bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interaction of Nitrapyrin and Dicyandiamide with Soil Humic Compounds
Authors: Jacinthe P. A. , Pichtel J. R. 
Published: July 2010

AbstractSorption to organic matter is a primary factor influencing the effectiveness of nitrification inhibitors applied to soils. Interaction of the nitrification inhibitors nitrapyrin [2‐chloro‐6‐(trichloromethyl)‐pyridine] and dicyandiamide (DCD) with humic acid (HA) and fulvic acid (FA) was studied to compare the adsorptivity of the humic materials and elucidate adsorption mechanisms. Ten milligrams of HA or FA were suspended in aqueous solutions (10 mL) of either nitrapyrin (2, 4, 6, 8, and 12 mg L−1) or DCD (5, 10, 20, 40, and 80 mg L−1). The quantity of nitrification inhibitor adsorbed was measured after shaking the suspension of nitrapyrin for 24 h or DCD for 48 h. Results of adsorption experiments along with Freundlich K values indicate that FA adsorbed more DCD than HA, and HA was a better adsorbent for nitrapyrin. Infrared spectra provided evidence that adsorption occurred predominantly through an ionic‐bonding mechanism involving the protonated amino group of DCD or the N of the pyridine ring of nitrapyrin and the negatively charged functional groups of the humic materials. The contribution of hydrophobic forces in the adsorption of the nitrification inhibitors was minimal.
In Situ Measurement of the Effective Transport Volume for Solute Moving Through Soil
Authors: Clothier B. E. , Kirkham M. B. , McLean J. E. 
Published: July 2010

AbstractA simple field method for measuring the soil's effectively mobile water fraction during near‐saturated flow is presented. Initial charging of the immobile fraction θim is achieved by first wetting the soil with a disk permeameter until steady conditions prevail. The disk is then removed and rapidly replaced, but now filled with a tracer solution. Subsequently after a period of infiltration with tracer (0.1 M KBr), the soil underneath is sampled. The ratio of the measured to applied concentration, c*/cm, in the samples will be the fraction of the soil's water that is effectively mobile. We assume that the antecedent tracer concentration is zero, and that the mobile fraction, θm, is at concentration cm. Disk permeameters, set at the slightly unsaturated potential head ψo = −20 mm, wetted Manawatu fine sandy loam to a water content of θo = 0.414 m3 m−3. From analysis of the tracer concentrations measured under the disk, we deduced θm to be just 0.203. This semimobility was in accord with the observed depthwise penetration of tracer, as well as other measures of mobility previously found by others from longer term leaching studies carried out nearby.
Mineralization of Nitrogen and Phosphorus from Soil Organic Matter in Southern Pine Plantations
Authors: Polglase P. J. , Comerford N. B. , Jokela E. J. 
Published: July 2010

AbstractSustained weed control and/or annual applications of fertilizer have accelerated stand development of young slash pine (Pinus elliottii Engelm. var. elliottii) and loblolly pine (P. taeda L.) growing on Spodosols in Florida. Productivity of these plantations will depend largely on the extent to which nutrients are recycled through soil organic matter derived from decomposition of fresh residues. We attempted to sample this newly formed soil organic matter and measured the effects of weed control and fertilizer treatments on N and P mineralization under laboratory conditions (42‐d aerobic incubation). Sequential in situ containments using interbed soil were used to provide information on field rates of mineralization. The laboratory study demonstrated that specific N mineralization was little affected by cultural treatment. In contrast, specific P mineralization was consistently increased by fertilizer application, both in the laboratory and in situ. This suggests that, in organic residues, the general composition of P substrates was altered by fertilizer application, while organic‐N substrates remained unaffected. The effect of weed control inhibited specific N and P mineralization in the laboratory, indicating that organic residues of understory vegetation are a better supply of available N and P than are organic residues of pine. In fertilized plots and for P, annual rates of in situ mineralization were large relative to demand (uptake) by vegetation. The recycling of P through organic residues of fertilized plots has the potential to enhance long‐term productivity beyond the immediate benefits derived from fertilizer uptake.
Predicting Removal of Major Soil Cations and Anions during Acid Infiltration: Model Evaluation
Authors: Gaston L. A. , Mansell R. S. , Selim H. M. 
Published: July 2010

