bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculation of Soil Color from Reflectance Spectra
Authors: Fernandez R. N. , Schulze D. G.
Published: July 2010

Procedures were developed for obtaining visible spectra of dry and moist soil powders on a Cary 17D spectrometer. Accuracy and precision were checked by measuring the colors of: (i) 28 chips of the Inter‐Society Color Council‐National Bureau of Standards (ISCC‐NBS) Centroid Color Chart, (ii) 279 chips of the Munsell Soil Color Chart, and (iii) 12 selected soil samples. Measured Munsell values were not significantly different from nominal values. Measured hue and chroma were significantly different from nominal hue and chroma, but the difference was approximately 0.25 units of chroma and, thus, is relatively small. Average deviations for duplicate measurements of Munsell hue, value, and chroma of 12 silt loam and silty clay loam soil samples were <0.1 unit of hue, value, or chroma and maximum deviations were <0.2 units. Precision was similar for both dry and moist samples. Increased accuracy and precision make it possible to quantify small differences in soil color that are difficult to quantify using only visual color matching.
Nitrogen and Potassium Fertilization Effects on Yield and Quality of Burley Tobacco
Authors: Evanylo G. K. , Sims J. L.
Published: July 2010

Field studies were conducted in 1983 and 1984 at Lexington, KY to examine the effects of N and K fertilizer on yield and chemical quality of burley tobacco (Nicotiana tabacum L. cv. Ky 14). Treatments included: NH4NO3 at rates of 112, 280, and 448 kg N ha−1; and two sources (K2SO4 and KCl), each at rates of 0, 112, 224, and 448 kg K ha−1. The following agronomic and chemical characteristics were examined: yield, price, leaf N, P, K, Ca, Mg, Cl, Mo, total alkaloid, and solanesol concentrations. Cured leaf yield, price, and solanesol concentration were strongly influenced by N × K interactions. Each was raised by increasing N rates when no K was applied; however, at higher K levels, increasing N rates resulted in smaller price increases, no yield changes, and reductions in solanesol concentrations. Reductions in cured leaf Mo concentration relative to N, K, and Mg levels with increasing K fertilization beyond 0 kg ha−1 were exaggerated as N rates were raised. No effect of N rates on total alkaloids or solanesol concentrations were noted while increased K rates increased concentrations of both. Greater cured leaf yields and Mo concentrations were achieved with KCl than with K2SO4. The positive effect of KCl on Mo concentration at low N application rates was reduced by increased N fertilization suggesting that Mo uptake was enhanced by Cl‐ but reversed at high levels of NO‐3 application.
Interrill Soil Erosion Processes: I. Effect of Surface Sealing on Infiltration, Runoff, and Soil Splash Detachment
Authors: Bradford J. M. , Ferris J. E. , Remley P. A.
Published: July 2010

Soil erosion from interrill areas is a function primarily of soil detachment by raindrop impact and transport capacity of thin sheet flow. Soil detachment normally is the rate‐determining process and is controlled, to a large extent, by surface sealing and crusting. The purpose of this study was to measure the effect of surface sealing on infiltration, runoff, and soil loss for 20 soils ranging in texture from sand to clay. Wash and splash erosion were measured for near‐saturated soils in 0.14‐m2 Al pans exposed to laboratory simulated rainfall with an intensity of about 63 mm/h for 1 h. For most soils, wash and splash amounts decreased with time due to surface sealing with the decrease in wash being much less than the decrease in splash. Comparing the 20 soils, surface sealing caused a reduction in infiltration rate ranging from 1.2 to 36.0 mm/h and an increase in shear strength ranging from 2.6 to 42.3 kPa, resulting in a decrease in total soil loss ranging from 13.3 to 56.8 g/5 min. Total soil loss, splash, and wash were highly intercorrelated (p < 0.001).
Impacts of Acid Atmospheric Deposition on Woodland Soils in the Netherlands: I. Calculation of Hydrologic and Chemical Budgets
Authors: van Grinsven J. J. M. , van Breemen N. , Mulder J.
Published: July 2010

To study effects of acidic atmospheric deposition on woodland soils in the Netherlands, chemical budgets were determined from simulated water fluxes and measured soil solution concentrations. Solute concentrations were determined in soil solutions that were sampled monthly over a 3‐yr period at various depths in four different soils. Soil‐water fluxes were calculated with the SWATRE model. Rainfall and canopy troughfall were measured at the study site. Potential evapotranspiration was estimated by an adapted Penman method. Hydraulic conductivity was calculated from the soil‐water retentivity curves according to the Van Genuchten method. Simulated pressure heads could be fitted to field observations after reduction of conductivities by a factor between 6 and 60. Coefficients of variation for chemical budgets were determined by sensitivity analysis of the simulated soil‐water flux, and by measuring spatial, temporal, and analytical variability of the solute concentrations. Coefficients of variation of solute fluxes for Al and NO3 ranged from 10 to 30% between the 10‐ and 90‐cm depth, with spatial variability as the most important source of uncertainty. Coefficients of variation of chemical budgets (difference between inputs and outputs of solutes) for soil compartments that include the soil surface were also 10 to 30%, whereas those for deeper soil layers were larger, ranging from 40 to 200%.
Rate of Phosphorus and Potassium Buildup/Decline with Fertilization for Corn and Wheat on Nebraska Mollisols
Authors: McCallister D. L. , Shapiro C. A. , Raun W. R. , Anderson F. N. , Rehm G. W. , Engelstad O. P. , Russelle M. P. , Olson R. A.
Published: July 2010

