bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in Nitrogen, Carbon, and other Surface Soil Properties During Secondary Succession
Authors: Bush J. K. , Van Auken O. W.
Published: July 2010

Soils were analyzed from 10 river terrace plant communities ranging in age from 5 yr to more than 150 yr. Soil C and N concentrations increased significantly with plant community development up to 25 yr. When quadratic transformations were used, soil N accretion was correlated with huisache (Acacia smallii Isely) stem basal area. Texas sugarberry (Celtis laevigata Willd.) basal area was correlated with the soil N concentration and soil C accretion was correlated with total community basal area. Plant community development (measured as basal area) was examined using stepwise multiple linear regression analysis. Seventy‐six percent of the variance of huisache basal area could be explained by community age, soil N, K, Mg, and silt content. Seventy‐seven percent of the variance of Texas sugarberry basal area could be explained by community age, soil N, Mg, and clay content. Ninety‐one percent of the variance in total community basal area could be explained by community age, soil pH, N, and clay content. Changes in other soil chemical and physical properties occurred during succession and may be important in determining community species composition and structure.
Influence of Selected Organic Ligands on the Formation of Allophane and Imogolite
Authors: Inoue K. , Huang P. M.
Published: July 2010

The role of organic ligands of different ability to complex with Al3+ in affecting the formation of allophane and imogolite and the nature of the precipitation (>0.01 µm) and soluble (<0.01 µm) products was investigated at initial Si concentration of 1.6 × 10−3 mol.L−1, Si/Al molar ratios of 0.5 and 1.0, OH/Al molar ratios of 2.0, and 3.0, and organic ligand/Al molar ratios of 0 to 0.2. DL‐aspartic and p‐hydroxybenzoic acids showed a very weak impeding effect on the formation of allophane and imogolite; salicylic acid showed a weak to moderate impeding effect on the formation. Tannic, DL‐tartaric, citric, and DL‐malic acids with a strong affinity for Al greatly perturbed the interaction of hydroxy‐Al ions with orthosilicic acid at Si/Al ratio of 0.5, OH/Al ratio of 2.0, organic ligand/Al ratios of 0.03 to 0.1, and thus hindered the subsequent formation of imogolite, leading to the formation of pseudoboehmites, hydroxy‐Al‐organic complexes, and/or ill‐defined aluminosilicate complexes. These strong complexing organic ligands also hampered the formation of allophane at Si/Al ratio of 1.0, OH/Al ratio of 3.0, and organic ligand/Al ratios of 0.1 to 0.2, resulting in the formation of ill‐defined aluminosilicate complexes and/or hydroxy‐Al‐tannate complexes. Chemical composition, size, number, and nature of the functional groups, and concentration of organic ligands played a vital role in perturbing the formation of allophane and imogolite in the precipitation products. The order of effectiveness of organic ligands was: tannic >> DL‐tartaric > citric > DL‐malic >> salicylic > DL‐aspartic ≥ p‐hydroxybenzoic. Organic ligands with a strong affinity for Al significantly modified the nature of the soluble products which range from “proto‐imogolite” sol complexed with organic acids to hydroxy‐Al‐organic complexes.
Rapid and Slow Phosphate Sorption by Mediterranean Soils: Effect of Iron Oxides
Authors: Torrent J.
Published: July 2010

The rate of phosphate sorption (for different levels of P application) by the clay fractions of 20 soils of Mediterranean Spain ranging widely in mineralogical properties could be described by a modified Freundlich equation. The coefficient giving the P sorbed at unit concentration and unit time (taken as a measure of the rapid sorption) was significantly correlated with the amount of crystalline Fe oxides but not with other properties. The time course of the slow P sorption could not be visualized adequately by the modified Freundlich equation. For that particular purpose a simple Elovich type equation was used. This equation fitted the data well and its coefficient describing slow sorption was also correlated with the crystalline Fe oxide content. Both rapid and long‐term P sorption decreased when clays were treated with citrate‐bicarbonate‐dithionite to dissolve Fe oxides.
The Effect of Growing Plants on Denitrification at High Soil Nitrate Concentrations
Authors: Haider K. , Mosier A. , Heinemeyer O.
Published: July 2010

The availability of plant rhizosphere C deposits and its influence on microbial denitrification is not clearly defined. Conflicting reports as to the influence of plants and root exudation on denitrification continue to appear in the literature. The results of our earlier phytotron study indicated that denitrification was not stimulated in soils planted with corn or wheat compared to unplanted soils. Lower nitrate concentrations in the planted soils, however, may have led to misinterpretation of this data. A second study was conducted, to evaluate the effect of actively growing plants on denitrification where the NO‐3 content of planted soils was maintained similar to unplanted soils. Simultaneously the C fixed by corn (Zea mays) and the fate of fertilizer N applied to the soil during the growing season were quantified. The corn was grown in a phytotron under a continuous supply of 14CO2 in 15N fertilized soils to which 15N‐NO‐3 was added periodically during the growing season. The results of these studies showed that denitrification was not stimulated in soils planted with corn during active plant growth phase even when soil NO‐3 was relatively high. Denitrification was, however, greater in corn planted than unplanted soil when the recoverable root biomass began to decrease. Less N was immobilized and net 15N immobilization was lower in planted soils than in unplanted soils. As denitrification was lower in planted soils during the time of active plant growth, the study suggests that root exudates did not stimulate either process.
Competition for Nitrogen‐15 Depleted Ammonium Nitrate and Nitrogen Fixation in Arrowleaf Clover‐Gulf Ryegrass Mixtures
Authors: Morris D. R. , Weaver R. W.
Published: July 2010

