Range In pH Research Articles

Influence of humic substances on Co 2+ sorption by a subsurface mineral separate and its mineralogic components

The sorption of Co 2+ (10 −6 mol/L) was measured on subsurface mineral materials in the absence and presence of a sorbed leonardite humic acid (LHA) to 1. (1) evaluate the sorptive role of mineral-bound humic substances, and 2. (2) establish approaches to model metal ion binding in composite materials. The subsurface materials were a < 2.0 μm size fraction of an ultisol saprolite (CP) and this same material treated with dithionite-citrate-bicarbonate (DCB) to remove Fe-oxides (DCP). Comparable experiments (with and without LHA) were also performed with mineral sorbents representing dominant phases in the CP separate (gibbsite, Al-goethite, and kaolinite) to evaluate their potential contributions to Co sorption. The mineral-bound LHA ranged in concentration between 0.1–0.4 mg-C/m 2, representing approximately 0.7% of the subsurface isolate by mass. The sorption-desorption of LHA on the mineral surfaces, and its affinity for Co as a aqueous phase complexant were also determined. Batch measurements were employed (sorbents at 20–90 m 2/L; LHA-DOC at ≈11 mg-C/L) over a range in pH and ionic strength ( I) at I = 0.01 and 0.1 in NaClO 4. The LHA strongly sorbed to the subsurface mineral isolates (CP and DCP), and to all the specimen sorbents except kaolinite. Maximum sorption of LHA occurred at lower pH (≈4.5). In solid-free suspensions, the affinity of LHA for Co increased with pH and decreasing I ( K d ranging 20–450 L/g). Mineral-bound LHA increased Co sorption on all the sorbents by factors of 10–60 %, with the greatest augmentation noted at pH values (4.5–6.5) where 1. (1) maximum LHA sorption occurred, and 2. (2) Co sorption to the mineral phase was weak and dominated by ion exchange. The LHA appeared simply to augment, rather than to change the intrinsic adsorption behavior of the mineral sorbents. Accordingly, predictions of the K d for Co on the LHA-coated subsurface materials (DCP, CP) based on a linear additivity model agreed well with the experimental data, suggesting that the complex humic-mineral association acted as a noninteractive sorbent mixture at low aqueous Co concentrations.

Soil fertilization and pH effects on meadowfoam growth and flowering1

Abstract Meadowfoam (Limnanthes alba Hartweg ex. Bentham) is a new oilseed crop. Published information on nutritional requirements and optimum soil pH for growing meadowfoam in controlled environments is currently lacking. This study evaluated the effects of application rates and timing of a modified Hoagland's solution and a range in initial potting medium pH on meadowfoam (L. alba subsp. alba, cv Mermaid) growth and development under controlled environment conditions. Weekly application of 50 mL of nutrient solution at a nitrogen (N) concentration of 840 mg/L (four times higher than the concentration in modified Hoagland's solution) resulted in good Mermaid growth and flower production. Optimum fertilizer application timing is apparently from one week after transplanting (38 days after seeding) until the flowering stems begin to elongate above the rosette leaves. Optimum soil pH seemed to be between 5 and 6, although Mermaid grew relatively well under initial soil pH ranging from 3.8 to 7.3.

Abundance, body composition and reproductive output of Gammarus minus (Crustacea: Amphipoda) in ten cold springs differing in pH and ionic content