A 12‐yr study was conducted on four Mollisols in Nebraska to evaluate response of corn (Zea mays L.) and wheat (Triticum aestivum L.) to P and K fertilizers and to determine the rate of buildup or decline of these nutrients in soil. Rates of P were 0, 11, 22, and 33 kg ha−1 applied annually or in less frequent applications of higher rates in order to maintain the same average seasonal amount, along with 27 and 54 kg annual K rates ha−1 in association with 22 kg P. The P and K fertilizers were broadcast and incorporated before planting with an appropriate blanket N treatment for the two crops. Positive yield response to applied P resulted when soil test P by Bray and Kurtz no. 1 procedure was below 15 mg kg−1 for corn and 22 mg kg−1 for wheat. No positive yield response to applied K was measured in these soils of high exchangeable K but rather a yield depression was observed at the high K rate. No significant differences in yield existed between annual applications of P and the heavier less frequent applications. Soil test P level was maintained by annual P rates of 4 to 13 kg ha−1 on the eastern soils, with none applied in the west, and was more than doubled on all soils at the end of the experimental period with 33 kg applied. Three of the soils evidenced distinct increases in soil test K without K application; the fourth a slight decline. Results from P fractionations of the test soils are reported to aid in interpreting the yield results.
Clay Mineralogy as Related to Morphology of Florida Soils with Sandy Epipedons
Authors: Harris W. G. , Carlisle V. W. , Chesser S. L.
Published: July 2010

The clay mineralogy of Coastal Plain soils with sandy epipedons was studied with respect to taxonomic class, horizon, and the presence or absence of sand grain coatings. Relative estimates of claysized minerals were based on x‐ray diffraction peak height ratios after calibration with standards and normalization. Clay mineralogy of sandy horizons was related to whether the clay occurred as grain coatings or as loosely adhering floccules. Clays from coated (⩾5% silt + clay) and slightly coated (<5% silt + clay) sands were consistently high in hydroxy‐interlayered minerals (HIM), and usually contained gibbsite. Clays from floccules in the matrix of stripped (coating‐free) sands contained large amounts of quartz, variable smectite, little or no HIM, and no gibbsite. Mineralogical differences between clays associated with stripped sands vs. coated/slightly coated sands were highly significant statistically. Clay mineralogy of coated/slightly coated sandy horizons was similar regardless of taxonomic class or horizon depth. The A and E (stripped) horizons of Haplaquods were similar to stripped Quartzipsamment horizons in being depleted in HIM relative to other phyllosilicates. Haplaquod Bh and E′ horizons (coated to some degree) were relatively high in HIM and therefore were mineralogically similar to coated/ slightly coated Quartzipsamment horizons and to Arenic and Grossarenic Paleudult epipedons. Clay fractions from chemically reduced loamy horizons of Paleudults and Haplaquods were depleted in HIM relative to overlying coated sandy horizons. Results suggest that pedogenic processes that promote the destabilization of grain coatings (i.e., podzolization, chemical reduction) also promote the loss or redistribution of HIM associated with these coatings.
Application of the Convection‐Dispersion Model to Solute Transport in Finite Soil Columns
Authors: Barry D. A. , Sposito Garrison
Published: July 2010

The one‐dimensional convection‐dispersion model is investigated with respect to the proper boundary conditions to impose in applications to tracer movement in freely draining soil columns. It is shown that the model can be interpreted probabilistically and that this interpretation leads to physical restrictions on solute molecule transport through the inlet and exit boundaries of a soil column. These constraints, in turn, show that the correct exit boundary condition for a freely draining soil column is zero resident concentration or, equivalently, zero gradient in the flux concentration. This boundary constraint is combined with conditions appropriate to either an open or a closed inlet boundary to derive a variety of mass‐conserving solutions (some apparently new) to the convection‐dispersion model for both resident and flux concentrations. In particular, a new solution is presented for the resident concentration under a closed inlet boundary. The corresponding flux concentration solution for a constant solute flux at the inlet is shown to be the same as a solution first obtained by R.W. Cleary and D.D. Adrian (1973).
Ion and Sulfate‐Isotope Ratios in Arid Soils Subject to Wind Erosion in the Southwestern USA
Authors: Schlesinger William H. , Peterjohn William T.
Published: July 2010

Our objective was to evaluate the potential for arid‐land soil dusts to contribute significantly to the content of SO2‐4 and other ions in precipitation. Soil samples collected at 102 locations throughout southwestern USA deserts were extracted with distilled water and analyzed for major ionic constituents and the stable isotope ratios (34S/32S) in soluble sulfate. Most samples were dominated by Ca2+ and HCO‐3, and were undersaturated with respect to gypsum. Only a weak correlation was found between Ca2+ and SO2‐4 in samples from upland sites. Median δ 34S of soil SO4 was +6.2‰ compared to +3.9‰ reported for precipitation. However, the median ratios for Ca/SO4 (12.00) and Mg/SO4 (1.84) in soil extracts were much larger than the same ratios in precipitation, suggesting that wind erosion of undisturbed desert soils is not a major source of the SO4 in precipitation. Calcite aerosols from desert soils may act to neutralize acid rain in the western USA.
Comparison of Three Spectrophotometric Methods for Differentiating Mono‐ and Polynuclear Hydroxy‐Aluminum Complexes
Authors: Parker D. R. , Zelazny L. W. , Kinraide T. B.
Published: July 2010