‘Yuchi’ arrowleaf clover (Trifolium vesiculosum Savi) and ‘gulf’ ryegrass (Lolium multiflorum Lam) are commonly grown together but their competitive relationship for fertilizer N has not been determined. Two greenhouse experiments were conducted to examine this relationship and to determine the effects on biological N2 fixation. Seeds were sown in a Norwood soil (fine‐silty, mixed [calcareus], thermic Typic Utifluvent) that was mixed with vermiculite (Exp. I) or sand (Exp. II). Nitrogen was applied at different rates during the seedling stage to plants sown in pure and mixed stands. In Exp. I, plants were grown for 8 weeks. In Exp. II, plants were grown for 20 weeks and three clippings were taken. The N source was 99% 15N depleted NH4NO3. Ryegrass in mixed stand accumulated several times more fertilizer N than its clover component. But clover in pure stand accumulated similar quantities of fertilizer N as the ryegrass in pure stand. The percentage of total N2 fixed in the clover was usually decreased with increasing fertilizer N rates due to increased fertilizer N uptake. Total N in the clover from N2 fixation was often not significantly altered with increasing fertilizer N rates which indicates that fixed N was complimenting the N taken up from the fertilizer.
Characterization and Classification of Soils with Spodic Morphology in the Southern Appalachians
Authors: Lietzke D. A. , McGuire G. A.
Published: July 2010

Sixteen pedons with varying degrees of spodic morphology were sampled for characterization and classification on upland landforms in three areas of the southern Appalachians. Sites were located on Clingmans Dome and Unaka Mountain, both astride the Tennessee‐North Carolina border, and Poor Mountain located in southwestern Virginia. Vegetation is dominately spruce (Picea rubens)‐fir (Abies frazieri) with an ericaceous understory. Parent materials are almost exclusively feldspathic‐quartzites that were extensively frost shattered during the late Pleistocene and are now being chemically weathered. Coarse fragments that have been softened by chemical weathering cause pronounced tonguing and streaming of organic compounds from the 0 horizons through the E horizon into the Bhs/Bs horizon beneath. This results in highly variable vertical and lateral expression of spodic morphology over very short distances. Soils with few or without coarse fragments had a more typical expression of spodic morphology. High organic C contents of O and A horizons when mixed with underlying E horizons to a depth of 18 cm imparted umbric colors to all pedons. All Bhs/Bs horizons had accumulations of C, Fe, Al, and clay‐sized particles. Three of the 16 pedons met all three chemical criteria for spodic horizon determination. The pyrophosphate extractable Al and Fe to clay ratio was the most critical criterion in this study. The clay content, 14 to 35% in Bhs/Bs horizons reduced this ratio to less than the required 0.2. We propose that this Al + Fe to clay ratio be lowered to >0.1 and <0.2 to identify Entic Haplorthods, and >0.2 to recognize Typic Haplorthods in soils with loamy Bhs/Bs horizons. Two chemical field tests differed in their ability to distinguish spodic horizons from other horizons with spodic character.
Comparisons of Human‐influenced and Natural Soils at the San Luis Archaeological Site, Florida
Authors: Collins M. E. , Shapiro Gary
Published: July 2010

Soil‐human relationships of 10 archaeological test excavations were investigated at the San Luis Archaeological and Historic Site, Tallahassee. San Luis was a Spanish mission and Apalachee Indian village during the 17th century. The oldest dated archaeological soils are known to postdate 1520 (± 80) AD. A detailed topographic survey showed the locations of several 17th century features. Artifact distribution data indicated areas where soil development was affected by deposition of archaeological materials. Soil and archaeological observations were made at each excavation. Morphological features there (such as abrupt, smooth boundaries between layers; abrupt, laterally discontinuous layers; dark matrix colors extending to depths greater than expected; weakly‐developed soils as indicated by the lack of argillic or cambic horizons; and textures high in sand with mixings of clay in lower layers) were interpreted as the result of human activities. Several soil chemical and physical properties in the archaeological and buried soils differed. Total P contents were surprisingly low in the archaeological and buried soils, but extractable P amounts were high. Acidity values did not differ greatly in the archaeological and buried soils. Sand dominated the particlesize fraction in the archaeological soils. Clay contents increased as the buried soils were approached. Several of the soil properties studied in the archaeological and buried soils differed from the naturally occurring Orangeburg soil. Investigations at San Luis offered a rare opportunity in Florida to study anthrogentic soils.
Influence of Corn Residue on Compression and Compaction Behavior of Soils
Authors: Gupta S. C. , Schneider E.C. , Larson W.E. , Hadas A.
Published: July 2010