SUMMARY1. A survey of thirty‐two rheocrene springs in central Pennsylvania revealed that, Like Gammarus in lakes and streams, Gammarus minus is absent from springs with pH &lt;6.0 and conductivity &lt;25μS cm−1 (total range in pH = 4.6–7.7, and in conductivity = 14–411 μS cm−1).2. In ten springs G. minus density was positively correlated with Ca2+ and Mg2+ hardness, but not with pH, unless three springs with either an exceptionally high velocity or extremely high densities of the potentially competing snail Fontigens nickliniana were omitted.3. Adults were larger in the springs with few or no large predators than in those with more predators. In all ten springs, adult dry mass was unrelated to spring pH and ionic content, but brooding female dry mass covaried positively with Ca2+ and Mg2+ hardness in the five predator‐poor springs.4. Body water, Na and Ca contents and body mass/length ratios varied independently of spring pH and ionic content. Water content was inversely correlated with fat content, but even when expressed as a percentage of fat‐free wet mass, it was unrelated to water chemistry.5. In juveniles, males and non‐brooding females, fat content varied independently of spring pH and ionic content, but in brooding females it was correlated with alkalinity and Ca2+ and Mg2+ hardness. The cost of reproduction in brooding females may have been a factor here; they had significantly lower per cent fat than did non‐brooding females. Juvenile fat content did not differ significantly among spring populations, whereas adult fat content did. The per cent fat of brooding females covaried positively with body size among springs, and this was marginally true for non‐brooding females, as well. The residuals of brooding female per cent fat against dry mass were not related to water chemistry.6. Brood size (number of embryos in a brood) and brood mass varied significantly among populations, but independently of spring pH and ionic content. Both covaried positively with maternal body size among springs. The residuals of these relationships were unrelated to water chemistry, as was the percentage of females brooding.7. G. minus from a pH 6 spring survived better and lost less body mass in acidic soft water than did those from a pH 7.6 spring. However, although G. minus has apparently been able to adapt (or acclimate) to pH 6 water it has failed to adapt to more acidic waters. A physiological or structural constraint may be involved because this species has probably had ample opportunity to evolve resistance to dilute acidic water. This hypothesis is consistent with the threshold effect observed: above pH 6 G. minus shows very little evidence of osmotic or metabolic stress, but beiow pH 6 viable populations apparently cannot survive at all. However, the gradual linear decrease in population density of G. minus with decreasing alkalinity and Ca2+ and Mg2+ hardness suggests that other factors may also be involved (e.g. a decrease in food quality).

Individual Sorbent Contributions to Cadmium Sorption on Ultisols of Mixed Mineralogy

AbstractA multisite model was applied to Cd‐sorption data across a range in pH and at ionic strength (I) = 0.1 and 0.01 on specimen layer silicates and on untreated and dithionite‐citrate‐bicarbonate (DCB) treated isolates from two Utisols. The two isolates contained different mass concentrations of kaolinite, 2:1 layer silicates, Al‐substituted crystalline Fe oxides, and gibbsite. The multisite model included the exchange of Cd2+ on fixed‐charge sites on the layer silicates, complexation to hydroxyl sites on the layer silicates and Fe oxides, and electrostatic interaction between positively charged sites on Fe oxides and fixed‐charge sites on the layer silicates. Site concentrations for the specimen layer silicates and DCB‐treated and untreated isolates were estimated from cation‐exchange capacity (CEC) data and N2‐specific surface area. Equilibrium constants for specific surface reactions were estimated from Cd‐sorption data on the specimen layer silicates, KGa‐1 and SWy‐1, and the DCB‐treated soil isolates. The combined modeling results indicated that (i) Cd2+ ion exchange to fixed‐charge sites was the dominant sorption reaction for pH &lt; 6.5 and I = 0.01, (ii) mass action with Na suppressed ion exchange at I = 0.01, (iii) Cd complexation to hydroxyl sites produced strong pH dependency in Cd sorption and was responsible for all the Cd sorption at I = 0.01 and above pH 6.5 at I = 0.01, and (iv) Fe oxides decreased Cd sorption by blocking access of Cd to exchange sites. The modeling results were unable to determine whether Fe oxides were important sorbents for Cd. Either with or without Cd sorption on Fe oxides, this model was able to describe the Cd sorption on the soil isolates reasonably well.

Eustoma Quality is Adversely Affected by Low pH of Root Medium

Foliar chlorosis or bleaching, interveinal chlorosis, leaf edge and tip necrosis, a poor root system, and stunted growth of Eustoma grandiflorum (Raf) Shinn seedlings were associated with a medium pH of 5.0 or 5.5 but not when the values ranged from 6.4 to 7.5. The range in medium pH resulting in the best growth of seedings and flowering plants was 6.3 to 6.7. Responses to medium pH were similar, regardless of fertilizer solution pH or cultivar. Eustoma seedling and shoot fresh weights for pH 5.0 and 5.5 were only 23% to 66% of corresponding values for plants grown at pH 6.4. Leaf tissue Zn was extremely high (1050 mg·kg-l dry leaf tissue) at a medium pH of 5.0, but other macro- and micronutrients in leaves were not at abnormal levels.

