Microfungi in coniferous forest soils treated with lime or wood ash

Summary Microfungal species composition was studied in coniferous forest soils which had been treated with lime or wood ash. The pH increased by about 2.5 units at the highest rate of application. Fungi were isolated 4–5 years after the treatments using a soil washing technique. At one site, Öringe, clear differences in species composition due to liming were found. Penicillium spinulosum, Oidiodendron cf. truncatum, Mortierella spp., and two sterile taxa decreased in abundance in limed areas, while Geomyces pannorum, Penicillium cf. brevicompactum, Trichoderma polysporum, and Trichosporiella sporotrichioides increased in isolation frequency. At another site, Torrmyra, the effect of liming was less pronounced, although the pH changes due to the treatments were larger compared to the Öringe site. However, T. polysporum increased, while a sterile taxon decreased in abundance in lime- and wood ash-treated plots. The changes in microfungal species composition after liming were similar to those found earlier in urea-treated soils, and opposite to those found in artifically acidified or ammonium nitrate-fertilized soils.     

The sensitivity of Swiss forest soils to acidification and the risk of aluminum toxicity

In the context of pollution‐control strategies to minimize the detrimental effects of soil acidification, there is a need to know how and to what extent soils respond to acidifying substances. The purposes of this study were to assess the sensitivity of soil to acidification, in particular to a decrease in pH and in base saturation (BS), and the risk of Al toxicity for vulnerable plants using chemical indicators. These indicators were derived from soil data (pH, exchangeable cations, amount of fine earth) measured in the mineral horizons of 257 soil profiles throughout Switzerland. Based on the analysis of the distribution of pH and BS values in the soil collective, we assessed the sensitivity of soils to a decrease in pH and in BS. Soils that were considered sensitive to a decrease in pH had pH values between 4.8 and 7.0. The degree of sensitivity was estimated with the proportion of fine earth in the critical pH range to a depth of 100 cm. Soils that were considered sensitive to a decrease in BS had pH values between 3.6 and 5.5 and a BS between 10% and 95%. Since the effective cation‐exchange capacity (CEC_eff) of the fine earth might dampen the decrease in BS when acidity is added, the disposition for a decrease in BS was related to the relative amount of fine earth in the sensitive BS and to the mean CEC_eff of this fine‐earth fraction. The risk of Al toxicity for vulnerable plants was estimated using the ratio of base cations to Al at the cation‐exchange sites (BC : Al_exc). A BC : Al_exc of 0.2 was taken as a threshold value below which the risk for sensitive plants increases. The degree of risk was based on the proportion of fine earth in the critical BC : Al range (≤0.2) in the soil profile. These indicators taking into account the various aspects of soil acidification are derived from usually available data and represent therefore a cost‐effective tool to assess the sensitivity of soils to an input of acidity.     

Principal geographic variation in the acidification of Swedish forest soils

The principal geographic variation in acid-base status of 25 deep soil profiles (maximum 2.6 m deep) was investigated along three transects across Sweden. The transects represent gradients in the atmospheric deposition of acidifying compounds. A latent variable describing the acidity of the profile was extracted by Principal Component Analysis (PCA) and found to contain information that could be geographically interpreted. The variable was correlated more strongly with the atmospheric deposition of S (r=?0.86) than with groundwater recharge (r=?0.30) or base mineral index (r=0.45). It was concluded that variation in the deposition of S, in the form of H₂SO₄, is the main factor responsible for the large geographical differences in acidity in forest soils along transects from west to east in southern and middle parts of Sweden.     

Effects of lime and nutrient salts on the microbiological activities of forest soils

Summary In pot experiments, lime and mineral salts were applied to forest soils taken from three different sites. Microbial biomass, basal respiration, N turnover, and the activities of protease, phosphatase, and CM-cellulase were determined monthly. The fertilized soils showed a great increase in biomass, respiration and N turnover, and some increase in protease activity, whereas phosphatase activity decreased in comparison with the untreated soils. Estimates of the number of colony-forming units of different classes of microorganisms showed an increase in treated soils in most cases. The untreated soils had the lowest biological activity but the maximum application of lime and mineral salts did not automatically lead to maximum activity.     

