm{NH}}_4^{+}\text{-}N$ oxidation and nitrification ( ${\mathrm{NO}}_3^{-}\text{-}N$). In general, medicinal plant materials were more effective in regulating N transformations and, thus, offer a suitable alternate fertilization practice to reduce N losses and improve fertilizer utilization.