Response of eleven forage species to treatment of acid soil with calcitic and dolomitic lime

Abstract

The cost and difficulty of applying lime on hilly pastures or small forage fields makes it appropriate to devote attention to efficiency of lime utilization. This study evaluated effects of calcitic and dolomitic lime on yield and mineral composition of 11 forage species grown on soil with a low base status of 0.46 cmol_c as Ca and 0.18 cmol_c as Mg kg^‐1. Both lime types increased dry matter production, but only Lolium multiflorum responded more positively to dolomitic lime. The low Mg level in the soil was not a major factor limiting yield. Increase in yield was mainly attributed to the increase in pH with the concurrent decrease in Al level and to an increased Ca availability to plants. The species ranked as follows according to the magnitude of yield increase due to calcitic liming: Trifolium fragiferum > Trifolium pratense > Vicia sativa > Vicia villosa > Trifolium repens > Lolium perenne > Lolium multiflorum > Festuca arundinaceae = Lolium (multiflorum x perenne x perenne) > Trifolium subterraneum > Dactylis glomerata. The most responsive, Trifolium fragiferum, did not grow without lime. The least responsive, Dactylis glomerata, showed a yield increase of 36%. A similar ranking was obtained when all species were evaluated for Al tolerance using a 48 hour root elongation bioassay. In both unlimed soil and soil limed with calcitic lime, Mg concentrations of all species were relatively low. Although they were generally not low enough to have an effect on yield, they barely met the Mg nutritional requirement of cattle. By adding dolomitic lime, Mg content increased in grasses an average of 3.7 fold and in legumes by 2.4 fold. Grasses were similar in Ca, Mg, and K concentrations within a soil treatment. Legumes showed a greater range with the two vetches having the lowest Ca and Mg concentrations and red clover the highest.     

Monthly variation of forage and soil minerals in central Florida. I. macro‐minerals

Abstract

A two‐year study was conducted to determine the macromineral status of cattle grazed forages, mostly bahiagrass, and soils in central Florida. Soil and forage samples were collected every month for two years. Month differences (P < 0.01) were observed in all forage macrominerals and in crude protein (CP) for both years. No month effect (P > 0.05) was observed in IVOMD level during year 1. Year effects (P < 0.05) were observed in calcium (Ca), sodium (Na) and CP. Concentrations below the critical level were observed in all macrominerals studied. Higher forage macro‐mineral concentrations were found during spring‐summer months. In general, higher (P < 0.05) soil aluminum (Al), Ca, magnesium (Mg), phosphorus (P), and organic matter (OM) were observed during fall‐winter months, while Na was higher in winter. Soil Ca and Mg were adequate and potassium (K), Na and P were deficient. Year 2 showed higher (P < 0.05) soil macromineral concentrations. Correlation coefficients (r >|0.5|, P < 0.05) were present between forage K and forage CP (r = 0.557) and between forage P and forage CP (r = 0.554). Low correlations were found between soil and forage macrominerals. Percentages of total forage samples with macromineral and CP concentrations below critical levels (in parentheses) and suggestive of deficiency were as follow: in forage, Ca (0.30 ppm), 21%; Mg (0.18 ppm), 34%; K (0.60 ppm), 47%; Na (0.06 ppm), 89%; P (0.25 ppm), 85%; and CP (7%), 18%.     

Ammonium Chloride Solution as an Alternative Laboratory Procedure for Exchangeable Cations in Southern Brazilian Soils