Sorption of divalent metals on calcite

The sorption of seven divalent metals (Ba, Sr, Cd, Mn, Zn, Co, and Ni) was measured on calcite over a large initial metal (Me) concentration range (10 −8 to 10 −4 mol/L) in constant ionic strength ( I = 0.1), equilibrium CaCO 3(s)-CaCO 3(aq) suspensions that varied in pH. At higher initial Me concentrations (10 −5 to 1 −4 mol/L) geochemical calculations indicated that the equilibrium solutions were saturated with discrete solid phases of the sorbates: CdCO 3(s), MnCO 3(s), Zn 5(OH) 6(CO 3) 2(s), Co(OH) 2(s), and Ni(OH) 2(s), implying that aqueous concentrations were governed by solubility. However, significant sorption of all the metals except for Ba and Sr was observed at aqueous concentrations below saturation with Me-solid phases. Divalent metal ion sorption was dependent on aqueous Ca concentration, and the following selectivity sequence was observed: Cd > Zn ≥ Mn > Co > Ni > Ba = Sr. The metals varied in their sorption reversibility, which was correlated with the single-ion hydration energies of the metal sorbates. The strongly hydrated metals (Zn, Co, and Ni) were most desorbable. A sorption model that included aqueous speciation and Me 2+-Ca 2+ exchange on cation-specific surface sites was developed that described most of the data well. The chemical nature of the surface complex used in this model was unspecified and could represent either a hydrated or dehydrated surface complex, or a surface precipitate. A single exchange constant for Cd, Mn, Co, and Ni could describe the sorption of that metal over a wide range in pH, Ca concentration, and surface concentration. Zinc, however, exhibited nonlinear sorption behavior and required exchange constants that varied with surface coverage. Our data suggested that (i) Cd and Mn dehydrate soon after their adsorption to calcite and form a phase that behaves like a surface precipitate, and (ii) Zn, Co, and Ni form surface complexes that remain hydrated until the ions are incorporated into the structure by recrystallization.

Phosphorus sorption by sediments from a soft-water seepage lake. 1. An evaluation of kinetic and equilibrium models

Models describing kinetics and equilibria of sorption were compared by using phosphorus sorption data for sediments from Little Rock Lake (Vilas County, WI) at pH 4.5-6.0. A maximum sorption capacity was not exhibited by the sediments, but sorption continued to increase (slowly) as solution (P{sub i}) increased. Sorption equilibria and kinetics thus did not fit well to simple models that assume homogeneous binding sites but were described by models that incorporate either a distribution of intrinsic binding energies or variable binding caused by a change in electrostatic potential with increasing surface coverage. The variance in sediment affinity for P{sub i} described by current models (log K = 5.99 {plus minus} 5.00) realistically cannot be ascribed solely to variation in intrinsic binding energies among different sites, but can be accounted for by a range in pH{sub zpc} values of 3 pH units. Sediments were slow to reach equilibrium (>54 h), especially at high pH and low initial P{sub i}, consistent with a conceptual model of rapid adsorption followed by a period of intraparticle diffusion.

Sorption of phosphorus by the iron oxide-impregnated filter paper (Pi soil test) embedded in soils

Incubation experiments were carried out to evaluate the feasibility of extracting phosphorus from soil by embedding iron oxide-impregnanted filter paper strips (Pi strips) in soils having a wide range in pH, texture, and extractable-P contents. Under flooded conditions, the amount of P extracted by the Pi strips increased with the period of submergence and embedding time of the Pi strips. Under unsaturated conditions, the Pi strips were found to extract P from soils over a wide range in moisture conditions; however, keeping the soil at moisture level between saturation and field capacity was found to result in maximal sorption of P by the strips. An embedding time of 16 h was found to be adequate.

Solution ion effects on the surface exchange of selenite on calcite

The adsorption of SeO 3 on CaCO 3(s) was evaluated in equilibrium CaCO 3(aq) suspensions over a range in pH and SeO 3 concentration in the absence and presence of the cosolutes, Mg, SO 4, and PO 4. Selenite was adsorbed by CaCO 3(s) in a manner consistent with its exchange on anionic specific surface sites saturated with CO 3 2−/HCO 3 − that were quantified by H 14CO 3 isotopic exchange. This exchange process was described very well using the computer program FITEQL and half-reactions for the surface exchange of HCO − 3, CO 3 −, HSeO 3 −, and SeO 3 2−. The cosolutes SO 4 and PO 4 decreased SeO 3 sorption by direct competition or site blockage, and these effects were also predicted using the surface exchange model. By contrast, the sorption of SeO 3 was not influenced by Mg because the two ions sorbed over different pH regions and exchanged with different surface sites that appeared to be distinct and noninteractive. Evaluation of SeO 3 sorption over a wide concentration range suggested that the surface of CaCO 3(s) was heterogeneous and that SeO 3 had access to less than 5% of the total anion specific surface sites.