AbstractModels for the effects of acid deposition on soil acidification generally have not been adequately validated, especially under conditions of simultaneous water flow. The objective of this study was to assess the capability of a simple model for soil acidification and solute transport to describe changes in solution‐ and sorbed‐phase compositions of acid soil subjected to inputs of H ion. Columns of Cecil series (clayey; kaolinitic, thermic Typic Kanhapludult) and Candler series (hyperthermic, uncoated Typic Quartzipsamment) soils were leached with pH 3.0, 3.7, and 4.7 solutions. Effluent was collected in fractions and analyzed for ionic composition. Evaluation of model performance was based on a comparison of soil column leachate compositions to model predictions. The model adequately described effluent pH. However, it tended to overpredict concentrations of basic cations removed by infiltration of pH 3.0 and 3.7 solutions. Conversely, the model underpredicted concentrations of Al in the effluent from columns leached with pH 4.7 acid. These discrepancies may reflect an inadequacy of simple equilibrium models for cation exchange and Al solubility. Extension of the model to include exchange kinetics improved predictions of effluent Ca and Mg concentrations. An empirical model for Al solubility better described effluent Al concentrations than did the equilibrium dissolution of gibbsite.
Water‐Insoluble Impurity Effects on Phosphorus Availability in Monoammonium Phosphate Fertilizers
Authors: Bartos J. M. , Mullins G. L. , Williams J. C. , Sikora F. J. , Copeland J. P. 
Published: July 2010

AbstractWater‐insoluble, P‐containing impurity compounds can form during the production of commercial monoammonium phosphate (MAP, NH4H2PO4) fertilizers. Increased reliance on lower grade phosphate rock (PR) could result in an increase in these water‐insoluble fertilizer impurity compounds, thus lowering the percentage of water‐soluble P in commercial P fertilizers. There is some concern regarding the effect that impurity compounds may be having on P‐fertilizer effectiveness. Therefore, a greenhouse study was initiated to determine the concentration at which water‐insoluble impurity compounds will reduce MAP‐fertilizer effectiveness. Five commercial MAP fertilizers, representing the major U.S. sources of PR (Florida, North Carolina, and Idaho), were selected for study. Fertilizer impurities were collected as water‐insoluble residues by washing the MAP fertilizers with deionized water. Mixtures of water‐soluble, reagent‐grade MAP and the water‐insoluble fertilizer residues were prepared to give a wide range in water‐soluble P. The fraction of water‐soluble P was controlled by supplying 0, 20, 40, 60, 80, and 100% of the total P as reagent‐grade MAP. Fertilizer mixtures were applied at a rate of 80 mg P kg−1 soil, and sorghum‐sudangrass [Sorghum bicolor (L.) Moench] was grown in the treated soil. Four harvests were taken at 21‐d intervals. Forage yields and P uptake were affected by the content of water‐soluble P and the source of fertilizer P. Statistical analysis of the data for the five sources produced two separate regression yield models. The two respective fertilizer groups required 57 and 68% water‐soluble P to obtain 90% of the maximum yield. Results from this study indicate that current impurity levels in MAP fertilizers are not a major agronomic problem.
Revised Quasiparticle Model of Protonation and Metal Complexation Reactions
Authors: Sposito Garrison , Blaser Peter 
Published: July 2010

AbstractA Scatchard quasiparticle model was developed previously by the authors to account for protonation side reactions in trace metal complexation by organic ligands in an aqueous leaf litter extract. This model is inconsistent with the typical acid‐base behavior of organic acid mixtures expected at low pH. A detailed investigation of a mixture of monoprotic quasiparticles led to a new expression for the protonation side‐reaction coefficient that yields correct acid‐base chemistry at any pH. The new expression also requires quantitative revision of the reaction stoichiometries and pH‐independent conditional stability constants reported previously by the authors based on a Scatchard quasiparticle model of metal‐ organic complexes involving Cu or Al. Besides these quantitative effects, the revised results also emphasize the important conceptual point that quasiparticle models of protonation and metal complexation reactions are formulated and tested independently of one another.
Dynamics of Potassium Chloride Induced Manganese Release in Different Soil Orders
Authors: Krishnamurti G. S. R. , Huang P. M. 
Published: July 2010