Logging residue harvest may decrease enzymatic activity of boreal forest soils

Nowadays conventional stem-only harvest where logging residues are left on the site is often displaced by whole-tree harvest, in which logging residues are harvested for use as bioenergy. Logging residues consist of tree branches and tops of stems with needles. The aim of this study was to evaluate the effect of logging residue harvest on soil enzyme activities involved in C, N and P cycling, namely β-glucosidase, β-glucosaminidase, protease and acid phosphatase in relation to other soil characteristics (i.e. soil respiration, net N mineralization, microbial biomass C and N). Soil samples were taken from the humus layer of five study sites, differing in fertility, dominating tree species and time elapsed after treatment. The study sites were Norway spruce (Picea abies, (L.) Karst) and Scots pine (Pinus sylvestris L.) stands in different parts of Finland. Four of the study sites were single-tree experiments, where thinning was performed 4–5 years before this study and 3–4 different doses of logging residues (from 0 up to 37.5 Mg ha⁻¹) were distributed on a circle around a single tree in 3 replicates. The last field experiment had been thinned twice, 23 and 13 years ago; the treatments in 3 replicates were whole-tree harvest and stem-only harvest. In the whole-tree harvest vs. stem-only harvest experiment, activities of β-glucosidase, β-glucosaminidase, acid phosphatase were similar in both treatments. In general, in the single-tree experiment with pine, enzymes raised the activity in response to increasing amount of logging residue. The pattern was less clear for the spruce single-tree experiment, but acid phosphatase and protease activities increased with the increase in amount of logging residue. In general, other soil characteristics were less affected than enzyme activities by logging residue removal; however, in some sites logging residues seemed to increase net C and N mineralization with increasing logging residue amount. Our results suggest that retaining logging residues on the site can increase soil enzyme activities and C and N mineralization.     

Effects of acidification and liming on feeding groups of nematodes in coniferous forest soils

Summary Nematodes were sampled in untreated, acidified, and limed plots in a Norway spruce (Fexboda) and a Scots pine (Norrliden) stand. At Fexboda, the total number of nematodes was significantly reduced after the acidification. This reduction was probably due to a shock effect, because the samples were taken only 5 months after an application of 200 kg H₂SO₄ ha^-1 to the forest floor. However, the root/fungal-feeding Aphelenchoides was not reduced, probably because it is more tolerant of high acid concentrations than most other nematodes. At Norrliden, where the samples were taken 7 years after the last application of H₂SO₄, no significant differences were found between the acidified and untreated plots. If the treatment with H₂SO₄ caused similar effects as at Fexboda, the results indicate a recovery of the nematode populations. Decreased predation from lumbricids rather than a recovery of microfloral populations probably allowed this recovery. No marked effect of lime, spread 2 (Fexboda) and 12 years (Norrliden) before the sampling on the numbers of any of the nematode feeding groups was found. This correlated with almost no change in bacterial biomass after liming, while the active fraction of fungal hyphae was unaffected by liming at Fexboda and reduced by liming at Norrliden. A tendency for decreasing numbers of all nematode feeding groups in the limed plots at Norrliden coincided with increasing numbers of lumbricids.     

Mobility of heavy metals in pine forest soils as influenced by experimental acidification

The mobility of Pb, Zn, Cd and Cu was examined at two adjacent experimental plots at åmli, southern Norway, B-1 and B-2. Both experiments were established on the same glacifluvial deposits, with forest consisting of uniform stands of Pinus sylvestris L. The forest in B-1 was planted between 1968 and 1970, while B-2 consisted of naturally regenerated trees. The experiments included plots supplied with artificial rain of varying acidity over a period of seven and eight years for B-1 and B-2, respectively, in addition to control plots. In experiment B-1, experimental acidification was carried out both in unlimed plots and in plots applied with three different levels of lime. The two experiments showed distinct differences with respect to effects of the acidification on mobilization of heavy metals from the O horizon. In experiment B-1, the amount of Zn and Cd decreased with decreasing pH in artificial rain, while Pb and Cu were not appreciably affected. The reduction in Zn and Cd concentrations ceased after termination of the acidification experiment. Liming reduced the leachability of Zn, but still appreciable amounts of Zn were obviously leached from the O horizon during the experiment. In experiment B-2 a high retention even of Zn and Cd was observed in the O horizon, probably due to microbial uptake and accumulation.     