Crop residues have low densities and are somewhat elastic in nature. The presence of these residues in the soil or at the soil surface might reduce the severity of soil compaction. The objective of this study was to investigate the compression and compaction behavior of soils in the presence of corn residue. Compression behavior of soil‐residue mixtures was studied in the laboratory using the uniaxial compression test. Treatments included three size fractions (0.25‐0.50, 1.00‐2.00, and 3.36‐5.66 mm) of corn residue, four amounts of residue addition, three soil water contents, and three soils (Webster clay loam, Sargent silt loam, and Zimmerman sand). Compression samples consisted of 60 g of wet soil mixed with 0.0, 0.5, 1.0, and 2.0 g of corn residue. The compression index of residue mixed Webster clay loam or Sargent silt loam was approximately the same for various amounts and sizes of corn residues. The compression index of Zimmerman sand increased slightly with an increase in the amount of corn residues. However, for a given amount of corn residue, there was no difference in the compression index of Zimmerman sand for various residue fractions. Bulk density at a reference stress (σk = 100 kPa) decreased slightly with an increase in the amount of corn residue addition. Assuming that the residues are uniformly mixed in the top 15 cm of soil or concentrated in the wheel track (one fourth of the surface area), calculations showed that corn residues available on the farm (6.7 t/ha assuming 100 bushel/acre corn yield) will have little influence on compression parameters and thus on compaction of soils. Influence of surface residues on field soil compaction was tested in an aboveground soil bin containing a top layer of Waukegan silt loam. Residue treatments included 0.0, 3.4, 6.7, and 10.1 t/ha of corn residues on the soil surface. Measurements included normal stress at 200‐mm depth under the center of a wheel track during the passage of a tractor, and soil sinkage and bulk density profile after the passage of a tractor. Differences in the maximum normal stress at 200‐mm depth were <80 kPa between bare and residue‐covered plots. This reduction in maximum normal stress is equivalent to a reduction in bulk density of 0.12 Mg m−3 due to the presence of corn residues. However, because of the soil variability, the bulk density profile showed no significant difference due to the presence of surface residues. In summary, both laboratory and field tests in this study showed minimal beneficial effects of using corn residues in reducing the compression and compaction of soils. This conclusion, however, assumes a maximum amount of 10.1 t/ha chopped corn residue that is approximately equal to a yield of 150 bushel/acre (assuming a grain to straw ratio of 1:1).
Relation Between Soil Properties and Effectiveness of Low‐cost Water‐harvesting Treatments
Authors: Emmerich W. E. , Frasier G. W. , Fink D. H.
Published: July 2010

Knowledge of the relationship between soil properties and treatment performance is important to obtain maximum benefit from low‐cost water‐harvesting treatments. Six low‐cost water‐harvesting treatments were field tested on small plots by determining runoff percentages and threshold values at eight sites for 164 weeks. Effectiveness of all treatments decreased over time, with the order of effectiveness being: waxes > silicones ≥ control (smoothed soil). Regression equations were developed to predict runoff percentages and threshold values based on soil properties. These equations can be used in determining which water‐harvesting treatment would be most appropriate for a specific soil. All soil properties evaluated influenced the effectiveness of the water‐harvesting treatments. Therefore, relationships between specific soil properties and the effectiveness of the treatments could not be established. A set of important soil properties were identified for each treatment in the regression equations, but more research is needed to determine the absolute importance of the individual soil properties in the effectiveness of the treatments.
Ammonium Retention in Sand Amended with Clinoptilolite
Authors: Ferguson G. A. , Pepper I. L.
Published: July 2010

Clinoptilolite zeolite has a rigid three‐dimensional lattice with 10−9 m sized tunnels, and an affinity for NH+4 on its internal exchange sites. These internal tunnels are too small for 10−6 m size microbes to access; hence, clinoptilolite has the potential to physically protect NH+4 from nitrification by microbes, and may reduce volatilization losses. The objective of this study was to evaluate NH+4 retention of sand amended with clinoptilolite. Retention of NH+4 on clinoptilolite amended sands incubated at 20% volumetric water content, was studied in the laboratory. Treatments were washed mortar sand amended with 0, 5, and 10% clinoptilolite by volume and 2.38 and 3.57 moles of NH+4 m−3 of soil. Retention was evaluated by monitoring NH+4 loss from the soil mix. Loss of NH+4 decreased with increasing clinoptilolite amendment. Losses also decreased when the amount of NH+4 initially applied was decreased. The effect of clinoptilolite in retaining NH+4 was more pronounced when the amount of NH+4 initially applied was increased. Clinoptilolite reduced NH+4 losses from the soil mix and would allow increased plant N fertilizer‐use efficiency. Thus clinoptilolite‐amended sands have potential as a growth medium for turfgrasses on golf greens, where N use efficiency is typically low.
A Quick Method to Extract Organic Phosphorus from Soils
Authors: Soltanpour P. N. , Fox R. L. , Jones R. C.
Published: July 2010

The objective of this study was to develop a quick method for extracting organic P from soils. Organic P was extracted from soils by a proposed quick method (0.3 M NaOH sonified for 3 min) and compared with other methods: (i) sequential extraction with 0.3 M NaOH, concentrated HC1, and 0.5 M NaOH (modified Mehta method), and (ii) extraction of ignited (540°C) and nonignited samples with 0.5 M H2SO4 (Saunders and Williams method). The study used four soils with different mineralogies belonging to the following great groups: Hydrandepts, Fluvaquents, Haplustolls, and Gibbsiorthoxs. The proposed quick method extracted, on the average, 89% as much organic P as the modified Mehta method from the soils studied. In six out of ten samples the Saunders‐Williams method yielded more organic P than the other two methods, probably due to an increase in solubility of Fe and Al phosphate minerals after heating. It is concluded that the proposed quick method can be used to extract organic P from soils. It gives results comparable to the more tedious method of Mehta and is probably more accurate than the Saunders and Williams method for highly weathered soils.
A Method for Application of Nitrogen‐15‐Labeled Anhydrous Ammonia to Small Plots
Authors: Sanchez C. A. , Blackmer A. M.
Published: July 2010

