bluuebunny/crossref_metadata_2025_split huggingface dataset:
Corn Uptake and Soil Accumulation of Nitrogen: Management and Hybrid Effects
Authors: Ferguson R. B. , Schepers J. S. , Hergert G. W. , Lohry R. D. 
Published: July 2010

AbstractInefficient use of fertilizer N by corn (Zea mays L.) can result in the accumulation of excessive amounts of NO‐3 subject to leaching losses in the crop root zone. The fate of fertilizer N as influenced by N rate, nitrapyrin [2‐chloro‐6‐(trichloromethyl)pyridine], and corn hybrid was evaluated in a 3‐yr study with sprinkler‐irrigated corn. Variables were fertilizer‐N rate (75, 150, and 300 kg N/ha); nitrapyrin (0 and 0.5 kg/ha); and corn hybrid (Pioneer hybrids 3377, 3475, and 3551). Nitrogen was applied as late‐sidedressed (V6‐V9) NH3. The fate of fertilizer N was evaluated by measurement of apparent fertilizer‐N uptake (AFU), form of N in the fertilizer band prior to and following anthesis, and accumulation and distribution of N in the soil profile. There were no significant effects of hybrid on AFU across years, and no significant hybrid × nitrapyrin interactions on AFU. Nitrapyrin significantly reduced AFU across N rates and hybrids in 2 of 3 yr. Nitrate‐N concentrations in the fertilizer band, in the presence of nitrapyrin, were reduced prior to anthesis in 1986. Higher NH+4‐N concentrations in the fertilizer band in 1986, as well as trends towards higher total inorganic‐N concentrations all 3 yr following anthesis, suggest mineralization of temporarily immobilized fertilizer NH+4. Reduced AFU in the presence of nitrapyrin in 1986 and 1987 indicates reduced availability of fertilizer N consistent with a temporary immobilization process. Nitrate accumulation in the soil to a depth of 1.8 m after three growing seasons indicates a trend toward less NO‐3 accumulation where nitrapyrin was applied at N rates of 75 and 150 kg/ha. Nitrate concentrations in the soil at a depth of 1.8 m were significantly greater at the 150 and 300 kg N/ha rates, compared with the 75 kg N/ha rate or unfertilized soil, indicating probable movement of fertilizer N below the 1.8‐m depth at the higher rates. These results indicate that nitrapyrin should not be applied with NH3 at late‐sidedress time for this soil.
Variability of an Unsaturated Sand Unit Underlying a Radioactive‐Waste Trench
Authors: Healy Richard W. , Mills Patrick C. 
Published: July 2010

AbstractProperties of soils vary considerably within any field. This study was conducted to investigate the variability in properties of an unsaturated sand unit that lies at a depth of 13 m below land surface. Four‐hundred‐forty soil core samples, obtained from a 1.75 by 18‐m horizontal plane within a sand unit underlying a waste trench, were used to describe the variability of moisture content, tritium concentration, and several physical properties. A simple model based on unit‐gradient theory was used to calculate fluxes of water and tritium through the study plane. The effects of including spatial variability of properties in model calculations were examined. The sand was uniform in terms of median particle size, bulk density, and proposity, but several variables, including saturated hydraulic conductivity (Ks) and tritium concentration, showed considerable variability. In general, correlation coefficients calculated between variables were low. Spatial correlation structures were identified for moisture content, tritium concentration, and a few particle‐size variables, but were absent for Ks and most other variables. Variances of Ks and field‐measured volumetric moisture content (θ) were lower than published values for soils. Model‐calculated fluxes of water and tritium that accounted for spatial variability of properties were considerably higher than those that did not account for the variability. Model results were more sensitive to changes in θ and residual moisture content (each parameters of the relative hydraulic conductivity function) than to changes in Ks.
Hydraulic Conductivity of Saprolite as Determined by Channels and Porous Groundmass
Authors: Vepraskas M. J. , Hoover M. T. , Jongmans A. G. , Bouma J. 
Published: July 2010