Most Brazilian soil-testing laboratories use Mehlich 1 and 1.0 M potassium chloride (KCl) solutions as extractants for the determination of phosphorus (P), potassium (K), and sodium (Na) and for exchangeable calcium (Ca), magnesium (Mg), manganese (Mn), and aluminum (Al) in agricultural soil samples. Other laboratories use a combination of exchangeable ionic resin and KCl procedures. With recent adoption of the inductively coupled plasma (ICP-OES) in routine soil-testing laboratories, soil extraction with 1.0 M ammonium chloride (NH₄Cl) became an alternative due to the possibility of determining all exchangeable elements in one run (Ca, Mg, K, Mn, Na, and Al), leaving determination of phosphorus (P) with Mehlich 1 or exchangeable ionic resin. To evaluate the performance of the NH₄Cl solution, an experiment was carried out with thirty-seven samples of soils representative of the southernmost state of Brazil, Rio Grande do Sul. Four extraction solutions [Mehlich 1 at soil/solution ratio of 1:10 and 1.0 M ammonium acetate (NH₄OAc), 1.0 M KCl, and 1.0 M NH₄Cl at soil/solution ratio 1:20] were used with three different shaking times (5, 30, and 60 min). Correlation coefficients among all methods were high. Mehlich 1 did not perform well against NH₄OAc and NH₄Cl, despite the high correlation coefficients, with values consistently lower for K, even when the time of extraction was increased from 5 to 30 or 60 min. However, for concentrations less than 0.30 cmol kg^?1 (i.e., in the range of K deficiency), both solutions performed similarly. Calcium and Mg increased with time of shaking. Comparable values of exchangeable Ca, Mg, and K, as well as of Al and Mn, were obtained with 1.0 M NH₄Cl with 60 min shaking and the standard procedures of 1.0 M NH₄OAc and 1.0 M KCl. The determination of Al by traditional titration/back-titration of the 1.0 M KCl solution gave slightly greater results compared to ICP-OES obtained using extraction with 1.0 M NH₄Cl. The results indicate that for Ca, Mg, Mn, and Al, it is possible to replace the traditional 1.0 M KCl extraction with 1.0 M NH₄Cl solution, with 60 min shaking time and a soil/solution ratio of 1:20.     

The Transfer of Chemical Elements within a Heath-Ecosystem (Calluna vulgaris) in Northwest Germany

The purpose of this investigation was to describe the element budget of a heathland area in Northwest Germany by measuring the fluxes of elements within the ecosystem. The following fluxes were considered: input by precipitation, canopy-drip, mineralisation, ion uptake, litterfall, output with seepage water. The elements H, Na, K, Ca, Mg, Mn, Fe, Al, S, P, CI, NO, NH, N_org were analysed, the period of investigation was one year. The results demonstrate the high importance of deposited nutrients like N (especially No3), Ca and Mg for the element budget and the stability of a heath-ecosystem. The internal turnover of K, Ca, Mg and Mn within the ecosystem mainly took place by leaching. No leaching was found for N, P, AI, Fe, S, CI, Na. For these elements litterfall was the dominant internal way of cycling. The humus layer was a sink for total-N, NO, Ca, Mg, Mn, Fe and S. NO, Ca, Mg, Mn and S were removed from the percolating solution, while for Fe and especially N and Mn an inhibition of mineralisation was found. The element balance for the mineral soil showed that this part is a sink for Hand a source mainly for Al, Ca and Mg, less for K and Na. From the cation/anion balance of the storage changes in mineral soil the ecosystem-internal H ion production was calculated as 0.4 keq per ha and year. It may be traced back to an uptake of NH, and dissociation of fulvic acids in the mineral soil. The results are discussed with respect to the development, stability and management of heath-ecosystems.     

Use of near infrared spectroscopy to determine biological and chemical characteristics of organic layers under spruce and beech stands

The chemical composition of organic layers of forest soils shows a high spatial variability and fast methods may be required for its study at a landscape level. The objective was to assess the applicability of near infrared spectroscopy (NIRS) to measure several chemical and biological properties of organic layers in spruce, beech, and mixed spruce‐beech stands. Spectra in the VIS‐NIR region (400—2500 nm) were recorded for 406 samples representing Oi, Oe, and Oa layers of forest soils from Solling (Germany), 195 of them were used for calibration and 211 for validation. The calibration equations for each constituent were developed using the whole spectrum (0^th to 3^rd derivative). Humus samples were analyzed for contents of C and N and contents of P, S, Na, K, Ca, Mg, Mn, Fe, and Al after pressure digestion in HNO₃. Additionally, basal respiration and microbial C (C_mic) were measured. NIRS predicted well the contents of C, N, P, S, Ca, Na, K, Fe, and Al and C/N and C/P ratios: the regression coefficients (a) of a linear regression (measured against predicted values) ranged from 0.9 to 1.1, and the correlation coefficients (r) were greater or equal 0.9. C_mic (a = 0.87, r = 0.83) was predicted satisfactorily, whereas the prediction of the basal respiration (a = 0.74, r = 0.87) was less satisfactory. Due to liming of some of the plots NIRS failed to predict contents of Mg (a = 1.27, r = 0.68). For all chemical and biological characteristics the best prediction performances were achieved using the whole sample population. Splitting the samples into smaller groups according to a dominant tree species or an organic layer did not improve the predictions.<?show $6#>     