A method is described that permits precise application of anhydrous ammonia in bands to plots of the size often used in 15N‐tracer studies. This method involves placing a stainless‐steel capillary tube in the soil where the ammonia is to be banded, attaching this tube to a cylinder of ammonia, and then pulling the tube through the soil with deposition of ammonia as an even band. The procedure has marked advantages over previously described methods because it can be used with mixtures of anhydrous ammonia and nitrificaton inhibitors and because the soil environment at the point of application is representative of the soil environment found when a conventional applicator is used.
Calculations of Error Variances with Standardized Variograms
Authors: Warrick A. W. , Myers D. E.
Published: July 2010

Sample error calculations are presented for five common variogram models: exponential, spherical, Gaussian (double exponential), Langmuir (Michaelis‐Menton) and linear. Numerical results for standardized variograms are presented in a 9 × 10 table useful for finding the maximum estimation (kriging) variance for a rectangular pattern valid for any spacing, slope, integral scale, etc., for zero nugget. Results are calculated based on the use of four or twenty‐five nearest neighbors.
A Rapid Centrifugation Method for Obtaining Soil Solution
Authors: Elkhatib E. A. , Hern J. L. , Staley T. E.
Published: July 2010

A modified centrifugation technique for obtaining soil solutions was developed and compared to immiscible displacement technique using different immiscible liquids. Coefficients of variation and standard deviations for ionic composition of soil solutions obtained by the modified centrifugation method were consistently lower than those of immiscible liquids. Differences in the estimated concentrations and activities for Ca, Mg, K, and Al among the methods employed to obtain soil solutions were noticed. The largest disagreement between activity values occurred for Al species. Such discrepancies necessitate the use of the modified centrifugation technique to obtain soil solution especially when Al determination and speciation are critical. The modified centrifugation technique offers a reliable, rapid, contamination‐free, and inexpensive method for obtaining soil solution for chemical characterization. Practical aspects of the technique (relative centrifugal force, centrifugation time, and filtering materials) are discussed.
Effect of Phosphorus and Zinc Fertilization on the Solubility of Zn2+ in Two Alkaline Soils
Authors: Norvell W. A. , Dabkowska‐Naskret H. , Cary E. E.
Published: July 2010

Concentrations of Zn2+ in equilibrium with two alkaline soils were calculated from the reactions of EDTA (ethylenediaminetetraacetic acid) chelates. The initial speciation of EDTA was varied to allow equilibrium with Zn2+ concentrations in the soil to be approached from above and below. Fertilizer Zn was added at 0 to 5 mg kg−1 as ZnSO4 and reacted thoroughly with the soil before additions of P or EDTA chelates. Phosphorus was added at 0 or 62 mg kg−1 as a mixture of KH2PO4 and K2HPO4. Concentrations of soluble Zn2+ in unfertilized soil were extremely low, approximately 5 × 10−10 M in the noncalcareous soil at pH 7.2 and 1 × 10−10 M in the calcareous soil at pH 7.6. These Zn2+ concentrations were raised 7‐ to 14‐fold by 5 mg kg−1 of added Zn, and the higher levels persisted for at least 11 weeks. Buffering of Zn2+ by the soils was substantial, ranging from about 15 to 45 (nmol g−1)/(nmol L−1). Additions of P caused small decreases in the concentrations of Zn2+ and other divalent cations in solution. Only in the Zn‐fertilized calcareous soil were the percent decreases in Zn2+ greater than those of the major divalent cations, Ca2+ and Mg2+. This effect of P in the calcareous soil is of special interest because of its apparent selectivity for Zn, but the effect was small as shown by reductions of only 12 to 19% in the [Zn2+]/[Ca2+ + Mg2+] concentration ratio.
Supercritical Gas Extraction of a Soil with Solvents of Increasing Polarities
Authors: Schnitzer M. , Preston C. M.
Published: July 2010

The surface horizon of the Bainsville soil, an Aquoll, was extracted by supercritical gas (SCG) extraction with solvents of increasing polarities. These included n‐pentane, ethanol, and mixtures of ethanol and acetone with water. Each extract was analyzed by chemical and 13C nuclear magnetic resonance (NMR) methods. Proportions of alkanes, alkanoic acids, and carbohydrates in the extracts decreased as the polarity of the solvent increased. Conversely, proportions of aromatics increased with increasing polarity of the solvent. The presence of carbohydrates and amino acids in the SCG extracts, as indicated by 13C NMR, was confirmed by chemical methods. As the polarity of the solvent increased, concentrations of hexoses increased while those of pentoses, except for arabinose, decreased. Similarly, concentrations of basic amino acids increased under these conditions. Hydrolyzates of SCG extracts contained high concentrations of NH3. A mixture of acetone and water (40:60 v/v%) was found to be the most efficient supercritical gas extractant under the experimental conditions employed. Carbon‐13 NMR spectra of the SCG extracts were exceptionally well‐defined with sharp and distinct peaks revealing fine chemical structure. The distortion‐less enhancement by polarization transfer (DEPT) NMR technique was used to determine C multiplicity and to further enhance resolution. The combination of supercritical gas extraction with 13C NMR provides soil scientists with a powerful tool for generating important information on the chemical composition and structure of soil organic matter.
Effect of Zinc Deficiency on the Accumulation of Boron and Other Mineral Nutrients in Barley
Authors: Graham Robin D. , Welch Ross M. , Grunes David L. , Cary Earle E. , Norvell Wendell A.
Published: July 2010