AbstractThe salt‐induced Mn release from soils has been known for more than two decades; its kinetics and mechanism still remain obscure. Manganese release from selected soils of different taxonomic orders was studied as a function of the concentration of KCl (0, 0.01, 0.1, and 1.0 M), reaction period (0–216 h), and temperature (277, 298, and 317 K) to understand the influence of KCl on the dynamics of the release of soil Mn. The soils were sampled from six countries located in temperate and subtropical regions. Total Mn contents of the soils varied from 2.9 to 32.5 mmol kg−1; Mn was generally concentrated in the <2‐µm size fractions. At the end of a 24‐h reaction period at 298 K, Mn release increased consistently by 12 to 161 times as the concentration of KCl increased from 0 to 1.0 M. The amount of Mn released from the calcareous Vertisols by 1 M KCl was very low (12–20 µmol kg−1) during the reaction period of 0 to 24 h, even though the total Mn content was among the highest (25.1–32.5 mmol kg−1). Manganese release from selected soils, an Oxisol (Pakua), two Alfisols (Hyderabad and Waitville), and a Mollisol (Oxbow Orthic) by 1 M KCl followed parabolic diffusion kinetics. The activation energy of Mn release, calculated from the overall diffusion coefficients, varied from 10.9 to 16.5 kJ mol−1 among the soils, indicating diffusion as the predominant process in limiting the rate of Mn release. Ionic‐strength effect coupled with complexation was mainly responsible for the enhanced Mn release by KCl from the soils in the common soil pH range.
Seasonal Microbial Biomass Dynamics after Addition of Lentil and Wheat Residues
Authors: Bremer E. , van Kessel C. 
Published: July 2010

AbstractThe dynamics of soil microbial biomass after the addition of plant residues have a considerable influence on nutrient availability for plants, and can be quantified using the chloroform‐fumigation‐extraction method. The dynamics of microbial C and N following addition of 14C‐ and 15N‐labeled lentil (Lens culinaris Medik.) green manure, lentil straw, and wheat (Triticum aestivum L.) straw were investigated under field conditions at a site located at Outlook, Saskatchewan, on a Bradwell sandy loam (Typic Boroll). Plant residues were incorporated into microplots on 5 Oct. 1988, and the fraction of added 14C and 15N in microbial biomass was determined on four dates during the 1989 growing season. Maximum levels of labeled and unlabeled microbial biomass were observed at the time of planting (8 May) in 1989. Of added 14C, 26 and 15% was in the microbial biomass in the green manure and straw treatments, respectively, on 8 May; greater microbial accumulation of green‐manure 14C was due to a higher proportion of 14C being available rather than to a higher efficiency of 14C assimilation. Microbial 15N accounted for 65 to 81% of added residue 15N on 8 May. Plant‐residue 15N was readily available to decomposer microorganisms from all residue types, whereas 14C was more available from green manure than straw. During the 1989 growing season, microbial 14C declined by 51 and 40% in the green manure and straw treatments, respectively, while microbial 15N declined by 54% in all treatments. The decline in microbial 15N during the 1989 growing season was approximately five times greater than the amount of 15N mineralized in all sampling periods except the first for the green‐manure treatment. The highest levels of labeled and unlabeled microbial biomass observed at the time of planting indicates that microbial biomass may reduce losses of N and other nutrients during periods of low crop demand, and may act as a source of nutrients during active crop growth.
Automated Monitoring of Nitrous Oxide and Carbon Dioxide Flux from Forest Soils
Authors: Loftfield N. S. , Brumme R. , Beese F. 
Published: July 2010

AbstractGas flux determinations at the soil‐atmosphere interface are of value when modeling either soil or atmospheric chemistry. We describe a system for the automated analysis of N2O and CO2 flux from the soil surface. Fluxes are measured by monitoring increases in N2O and CO2 in double‐walled Plexiglas chambers at 30‐ and 60‐min intervals after the chamber lids are closed. Opening and closing of the chamber lids, gas sampling operations, and data collection and analyses are all controlled by a personal computer. In addition to gas fluxes, air and soil temperature as well as light intensity can be monitored. Using this system, up to 12 chambers can be continuously monitored within a 300‐m2 area.
Heterogeneity of Soil Mineral Nitrogen in Pasture Grazed by Cattle
Authors: Afzal M. , Adams W.A. 
Published: July 2010