Stream macroalgae of the eastern boreal forest region of North America

Fifty-one stream segments were sampled in northwestern Newfoundland, central Labrador, and west-central Quebec during June and July 1987. There was a great range in stream size, current velocity, pH, and ion content. The eastern boreal forest was found to be one of the most diverse regions in North America for stream macroalgae, having a flora of 67 species. The major divisions in terms of species numbers were the Chlorophyta (43%), Cyanophyta (21%), Chrysophyta (19%), and Rhodophyta (16%). Mats were the most widespread form (51% of the species), followed by filaments (27%), colonies (13%), tissues (5%), and palmelloid forms (3%). Species number was positively correlated with water temperature and total cover and negatively correlated with pH. The most widespread species was Batrachospermum moniliforme, which occurred in 31% of the stream segments examined. Distribution was patchy, with total cover varying from &lt; 1 to ca. 60% of the stream bottom. Species numbers per segment ranged from 1 to 11. The most closely associated species were Microspora pachyderma, Mougeotia sp., and Batrachospermum keratophytum. The known distribution range of the rare rhodophyte Boldia erythrosiphon was extended north by ca. 1000 km.

Chromate Adsorption on Goethite: Effects of Aluminum Substitution

AbstractThe adsorption of CrO2‐4 to goethites varying in specific surface area and Al substitution was measured over a range in pH, sorbate and sorbent concentrations and ionic strength. The α‐(Fe, Al)OOH exhibited a lower pH50 (the pH at which 50% adsorption occurs) for the CrO2‐4 at all adsorbate concentrations (6 × 10−6 to 5 × 10−4 M CrO2‐4) than did the two α‐FeOOH samples; this difference could not be attributed to either variations in CrO2‐4 adsorption density or sorbent PZC. The overall proton coefficient (n), calculated from adsorption data for 5 × 10−7 M CrO2‐4, was identical for the two α‐FeOOH samples despite differences in the physical nature and sorbate‐to‐surface site ratio of the two samples. The observed n for the α‐ (Fe, Al)OOH system was larger than the n for the pure goethite systems. These data suggest that differences in the acid‐base properties and interaction with the background electrolyte for the Fe and Al sites affect the overall proton coefficient and CrO2‐4 adsorption on the substituted surface when compared to the pure surface. The surface coordination constants for the Triple Layer Model (TLM) were derived for CrO2‐4 adsorption on the α‐FeOOH solids using the FITEQL computer code. Using these and other TLM constants from the literature, adsorption on all three goethite samples was quantitatively simulated over a range in solute and sorbent concentrations, pH and ionic strength. The successful simulation of CrO2‐4 sorption onto α‐(Fe, Al)OOH required the use of a two‐site model which included the ionization and electrolyte complexation reactions of both Fe and Al sites. Site densities of Fe and Al were taken to be proportional to the mole fraction of each in the α‐(Fe, Al)OOH solid. However, the interaction of the CrO2‐4 species with the Al sites was not required to quantitatively describe the adsorption edge since the log K for the dominant FeOH+2‐HCrO‐4 species is three orders of magnitude greater than the ‐CrO2‐4 or ‐HCrO‐4 on Al sites.

Adsorption of Chromate by Subsurface Soil Horizons

AbstractChromate adsorption was measured with and without reactive cosolutes on four subsurface soil horizons differing in pH and mineralogy, and on clay fractions from two of the oxide‐containing subsoils. Chromate adsorption was greatest in lower pH materials enriched in kaolinite and crystalline iron oxides. Over a range in pH, chromate adsorption to subsoil was similar to that observed for pure‐phase oxides. Chromate binding was reversible to pH and was depressed in the presence of SO2‐4 and dissolved inorganic C, which compete for adsorption sites. A surface site density for crystalline Al‐substituted iron oxides in the subsoils was estimated from chromate adsorption on the clay fractions using the model FITEQL and outer sphere surface coordination constants from Al‐goethite. The estimated site density for soil crystalline iron oxides was well below that of clean oxides, suggesting surface saturation by indigenous soil ions. The calculated site density and surface binding constants for Al‐goethite were used in the Triple Layer Model to calculate the effect of ionic strength, cosolutes, solids concentration, and sorbate concentration on CrO2‐4 adsorption. Model calculations were in good qualitative agreement with experimental results.

