bluuebunny/crossref_metadata_2025_split huggingface dataset:
Agronomic Evaluation of New Ureaforms for Flooded Rice
Authors: Carter M. F. , Vlek P. L. G. , Touchton J. T. 
Published: July 2010

AbstractRice (Oryza sativa L.) seldom utilizes more than 20 to 40% of the applied urea. Inefficient N utilization is largely attributed to N loss through ammonia (NH3) volatilization and denitrification. Increased N efficiency can be obtained with a slow‐release fertilizer such as ureaform (UF), which is the condensation product of urea and formaldehyde. A recent development in the production process of UF utilizes paraformaldehyde (PFA) addition to urea, which produces a modified urea fertilizer containing unreacted urea and methylene urea polymers. The purpose of this study was to evaluate N uptake and yield response of flooded rice and to determine NH3 volatilization losses from applications of 15N urea, UF, and methylenediurea. The UF fertilizers evaluated had PFA additions to urea ranging from 0% (urea) to 15% (UF‐15). In a greenhouse study with flooded rice, N uptake was measured and apparent N losses were estimated from an 15N balance. Direct NH3 volatilization losses were measured in a forced‐draft volatilization system. There was an increase in N uptake and a reduction in apparent and measured N losses from the modified urea fertilizers as the proportion of PFA increased. Plant 15N uptake at maturity can be expressed by the quadriatic equation: % recovery in total plant = 18.53 + 1.10%PFA − 0.02%PFA2. Total 15N recovered ranged from 44% as urea to 64% as UF‐15. In the forced‐draft NH3 volatilization study, total NH3 losses were reduced from 55% of the applied N as urea to 34% as MDU, and as the proportion of PFA addition to urea increased, NH3 losses decreased: % of applied N volatilized = 54.74 − 1.25%PFA. Ammoniacal N concentrations in the floodwater peaked on the 1st d after fertilizer application with urea and UF but peaked on the 7th d with MDU.
Barium in Illinois Surface Soils
Authors: Jones Robert L. 
Published: July 2010

AbstractThe mean total Ba content determined in 174 upland, surface soil samples was 610 mg kg−1 and the contents of the samples formed a normal distribution. An isopleth map of Ba contents was produced from programs calculating contours on a grided surface overlaid on a base map of Illinois. The isopleths are related to loess isopachs in southern Illinois and uniformly decrease from about 700 mg kg−1 near the Mississippi River to near 500 mg kg−1 at the eastern boundary of the state. This change in Ba content may reflect both weathering intensity and aeolian sorting of Ba‐bearing minerals. In northwestern Illinois where loess is also an important parent material, Ba contents are rather invariant in the range 600 to 650 mg kg−1. Where loess is very thin or nonexistent, surface soils of northeastern Illinois contain about 500 mg kg−1, a content thought to reflect the concentration in the tills of this area.
Adsorption of Nonionic Oxyethylated Sulfonamides onto Sand and Kaolin from Aqueous Solution
Authors: Hampson J. W. , Cornell D. G. , Micich T. J. 
Published: July 2010

AbstractNonionic surfactants continue to be used as soil conditioners, principally as wetting agents, but optimum surfactant chemical structure has not as yet been completely established. This research using nonionic surfactants, alkyl substituted polyoxyethylated phenylsulfonamides, has determined the effect of varying the ethoxy content and the alkyl side chain on three surfactant characteristics, i.e., adsorption, wetting, and dispersion. It was found that surfactant adsorption on sand and kaolin, two soil components, at a constant pH of 6.0 decreased with higher surfactant ethoxy content. Changing the alkyl side chain from C6 to C8 to C10 increased the apparent surfactant attraction for the adsorbent surface but not the total amount of surfactant adsorbed. The amount of surfactant adsorbed determines the final nature of the adsorbent's surface and its hydrophobic or hydrophilic character. Thus, the wetting and dispersing properties of soil components can be set by the amount of surfactant adsorbed.
The Influence of Anions on Potassium Quantity‐Intensity Relationships
Authors: Evangelou V. P. 
Published: July 2010

AbstractQuantity‐intensity (Q/I) relationships for potassium (K+) of soils sampled from three Maury silt loam sites (fine‐silty, mixed, mesic, Typic Paleudalfs) representing different crop management practices were investigated in 10−2 molc L‐ each of Cl‐ or SO2‐4 solutions. Soil samples from the three sites were (i) low in exchangeable K+ and organic matter (LK‐LOM), (ii) high in exchangeable K+ with low organic matter (HK‐LOM), and (iii) high in exchangeable K+ with relatively high organic matter (HK‐HOM). A theoretical evaluation of K+ Q/I plots in Cl‐ or SO2‐4 solutions employing the Gapon equation, revealed that the potential buffering capacity for K+ (APBCk), the labile K+ (AExK0) and equilibrium activity ratio for K+ (ARK0) based on single ion activities and ion pairs of CaSO04, KSO‐4 and CaCl+ were independent of the type of solution anion. When considering total dissolved concentration of K+ and Ca2+, the potential buffering capacity for K+ (CPBCK) and equilibrium concentration ratio for K+ (CRK0) differed between Cl‐ and SO2‐4 solutions. The labile K+ (CExK0) remained the same. These results were due to the differences in ion pairing abilities between Cl‐ and SO2‐4 with K+ and Ca2+. The influences of the ion pairs are minimized at decreasing CRK0 values. The experimental data describing Q/I relationships for K+ for the three soil samples were not in full agreement with the theoretical observations. The data showed that the type of anion (Cl‐ or SO2‐4) had an effect on the CRK0 and CExK0, but the values were not significantly different except for the HK‐HOM sample. The experimental data for the soil samples HK‐LOM and HK‐HOM indicated agreement to some extent with the theoretical evaluation. For the same CRK values in the Cl‐ or SO2‐4 anions, a greater change in exchangeable K+ (ΔExK) was observed in the SO2‐4 system than in the Cl‐ system. However, for these two soil samples (HK‐LOM and HK‐HOM) when the Q/I plots were constructed considering single ion activities, differences remained in the Q/I plot components ARK0 and AExK0 between the two anionic systems. For the LK‐LOM soil sample the Q/I plots appeared to be nearly identical for the Cl‐ and SO2‐4 systems in terms of total cation solution concentrations and/or solution single ion activities. This agreed with the theoretical evaluation.
Effect of Liming on the Distribution of Manganese, Copper, Iron, and Zinc Among Soil Fractions
Authors: Shuman L. M. 
Published: July 2010