Application of leaf,soil, and tree ring chemistry to determine the nutritional status of sugar maple on sites of different levels of decline

Nutrient concentrations and D.R.I.S. indices of leaves, soil chemistry and dendrochronological changes of elemental concentrations in sugar maple (Acer saccharum Marsh.) were used to determine its nutritional status on three sites of contrasting levels of decline. We hypothesized that the ratio of Al to base cations in tree rings would increase more at the most severely declining site, and that the ratios of K⁺ to divalent cations (Ca²⁺ and Mg²⁺) would increase slower or decrease more rapidly over time than at the less severely declining sites. Forest health, based on percentage of foliage missing, and leaf K and Mg concentrations of the three sites were ranked as follows: Morgan Arboretum > Saint-Hippolyte > Entrelacs. Soil pH, Ca, Mg, E.C.E.C. and percentage of base saturation were highest at the Morgan Arboretum, and exchangeable Al in the organic horizon was highest at Entrelacs. Concentrations of K, Ca, Mg and Al, and ratios of these elements in wood were determined for each of the following periods: 1940–1956, 1957–1973 and 1974–1989. Variations in tree ring chemistry among sites were significant for K and Al and all elemental ratios except K:Mg. Al concentration and the ratios of Al to base cations in wood were all significantly higher at Entrelacs (7.0 vs 2.6 and 2.8 mg Al kg^?1 for the other two sites, respectively). Weak relationships were generally observed between leaf and soil elemental concentrations, and wood elemental concentrations. The D.R.I.S. K index and soil exchangeable K and Al showed good concordance with wood concentrations. With the exception of Mg, Al and Al:Mg, the effect of period was significant for all other elements and ratios of elements. The most severely declining stand (Entrelacs) differed from the healthiest stand by decreasing K:Ca and increasing A1:K from the 1940–1956 to the 1957–1973 period.     

Laboratory Dissolution Studies of Rocks from the Borrowdale Volcanic Group (English Lake District)

Laboratory studies were conducted to investigate the rates ofrelease of Na, Mg, Al, Si, K, Ca and Fe from 10 samples of metamorphosed igneous rock of the Borrowdale Volcanic Group (BVG), consisting mainly of plagioclase feldspars, chlorite andquartz, with minor amounts of hornblende, epidote and carbonates.Experiments were performed using freshly-prepared rock pieces (ca. 12 mm cubes), in batch mode, but with frequent changes of the solution phase so that accumulation of dissolved solutes wasminimised. The initial element release rates were relatively high, but declined with time to reach approximate (pseudo-) steady state conditions. Element release rates declined withpH in the pH range 2–7, the dependence upon pH decreasing in the order Al ～ Fe > Si > Mg ～ Ca > K ～ Na. Thepseudo-steady state rates for Si were comparable to steady state values for single minerals. Calcium showed the greatestsample-to-sample variation (more than 100-fold). Rock dissolutionwas far from stoichiometric, with Ca and Mg being present in thesolution phase in proportions greater than in the rock, and Al and Si in lower proportions. In some samples the release rates ofMg and Ca were equal, while in others the Ca rate was up to 100times that of Mg. The rate of release of Ca is correlated with the carbonate content of the rocks. The results indicate that the main source of Ca in the faster-dissolving samples is calcite, while the highest release rates of Mg are consistent with dissolution of dolomite. Aluminium, Si and Fe are probablyreleased predominantly from chlorite. The results are discussed in terms of the supply of base cations to stream waters drainingcatchments underlain by rocks of the BVG.     

EFFECT OF SOIL pH AND ORGANIC MATTER ON LABILE ALUMINIUM IN SOILS UNDER PERMANENT GRASS

The rates of extraction of Na, K, Mg, Ca, and Al with 1M NH₄ NO₃ from the mineral-and organic-rich layers of some Park Grass (Rothamsted) soils were measured at the pH of the soil. Below pH 3.7 exchangeable Al, derived from the kinetics curve, increases with decreasing soil pH and is less in the organic-rich layer. The sum of the basic exchangeable cations, ∑(Na + K + Mg + Ca), increases with increasing soil pH and is more in the organic-rich layer. The extraction of exchangeable Al obeys first order kinetics, the rate constant being similar for all the soils (mean value 36 ± 7 × 10^?6|s^?1), which implies that exchangeable Al is released from surfaces with similar properties for the adsorption of Al, and that the rate is not affected by soil pH and organic matter. The rate of extraction of non-exchangeable Al is the same in the mineral-and organic-rich layers of each soil, and is maximal at about pH 3.7, decreasing sharply at more and less acid pH values.     