The hypothesis that Zn deficiency enhances the accumulation of B in barley (Hordeum vulgare L.) was tested in plants grown in nutrient solutions containing varying concentrations of B. Mean daily B uptake rates in 3‐week‐old seedlings supplied no Zn (−Zn treatment) were from 2 to 2.5 times higher as in plants supplied 2 µM Zn (+ Zn treatment). These effects were observed after only 7 d growth without added Zn. During this time, Zn in grain reserves and contaminant‐Zn were still adequate to maintain all plants with an internal tissue Zn concentration well above the critical tissue concentration (about 15 mg kg−1 Zn on a dry weight basis), and no yield response to Zn supplementation occurred. The effects of Zn on B uptake, therefore, support the concept that Zn performs a protective role at the external surfaces of, or in, root‐cell membranes. When the concentration of B in the nutrient solution was extremely high (e.g., 3000 µM), this protective effect of Zn disappeared and plants in all treatments developed B toxicity symptoms and accumulated high B concentrations. Other nutrients were also accumulated under Zn deprivation—namely, P, NO3, S, Ca, Mg, K, and Cu, but not Fe. Higher concentrations of P in the nutrient solution resulted in higher uptake rates of all ions, especially in the ‐Zn plants. A similar but smaller effect of added P on ion uptake occurred in +Zn plants.
Soil Series Differentiae Selected by Discriminant Analysis Based on Ranks
Authors: Edmonds W. J. , Lentner M.
Published: July 2010

Soils derived from parent materials weathered from sedimentary rocks of different chronostratigraphic units have been correlated as members of the Berks and Weikert series in Virginia. These correlations assume similar lithostratigraphic units. In an attempt to discriminate soils derived from four groups of parent materials weathered from rocks of different chronostratigraphic units, 34 properties were evaluated as differentiae by similarity of distributions among the parent materials and by contributions to discriminant functions. Selected properties had nonnormal distributions for one or more parent materials. Therefore, α‐levels associated with the ANOVA F‐test would not be maintained for these data. For this reason, the distribution‐free Kruskal‐Wallis test provides a more appropriate basis for comparison. In addition, Hotelling's T2 test assumes multivariate normality. Therefore, ranks were used to calculate the discriminant functions. The discriminant functions indicate that distinct groups are formed by soils derived from the Chilhowee group and from the Rome‐Waynesboro formation. Soils derived from the Chilhowee group contain lower amounts of available plant nutrients while soils derived from the Rome‐Waynesboro formation contain more feldspar in the sand and silt fractions. Soils derived from rocks of the Brallier, Chemung, Millboro, Martinsburg, and Athens formations are not discriminated by any combination of the 34 soil properties. Differentiae selected by discriminant analysis explain differences in soil responses to use and management observed by field soil scientists. Therefore, we conclude that classes produced by discriminant analysis provide more accurate predictions of soil responses than classes produced by a priori‐selected properties and limits in a hierarchical system. The simultaneous consideration of several properties approximates responses of soils as integrated systems.
Compaction Characteristics of a Soil Cropped to Corn and Bromegrass
Authors: Angers D. A. , Kay B. D. , Groenevelt P. H.
Published: July 2010

This study was initiated in order to determine if the compaction characteristics of soils are modified by cropping history. Uniaxial compression tests were made on cores of aggregated soil. The tensile strength of individual aggregates was also measured. Four different cropping histories ranging from 15 yr of continuous corn (Zea mays L.), C15, to 15 yr of continuous bromegrass (Bromus inermis Leyss.), B15, were investigated. The bulk density of soil cores under standard compaction conditions (100 kPa load and 50% water saturation) did not vary with cropping history. However, interaggregate porosity under standard compaction conditions was 18% larger in B15 than in C15, and the aggregate strength, which was positively correlated with interaggregate porosity, was 50% larger. The compression index was 12% larger in B15 than C15 and was positively correlated with interaggregate porosity under standard compaction conditions. This suggests that the loss of porosity on compaction was strongly influenced by collapse of interaggregate pores. Soils with a recent history of bromegrass had a greater proportion of interaggregate pores and this benefit persisted across a range of pressures that would normally be encountered in the field (<500 kPa). Changes in the compression index, tensile strength and interaggregate porosity appeared to occur rapidly when cropping practices changed.
Effect of Subsoiling and Irrigation Regime on Dry Bean Production in the Pacific Northwest
Authors: Miller D. E.
Published: July 2010