A Zinc Soil Test Calibration Based upon Mehlich 3 Extractable Zinc, pH, and Cation Exchange Capacity

AbstractThe soil Zn critical level generally decreases as organic matter content increases. Certain other properties, notably cation exchange capacity (CEC) and optimum soil pH, also vary with organic content. These properties and Mehlich 3 extractable Zn (M3Zn) were used to calibrate a Zn soil test from greenhouse and field data. Soils were collected from four lime treatments in field experiments conducted on six Ultisols. An Inceptisol and a Histosol were also sampled and four lime treatments established, providing a range in pH and organic matter content. Three levels of Zn as ZnSO4 · 7H2O were added to each soil. Soybeans [Glycine max (L.) Merr., cv. Centennial] and corn (Zea mays L., cv. Pioneer 3369A) were grown successively in the greenhouse, each for 5 weeks. Mehlich 3 extractable Zn decreased with an increase in soil pH on only one of the eight soils, but Zn concentration in plants grown on all soils decreased with an increase in soil pH. Mehlich 3 extractable Zn alone accounted for little of the variation in the plant Zn concentration of the two crops. Including soil pH and CEC in the model increased the R2 to 0.56 and 0.50 for soybeans and corn, respectively. When the squared and first‐order interaction terms of these variables were considered, the R2 increased to 0.76 for soybeans and 0.66 for corn. For corn grown in the field, these same variables were found to be important in Zn soil test calibration. The form of the regression equation proved to be illogical, however, because the range in soil properties was not sufficient to produce a reliable prediction equation. Regression equations from the greenhouse were then adjusted to predict the leaf Zn concentrations of crops grown in the field. For corn, an equation that gave reasonable estimates of leaf Zn concentration in the field was developed. This equation may be used to interpret the need for Zn fertilization over a continuum of extractable Zn concentration, pH, and CEC in soils.

Reproductive differentiation in a Saxifraga hirculus population along an environmental gradient on a central Swedish mire

The perennial herbaceous mire plant Saxifraga hirculus was studied in different population densities along an environmental gradient on a mire in central Sweden. Tests were made whether the habitat conditions influenced the balance between vegetative growth of runners and seed production. Along a 30 m long transect the gradient was analysed for vegetation, hydrology, temperature and contents of ions in groundwater and surface peat. Three main zones were distinguished, a spring area, a rich fen area and an intermediate fen area. Range in concentration of ions in groundwater along the transect (mg 1−1): Ca 4–59, Mg 0.3–3.5, K 0.1–3.0, Na 1.0–4.1 and Fe 0.4–4.5. Range in pH: 5.8–7.5. Despite the gradient in ion concentration, the element content in S. hirculus was constant along the transect. Population density reached maximum in the rich fen, 52 floral shoots 0.25 m−2. In the spring area, S. hirculus was characterized by few flowers per floral shoot, low height, numerous runners and a large total length of runners. In the rich fen, high seed production was characteristic; in the intermediate fen, production of both runners and seeds were low. The flowering of S. hirculus starts early in the spring area. Consequences of this with regard to genetic variation along the transect are briefly discussed.

Lime Induced Magnesium Stress in Corn: Impact of Magnesium and Phosphorus Availability

AbstractPrevious research has indicated that lime additions to soils with variable surface charge resulted in reductions in measures of “exchangeable” Mg. The potential loss of Mg from “plant available” soil phases was evaluated in two greenhouse trials. These experiments were conducted in 1979 and 1980 to evaluate the potential for Mg nutritional problems in corn [Zea mays (L.) Merr.] grown on a Bradson clay loam (Typic Hapludults) over a wide range in soil pH and plant available P and Mg. Bulk soil samples were taken from each of three lime rate treatments in a field trial last amended with dolomite in 1967. In the first experiment three levels of lime and P were imposed in a complete factorial combination on each bulk sample. In the second experiment, the bulk soil sample with the lowest native level of extractable Mg was amended with eight rates of lime and two rates of Mg in a complete factorial combination. Increased Mg availability was associated with increased tissue Mg concentrations and shoot dry matter productivity. Added lime generally decreased extractable soil Mg, tissue Mg, and shoot dry matter. Applied P reduced “overliming” stress in the first experiment. Magnesium, P, and Zn were implicated in the nutritional stress associated with lime induced yield depressions.

Phosphate adsorption by dark alkaline vertisols in Greece

Phosphorus adsorption isotherms are presented for samples from agricultural areas in central Greece. The soils contain montmorillonitic clays, have high exchange capacities and range in pH from 6.8 to 8.1. The amounts of P adsorption are high for surface and subsurface samples and are comparable to the adsorption observed in acid kaolinitic soils. The fit of the Freundlich equation to the experimental data was significantly improved when NaHCO 3 extractable P was used as an estimate of the labile soil P to account for P already adsorbed in the soil. No conclusive relationship was established between the Freundlich parameters and selected soil properties though in some cases a values (capacity term) increased with increasing organic carbon content.