Increasing interest in the relationships between aluminum (Al) speciation and biological toxicity has created a need for accurate methods for speciating aqueous Al. Polynuclear hydroxy‐Al complexes are generally viewed as metastable species, and are thus more amenable to empirical than to computational approaches to speciation. The objectives of this study were to evaluate and compare the ferron (8‐hydroxy‐7‐iodo‐5‐quinoline‐sulfonic acid), aluminon (aurintricarboxylic acid, triammonium salt), and 8‐hydroxyquinoline methods for their ability to differentiate mono‐ and polynuclear Al in solutions typical of those used in related phytotoxicity studies. Test solutions were 20 µM in AlCl3, 0.4 mM in CaCl2 or 40 mM in NaCl, and had basicities (molar OH/Al ratios) ranging from −1 to 2.25. Reactions between test solutions and ferron or aluminon were kinetically modeled as two parallel irreversible reactions to yield estimates of the mononuclear fraction, fm. The reaction of 8‐hydroxyquinoline with mononuclear Al was essentially instantaneous, and use of an arbitrary cutoff was unavoidable. Estimates of fm were in the order 8‐hydroxyquinoline > ferron > aluminon at low basicities, while at a basicity of 2.25 the general order was aluminon ≥ 8‐hydroxyquinoline > ferron. Increasing ionic strength of test solutions increased estimates of fm by all methods. Significant quantities of polynuclear Al were detected even in solutions without added base or with slight acidification. Aging solutions up to 32 d resulated in decreased estimates of fm using aluminon, but estimates using ferron and 8‐hydroxyquinoline were only minimally affected. All three methods yield results of adequate precision for most purposes, although the ferron procedure is somewhat less sensitive than the other two. Additional studies using ferron demonstrated its utility for characterizing the nonmononuclear Al fraction using kinetic analyses. Ferron may be the preferred method based on its simplicity, level of precision, and moderate reaction rate with Al.
Boron and Silicon Adsorption on an Aluminum Oxide
Authors: Goldberg Sabine , Glaubig R. A.
Published: July 2010

Boron and Si adsorption on the Al oxide, alon (δ‐Al2O3), were investigated under changing conditions of pH, total solution anion concentration, reaction time, and order of anion addition. Boron adsorption increased at low pH, exhibited a peak near pH 8, and decreased at high pH. The constant capacitance model was successfully used to describe B adsorption over the pH range 5 to 9 and at initial B concentrations ranging from 0.185 to 1.85 mol m−3 using only one adjustable parameter, the B surface complexation constant. Silicon adsorption was much greater than B adsorption and exhibited a broad maximum extending from pH 6 to 10. Simultaneous B and Si adsorption produced a small, significant reduction in B adsorption but had no effect on Si adsorption, indicating that some of the sorption sites showed anion preference. The magnitudes of the adsorption maxima for B and Si remained essentially constant for total reaction times ranging from 10 min to 24 d. The Al oxide was very soluble, solutions were supersaturated with respect to gibbsite after 10 min at pH 4.6 to 5.7. We therefore recommend short reaction times (<2 h) for the study of adsorption reactions on δ‐Al2O3 and amorphous Al oxide.
Previous Sludge Addition Effects on Nitrogen Mineralization in Freshly Amended Soil
Authors: Lindemann W. C. , Connell G. , Urquhart N. S.
Published: July 2010

An experiment was conducted to determine the effects of previous sludge additions on N mineralization in a freshly amended soil. A secondary objective was to further delineate statistical models of N mineralization potential (No) and the mineralization rate constants k and h. The Glendale clay soil (fine‐silty, mixed thermic, Typic Torrifluvents), with either no previous sludge amendment or sludge applied at the rate of 67.3 Mg ha−1 in 1982 or 1983 in the field, was freshly amended with 30 g kg−1 of gamma irradiated, dried, anaerobically digested sewage sludge in 1985. Triplicate samples of each soil (unamended, amended in 1982, and amended in 1983) and each sludge treatment (no amendment and freshly amended) were incubated aerobically for 16 wk at 0.01‐MPa moisture potential and 35 °C. Periodically the soils were leached with 0.01 M CaCl2, and the leachate was analyzed for inorganic and organic N. Previous sludge amendment had no effect on the mineralization of resh sludge. Soils previously amended in 1982 and 1983 leached 56 to 60 mg kg−1 more NO‐3 + NO‐2 than unamended or freshly amended soils never amended with sludge. Total organic N mineralization averaged 65.4% and was independent of soil amendment history or fresh sludge amendment. Values of No, k, and h were estimated by nonlinear least squares for several nonlinear models. The best fit of the data resulted from modeling N mineralization as the sum of an exponential equation (of the rapidly decaying organic N fraction) and a constant (of the slowly decaying organic N fraction). Mineralization curves failed to flatten after 16 wk, suggesting that the experiment should have run longer before a two‐exponential equation would have satisfactorily explained the data.
Reductions in Exchangeable Magnesium with Liming of Acid Ohio Soils
Authors: Myers J. A. , McLean E. O. , Bigham J. M.
Published: July 2010