Rainwater Composition at a Regional Representative Site of a Semi-Arid Region of India

Rainwater samples (N = 51) were collected at Rampur, an areafree from anthropogenic activity during the monsoon of 1997 and1998. The concentration of ions follows a general pattern as Ca> NH₄ > Mg > SO₄ > Cl > F >Na > NO₃ > K > HCOO >CH₃ COO. The pH of precipitation ranges between 5.9 and 7.4. The levels of Ca and Mg at this site are higher than otherremote sites, probably dominated by particles of soil origin.Good correlation between Ca, NO₃, SO₄, HCOO and CH₃COO indicate that a fraction of NO₃, SO₄, HCOOand CH₃COO may be derived from soil or associated with Ca and Mg after neutralization. The order of neutralization factorCa (2.19) > NH₄ (1.26) = Mg (1.26) indicates that majorneutralization occurred by Ca. Factor analysis suggested thatCa, Mg, Na, K, NO₃, SO₄, HCOO and CH₃COO arecontributed by soil. NH₃ is known to exist as(NH₄)₂SO₄, NH₄NO₃ and NH₄Cl. Theymay be formed in the atmospheric water droplets by scavenging ofaerosols and reaction of gaseous species.     

Annual and Seasonal Variations of Trace Metals in Atmospheric Suspended Particulate Matter in Islamabad, Pakistan

Total Suspended particulate matter (TSP) in urban atmosphere of Islamabad was collected using a high volume sampling technique for a period of one year. The nitric acid–perchloric acid extraction method was used and the metal contents were estimated by atomic absorption spectrophotometer. The highest mean concentration was found for Ca at 4.531 µg/m³, followed by Na (3.905 µg/m³), Fe (2.464 µg/m³), Zn (2.311 µg/m³), K (2.086 µg/m³), Mg (0.962 µg/m³), Cu (0.306 µg/m³), Sb (0.157 µg/m³), Pb (0.144 µg/m³) and Sr (0.101 µg/m³). On an average basis, the decreasing metal concentration trend was: Ca > Na > Fe > Zn > K > Mg > Cu > Sb > Pb > Sr > Mn > Co > Ni > Cr > Li > Cd ≈ Ag. The TSP levels varied from a minimum of 41.8 to a maximum of 977 µg/m³, with a mean value of 164 µg/m³, which was found to be higher than WHO primary and secondary standards. The correlation study revealed very strong correlations (r?>?0.71) between Fe–Mn, Sb–Co, Na–K, Mn–Mg, Pb–Cd and Sb–Sr. Among the meteorological parameters, temperature, wind speed and pan evaporation were found to be positively correlated with TSP, Ca, Fe, K, Mg, Mn and Ag, whereas, they exhibited negative relationships with relative humidity. On the other hand, Pb, Sb, Zn, Co, Cd and Li revealed significant positive correlations with relative humidity and negative with temperature, wind speed and pan evaporation. The major sources of airborne trace metals identified with the help of principle component analysis and cluster analysis were industrial emissions, automobile exhaust, biomass burning, oil combustion, fugitive emissions, resuspended soil dust and earth crust. The TSP and selected metals were also studied for seasonal variations, which showed that Na, K, Zn, Cu, Pb, Sb, Sr, Co and Cd peaked during the winter and remained lowest during the summer, while Ca, Fe, Mg and Mn were recorded highest during the spring.     

Ionic equilibria,selectivity and diffusion of cations in soil as influenced by anion additions

Abstract

An experiment was carried under controlled conditions to investigate the influence of the anions, H₂PO₄ ^‐. and Cl on the ionic equilibria, selectivity and effective diffusion of Rb, K, Na, Ca, Mg in two Indiana soils.