Soil Lime Level (pH) and VA-Mycorrhiza Effects on Growth Responses of Sweetgum Seedlings

Sequential greenhouse experiments limed a strongly acid surface and subsurface horizons of phosphorus-deficient Jory clay loam with increments of calcium carbonate to attain a range in soil pH from 5.0 to 8.1. In the absence of vesicular-arbuscular mycorrhizae (VAM), neither the organic matter-rich surface nor the organic matter-poor subsurface horizon supported growth of sweetgum seedlings at any pH despite regular nutrient supplements. The effects of pH, VAM, and soil horizon on nutrient accumulation and plant nutrient concentrations were variable. Nitrogen and phosphorus concentrations were generally higher in the VAM than in control seedlings, which suggests that host plant should be matched with VAM species adapted to particular soil and climate conditions to obtain maximum benefit from a mycorrhizal association. 18 references, 2 figures, 3 tables.

Nitrification in some tropical soils

Nitrification of soil N in 8 mineral and 2 histosols having a wide range in pH (3.4 to 8.6), organic C (1.22 to 22.70%) and total N (0.09 to 1.20%) was studied by measuring nitrate fromation under aerobic incubation of the soil samples at 30°C for 4 weeks. The amounts of NO3-N produced in the soils varied from 0 to 123 μg/g of soil. Soil N in the two acid sulfate soils and one other acid soil did not nitrify under conditions that stimulate nitrification. Soils having pH more than 6.0 nitrified at a rapid rate and released NO3-N ranging from 98 to 123 μg/g. The two organic soils differed considerably in their capacity to nitrify though the total amounts of mineral N released were similar in these soils. The amounts of NO3-N formed in the soils was highly positively correlated with the soil pH but was not significantly correlated with the organic C of total N content of the soils. Statistical analysis also showed that nitrate formation was not significantly correlated with soil pH in soils having pH higher than 6.0.

Evaluation of some chemical indexes for predicting mineralizable nitrogen in tropical rice soils

Abstract Five chemical indexes were evaluated for predicting mineralizable nitrogen in 39 rice soils from the Philippines having a wide range in texture, pH and organic matter. The indexes evaluated were based on oxidative release of soil ammonium‐N by alkaline permanganate, acid permanganate, acid dichromate, hydrogen peroxide and dilute sulfuric acid. The amounts of mineralizable N obtained by the chemical indexes were correlated to varying degrees with those determined by anaerobic incubation methods. The basis of good agreement for mineralizable N determined by chemical arid biological indexes appears to be due to the fact that both derive the mineral N from the pool of organic nitrogen in soils. The support for this conclusion was obtained by highly significant correlations between mineralizable N determined by chemical and biological indexes with soil organic C and total N contents of soils. These results alongwith other evidence suggest that the chemical indexes may be useful for predicting pools o...

The effect of level of CaCO3, inoculation and lime pelleting on the nodulation and growth of beans in five acid soils

The effect of level of CaCO3, inoculation and lime pelleting on the nodulation, dry matter yield and % N content of common bean plants (Phaseolus vulgaris) grown in five acid soils was investigated in a greenhouse study. The soils represented a range in pH from 3.9 to 5.1, in exchangeable Al from 0.0 to 4 meq/100 gm, in exchangeable Mn from 0.35 to 2.32 me/100 gm, and in %C from 0.69 to 5.60. Nodule weight decreased with increasing %C and for the soil with highest %C (5.60) no nodules were observed. In soils with low organic matter and low exchangeable Al and Mn, inoculation increased nodule weight, dry matter yield and %N especially at the lowest pH level. Where the seeds were not inoculated, nodule weight and dry matter yield increased with soil pH. No such increases were observed where the seeds were inoculated. There was no apparent advantage in lime pelleting in such soils. In soils with low organic matter content and with substantial amounts of Al and/or Mn, liming increased nodule weight and dry matter yield, and decreased exchangeable Al and/or Mn. Lime pelleting was superior to mere inoculation in increasing nodule weight particularly at low lime rates. In soils with relatively high organic matter content, nodulation was very low or none at all. Low lime rates had little effect on exchangeable Al and Ca and dry matter yield. Higher lime rates, however, decreased exchangeable Al and dry matter yield but increased exchangeable Ca.