Reductions in exchangeable Mg with liming have frequently been reported in acid soils. It has been suggested that such reductions are due to an interaction between exchangeable Mg and soil Al; however, the form(s) of Al responsible for the interaction has not been adequately defined. Consequently, the objectives of this study were to fractionate the Al occurring in a series of acid Ohio soils and to determine if a relationship between Al and Mg could be defined in order to predict those soils where reductions in exchangeable Mg with liming may pose a potential problem for plant nutrition. Laboratory treatments were applied to seven soil materials in a 4 × 2 factorial, with four lime (no lime, pH 5, pH 6, pH7) and two Mg levels (0 and 25% of the cation exchange capacity, CEC). Losses in exchangeable Mg were regressed against Al solubilized by six extractants commonly used for Al fractionation, including KCl, NH4‐acetate, CuCl2, Na‐citrate‐dithionite, NH4‐oxalate, and Na‐pyrophosphate. Reductions in exchangeable Mg with liming were observed over a range of equilibrium pH values; however, the effect was clearly enhanced by increasing the soil pH to neutrality. Addition of supplemental Mg to the soils increased the absolute amount of exchangeable Mg lost with liming but had little effect on the nature of the response. Decreases in exchangeable Mg in those soils limed to near neutrality ranged from 17 to 34% of that initially present. The reduction in exchangeable Mg was positively correlated with several soil Al fractions including exchangeable, organically chelated, and poorly crystallized inorganic species; however, exchangeable Al produced the best correlation supporting the hypothesis that Mg “fixation” is due to the occlusion or coprecipitation of Mg with Al upon liming.
Effect of Phosphorus Level on Extractable Micronutrients and Their Distribution Among Soil Fractions
Authors: Shuman L. M.
Published: July 2010

Reduced tillage can cause high P levels at the soil surface which may influence soil properties so as to redistribute micronutrient metals among soil fractions and alter their plant availability. The objective was to determine the effect of P levels on the distribution of Mn, Cu, Fe, and Zn among soil fractions and on their extractability by commonly used soil extractants. Eight topsoils were treated with 0, 30 and 60 mg P kg−1 soil and none or one level of a blend of Mn, Cu, and Zn. After 22 wks, the soils were sequentially extracted to separate the exchangeable, organic, Mn oxide, amorphous Fe oxide, crystalline Fe oxide, and residual fractions. Mehlich‐1, Mehlich‐3, and DTPA (diethylenetriamine‐pentaacetic acid) extractable metals and Mehlich‐3 P were also determined. Increasing P moved Mn from the less‐soluble fractions (crystalline Fe oxide and residual) to the intermediately‐soluble fractions (Mn oxide and amorphous Fe oxide) and had little effect on the plant‐available fractions (exchangeable and organic). Copper moved to the exchangeable from the residual fraction for the fine‐textured soils. Zinc moved from the Mn oxide and crystalline Fe oxide fractions to the exchangeable fraction for all soils. Added Cu and Zn were evident in the more plant‐available fractions for most soils. Increased P increased extractable Mn and Fe for Mehlich‐1 and −3 and DTPA. Phosphorus treatments increased soil pH probably because of reactions with Fe and Al oxides producing hydroxyl ions. However, initial reactions may have lowered soil pH causing metals to be more soluble.
Acid‐Subsoil Amelioration: I. A Comparison of Several Mechanical Procedures
Authors: Farina M. P. W. , Channon P.
Published: July 2010

In many high potential cropping areas, particularly of the tropics and subtropics, crop exploitation of subsoil moisture reserves is prevented or severely curtailed by high levels of exchangeable Al. Since the effects of surface incorporated lime on subsoil acidity are minimal in most highly weathered soils, specialized mechanical and/or chemical procedures are required to overcome the problem. This work was conducted in order to assess the practicalities of mechanical profile modification and to compare the efficacy of several possible procedures. In a field experiment with maize (Zea mays L.) on a strongly acidic Plinthic Paleudult conventional moldboard incorporation of lime was compared to lime incorporation using a deep moldboard plow, the Wye‐double‐digger, a modified subsoiler capable of incorporating vertical bands of ameliorated topsoil to depths of 0.7 m, and a deep limer designed to ameliorate vertical bands of soil to a similar depth. All the procedures tested proved superior to conventional liming, the average response to profile modification ranging from over 1 400 kg ha 1 in a season in which severe moisture stress was experienced to approximately 400 kg ha−1 in an exceptionally high rainfall season. Yield responses were related to increases in rooting volume and to changes in root configuration. Segmental liming proved as effective as deep plowing or double digging.
Acid‐Subsoil Amelioration: II. Gypsum Effects on Growth and Subsoil Chemical Properties
Authors: Farina M. P. W. , Channon P.
Published: July 2010

In many highly weathered soils crop exploitation of subsoil moisture reserves is severely curtailed by toxic levels of Al. Since vertical movement of lime is usually extremely slow in such soils, specialized mechanical and/or chemical procedures are required to overcome the problem. A field experiment with maize (Zea mays L.) on a strongly acidic Plinthic Paleudult examined the effects of surface‐incorporated gypsum on yield, root development, and profile chemical properties for four cropping seasons. The effects of gypsum (10 Mg ha−1) were time dependent, but by the fourth season had resulted in a cumulative grain yield gain of 3.4 Mg ha−1. Progressive depressions in the level of exchangeable Al were accompanied by increases in subsoil Ca, Mg, and SO4‐S. Water pH increased markedly in the zone of maximum SO4‐sorption/precipitation, but pH determined in KCl remained unchanged. By the fourth season the effects of gypsum on subsoil root development were striking. These results indicate that surface incorporation of gypsum is an economically viable approach to subsoil amelioration on soils such as that studied here.
Soil Compaction and its Effect on Alfalfa in Zone Production Systems1
Authors: Meek B. D. , Rechel E. A. , Carter L. M. , DeTar W. R.
Published: July 2010