Zones of high strength are common in irrigated soils. Root penetration may be reduced if soil strength exceeds 1 to 3 MPa, resulting in a decreased supply of water and nutrients to the plant. On sandy soil this may allow plant water stress to develop between irrigations. Bean plants (Phaseolus vulgaris L.) are particularly sensitive to high soil strengths. A study was conducted on two soils to determine the effect of subsoiling on soil strength, bean root development, and plant reaction to different irrigation regimes. On a rigid uncemented matrix sandy soil, subsoiling reduced soil strength from >3 to <1 MPa, promoted deep rooting, and increased foliage. Without subsoiling, plants frequently suffered water stress between irrigations applied at 4‐d intervals. This resulted in blossom drop and delayed maturity by about 2 weeks. The deeper rooting associated with subsoiling reduced water stress and bean plants grew and matured normally. On a loam soil subsoiling also reduced strength to about 1 MPa or less and increased rooting depth and foliage density compared to normal tillage. With the dense foliage, 65 to 80% of the bean plants were infected with Sclerotinia white mold and dry bean yields were low. Because of the Sclerotinia injury, results were inconclusive.
Late Season Changes in Fascicle Nutrient Content, Weight, and Phosphorus Uptake by Slash Pine
Authors: Comerford N. B. , Mollitor A. V. , McFee W.
Published: July 2010

The autumn to winter season in Georgia's and Florida's lower coastal plain is marked by a mild climate and warm soil temperatures. While height growth of pine ceases in late August, climate conditions sustain root growth and needle weight gain. The purpose of this study was to (i) investigate the changes in the needle weight and N, P, K content of slash pine (Pinus elliottii Englm. var. elliottii) crowns that occur between September and January, and (ii) to investigate whether there is measurable uptake of P when applied as fertilizer late in the growing season. In the 12 locations studied, needle weight and total needle content of N and P increased during the fall and winter months. Increases in N and P total needle content ranged from 12 to 95 and 6 to 92%, respectively. Potassium content generally decreased throughout the crown or increased in the bottom portion of the crown only. Measurable uptake of P occurred during this period. Trees fertilized in late September had 49 to 57% more P in their needles by November than those that were unfertilized. This suggests that, in the southern coastal plain, plant uptake of fertilizer or native nutrients should be considered an important process throughout, at least, the autumn season.
A Simple Device for Sectioning Saturated Soil Cores Under Laboratory Conditions
Authors: Jugsujinda Aroon , Khind C. S. , Patrick W. H. , Lindau C. W.
Published: July 2010

The laboratory technique described for obtaining thin horizontal sections of prepared saturated soil cores is very simple, quick, and employs a one‐piece assembly. It can be used effectively for monitoring various chemical, electrochemical, and physical parameters of soils incubated under flooded conditions. An average coefficient of variation in sample weights of 4.79% was obtained with this technique for sectioning of the cores prepared in the laboratory, which compares well with results obtained using other more complex apparati.
Influence of Inorganic Anions on the Speciation of Mononuclear and Polynuclear Aluminum by Ferron
Authors: Jardine P. M. , Zelazny L. W.
Published: July 2010

The kinetic reactions of ferron (8‐hydroxy‐7‐iodo‐5‐quinoline‐sulfonic acid) with unneutralized and partially neutralized Al solutions in the presence of various inorganic anions were investigated for the purpose of differentiating mononuclear and polynuclear Al. Development of a general order reaction function indicated that ferron interactions with Al were modeled best by second‐order rate expressions. Mononuclear Al solutions containing ClO‐4, Cl‐, NO‐3, SO2‐4, H2PO‐4, and F‐ with anion to Al molar ratios of 13, 21, 15, 5, 0.75, and 0.08, respectively, expressed similar reactions with ferron that conformed to a single second‐order reaction. Ferron interactions with partially neutralized Al‐anion solutions were described by two simultaneous second‐order reactions that provided the rate of Al‐polymer interactions with ferron, kb, and the mole fraction of mononuclear Al species present, fa. Distinction of mononuclear and polynuclear Al in partially neutralized solutions with various anions is possible using ferron if the H2PO‐4/Al and F‐/Al molar ratios do not exceed ≈ 0.75 and 0.08, respectively. Phosphate and F‐ concentrations that reduce these ratios and SO2‐4/Al ratios of ≈ 5 still form complexes with Al, but are easily degraded by ferron and react identically to uncomplexed mononuclear Al solutions. Such complexes must be accounted for if an estimate of toxic mononuclear Al [Al(H2O)3+6, AlOH(H2O)2+5, Al(OH)2(H2O)+4] is desired.
The Kinetics of Soil Potassium Desorption
Authors: Sharpley A. N.
Published: July 2010

The kinetics of soil K desorption from five soils was investigated at different water/soil ratios (10:1–400:1), over a short period of time (30 min), so that the results could be related to K desorption from agricultural soils to rainfall and drainage water. Potassium desorption (Kd) was logarithmically related to contact time (t) at any given water/soil ratio (W) and K addition and to W at any given contact time and K addition. Potassium desorption was also directly related to the initial exchangeable K content of soil. The following kinetic equation previously developed for soil P desorption, described soil K desorption, Kd = k K0 tα WB where k, α, and β are constants. The kinetic constants, k (r2 = 0.91), α (r2 = 0.91), and β (r2 = 0.92) were related to cation exchange capacity (CEC). Unlike previous K desorption equations—(i) the uniformity of k, α, and β for a given soil, in accounting for the effects of reaction time, water/soil ratio, and soil K status on K desorption, and (ii) the fact that the constants can be estimated from CEC—may allow application of the equation to the prediction of soil K desorption in surface and groundwater quality and plant nutrient uptake modeling.
Dispersion of Clay From Some Salt‐Affected, Arid Land Soil Aggregates
Authors: Yousaf M. , Ali O. M. , Rhoades J. D.
Published: July 2010