Earthworm communities in temperate beech wood forest soils affected by liming

To monitor the effects of liming on forest ecosystems, experimental plots were installed in forests in mid-western Germany. In addition to soil chemical indices, earthworm communities were investigated on these plots about 15 years after first lime applications took place. As a “natural reference”, communities were compared to earthworm records that derived from a beech forest on limestone. In the non-acidified plots that had never been limed only epigeic earthworms were detected in small numbers and low species richness. Forest liming caused higher pH and a higher base saturation in the mineral topsoils. To a large extent, epigeic earthworm species seemed to benefit from this and had increased in number and biomass at all three different locations selected for the investigations. The epigeic dominated communities were completed by anecic Lumbricus terrestris that was rarely found in some of the samples from one location and a number of endogeic species that showed a very patchy distribution in limed plots. In contrast to this, the soil of the beech forest on limestone showed a different community composition. It was dominated by endogeic species in abundance and by anecic species in biomass. On limestone the total biomass of earthworms clearly exceeded the biomass values from all other plots. In conclusion, a long-term support of forest earthworm fauna due to liming was detected. This support was mainly effective for epigeic species, but in some cases for endogeic and anecic species, too.     

Influence of tree species on acidification and mineral pools in deciduous forest soils of South Sweden

The influence of tree species on chemical properties of the soil profile (0 to 70 cm), especially acidity and cation pools, was studied below canopies of 100 to 150 yr old individuals of Fagus sylvatica L., Quercus robur L., Carpinus betulus L., Tilia cordata Mill, and Acer platanoides L., in three mixed deciduous forests. The pH(H₂O) range in the topsoil (0 to 5 cm) was 4.2 to 5.3 at the different sites and increased for all species by about 0.2 pH units to the upper C-horizon (50 to 70 cm). Carpinus had higher pH and base saturation, and the total exchangeable store of Ca (0 to 70 cm) at the ‘poorest’ site was ca 1.5 times greater than for Fagus and Quercus. Soils were less acid under crowns of Quercus than under Fagus and Carpinus in the upper 20 cm of the soil profile in the ‘richest’ site, but more acid at the deeper levels. The total exchangeable pools (0 to 70 cm) of K and Zn were 2 and 1.6 times greater under Quercus at the ‘richest’ site. Tilia had 10 to 20% units higher base saturation values and twice as much exchangeable Ca and Mg than the other species. It was concluded that out of all tree species studied, Tilia acidified the soil the least. The current annual total proton load (TPL) on the soil was 1.3 to 3.0 kEq ha^?1 yr^?1. The annual acid load due to cation excess accumulation in biomass was 30 to 50% of TPL. The remainder originated from atmospheric deposition. Quercus had the highest annual TPL at all sites, mainly because of greater input of atmospherically derived acidity, but also by a greater cation excess accumulation in biomass. Carpinus, compared to Fagus and Quercus, tended to have the lowest TPL at all sites, and Tilia had the lowest TPL at the intermediate site.     

Indicative properties of fly‐ash affected forest soils in Northeastern Germany

Many forest ecosystems in Germany are strongly influenced by emissions of pollutants like SO₂ and alkaline dusts. To quantify and evaluate the consequences of long‐term fly ash deposition on forest soils, a study was conducted in pine stands (Pinus sylvestris) in the Dübener Heide in Northeastern Germany. This forest area has been influenced mainly by emissions from coal‐fired power plants and the chemical industry of the industrial region Bitterfeld‐Wolfen‐Zschornewitz since the early 1900. The study sites are located along a fly ash deposition gradient of 8, 16, 14, 18, and 25 km away from the main emission source in Bitterfeld (sites 1, 2, 3, 4, and 5, respectively). Samples of the organic horizons (Oi, Oe, and Oa) and mineral topsoil (0—10 cm) were taken in fall 1998 and analyzed for their ferromagnetic susceptibility and total ash content. Scanning electron microscopy (SEM) and energy dispersive X‐ray microanalysis (EDX) were performed on selected samples to differentiate between the pedogenic and atmospheric origin of the mineral components in the organic horizons. As a result of the long‐term deposition, ferromagnetic fly ash components are mainly accumulated in the Oe and Oa horizons of the forest soils studied. Ferromagnetic susceptibility was significantly higher (p ≤ 0.05) in the Oe horizon of sites 1 and 2 compared to sites 3, 4, and 5. Unusually high total ash contents for organic horizons of > 74 % were determined in the Oa at all sites. SEM revealed 3 distinct features of persistent fly ash deposits from coal‐fired power plants within the organic horizons that can be defined as ”︁stable glasses” with magnetic properties, aluminum‐silicate‐minerals, and slag fragments. SEM and EDX indicated that a great portion of the mineral particles found in the organic horizons of forests soils influenced by fly ash are from atmospheric sources. For detection of atmospheric lignite‐derived deposition into forest soils, the Oe and Oa horizons have to be considered as specific diagnostic horizons because they show indicative properties for such soils.     