Alfalfa (Medicago sativa L.) was grown under two zone production systems (no harvest traffic) (i) preplant compaction and (ii) no preplant compaction and compared to two systems where traffic was applied (i) to 100% of the area during each harvest and (ii) to lanes simulating the traffic a grower would apply during harvest. The experiment was done in a semiarid area under irrigation on a Wasco sandy loam (coarse‐loamy, mixed, nonacid, thermic Xeric Torriorthent), which is easily compacted. Without traffic the soil settled to a bulk density of 1.6 to 1.70 Mg m−3. Traffic increased the bulk density to the 1.8 to 1.9 Mg m−3 range. Increases in bulk density at the 0.05‐ and 0.15‐m depths occurred only during the first five passes of traffic, but 10 passes were required to reach a stable bulk density at depths of 0.25 to 0.5 m. Traffic similar to what a grower would apply reduced yields by 10% compared with no traffic. Compacting 100% of the soil surface after each harvest reduced yields 17% compared with no traffic.
A Method for Measuring Hydraulic Properties of Brittle Soil Horizons
Authors: Vroon H. R. J. , Dekker L. W. , Hendrickx J. M. H.
Published: July 2010

A method is presented for measuring hydraulic properties of undisturbed samples of brittle soil horizons oriented vertically or horizontally. A soil pedestal is carved out in situ and covered with a mixture of nitrocellulose lacquer and thinner. The saturated hydraulic conductivity is measured by infiltrating water into the exposed upper surface and by collecting it below the exposed lower surface of the pedestal. In brittle soil horizons, the method yielded more representative conductivity values than the method that uses steel cylinders for taking “undisturbed” soil cores. Measurements of water retention and hydraulic conductivities showed that the latter method often disturbed the structure of the sample. Therefore, artificially high conductivity values were obtained. The method presented allows measurement of vertical and horizontal conductivities and soil‐water retention using the same sample. The method is simple and allows adjusting the sample volume to the phenomenon under study. Therefore, the method facilitates the study of hydraulic properties of brittle horizons, such as sandy humus hardpans.
Fluorescence Quenching and Copper Complexation by a Chestnut Leaf Litter Extract: Spectroscopic Evidence
Authors: Sposito Garrison , Holtzclaw Kenneth M. , Senesi Nicola
Published: July 2010

Fluorescence quenching on addition of Cu(II) to aqueous solutions of chestnut (Castanea sativa L.) leaf litter extract (LLE) has been interpreted previously in terms of Cu complexation by LLE organic ligands. In order to provide direct evidence for the existence of these complexes, as well as information about their coordination structures, infrared (IR) and electron spin resonance (ESR) spectroscopy were applied to investigate Cu/LLE mixtures that showed increasing fluorescence quenching with increasing pH. The Cu/LLE mixtures were prepared with approximately equimolar concentrations of Cu and LLE binding sites (200 mmol m−3) at pH values in the range 4 to 7. The IR spectra indicated the existence of Cu complexes involving carboxylate groups, even at pH 4. The more sensitive ESR spectra showed that Cu(II) could displace Fe(III) and Mn(II) from LLE binding sites, and that inner‐sphere complexes between Cu and LLE ligands were formed. These complexes involved carboxylate ions and H2O molecules at pH < 6, and both O‐ and N‐containing ligands at pH 6 and 7. These results confirmed the hypothesis that fluorescence quenching is associated with strong Cu complexation by organic ligands in the LLE.
Competitiveness of Selected Bradyrhizobium japonicum Strains in Midwestern USA Soils
Authors: Klubek B. P. , Hendrickson L. L. , Zablotowicz R. M. , Skwara J. E. , Varsa E. C. , Smith S. , Islieb T. G. , Maya Jaime , Valdes Maria , Dazzo F. B. , Todd R. L. , Walgenback D. D.
Published: July 2010

The competitiveness of 19 selected Bradyrhizobium japonicum strains in the midwestern USA was evaluated in field studies during 1984 and 1985. Of the 11 selected strains evaluated in 1984, a range in nodule occupancy of 0.3 to 15.7% was observed across three locations in Illinois and Wisconsin. During the second year of the study, 7 of 12 strains showed nodule occupancy averaging between 14.8 to 26.6% for eight locations in Illinois, Michigan, South Dakota, and Wisconsin. Strain An‐11 exhibited an average nodule occupancy of 15.7% in 1984 and 26.6% in 1985 which was significantly greater than any of the other 18 strains tested. Estimates of biologically‐fixed N via non‐nodulating isolines of soybean (Glycine max L.) showed a significant difference between one inoculum treatment (strain An‐14) and the noninoculated control for only one location (Plainfield, WI) during the second year of the study. No significant differences in grain yield were observed in either year of the study. The data suggests that selected strains of B. japonicum can be more successfully introduced into midwestern USA soils if they are adapted for the soils and cultivars in that geographic region.
Direct Measurement of Dinitrogen and Nitrous Oxide Flux in Flooded Rice Fields
Authors: Buresh R. J. , Austin E. R.
Published: July 2010