The dispersion characteristics of five arid land soils were determined upon reaction with solutions having various levels of electrolyte concentration, C (C = 0, 1, 4, 10, 30, 50, and 100 mmolcL−1), and sodium adsorption ratios, SAR (0, 5, 10, 20, and 40) with either Ca or Mg as the divalent counter‐ion. With either divalent cation, clay dispersion increased as SAR increased and C decreased. Greater dispersion was observed with Mg as the divalent counter‐ion due to the higher SAR and lower C levels, which resulted in the Mg systems compared to the Ca systems when the soils were reacted with comparable SAR and C treatment solutions. Dispersion threshold relations are concluded to be a useful criterion for screening soils for their sodicity hazard potentials.
Utilization of Anhydrous Ammonia Fixed by Clay Minerals and Soil Organic Matter
Authors: Norman R. J. , Gilmour J. T.
Published: July 2010

A portion of anhydrous NH3 fertilizer applied to soil can be rendered nonexchangeable through fixation by clay minerals and soil organic matter. The plant availability of anhydrous NH3 fixed by these two soil fractions can be important agronomically if such fixation limits plant uptake of the fertilizer N. In this study, three soils (Drummer, Typic Haplaquoll; Blount, Aeric Ochraqualf; Cisne, Mollic Albaqualf) with clay and organic C contents ranging from 120 to 310 and 7.8 to 30.1 g kg−1, respectively, were injected with 15N‐labeled (2 atom % 15N) liquid anhydrous NH3 at a rate equivalent to 245 kg N ha−1. Soluble and exchangeable N were removed by leaching and the soil was cropped to ryegrass (Lolium multiflorum Lam.) in pots. Soils were analyzed before and after cropping for clay fixed N and organic matter fixed N. Four cuttings (harvests) were made at 3‐ to 4‐week intervals and roots were collected at the termination of the experiment. Aboveground dry matter, total N uptake, and fertilizer‐derived fixed N uptake (mg N pot−1) increased from the first to the second harvest and declined thereafter. Nitrogen recovered in the roots accounted for <11% of the total N and <7% of the fixed N utilized, and root dry matter accounted for 13 to 14% of the total dry matter produced. The ratio of fertilizer‐derived fixed N uptake to total N uptake declined with harvest suggesting that the fixed N became less available to the ryegrass with time. Fertilizer‐derived fixed N recovered in the ryegrass ranged from 19 to 26% of that originally fixed by the soil. The percentages of fertilizer‐derived clay fixed N removed from the soils during cropping (35–72%) were much larger than those of the fertilizer‐derived organic matter fixed N (<12%) suggesting that a majority of the plant uptake of fixed N originated in the clay fraction. Overall, fertilizer‐derived fixed N removal from the soils (21–30%) agreed well with plant uptake data.
Silica in Duric Soils: I. A Depositional Model
Authors: Chadwick O. A. , Hendricks D. M. , Nettleton W. D.
Published: July 2010

Many alluvial Argids in central Nevada are cemented by illuvial silica and CaCO3. In loamy soils, microsite deposition of these authigenic components tends to be mutually exclusive, with silica being finely distributed throughout the plasma phase and calcite plugging packing voids formed by skeleton grains and root channels. The following model is proposed to explain the differences in depositional locations of silica and CaCO3. As soils dry, calcite precipitates rapidly in an ionic, diffusion‐controlled reaction while monosolicic acid, which requires greater activation energy for Si‐O bond breakage prior to precipitation, is concentrated in the solution phase. Monosilicic acid [Si(OH)4] can diffuse away from the evaporation front into smaller pores where, in contact with higher surface areas, it is absorbed onto clay, sesquioxide, and weathered primary mineral surfaces. Adsorbed silica is a template for further adsorption, and on drying, the precipitation of opaline silica (SiO2). The resulting SiO2 polymers form bonds between adjacent Si(OH)4 absorbing soil particles without necessarily plugging the voids between them. In contrast, CaCO3 plugs large voids by preferentially precipitating on previously deposited calcite crystals. Calcite is more easily redissolved than opaline silica and tends to move lower in the soil profile during wet years. Differences in precipitation processes result in silica‐rich, calcite‐poor argillic and upper duric horizons that grade to more strongly cemented duric/calcic horizons. The latter are characterized by horizontally distributed low calcite durinodes interspersed by more calcareous internodal areas.
Effect of Phenylphosphorodiamidate on Ammonia Volatilization as Affected by Soil Temperature and Rates and Distribution of Urea
Authors: O'Connor M‐J. , Hendrickson L. L.
Published: July 2010