AbstractSaprolite (weathered bedrock) is being evaluated in some regions for use in on‐site disposal of household wastewater. As part of this evaluation, contributions of channels and planes to the saturated and unsaturated hydraulic conductivities were estimated for a mica‐schist saprolite. Undisturbed cores (76 mm in diam. by 76 mm in height) were collected from a 5‐ha forested site. Cores were oriented both vertically and parallel to saprolite foliation, and some contained continuous shear planes. Saturated hydraulic conductivity (Ksat) was measured on all cores, and then a dye tracer was passed through the cores. Unsaturated hydraulic conductivities were estimated for nine additional core samples. Volume percentages of dyed (water‐conducting) and undyed components, channels, groundmass, and other characteristics were determined from thin sections made from all dyed core samples. The Ksat values ranged from 0.01 to 1.71 cm h−1 and had a geometric mean of 0.27 cm h−1. Channels (primarily 0.1–0.5 mm in diam.) comprised 1.9% of the sample volume and accounted for 93% of the Ksat. At a soil water potential of −10 cm, 50% of the K value was due to flow through channels. The channels conducted no water when the soil water potential was ≤‐30 cm and the hydraulic conductivity was ≤0.02 cm h−1. Foliation planes and shear planes were plugged with Fe‐Mn oxides or clay, and their effect on hydraulic conductivity was negligible.
Effect of Chloride Ions on Sodium‐Calcium and Sodium‐Magnesium Exchange on Montmorillonite
Authors: Sposito Garrison 
Published: July 2010

AbstractRecent theoretical and experimental studies of the effect of Cl− ions on Na‐Ca and Na‐Mg exchange reactions with montmorillonite have produced conflicting data and conceptual models. A discussion is given of three of the key issues involved in this controversy with the objective of posing them more precisely as a guide to future research. The importance of clay mineral suspension characteristics (mineral purification, particle‐size fraction, suspension density) is emphasized, and a charge balance condition on the surface excesses of Na+ and CaCl+ or MgCl+ species is pointed out. The role of anion exclusion in generating differences of adsorbed metal charge between Na‐ and either Ca‐ or Mg‐montmorillonite also is clarified as it relates to exchange reactions in Cl− vs. ClO−4 ionic media.
Nitrogen Mineralization: Root and Microbial Interactions in Pitch Pine Microcosms
Authors: Tate Robert L. , O'Reilly Laurie , Parmelee Robert W. , Ehrenfeld Joan G. 
Published: July 2010

AbstractIn forest ecosystems, mineralization of native organic N provides the primary plant N nutrient source. The rate of this N mineralization is affected directly and indirectly by interactions with plant root biomass and is also probably impacted by interactions with the soil microbial community. Thus, the objectives of this study were to evaluate the relationship of N‐mineralization rates in an acid forest soil (Lakehurst sand, a mesic, coated Haplaquodic Quartzipsamment) with microbial metabolic and enzymological activities and to determine the impact of proximity to the growing roots of pitch pine (Pinus rigida Miller) on these interactions. Potential proteolytic activity, amino acid metabolism, N mineralization, microbial growth rate, glucose metabolism, and microbial biomass N were measured in microcosms planted with varying densities of pitch pine seedlings. Nitrogen mineralization, amino acid metabolism, and proteolytic activity in the organic‐matter‐poor A horizon soil were 0.01 to 0.5 of the levels in the organic‐matter‐rich O horizon of the soil. After 21 to 22 wk of growth of pine seedlings in the soil, amino acid metabolic rates in the O horizon soil were not affected by root mass. Amino acid metabolism rates declined between 10 and 25% in soils from the A horizon with increasing root density. Proteolytic activity was reduced between 10 and 50% in both soils due to root growth. In the O horizon soil, amino acid metabolic rates correlated with microbial growth rate, glucose metabolism, and microbial biomass C and N, but not with protease activity in both rhizosphere and near‐rhizosphere soils. Proteolytic activity varied independently of microbial growth rate, glucose metabolism, and biomass C and N. Except for a highly significant relationship to microbial growth rate, net N‐mineralization rates were not correlated with the measured microbial and enzymological activities. Glucose metabolism and microbial biomass N correlated with protease activity in rhizosphere soils, but not in near‐rhizosphere soils; otherwise, proximity to the pine tree roots had little effect on the relationship of N‐metabolism parameters in the acid soils used in this study.
Topsoil Depth, Fertility, Water Management, and Weather Influences on Yield
Authors: Thompson A. L. , Gantzer C. J. , Anderson S. H. 
Published: July 2010