A direct 15N method was used to measure N2 and N2O flux in flooded rice (Oryza sativa L.) fields. The method involved application of a highly 15N‐enriched source to a 0.4‐m by 0.4‐m microplot, collection of evolved N2 and N2O in a chamber placed over the flood‐water, removal of NH3 from the air sample, conversion of some (N2 + N2O)‐N in the air sample to NH+4‐N, and determination of 15N content with a mass spectrometer. The flux of (N2 + N2O)‐15N was measured for 17 d following urea application by three methods, each replicated four times, on a Vertic Tropaquept. In all cases, the (N2 + N2O)‐15N flux was much smaller than total gaseous 15N loss as estimated from unaccounted for 15N in the 15N balance after 18 d. The (N2 + N2O)‐15N flux and total 15N loss were 1.1 and 40%, respectively, following basal broadcast and incorporation of 58 kg urea‐N ha−1 with 2‐cm standing water; they decreased to 0.2 and 26%, respectively, when the urea basal incorporation was without standing water. The (N2 + N2O)‐15N flux and total 15N loss were 0.5 and 46%, respectively, following application of 44 kg urea‐N ha−1 to 50‐mm floodwater at 10 d after transplanting. The methodology could detect a flux of 10 g N ha−1 d−1 from the added 59 to 64 atom % 15N‐labeled urea. Additional studies with 15N‐labeled NO‐3 evaluated the possibility that the low (N2 + N2O)‐15N flux was due to incomplete recovery of N2 and N2O formed from added fertilizer. Direct recovery of (N2 + N2O)‐15N following addition of labeled NO‐3 ranged from 41 to 73% of the total 15N loss. No 15N was lost by leaching or runoff, and dissolved N2O in the floodwater calculated from published solubility data was less than 1% of the added 15N.
Irrigated Corn Response to Soil‐Test Indices and Fertilizer Nitrogen, Phosphorous, Potassium, and Magnesium
Authors: Obreza T. A. , Rhoads F. M.
Published: July 2010

Improved soil‐water management techniques have made irrigated corn (Zea mays L.) yields of more than 12.5 Mg ha−1 possible in the southeastern USA. Data relating fertilizer rates and soil test indices to grain yield under intensive water management are needed to maximize fertilizer use efficiency. The objective of this study was to generate fertility index‐yield response data from which critical levels of Mehlich 1 soil test P, K, and Mg could be calculated. Irrigated corn was grown at Quincy, FL during 1980 and 1981. Nitrogen was applied at 168, 336, and 504 kg ha−1, P at 0, 29, 59, and 118 kg ha−1, K at 0, 209, and 418 kg ha−1, and Mg at 0, 67, and 134 kg ha−1 in a total of 11 treatments. Indices of available nutrients were measured via the Mehlich 1 soil test prior to each season. For both years, a minimum application of 168 kg ha−1 of N, 29 kg ha−1 of P, and 0 kg ha−1 of Mg was required for maximum grain yield, which averaged 11.2 Mg ha−1. For K, maximum yield occurred with minimum applications of 209 and 0 kg ha−1 in 1980 and 1981, respectively. Calculated critical Mehlich 1 soil test levels were 9, 45, and 33 mg kg−1 for P, K, and Mg, respectively. Comparison of our results with current soil test rating categories and corresponding recommended fertilizer rates indicated that maximum corn yield was obtained with a P fertilizer rate which was 50 kg ha−1 lower than the recommended rate.
Mineralogy and Incipient Pedogenesis of Entisols in Anorthosite Terrane of the San Gabriel Mountains, California
Authors: Graham R. C. , Herbert B. E. , Ervin J. O.
Published: July 2010

Entisols on anorthosite and associated mafic dikes in the San Gabriel Mountains were examined to determine the influence of contrasting parent materials on soil mineralogy and incipient pedogenesis. Soils are shallow Xerorthents on chaparral‐covered slopes of 50 to 65% gradient. The anorthosite is composed almost entirely of plagioclase and laumontite, a hydrothermally produced Ca‐rich zeolite. Hornblende is the major constituent of the mafic rock, while plagioclase and laumontite are much less abundant. Soil properties are strongly influenced by the parent material. Soils on the aphanitic mafic rock have much higher silt contents than those on the coarsegrained anorthosite. Calcium dominates the exchange of soils on both lithologies, but exchangeable Mg values are higher in the mafic soil than in the soil on anorthosite. A soil pH of up to one unit higher in the anorthosite‐derived soil is probably the result of the hydrolysis reaction in which the abundant, easily weathered plagioclase and zeolite weather to kaolin. Poorly crystalline kaolinite and halloysite are the dominant clay minerals in the anorthosite‐derived soil. The soil developed from mafic rock contains a large proportion of well‐crystallized trioctahedral smectite in addition to kaolin. The smectite is inherited from the mafic rock which has been somewhat hydrothermally altered. X‐ray diffraction and optical analysis of the parent rock and soil fractions coarser than clay also detected smectite and averted its misinterpretation as pedogenic. Cation exchange capacities (CEC) that are excessively high for the amount and kinds of clay present are apparently caused by CEC contributions of smectite and zeolite in the silt and sand fractions. Slight weathering of hornblende is responsible for the citrate‐bicarbonate‐dithionite‐extractable Fe, which is generally low, but is highest in the mafic soil and increases in A and AC horizons. The A and AC horizons of all soils exist in a quasi‐stable colluvial mantle and have mineral components from both lithologic sources, whereas the mineralogy of C and Cr horizons reflect only the underlying rock. Denudation rates on the steep, chaparral‐covered slopes indicate that no part of the soils, including the Cr horizons, can be older than 400 yr. Pedogenesis is inhibited by high erosion rates on this steep terrain.
Soil Cohesion as Affected by Freezing, Water Content, Time and Tillage
Authors: Bullock M. S. , Nelson S. D. , Kemper W. D.
Published: July 2010

This study was developed to determine whether there are substantial annual changes in soil cohesion and to identify major factors causing those changes. Aggregate stability was measured throughout the year on soils in Utah and Idaho using wet sieving techniques. Stability generally increased during spring and summer months. Major decreases of cohesion, found when minimum daily air temperatures fell to or below 0 °C during winter and early spring months, were attributed to pressures and associated shearing forces caused by freezing at high water contents. Equivalent disruption occurred when confined soils were frozen in controlled laboratory studies. Disruption also increased as water content at the time of freezing increased for all soils studied. Disruption of soil by rototilling and compaction significantly decreased soil cohesion.
Predicting Norway Spruce Growth From Soil and Topographic Properties in New York
Authors: Jokela E. J. , White E. H. , Berglund J. V.
Published: July 2010