Additon of anions to the soils increased the concentration of cations in soil solution. In both the soils receiving H₂PO₄ ^‐, lower cation concentrations were found in the soil solution than in those receiving Cl^‐ . Additon of H₂PO₄ ^‐and Cl^‐ reduced the ion selectivity coefficient, k, for various homovalent (Rb/K, Rb/Na, K/Na, Ca/Mg) and mono‐divalent ion pairs (Rb/Ca, Rb/Mg, K/Ca, K/Mg). In Zanesville soil treatments receiving H₂PO₄ ^‐ had lower k values for mono‐divalent cations than treatments receiving Cl^‐. However, no such conclusions could be drawn for Raub soil. Soils treated with H₂PO₄ ^‐ had higher k values for homovalent cations than Cl^‐ treated soils. The differences in the selectivity of adsorption in these two soils might be attributable to the differences in the type and nature of exchange materials and cation concentrations on the exchange phase.

Addition of H₂PO₄ ^‐ or Cl^‐ enhanced the magnitude of effective diffusion coefficient. (De) of all the cations under considerations. The magnitude of effective diffusion coefficient for cations was lower for H₂PO₄ ^‐ treated soils than Cl^‐ treated soils. Such a reduction in De is related to the reduction in cation concentration in soil solution thereby increasing the buffer capacity for the ions under consideration.     

Nutrient storage in soil and biomass of native Brazilian Cerrado

The removal or burning of the biomass which frequently includes main roots results in significant nutrient losses from the Brazilian savanna, the Cerrado. To estimate these losses, we quantified above‐ and belowground plant biomass and total nutrient storage in biomass and soil of a typical Cerrado. Dominant tree species in the layer > 2 m were Pouteria torta (MART. ) RADLK ., Ouratea spectabilis (MART .) ENGL ., Roupala montana AUBL ., Byrsonima coccolobifolia H.B. et K., Dalbergia miscolobium BENTH ., Kielmeyera coriacea MART ., and Caryocar brasiliense CAMBESS . which together represented 70 % of the biomass of the > 2 m layer. In the 0.5—2 m tree layer, many different species were found of which Ouratea hexasperma (ST .‐HIL .) BAILL . representing 33 % of the biomass in the 0.5—2 m layer was most abundant. The dominant shrub species were Miconia holosericea DC., Hortia brasiliana VAND . ex DC., Myrcia rostrata DC., Parinari obtusifolia HOOK . f., and Campomanesia velutina BLUME , contributing 93 % to the total shrub biomass. Total aboveground plant biomass was 22.7 Mg ha^—1, total belowground plant biomass was 30.4 Mg ha^—1. The tree layer > 2 m comprised the largest proportion of the aboveground biomass (64.6 %) > grass/herb (13.0 %) > shrub layer (11.6 %) > tree layer 0.5—2 m (10.8 %). Three quarters of the fine root biomass (17.6 Mg ha^—1) were located in the upper 0.3 m of the soil. The element storages (in kg ha^—1) were C: 10900, N: 173 N, P: 20, K: 51, Ca: 66, Mg: 20, S: 25, Fe: 10, Mn: 4.2, Zn: 0.35, and Al: 27 in the aboveground biomass, C: 12900, N: 214 N, P: 14, K: 41, Ca: 52, Mg: 10, S: 33, Fe: 2060, Mn: 2.9, Zn: 0.60, and Al: 648 in the belowground biomass, and C: 55400, N: 3510 N, P: 631, K: 366, Ca: 86, Mg: 75, S: 529, Fe: 159000, Mn: 124, Zn: 49, and Al: 434000 in the soil (0—0.3 m). If the above‐ and belowground biomass was completely removed from the Cerrado ecosystem losses would range from 5 % of the total nutrient storage for P to 58 % for Ca referred to a lower ecosystem boundary at 0.3 m mineral soil depth.     

Leaching of metals from a spruce forest soil as influenced by experimental acidification

Acidified (H₂SO₄+HNO₃, 3:1) throughfall waters (pH 3.16 and 3.40 as volume weighted means or control (untreated throughfall water, pH 3.72) were applied for 3.5 yr by an automatic irrigation device to lysimeters containing podzolized spruce forest soils of 0–5, 0–15 and 0–35 cm soil depth. The total volume of the leachates was measured together with their pH and total content of DOC, Na, K, Ca, Mg, Fe, Mn, Al, Cu, Zn, Cd and Pb and the initial amounts of metals and H in the soil. The main part of H⁺ added with the throughfall waters was retained within the soil. Concentrations and fluxes of Mg, Ca, Mn, Zn and Cd in the soil were significantly increased by addition of acidified throughfall waters; K was less affected. As a consequence of lowered flux of DOC in the A horizon as acid input increased, Fe, Al, Cu, and Pb fluxes also decreased. The mobility of these metals in the A horizon was shown to be regulated mainly by the formation of watersoluble organic compounds rather than directly by pH variations. Compared to the control, the additional annual loss of Mg from the soil profile in the most acid treatment was c. 10% of the currently exchangeable amount.     