Laboratory incubation studies were conducted to evaluate the ability of phenylphosphorodiamidate (PPD) to inhibit urea hydrolysis and control NH3 volatilization losses. Complete hydrolysis of the uninhibited urea occurred within 8 d at all temperatures studied, and resulted in volatilization of more than 25% of the applied N within 10 d. Application of 20 mg PPD kg−1 of soil essentially prevented urea hydrolysis and resultant NH3 losses for 1, 2, 4, 8, and 17 d at 35, 25, 15, 10, and 5°C, respectively. This delay in the onset of NH3 losses due to PPD application kept NH3 losses during the first 10 d to <7% of the applied N at the three lower temperatures, but had little effect upon NH3 losses at 25 and 35°C. Such limited effectiveness of PPD at higher temperatures will no doubt reduce its utility for application to soils with surface temperatures above 25°C. Application of lower concentrations of urea gave reduced NH3 losses, both with and without PPD, likely due to a greater ability of other N transformations to compete for the reduced ammonium pools. Ammonia losses were also reduced, with and without PPD, when the urea was distributed throughout a larger soil volume, presumably due to a greater proportion of the urea being hydrolyzed below the immediate soil surface.
Low Temperature Dehydration Kinetics of Aluminum‐ and Calcium‐saturated Soil Clays
Authors: Karathanasis A. D. , Evangelou V. P.
Published: July 2010

The kinetic parameters of the isothermal dehydration of standard bentonitic and soil clays with montmorillonitic, mixed, illitic, and kaolinitic mineralogy were studied under Al and Ca saturation. The isothermal temperatures employed under a constant water vapor pressure of P/Po = 0.995 were 32, 38, 46, and 54°C. Dehydration rates under Al saturation were lower than those observed under Ca saturation in all clays. The differences were greater in clays with abundant interlayer space. The reaction mechanisms best describing the dehydration process were either a first‐order, random nucleation (F1) or a phase‐boundary controlled mechanism with spherical (R3) or cylindrical (R2) symmetry. The cylindrical symmetry, phase boundary was only applicable to the kaolinitic clays. The mechanisms were mostly independent of the type of the saturation (Al or Ca). Dehydration rate constants (k) were consistently lower and activation energies (Ea) of dehydration were generally higher in Al‐saturated clays. These kinetic relationships indicate that increased Al saturation of the exchange phase may slow down considerably the dehydration process by reducing dehydration rate constants and by requiring greater energy for the initiation of the desorption reaction.
Direct Measurement of Dinitrogen Evolution from Soil Using Nitrogen‐15 Emission Spectrometry
Authors: Kjeldby M. , Eriksen A. B. , Holtan‐Hartwig L.
Published: July 2010

When a 15N‐enriched N source is added to the soil, denitrification results in a nonrandom distribution of N2 isotopes. As a result, it has been necessary to apply highly enriched 15N‐fertilizers to allow mass spectrometry (MS) determinations of 28N2, 29N2, and 30N2 to quantify the N2 evolution. An alternative method, based on the determination of N2 evolution by measurement of the 28N2/29N2 ratio with emission spectrometry (ES), is proposed. An apparatus consisting of a cuvette and a sampling system was developed. The sampling system was evacuated to <10−1 Pa before gas from the cuvette system was fed into a reservoir (10 mL), through a liquid N2 trap and into five discharge tubes for ES. The final pressure in the tubes was 4 to 5 × 102 Pa before they were sealed off, and the 28N2/29N2 ratios in the gases were determined with ES. It was verified that random distribution of 28N2, 29N2, and 30N2 was obtained in different N2‐gas mixtures made from natural atmosphere and 98 atom % 15N‐N2 by the high frequency discharge of the ES. The system was used to measure fertilizer N2 loss when 15N‐enriched KNO3 was applied at a depth of 2.5 cm in flooded soil. After 60 d, 18% of the applied KNO3 was lost as N2.
Evaporite Mineralogy and Groundwater Chemistry Associated with Saline Soils in Eastern North Dakota
Authors: Skarie R. L. , Richardson J. L. , McCarthy G. J. , Maianu A.
Published: July 2010

Soil salinization has resulted from seepage of water from drainage ditches in eastern North Dakota. The present study was undertaken to determine the effect of these processes on the geochemistry of shallow groundwater and on the evaporite mineralogy of the affected soils. In the chloridic system studied, SO2‐4 concentrations of groundwater and saturation extracts were controlled by the solubility of gypsum. Calcium concentrations were controlled by gypsum solubility in the sulfatic system. Shallow groundwater samples collected near the recharge sources were undersaturated with respect to gypsum and oversaturated with respect to calcite. Considerable redistribution of gypsum was observed in soil profiles of strongly salinized transects of the chloridic system. Sulfate enrichment relative to Ca2+ was observed in groundwater and soil extracts collected near drainage ditches of chloridic sites. Mineralogy of efflorescent crusts included gypsum, epsomite, hexahydrite, thenardite, and konyaite in the sulfatic system, and halite, eugsterite, thenardite, konyaite, bloedite, and gypsum in the chloridic system.
Soil Science in the Next Twenty‐Five Years: Does Biotechnology Play a Role?
Authors: Läuchli A.
Published: July 2010

There is ample opportunity for biotechnology applications in future soil science research. In principle, all organisms are amenable to genetic engineering, including soil organisms and plants. Obviously, the researcher needs to have molecular biology and genetics skills to tackle genetic improvement of organisms. But for the geneticist to succeed in this endeavor, the input by soil and plant scientists is crucial, because geneticists usually do not have the basic understanding of the issues in soil science that are involved, nor do they know how to assess the relative merits of the genetically engineered organism in its specific environment. Notwithstanding the complex legal aspects of releasing genetically engineered organisms, biotechnology opens exciting new possibilities in soil science. Close cooperation between geneticists on the one side and soil scientists and plant scientists on the other must be fostered if biotechnology is to be utilized for the benefit of maintaining the quality of our natural, agricultural, and urban environments.