Soil‐site productivity relationships for Norway spruce (Picea abies (L.) Karst.) were studied on a single, but widespread soil catena (Bath‐Lordstown‐Mardin‐Volusia; ∼1.1 million ha) in central New York. Soils and vegetation data collected from 37 unthinned plantations (45‐55‐yr old) were used to develop multiple regression soilsite predictor equations and discriminant classification functions. Efforts were made through sampling procedures to reduce extraneous sources of variation inherent in many previous soil‐site studies (e.g., parent materials, geographic area, stand density, stand age, cultural practices, and seed sources). Results of regression analyses showed that three to seven independent variables could explain 53 to 82% of the variation in mean annual volume increment (MAI). Stratifying the data set by a common planting density (2990 stems ha−1) generally improved the precision of the regression equations. Independent tests of the soil‐site equations across diverse drainage conditions showed a significant correlation between predicted and measured values of MAI (r = 0.70). More accurate predictions resulted (r = 0.80) when the equations were restricted to moderately well‐ and well‐drained soils only. Discriminant functions correctly reclassified (jackknifed analysis) 81% of the 37 stands into two MAI productivity groups. In general, results from the discriminant analyses supported interpretations made from the regression analyses. Soil properties, such as textural components, coarse fragments, pH, exchangeable cations, organic C, and cation exchange capacity (CEC), were most consistently correlated with Norway spruce volume production. Topographic properties made little or no independent contribution to the predictive models developed for growth. Results should aid yield predictions and site classification decisions for Norway spruce in New York.
Volatilization and Foliar Recapture of Ammonia Following Spring and Fall Application of Nitrogen‐15 Urea to a Douglas‐fir Ecosystem
Authors: Nason G. E. , Pluth D. J. , McGill W. B.
Published: July 2010

Seasonal effects on the volatilization and vegetal recapture of NH3 following application of pelleted 15N urea at 200 kg N ha−1 to a 40‐yr‐old Douglas‐fir [Pseudotsuga menziesii (Mirb.) Franco] ecosystem were investigated. Volatilization totalled 14 and 0.7% of applied N in spring and fall, respectively, and the difference appeared to be related to precipitation patterns following fertilization. Volatilization was generally enhanced by small spring rainfalls while depressed by larger fall rains. The isotopic abundance of evolved NH3 fluctuated from >90 to <10% of that of the fertilizer source. These fluctuations reflected the role of precipitation in the regulation of spatial heterogeneity of urea and urease in soil. Under spring conditions NH3 was recaptured by potted Douglas‐fir seedlings. Seedlings at 10 cm above the forest floor captured 16 times as much NH3 as seedlings positioned at the 150‐cm elevation. Labelled N was distributed among seedling tissues in the order: current foliage > 1‐year‐old foliage > roots which is consistent with anabolic incorporation and translocation. This mechanism may have a significant role in plant nutrition when conditions favorable to NH3 volatilization follow urea fertilization.
Vertical Distribution in Soil of Sprinkler‐applied Phosphorus
Authors: Lauer D. A.
Published: July 2010

Soil‐immobile plant nutrients, such as P, accumulate near the soil surface in conservation cropping systems where tillage leaves crop residues on or near the soil surface and limits soil mixing. The objective was to determine, in field and laboratory experiments, the vertical distribution in soil of P applied in sprinkler irrigation water. Following P applications, distribution was determined from depth increment (1 or 2 cm) sampling on a Warden silt loam (coarse‐silty, mixed, mesic, Xerollic Camborthids) and a Quincy sand (mixed, mesic, Xeric Torripsamments). The fertilizer materials applied in 10‐mm irrigations were: monoammonium phosphate (227 g P kg−1), urea phosphate (192 g P kg−1), commercial white phosphoric acid (238 g P kg−1), and ammonium polyphosphate (149 g P kg−1) containing 61 g P kg−1 as polyphosphate. Application rates ranged from 50 to 400 kg P ha−1. Movement of P was about the same for all P fertilizer materials except ammonium polyphosphate, from which P moved only 60 to 70% of the depth of the other materials. Postapplication irrigation totals up to 160 mm at 10 mm d 1, which was applied without drying cycles, distributed P more uniformly with depth. The overall mean depths of P penetration across all treatments were 10.4 cm (SD = 4.04 cm) on the Quincy sand and 7.3 cm (SD = 4.93 cm) on the Warden silt loam. These depths of penetration and vertical distribution of sprinkler‐applied P are probably sufficient to supply the P needs of crop plants under sprinkler irrigation.
Determination of Organic and Carbonate Carbon in Calcareous Soils Using Dry Combustion
Authors: Rabenhorst M. C.
Published: July 2010

A procedures is proposed which utilizes dry combustion and gravimetric determination of evolved CO2 for the determination of both organic and carbonate C in soil samples. A series of experiments was designed to determine the optimum temperature and duration of combustion that would be consistent with efficiency of analysis. Heating at 575 °C for 900 s using an O2 flow rate of 3.3 mL/s allows for determination of organic carbon (OC). Carbonate C from CaCO3 and dolomite is then determined by subsequently heating the same sample at 1000 °C for 600 s using the same O2 flow rate. This method gives quantitative recovery of organic and carbonate C from standard materials. Values for organic and carbonate C from 14 soil samples are in good agreement with existing procedures. The method is simple, requires a minimum of equipment, and has the benefit of using essentially the same procedure for both organic and carbonate C.
Flourescence Spectroscopy of Humic Substances
Authors: Miano T. M. , Martin J. P. , Sposito Garrison
Published: July 2010