AbstractThe productive capacity of a soil is generally related to topsoil depth. This study was conducted to determine the influence of topsoil depth, soil fertility, and water management on grain yield for corn (Zea mays L.) and soybean (Glycine max [L.] Merr.). A field experiment at Columbia, MO, was initiated in 1983 and maintained through 1987 on a Mexico silt loam (fine, montmorillonitic, mesic Udolic Ochraqualf). The study was conducted using a split‐plot experiment for each crop. Main effects included topsoil (depth to claypan), soil fertility, and water management. Desurfaced plots were constructed having topsoil depths of 0, 125, 250, and 375 mm. Plots were either fertilized according to soil‐test recommendations or unfertilized. Water management was either rain fed or with supplemental irrigation. Overall, corn yield was 5.7 times more sensitive than soybean to topsoil depth when averaged over both fertility and water management. The topsoil × soil fertility interaction was characterized by a 34% reduction in corn yield with topsoil depths < 125 mm in the fertilized treatments when averaged across water management. Similar yield reductions for unfertilized plots were observed but were linearly related to topsoil depth. The fertility × irrigation interaction described a multiplicative increase in corn yield when corn was both fertilized and irrigated. Only topsoil depth and water management significantly influenced overall soybean yield.
Urea Transformations in Flooded Soil Columns: II. Derivation of Model and Implications to Ammonia Volatilization
Authors: Bouldin D. R. , Hongprayoon C. , Patrick W. H. , Lindau C. W. 
Published: July 2010

AbstractAmmonia volatilization from rice (Oryza sativa L.) paddies following urea application reduces the effectiveness of the urea‐N. The objectives of this study were to: (i) derive, for flooded soils, a model describing hydrolysis and diffusion of urea and diffusion of ammoniacal N; (ii) derive the necessary parameters from experimental data, and (iii) use the model to study implications of hydrolysis/transport parameters and management variables to NH3 volatilization. The parameters are diffusion coefficients of urea and NH4 in soil, hydrolysis coefficients of urea in the soil and overlying floodwater, and the sorption coefficient for NH4 on the soil. The effects on potential for NH3 volatilization of variation in these parameters and the management factors of depth of flood water and depth of fertilizer incorporation were calculated. The results illustrate that urea‐hydrolysis rates in the floodwater and soil are the most important factors influencing the potential for NH3 volatilization. If urea‐hydrolysis rates are very high, incorporation and shallow floodwater are the indicated management while, with low hydrolysis rates, deep floodwater and no incorporation are the indicated management.
Predicting Cation Mobility in Kaolinitic Media Based on Exchange Selectivities of Kaolinite
Authors: Gaston L. A. , Selim H. M. 
Published: July 2010

AbstractPredictive modeling of cation transport in soils requires knowledge of the distribution of exchangeable species between solution and adsorbed phases. Such distribution of exchangeable species may be described with an exchange selectivity coefficient. Typically, the selectivity coefficient for any cation‐exchange pair varies among soils. If the exchange complex of a soil is dominated by one type of exchanger, however, then the selectivity coefficient for that soil may be similar in magnitude to that for the principal mineral (or organic) constituent. Therefore, reasonably accurate predictions of cation transport in that soil might be obtained using exchange data for the dominant exchange material. This study was undertaken to determine whether exchange data for kaolinite could be successfully used in predicting Ca, Mg, and Na retention during movement in a Mahan series soil (clayey, kaolinitic, thermic Typic Hapludult). Binary‐exchange isotherms for Ca‐Mg, Ca‐Na, and Mg‐Na were generated for Ga‐1 kaolinite (well crystallized). Selectivity coefficients derived from these data were used to describe cation exchange during miscible displacement through columns of (i) kaolinite admixed with acid‐washed sand and (ii) Mahan soil. Use of the selectivity coefficients for kaolinite provided good predictions of cation transport in the kaolinite/sand mixture. Predictions for the kaolinitic Mahan soil were not as good. The presence of small amounts of 2:1 minerals may have influenced the overall exchange behavior of the Mahan soil. When the uncertainty in values for selectivity coefficients and other exchange or transport parameters was considered, however, the exchange selectivity data for kaolinite could adequately describe cation transport in the Mahan soil.
Spectroscopic and Chemical Evidence of Variability across a Pine Litter Layer
Authors: Tam Shuk‐Ching , Sposito Garrison , Senesi Nicola 
Published: July 2010