Volcanic ash additions control soil carbon accumulation in brown forest soils in Japan

Abstract

The objective of the present study was to clarify the influence of volcanic ash addition on soil carbon stocks and the carbon accumulation process in brown forest soils (BFS) in Japan. The degree of volcanic ash addition to the soil was estimated according to the acid ammonium oxalate extractable aluminum (Al_ox) and lithic fragment contents, and their vertical distribution patterns. The BFS was classified in order of increasing volcanic ash influence on the soil into the following types: high Al_ox content with no gravel (H-Al_ox-NGv), high Al_ox with a high gravel content (H-Al_ox-Gv), moderate Al_ox (M-Al_ox), and low Al_ox (L-Al_ox), and then analyzed for carbon content, carbon amount, carbon stock, Al_ox amount and pyrophosphate extractable aluminum (Al_py) amount. The correlation between the carbon and Al_py amounts and the relationship between the Al_py and Al_ox amounts in the BFS samples indicated that the amount of carbon is determined by Al—humus complex formation, which is defined by the active Al generated from additional volcanic ash in BFS soil samples of BFS. Therefore, soils with thicker horizons and greater amounts of Al_ox had higher carbon levels in deeper horizons. For this reason, soil carbon stocks at depths of 0–30 cm and 0–100 cm, and in the effective soil depth of BFS, were larger and followed the order H-Al_ox-NGv = H-Al_ox-Gv > M-Al_ox > L-Al_ox. Furthermore, successive accumulations of volcanic ash on the soil surface promoted soil carbon accumulation as a result of the development of the surface horizon in H-Al_ox-NGv BFS. Our results suggest that volcanic ash additions control the soil carbon accumulation of forest soil in Japan.     

Classification schemes for the acidity,base saturation,and acidification status of forest soils in Switzerland

Soil chemical parameters related to soil acidity were determined for 1450 soil samples taken from individual mineral soil horizons in 257 forest soils in Switzerland, 196 developed from carbonate‐containing and 61 from carbonate‐free parent material. The distribution of pH values and exchangeable base cations in corresponding pH ranges were related to the capacity and rate of buffer reactions in the soil. Based on this, five acidity classes for individual soil samples were defined. To describe and classify the status of soil acidity and base saturation (BS) of an entire soil body, the pH and the BS of the total fine earth in the soil were calculated from the pH and BS, respectively, of the individual soil horizons and the estimated volumetric content of fine earth. The status of soil acidification of soil profiles was assessed primarily using the total amount of exchangeable acidic cations in percent of the CEC of the fine earth in the entire soil profile. As a second factor, the gradient between the acidity class of the most acidic soil horizon and the estimated acidity class at the beginning of soil formation was used. The application of these classification schemes to our collection of soil profiles revealed the great influence played by the type of parent material. The acidification status of most soils on carbonate‐containing parent material was classified as very weak to weak, whereas soils on carbonate‐free parent material were found to be strongly to very strongly acidified. In terms of parent rock material, microclimate, and natural vegetation, the results of this study and the proposed classification schemes can be considered appropriate for large parts of Europe.     

Alberta油砂地区在两种水文流域森林土壤酸化敏感性研究

Input of large amounts of N and S compounds into forest ecosystems through atmospheric deposition is a significant risk for soil acidification in the oil sands region of Alberta. We evaluated the sensitivity of forest soils to acidification in two watersheds （Lake 287 and Lake 185） with contrasting hydrological regimes as a part of a larger project assessing the role of N and S cycling in soil acidification in forest ecosystems. Fifty six forest soil samples were collected from the two watersheds by horizon from 10 monitoring plots dominated by either jack pine （Pinus banksiana） or aspen （Populus tremuloides）. Soils in the two watersheds were extremely to moderately acidic with pH （CaCl2） ranging from 2.83 to 4.91. Soil acid-base chemistry variables such as pH, base saturation, Al saturation, and acid-buffering capacity measured using the acetic acid equilibrium procedure indicated that soils in Lake 287 were more acidified than those in Lake 185. Acid-buffering capacity decreased in the order of forest floor 〉 subsurface mineral soil 〉 surface mineral soil. The most dramatic differences in percent Ca and Al saturations between the two watersheds were found in the surface mineral soil horizon. Percent Ca and Al saturation in the surface mineral soil in Lake 287 were 15% and 70%, respectively; the percent Ca saturation value fell within a critical range proposed in the literature that indicates soil acidification. Our results suggest that the soils in the two watersheds have low acid buffering capacity and would be sensitive to increased acidic deposition in the region.     