AbstractHerbage growth on grazed pasture is commonly limited by N availability. The availability of N in soils is affected by inputs of fertilizer N through N mineralization from soil organic matter and by the return of N on local areas in animal excreta. Our objective was to describe the spatial and vertical heterogeneity in soil mineral N caused by the deposition of excreta on pasture grazed by dairy cattle (Bos taurus). The persistence and change in pattern of heterogeneity was examined both during and between grazing seasons. The soil is a Dystric Eutrochrept and perennial ryegrass (Lolium perenne L.) was the dominant species in the sward. Intact soil cores were taken at 10‐cm intervals on randomly selected 5‐m transects during the grazing season in 1989 and immediately prior to grazing in 1990. Fresh cattle dung and simulated cattle urine were applied both during and at the end of the grazing season. Spatial variation in soil mineral N developed during the grazing season with differences in NO3‐N up to 66 mg N L−1 and total mineral N (TMN) up to 250 mg N L−1 occurring between sampling points at 10‐cm centers. Sites unaffected by excreta had TMN concentrations of ≈11 mg L−1 with less than one‐quarter of this as NO3‐N. Dung patches applied in summer increased TMN in the 0‐ to 2‐cm depth range only. Left over winter, they increased the soil TMN content significantly but did not increase mineralizable N. Urine patches caused a much greater increase in TMN than dung and the pattern of heterogeneity with depth changed with time. Soil NO3‐N remaining in spring beneath simulated urine patches applied in autumn was distributed throughout a depth of at least 1 m and vertical heterogeneity persisted into the summer.
Corn Responses to Ammonium‐ and Nitrate‐Nitrogen Fertilization
Authors: Barber K. L. , Maddux L. D. , Kissel D. E. , Pierzynski G. M. , Bock B. R. 
Published: July 2010

AbstractStudies have indicated that, by maintaining relatively high solution culture or soil NH+4/NO‐3 ratios during the reproductive growth stage, certain corn (Zea mays L.) genotypes have a higher yield potential. Unfortunately, few data on soil NH+4 and NO‐3 levels have been reported. A 3‐yr field experiment was conducted in northeastern Kansas in 1987, 1988, and 1989 to evaluate the effects of time and form of applied N on fertilizer band NH+4/NO‐3 ratios and on the N nutrition, dry‐matter accumulation, and grain yield of two corn hybrids. Urea, urea‐NH4NO3, urea plus Ca(NO3)2, NH4NO3, and Ca(NO3)2 solutions having NH+4/NO‐3 ratios of 1:0, 3:1, 1:1, 1:1, and 0:1, respectively, were used at equivalent N rates. The nitrification inhibitors, nitrapyrin [2‐chloro‐6‐(trichloromethyl) pyridine] and dicyandiamide, as well as two‐way and three‐way timing of application schemes were used to maintain N as NH+4. Split applications of ammoniacal N with a nitrification inhibitor were effective in maintaining elevated soil NH+4 concentrations from planting through early grain fill. In 1988 only, grain yield was increased slightly (3–9% higher) when corn was fertilized with ammoniacal N compared with NO‐3 only. Overall, manipulation of soil NH+4/NO‐3ratios had few effects on corn development or yield.
Automated Nitrogen‐15 Analysis of Ammonium in Diffusion Disks by the Rittenberg Technique
Authors: Liu Y. P. , Mulvaney R. L. 
Published: July 2010