A simple rapid method for the measurement of exchangeable cations and effective cation exchange capacity

Abstract

A simple single‐extraction procedure for measuring exchangeable cations and effective CEC (ECEC, the CEC at natural pH and ionic strength) has been developed for routine advisory soil analysis. The method is based on the use of Sr (1.26M SrCl₂) to displace exchangeable cations and effective CEC is taken as the sum of the exchangeable cations. A ten minute shaking time at 5 g:80 ml, soil solution ratio, was found to be optimum. Good agreement was found between the proposed method and the standard neutral IN ammonium acetate leaching procedure with correlation coefficients (r) for the individual cations Mg, Ca, Na and K of 0.99***, 0.99***, 0.83*** and 0.96*** respectively. Strontium chloride extracted more Al but less Mn (P<0.01) than IN KC1, but because of the low levels of these cations in relation to the total cations present, there was still a good relationship (r= 0.99) between ECEC determined by 1.26M SrCl₂ and that determined as the sum of ammonium acetate extractable Mg, Ca, Na and K plus IN KCl‐extracted Al and Mn.     

Element mass balances for South Carolina Coastal Plain watersheds

Element mass balance estimates for South Carolina Coastal Plain watersheds indicate that fertilizers and liming materials are the major sources for inputs of Ca, Mg, K, Cl, and HCO₃ whereas precipitation is the major input for Na and SO₄. Stream flow is the chief mode of output for all of these elements. A balance between input and output is evident only for Cl. Retentions of 50% or more are shown by Ca, Mg, K, HCO₃ and SO₄ whereas Na shows an apparent net loss. The retention of Ca, Mg and HCO₃ suggests that less than 25% of the dolomitic liming materials applied to the landscape actually dissolve and that the carbonate chemistry of Lower Coastal Plain streams is therefore probably largely controlled by seepage of groundwaters from underlying calcareous aquifers. The retention of K and the loss of Na may be due to cation exchange reactions on soil clays whereas the apparent retention of SO₄ is probably due to reduction to H₂S in floodplain environments and soil adsorption.     

Metal chemistry of irrigation and drainage waters of Al-Ahsa Oasis of Saudi Arabia and its effects on soil properties

Water samples from 18 springs and 13 drainage canals and subcanals were collected from Al-Ahsa Oasis. Concentrations of total dissolved salts, Cl, SO₄ HCO₃, B, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, V, Ti, and Zn were determined. The soil salinity development (SSD), the adjusted Na ratio (adj. SAR), the adjusted Na adsorption ratio (adj. RNa), and exchangeable Na percentage (ESP) were calculated. Sodium was the most abundant cation in all water samples followed by Ca, Mg, Sr, and K in descending order. Concentrations of all other metals were below 0.1 mg L^–1. Chloride was the most abundant anion, followed by SO₄ and HCO₃ in these waters. A significant correlation (P < 0.05)=" between=" na=" and=" cl=" in=" water=" samples=" was=" found.=" thermodynamic=" calculations=" revealed=" that=" an=" appreciable=" fraction=" of=" ca=" and=" mg=" in=" spring=" and=" drainage=" waters=" were=" associated=" with=">₄ and HCO₃ ions. Calcium increased from less than 10 meq L^–1 in spring waters to > 16 meq L^–1, Mg was doubled, and Na and Cl increased several times in the drainage waters. The salinity and sodicity hazards of the spring and drainage waters were classified as C₄S₂ i.e. high salinity with medium sodicity problems.     