Boreal forest microbial community after long-term field exposure to acid and metal pollution and its potential remediation by using wood ash

A 2²-factorial design with sulphuric acid (pH 3.1) and Cu-Ni addition was used to assess the effects of moderate amounts of continuous acid (Acid and CuNi+Acid) and metal (CuNi and CuNi+Acid) deposition on humus microbial activity and community structure in the field after nine growing seasons. These 20 field experiment samples were also used to measure the suitability of wood ash for remediation. Microcosms were treated with wood ash at a fertilization rate of 5000 kg ha⁻¹, irrigated with water and incubated for 2 months in the dark at 20 °C and a constant relative humidity of 60%. Microcosms only irrigated with water served as a control. Microbial activity was measured as basal respiration. Microbial community structure was determined by phospholipid fatty acid analysis, which mainly targets bacteria. Fungal community structure was assessed by 18S rDNA-targeted polymerase chain reaction-denaturing gradient gel electrophoresis analysis. The bioavailability of Cu was tested with the Pseudomonas fluorescens DF57-Cu15 reporter strain, which bioluminescences in the presence of Cu. Our field study showed, that acid and metal treatments both changed the humus layer microbial community structure. Acid application decreased humus layer pH and base saturation (BS) and increased the amounts of both extractable and bioavailable Cu. Metal application increased the concentration of extractable Ni and changed the fungal community structure. In irrigated laboratory microcosms the above-mentioned treatment effects were still seen except for the acid and metal effects on microbial and fungal community structures. For ash-treated microcosms, neither acid nor metal effects were found for humus layer pH, BS, extractable Cu and Ni, or bioavailable Cu. Thus, wood ash can be used for remediation of acid and metal polluted humus.     

Application of wood ash accelerates soil respiration and tree growth on drained peatland

Forested peatlands contain large pools of terrestrial carbon. As well as drainage, forest management such as fertilizer application can affect these pools. We studied the effect of wood ash (application rates 0, 5 and 15 t ha^?1) on the heterotrophic soil respiration (CO₂ efflux), cellulose decomposition, soil nutrients, biomass production and amount of C accumulated in a tree stand on a pine‐dominated drained mire in central Finland. The ash was spread 13 years before the respiration measurements. The annual CO₂ efflux was statistically modelled using soil temperature as the driving variable. Wood ash application increased the amounts of mineral nutrients of peat substantially and increased soil pH in the uppermost 10 cm layer by 1.5–2 pH units. In the surface peat, the decomposition rate of cellulose in the ash plots was roughly double that in control plots. Annual CO₂ efflux was least on the unfertilized site, 238 g CO₂‐C m^?2 year^?1. The use of wood ash nearly doubled CO₂ efflux to 420–475 g CO₂‐Cm^?2 year^?1 on plots fertilized with 5–15 t ha^?1 of ash, respectively. Furthermore, ash treatments resulted also in increased stand growth, and during the measurement year, the growing stand on ash plots accumulated carbon 11–12 times faster than the control plot. The difference between peat C emission and amount of C sequestered by trees on the ash plots was 43–58 g C m^?2, while on the control plot it was 204 g C m^?2. Our conclusion is that adding wood ash as a fertilizer increases more C sequestration in the tree stand than C efflux from the peat.     

Proposal for advanced classification of brown forest soils in Japan with reference to the degree of volcanic ash additions

Abstract

The advanced classification of brown forest soils (BFS) is based on the specific properties of these soils, including the acid ammonium oxalate extractable aluminum (Al_ox) and lithic fragment contents, as well as their vertical distributions in the soil profile. In the present study, these properties were used to classify BFS, resulting in four types: (1) H-Al_ox-NGv BFS, (2) H-Al_ox-Gv BFS, (3) M-Al_ox BFS, (4) L-Al_ox BFS. H-Al_ox-NGv BFS is derived from volcanic ash characterized by a high Al_ox content and no lithic fragment, whereas L-Al_ox BFS is derived from weathered bedrock and has a low Al_ox content. H-Al_ox-Gv BFS and M-Al_ox BFS are derived from mixtures of volcanic ash and weathered bedrock. H-Al_ox-Gv BFS is characterized by high Al_ox content and many lithic fragments, whereas M-Al_ox BFS has moderate Al_ox content. H-Al_ox-NGv BFS and black soils (BLS) develop from accumulated volcanic ash, as indicated by declining Al_ox and clay content with decreasing depth in the surface horizons, as a result of successive additions of less-weathered volcanic ash to the soil surface.     