AbstractA recent development in 15N analysis of inorganic N in soil extracts involves diffusion of NH3 into acidified glass‐fiber disks in disposable specimen containers. A simple and convenient technique was developed for isotope‐ratio analysis of the NH4 in these disks using a mass spectrometer equipped with an automated Rittenberg apparatus (ARA‐MS). For collection of diffused NH3, the disks were treated with 10 µL of 1 M H2SO4. Following diffusion for 6 d, the disks, containing 50 to 150 µg of N, were transferred to a disposable plastic sample tray (96 wells per tray) and treated with 10 µL of 28.9 M (concentrated) HF, which digested the disks without affecting the tray. The tray was placed in a desiccator containing anhydrous CaSO4, for drying of the digested disks in 1 to 3 d. Good agreement was obtained between 15N analyses of diffused and nondiffused NH4‐N when correction was made for isotopic dilution by NH4 in the reagents used in diffusion. Trays containing the processed disks can be conveniently shipped to a service laboratory for analysis by ARA‐MS.
Chisel Tillage, Furrow Diking, and Surface Crust Effects on Infiltration
Authors: Baumhardt R. L. , Wendt C. W. , Keeling J. W. 
Published: July 2010

AbstractChisel tillage and furrow dikes (small earthen dams constructed in the furrow) are commonly used to increase infiltration and soil water storage in semiarid regions. Data quantifying the combined influences of these practices are limited. Our objective was to determine the effects of chisel tillage, furrow dikes (with and without ponding), and drop impact or surface crusts on infiltration. Infiltration rate (IR) and cumulative infiltration (CI) into an Olton clay loam (fine, mixed, thermic Aridic Paleustoll) were measured by applying water at 65 and 80 mm h−1 for 1 h using a rotating‐disk‐type rainfall simulator. Furrow dikes increased infiltration under both ponded and nonponded conditions. Cumulative infiltration was higher when raindrop impact energy was dissipated and, to some extent, when crusts were removed. Infiltration rate at the end of water application was lower with raindrop impact than when raindrop impact was eliminated; however, there were no differences in the final IR between the initially crusted and uncrusted soils. There were no differences in infiltration between chisel‐disk and disk tillage measured during the mid growing season. Furrow dikes not only detain water on the surface to provide more time for infiltration, but also increase infiltration through increased hydraulic head and additional tillage performed during dike installation or by moving loose soil from the furrow into the dikes. Our data do not support using the same hydraulic‐conductivity value for both diked and undiked field conditions, which may cause underestimation of water conservation in furrow‐diked fields.
Soil Nitrogen Dynamics following Harvesting and Conversion of Red Alder and Douglas Fir Stands
Authors: Van Miegroet H. , Homann P. S. , Cole D. W. 
Published: July 2010

AbstractDrastic reductions in NO3‐ leaching have been observed after harvesting of mature red alder (Alnus rubra Bong.) stands. Our objective was to examine whether these reduction were linked to changes in soil N dynamics. Adjacent alder and Douglas fir [Pseudotsuga menziessii (Mirbel.) Franco] stands on young glacial soils (Alderwood; a loamy‐skeletal, mixed, mesic, ortstein Aquic Haplorthod) in western Washington were harvested and replanted with either alder or Douglas fir seedlings; reference plots were established in nearby undisturbed stands. Three years after site conversion, when NO3‐ leaching declined most drastically in the harvested alder plots, net N mineralization and net nitrification in the upper soil were determined seasonally by in situ incubation using the buried‐bag technique. There were no significant increases in soil NH4‐N during incubation, indicating that nitrification rates closely followed net N mineralization in all plots. In the N‐poor soils of the harvested and uncut Douglas fir plots, nitrification was consistently <2 µg N g−1 per 30 d. In the N‐rich alder reference plot, nitrification was highest in summer (52 µg N g−1 per 30 d), lowest in winter (4 µg N g−1), and intermediate in spring (20 µg N g−1). Seasonal fluctuations in nitrification diminished in the harvested alder plots. Nitrification rates were significantly lower than in the uncut alder plot in summer only (5–9 µg N g−1 per 30 d), but this difference was insufficient to account for the lower NO3‐ leaching rates in the conversion plots. Soils in the harvested plots were drier and experienced greater temperature extremes, but these changes did not correlate well with the variability in N‐mineralization rates between uncut and harvested alder plots. Nitrification was positively correlated to soil temperature in the uncut alder plot only. The establishment of red alder seedlings did not appear to have influenced the N dynamics in either N‐poor or N‐rich soils.