Changes since 1950 of mineral pools in the upper C-horizon of Swedish deciduous forest soils

Soils from the C-horizon of deciduous forests in southern Sweden, originally sampled in 1947-52, were resampled in 1988. Air-dried soil from both periods were extracted in 1991 using M NH₄Ac, pH 4.8, and 0.2 M HNO₃ for analysis of exchangeable and acid soluble pools of Na, Mn, Ca, Mg, K, Sr, Zn, Fe, S, P, and Al. Using acid NH₄Ac as extractant nine elements had changed significantly (p<0.05) over 40 yr. In particular, the pools of exchangeable base cations and Mn had decreased, whereas those of Al, S, and Fe had increased. The HNO₃ extraction showed the same tendency as NH₄Ac for most elements, but the relative changes were always smaller. The largest decrease was measured in Na with both extractants (only 10 to 30% remaining in 1988). Of K, Mg, Ca, and Sr, about 40 to 60% remained with NH₄Ac and about 70% with HNO₃. The NH₄Ac exchangeable pool of Al, on the contrary, was twice as high in 1988 as in 1947–52. Amounts obtained with the two extractants were usually positively correlated (r>0.90 for Na, K, Mg, and Sr), but with the exception of S, values for HNO₃ were higher or much higher. It is concluded that a decided decrease of the exchangeable pools of base cations and an equally decided increase of exchangeable Al has occurred even in the C-horizon, well below the main rhizosphere. That also the acid soluble pools of base cations have decreased indicates mineralogical changes which may counteract a complete reversibility of the current soil acidification.     

Are Indicators for Critical Load Exceedance Related to Forest Condition?

The aim of this study was to evaluate the suitability of the (Ca?+?Mg?+?K)/Al and the Ca/Al ratios in soil solution as chemical criteria for forest condition in critical load calculations for forest ecosystems. The tree species Norway spruce, Sitka spruce and beech were studied in an area with high deposition of sea salt and nitrogen in the south-western part of Jutland, Denmark. Throughfall and soil water were collected monthly and analysed for pH, NO₃-N, NH₄-N, K, Ca, Mg, DOC and Al_tot. Organic Al was estimated using DOC concentrations. Increment and defoliation were determined annually, and foliar element concentrations were determined every other year. The throughfall deposition was highest in the Sitka spruce stand (maximum of 40 kg N ha^?1yr^?1) and lowest in the beech stand (maximum of 11 kg N ha^?1yr^?1). The Sitka spruce stand leached on average 12 kg N ha^?1yr^?1 during the period 1988–1997 and leaching increased throughout the period. Only small amounts of N were leached from the Norway spruce stand whereas almost no N was leached from the beech stand. For all tree species, both (Ca?+?Mg?+?K)/Al and Ca/Al ratios decreased in soil solution at 90 cm depth between 1989 and 1999, which was mainly caused by a decrease in concentrations of base cations. The toxic inorganic Al species were by far the most abundant Al species at 90 cm depth. At the end of the measurement period, the (Ca?+?Mg?+?K)/Al ratio was approximately 1 for all species while the Ca/Al ratio was approximately 0.2. The lack of a trend in the increment rates, a decrease in defoliation as well as sufficient levels of Mg and Ca in foliage suggested an unchanged or even slightly improved health condition, despite the decreasing and very low (Ca?+?Mg?+?K)/Al and Ca/Al ratios. The suitability of these soil solution element ratios is questioned as the chemical criteria for soil acidification under field conditions in areas with elevated deposition rates of sea salts, in particular Mg.     

Effects of acid rain on ion leaching in a danish forest soil

The mobility of major cations (H⁺, ammonium, Al, Ca, Na, Mg, K, Fe), heavy metals (Mn, Zn, Ni, Cd) and anions (chloride, sulphate and nitrate) was studied in the laboratory in an acidified brown soil from a Norway spruce forest. Lysimeters containing undisturbed soil columns of the A-horizon and the A- plus B-horizon were watered with 540 mm of throughfall precipitation collected in situ, either directly (pH 3.6) or adjusted to pH 3.3 or 2.8. The pH 3.3 treatment increased leaching of Mn and Cd from the B-horizon. The pH 2.8 treatment increased leaching of ammonium, Na, Ca, Mg, K, Mn, Zn and Cd from the A-horizon and ammonium, Al, Na, Ca, Mg, K, Mn, Zn and Cd from the B-horizon. Fe leaching from the A-horizon was decreased by both acidic treatments, and the pH of the leachates was not significantly affected. Sulphate retention was 138-161 meq m^?2 yr^?1 by all treatments. Due to experimental conditions nitrate leaching was observed in all lysimeters.