Phosphorus availability to corn from wood ash-amended soils

Wood ash is a residual material produced during biomass burning. In the northeastern United States up to 80 % of the ash is spread on agricultural lands as a liming amendment with the remainder being disposed of in landfills. As well as raising soil pH, wood ash also adds plant nutrients to soil. This study is an examination of the plant availability of the P in 8 different soils amended with one wood ash. Plant availability was assessed by measuring the biomass and P concentration of corn (Zea mays) L.) plants grown in the greenhouse for 28 d in soil amended with either CaCO₃ (control), wood ash to supply 200 mg kg^?1 total P, or monocalcium phosphate (MCP) to supply 200 mg kg^?1 total P and CaCO₃. Both corn growth and P uptake were highest in the MCP treatments, intermediate in the wood ash treatments, and lowest in the controls for all soil types. The soil property which seemed to have the greatest influence on P availability was pH buffer capacity. The soils with the greatest capacity to buffer OH additions also tended to exhibit the greatest absolute P uptake from wood ash-amended soils and the greatest P uptake relative to that from MCP-amended soils. The ability of soil test extractants to predict uptake of P in the three soil treatments was examined. A buffered ammonium acetate extradant overestimated P availability in the ash-amended soils relative to the MCP-amended soils. An unbuffered, acid, fluoride-containing extract provided a measure of P levels that was consistent with P uptake from all soil treatments. In this study the predictive relationship was as follows: P uptake = 0.017× (Bray P, mg kg^?1) + 1.19; r = 0.81.     

A greenhouse study of northern red oak seedling growth on two forest soils at different stages of acidification

The objective of this study was to determine whether or not Ca and P in soils from two forested sites at two different stages of acidification were limiting growth of red oak seedlings. The A and E horizons of a Berks soil from Watershed 4 at the Fernow Experimental Forest (cation exchange buffer range) and a Hazelton/Dekalb soil from Pea Vine Hill in Southwestern Pennsylvania (Al buffer range) were placed in pots and utilized as the growth medium for northern red oak seedlings in a greenhouse environment. Soil water NO₃-N, Ca, Mg, and K concentrations were significantly higher (α≤0.05) on the Berks soil. Soil exchangeable P and soil solution TP (total phosphorus) were significantly higher (α≤0.10) on the Hazelton/Dekalb soil. Both soils were amended with bone meal (CaPO₄) to determine the effects of Ca and P addition on the growth and nutrient uptake of the seedlings. Height growth of the control red oak seedlings was significantly (α≤0.05) greater on the Berks soil after 45 d, but amendment of Hazelton/Dekalb soil with bone meal eliminated this difference. Bone meal addition to the Hazelton/Dekalb soil resulted in significantly greater (α≤0.05) height growth of red oak seedlings when compared to red oak seedlings grown on unamended Hazelton/Dekalb soil, but did not have a similar effect for red oak seedlings grown on Berks soil. Bone meal addition to Hazelton/Dekalb soil resulted in greater (α≤0.05) concentrations of Ca and Mg in red oak leaves. Unfertilized Berks red oak seedling leaves had significantly higher (α≤0.05) concentrations of Ca and K than their Hazelton/Dekalb counterparts. Al/Ca molar ratios were significantly lower on the Berks soil. Red oak height growth was increased significantly by Ca addition to the Hazelton/Dekalb soil.     

The effect of lime on the response of soils to sodic conditions

The role of CaC0₃ in preventing clay dispersion and losses in hydraulic conductivity (HC) of sodic soils was determined directly by mixing two lime-free soils with 0.5 and 2.0 per cent CaCO₃. Whereas the HC of the lime-free soils dropped sharply when 0.01 n solutions of SAR 20 were displaced with distilled water, mixing the soils with powdered lime prevented both HC losses and clay dispersion. The response of a sandy soil mixed with lime was similar to that of a calcareous sandy soil. The beneficial effect ofCaC0₃ was not so pronounced in soils equilibrated with solutions of SAR 30. The increase in electrolyte concentration, due to CaCO₃ dissolution, was suggested as the mechanism responsible for the beneficial effect of lime.