AbstractChemical‐composition data and spectroscopic analyses are reported for three layers in a ponderosa pine (Pinus ponderosa Dougl. ex P. Lawson & Lawson) litter sample (O horizon) and for fresh needles sampled from a plantation site. The data were taken to obtain evidence for variability in chemical properties accompanying well‐known changes in the visual characteristics of a litter layer that result from the gradual humification of its organic matter. Composition data for Mg, Al, Si, P, S, Ca, Mn, Fe, Cu, and Pb showed that all but Mg, P, S, and Pb increased in content in the litter relative to the needles, and that the content of Al, S, Mn, and Fe increased, while that of Mg decreased, in passing from the Oi to the Oa layer. The increases for Al and Fe were especially large. Fourier‐transform infrared and electron spin resonance spectra of the litter samples indicated, respectively, the presence of a variety of aromatic and aliphatic structures with carboxyl and hydroxyl functionalities and an increase in organic free‐radical content with depth in the litter layer. The electron spin resonance spectra further indicated that Fe(III) was bound in inner‐sphere complexes uniformly down the litter layer, whereas Mn(II) was bound in outer‐sphere complexes. Aqueous extracts of the litter samples showed increases in pH and decreases in the concentration of organic C, carboxyl groups, and free organic acids with depth, some of the changes being as large as an order of magnitude. Composition data for aqueous extracts of the needle and litter samples showed that the water extractability of Mg, Al, P, Ca, and Mn was greater in the needles than in the litter, and that extractability decreased with increasing depth for all of the elements examined except Si and Pb. The largest relative decrease in water extractability (20‐fold) was for Al. These trends, which require confirmation for other Pinus species litter samples, were interpreted as an effect of the variability in organic structures in the litter that develop from differing degrees of humification, bioassimilation, and leaching/retention processes.
Phytoavailability Soil Test: Development and Verification of Theory
Authors: Yang J. E. , Skogley E. O. , Georgitis S. J. , Schaff B. E. , Ferguson A. H. 
Published: July 2010

AbstractA new approach to soil testing, designed to improve accuracy and usefulness, is being developed. A spherical, mixed‐bed ion‐exchange resin capsule is embedded in saturated‐paste soil samples and allowed to accumulate all nutrients the soil can deliver, as a function of diffusive ion movement. This simulates the action of nutrient movement to plant roots. The approach is called the Phytoavailability Soil Test (PST). Objectives were to determine if nutrient accumulation by the resin capsule was described by diffusion models, and to investigate rate‐limiting diffusion processes. Nutrient‐uptake curves were obtained on Ap horizon samples from 20 Montana agricultural soils by measuring time dependence of K, P, and S accumulation in resin capsules during 15 d. Also, a planar system was used in which both sides of a cylinder of resins accumulated P, K, and S from saturated pastes during 96 h. Fluxes to the resin were compared with nutrient gradients, measured by two other extraction methods, on soil slices from successive distances beyond the resin‐soil interface. The mass of nutrients adsorbed by the resin as a function of time was consistent with a diffusion process, as was the concentration of nutrients in the soil vs. distance from the resin‐soil interface. The process appeared to be that termed film diffusion. Results demonstrated independence of specific nutrient diffusion and resin adsorption. The PST may provide an improved approach to soil testing because it is sensitive to nutrient diffusion, a governing factor in plant availability of most nutrients.
Soil Adsorption Interactions of Band‐Injected Anhydrous Ammonia and Potassium Chloride Fertilizers
Authors: Stehouwer R. C. , Johnson J. W. 
Published: July 2010