Fluorescence spectroscopy has been underutilized as a method to investigate the nature of humic substances. This study was conducted to obtain fluorescence excitation and emission spectra systematically for a variety of humic and fulvic acids of diverse origin. Solutions containing 50 g m−3 humic or fulvic acid at pH values between 4 and 10 were investigated with excitation, emission, and synchronous‐scan excitation modes of fluorescence spectroscopy. The excitation spectra were markedly different for humic vs. fulvic acid and could be used to distinguish unambiguously between the two kinds of humic substance in aqueous solution. The fulvic acid excitation spectra also differed as a function of provenance. The fluorescence emission spectra, although broad, showed maximum‐intensity wavelengths that were lower for humic than for fulvic acids, indicating a greater degree of condensed, aromatic character in humic acids. Synchronous‐scan excitation spectra of the humic substances showed complex lineshapes that depended sensitively on the type of humic substance as well as on the pH value. These spectra, which are unique for fluorescence processes, may have important potential in resolving condensed aromatic structures in humic and fulvic acids.
Effects of Simulated Acid Rain on Soil Solution Composition and Orchardgrass Seedling Viability
Authors: Haun G. Wesley , Wolt Jeff , Reynolds John H.
Published: July 2010

Acid, low cation exchange capacity (CEC) surface soils in low intensity management forage ecosystems may be sensitive to acid rain. Alteration of surface soil chemical properties by acid rain may influence establishment of small seeded forage grasses. Viability of orchardgrass (Dactylis glomerata L.) seedlings was monitored concurrently with simulated acid rainfall applications (pH 4.3‐2.5) on Etowah (Typic Paleudults) and Statler (Humic Hapludults) surface soils sampled from established sod which had been unfertilized in the prior 2 yr. Simulated rainfall of pH 3.1 tended to result in increased seedling viability in comparison to other rainfall pH, but the effect of rainfall pH was significant in only six of 16 counting dates. Maximum seedling numbers and days to maximum were unaffected. Increased rainfall acidity (pH 4.3‐3.1) increased total seedling dry weight. Soil solutions from the surface 1.5 cm obtained by vacuum displacement were analyzed for pH, electrical conductivity (EC), and total concentrations of Ca, Mg, K, Na, Al, NH4, Cl, NO3, and SO4. Soil solution pH decreased and EC increased with increasing acidity of simulated rainfall. Generally, increasingly acid rainfall resulted in linear (sometimes quadratic) increases in cation and anion components of soil solution with the exception of Al, Na, and NH4. The rainfall pH × soil interaction was not significant for any solution component. Calcium ion activity was unaffected, while Al3+ activity increased from 5.62 × 10−8 to 3.16 × 10−6 with increased rainfall acidity (rainfall pH 4.3‐2.5). The Ca/Al activity ratio decreased 64‐fold with increasing acidity of simulated rainfall. No association between orchardgrass seedling responses and soil solution composition was apparent.
Subsoil Blocky Structure Formation in Some North Carolina Paleudults and Paleaquults
Authors: Southard R. J. , Buol S. W.
Published: July 2010

The relationships among subsoil blocky structure, soil drainage class and landscape position were studied on nine Ultisol pedons from the Middle Coastal Plain of North Carolina. The pedons represented fine‐loamy, fine‐silty, and clayey families of Typic and Aquic Paleudults and Typic Paleaquults. The grade of blocky structure was strongest in poorly drained soils and in moderately well‐drained soils below the seasonal high water table. Soils of fine‐silty families had the strongest blocky structure. Weighted mean ped diameter (WMPD), which was interpreted as a combination of ped size plus grade of structure, was highly and positively correlated with percent silt; WMPD decreased with increasing clay or sand content. Within a given particle‐size family, WMPD increased in more poorly drained soils. There was no consistent trend of WMPD with depth. Stronger grades of structure observed in the field were associated with the presence of thicker and more abundant clay films on peds and with thick oriented pore argillans in thin section. Plotting the location of the pedons relative to the edge of the Coastal Plain surface and to the location of the water table revealed that the subsoil zone with the strongest grade of structure coincided with the region of the subsoil that is saturated about 75% of the time. Poorly drained soils become better drained as the Coastal Plain is dissected by stream downcutting and saturation‐desiccation cycles occur less frequently. Blocky peds that formed when the soils were poorly drained are degraded by other soil forming processes such as eluviation and bioturbation.
Effects of Cultivation on Soils in Northern Great Plains Rangeland
Authors: Aguilar R. , Kelly E. F. , Heil R. D.
Published: July 2010

Paired rangeland and cultivated soils were characterized along toposequences formed in sandstone, siltstone, and shale parent materials in southwestern North Dakota to evaluate changes in organic constituents and total P resulting from 44 yr of cultivation. Cultivated and virgin grassland soils were compared on adjacent landscape segments in order to quantify losses or gains of organic C, N, P, and total P. Losses were generally greatest from the upper landscape segments where erosion resulted in significant reductions in solum thickness. Sediment accumulation through erosional processes and redistribution during tillage operations resulted in accretion on selected landscape segments along the cultivated fields. Soils derived from sandstone and siltstone appear to have lost larger proportions of organic C, N, and P through mineralization than the soils formed in shale. Mineralization losses of organic constituents were countered by accretion on depositional segments. Regression analyses indicated that losses of organic C, N, and P were more closely linked to erosion in the finer‐textured soils formed in shale. Changes in total P were closely linked to redistribution and sorting of soil particles because the total quantity of P in soils is independent of mineralization transformation.