AbstractFertilizer‐use efficiency of NH+4 and K+ can be low in soils that adsorb these ions in a nonexchangeable form. In a laboratory study, the soil adsorption interactions resulting from simultaneous proximal injection of anhydrous NH3 (AA) and KCl solution were investigated to determine if such interactions might have an effect on the availability of these nutrients. The fertilizers were injected separately and simultaneously into two soils, a Hoytville silty clay loam (fine, illitic, mesic Mollic Ochraqualf) and an Avonburg silt loam (fine‐silty, mixed, mesic Aeric Fragiaqualf). Following incubation for periods of 1, 7, 14, 28, and 84 d at 20 °C, soil in the injected‐fertilizer bands was sampled from four concentric zones of radii 0 to 2.0, 2.0 to 3.0, 3.0 to 4.5, and 4.5 to 6.0 cm around the injection point. In the Avonburg soil, very little interaction between the two fertilizer materials was observed. In the Hoytville soil, simultaneous injection of AA and KCl had little effect on NH+4 distribution, compared with AA injected alone. Relative to KCl injected alone, simultaneous injection of AA and KCl in the Hoytville soil increased exchangeable K+ and decreased fixed K+ within 3.0 cm of the injection point. The effect on fixed K+ persisted throughout 84 d of incubation, while the effect of exchangeable K+ was not apparent beyond 28 d of incubation. Decreased K+ fixation was attributed to preferential NH+4 fixation blocking K+ fixation. Increased exchangeable K+ was attributed to pH‐induced increases in cation‐exchange capacity (primarily in the organic fraction), and to decreased K+ fixation.
Effects of Root and Subirrigation Depth on Evaporation and Percolation Losses
Authors: Philip J. R. 
Published: July 2010

AbstractLoss from surface evaporation and from percolation limit the efficiency of subirrigation. This study yields bounds on the relative magnitude of the two types of losses. Quasilinear results on evaporation from buried steady sources are used to investigate the effects of source depth and root sink depth on soil evaporation and deep‐percolation losses from subirrigated crops. The study quantifies the concept that the deeper the source relative to the roots the smaller the soil evaporation loss and the larger the deep‐percolation loss.
Stability Constants of Copper(II)‐Humate Complexes Determined by Modified Potentiometric Titration
Authors: Stevenson F. J. , Chen Y. 
Published: July 2010

AbstractHumic substances form highly stable complexes with micronutrient cations. Little is known, however, regarding the nature of the complexes or of their stability constants. A ligand titration procedure using the Cu(II) ion‐selective electrode was investigated as a means of determining stability constants of the Cu(II) complexes with humic and fulvic acids. The procedure was superior to conventional titration (metal ion as titrant) because constants for binding at the strongest sites are measured. Furthermore, under the titration conditions employed (pH of 4 and 5; low ionic strength, 0.01 M; low Cu(II) concentration, 10−5 M), precipitation did not occur and thus did not adversely affect the binding measurements. A continuous‐distribution model showed promise for modeling the binding data. The binding affinity of some humates for Cu(II) followed the order: soil humic acid (SHA) > peat humic acid (PHA) > lignite humic acid (LHA) > soil fulvic acid (SFA) ≈ fungal melanin. Intrinsic stability constants (log Kint) at pH 4 and an ionic strength of 0.01 M for the five humate preparations were 8.3, 7.9, 7.4, 7.2, and 6.9, respectively; constants at pH 5 were 8.5, 8.4, 7.9, 7.6, and 7.6, respectively.
Modeling Magnesium Uptake from an Acid Soil: III. Determination of Root Magnesium Concentration
Authors: Rengel Z. 
Published: July 2010

AbstractResearch on the nutrient interactions in the rhizosphere of soil‐grown plants would benefit from a reliable estimate of root‐nutrient concentrations. Ryegrass plants (Lolium multiflorum Lam., ‘Wilo’) were grown for 35 d in a greenhouse on an acid Stough soil (coarse‐loamy, siliceous, thermic Fragiaquic Paleudult) amended with three rates of CaO and two rates of MgCl2. Careful washing of roots in water was followed by a digestion procedure involving HF. Root Mg concentration was corrected for soil contamination based on Ti content in the root tissue. Titanium‐corrected root Mg concentrations were lower than root Mg concentrations calculated by multiplying shoot Mg concentrations of soil‐grown plants by the ratio of root to shoot Mg concentrations of solution‐grown plants. Regression analysis showed that the Barber‐Cushman model overpredicted total Mg uptake when root Mg content was calculated either from Ti‐corrected root Mg concentrations (2.88 and 2.39 times for 0 and 36 mg Mg kg−1, respectively) or from root/shoot Mg concentration ratios in solution‐grown plants (1.98 and 1.66 times for 0 and 36 mg Mg kg−1, respectively). Partitioning of Mg between roots and shoots of ryegrass may be quite different in soil‐ and solution‐grown plants.