AbstractUnderstanding the effect of soil pH on the distribution of micronutrients among soil forms is a necessary precursor to designing micronutrient extractants that extract the form of the metal available to plants. An experiment was undertaken to determine effects of soil pH changes from different liming sources on the distribution of Mn, Cu, Fe, and Zn among soil fractions and to relate the amounts of micronutrients in the fractions to that extracted by the Mehlich I and DTPA extractants. A sandy soil was amended with rates of 0, 0.99, and 1.98 g kg−1 of three liming materials: calcitic limestone, dolomitic limestone, and an industrial by‐product containing 203 g kg−1 Mg. Following a greenhouse experiment, the soils were extracted with DTPA and Mehlich I and fractionated into exchangeable, organic, Mn oxide, amorphous Fe oxide, crystalline Fe oxide and residual fractions. The extracts and fractions were analyzed for Mn, Cu, Fe, and Zn, and there were very few differences among lime sources. Increasing lime rates decreased exchangeable Zn and increased organic fraction Zn and Mn. This increase in Zn and Mn in the organic fraction as pH is increased shows that pH does not influence metals in some fractions in the same manner as it does plant availability. Iron decreased in the exchangeable and organic fractions as pH increased. Correlations between DTPA‐ or Mehlich I‐micronutrients and those in the fractions were significant (P = 0.05) only for the exchangeable and organic fractions. DTPA‐extractable Fe and Zn values were well‐correlated with plant uptake (0.842** and 0.377*, respectively). The results indicate that a micronutrient soil extractant should remove the exchangeable fraction but none of the oxide fractions and for Mn and Zn, none of the organic fraction.
Managanese Oxide Minerals in Nodules of Two Soils of Texas and Alabama
Authors: Uzochukwu G. A. , Dixon J. B. 
Published: July 2010

AbstractElemental analyses were made to determine the total Mn and other selected metal elements in the nodules and whole soils of Benchley (Vertic Argiustolls) (Texas) and Decatur (Rhodic Paleudults) (Alabama). Also, DTPA‐extractable Mn in the whole soils was determined as a measure of Mn available to plants. Managanese oxide minerals in soil nodules were magnetically concentrated, and subsequently identified by x‐ray diffraction (XRD), selective chemical treatments and various thermal methods. Tentative identification of one Mn oxide was done by high‐resolution transmission electron microscopy. The greatest concentration of Mn was in the surface horizon of Decatur and in the subsoil of Benchley. Most of the Mn was in the coarser soil fractions. Zinc, Li, Ba, Cu, Mn, and Fe were more concentrated in the nodules than in the respective whole soil. The correlation between DTPA‐extractable Mn and total Mn was high for Benchley and Decatur whole soils. Two Mn oxide minerals, birnessite and lithiophorite, were identified in the nodules of Benchley. Preferred oriented slide mounts and magnetic concentration of the samples aided in Mn oxide identification by XRD. Lattice fringes attributed to todorokite also were observed in Benchley nodules. Lithiophorite was identified in the nodules of Decatur. Other minerals found in the nodules include smectite, kaolinite, quartz, and goethite in Benchley, and kaolinite, quartz, and hematite in Decatur. Calcium, Zn, Li, Ba, and Cu detected in Benchley and Decatur nodules may be part of the Mn oxide mineral structures.
Spatial Dependence and Interpolation of Soil Properties in West Sumatra, Indonesia: II. Co‐regionalization and Co‐kriging
Authors: Trangmar B. B. , Yost R. S. , Uehara G. 
Published: July 2010

AbstractCo‐kriging was used to interpolate values of topsoil 0.5 M NaHCO3‐extractable P at 234 locations in West Sumatra, Indonesia, by exploiting its spatial covariance with a more densely sampled property, 25% HCl‐extractable P. NaHCO3‐P and HCl‐P had been sampled at 52 and 107 locations, respectively, in a nongeometric pattern across the 106 650 has region. Isotropic semivariograms of NaHCO3‐P and HCl‐P and their cross semivariogram showed spatial dependence over 6.3, 4.2, and 10.4 km, respectively, at the sampling scale used. The map of co‐kriged values for NaHCO3‐P showed a similar regional pattern but more local detail than that achieved by kriging from NaHCO3‐P samples alone. Co‐kriging reduced estimation variances (relative to kriging) by up to 40% in areas where sampling density of NaHCO3‐P was lowest. Co‐kriging variances exceeded those of kriging by up to 10% in areas where sampling density of NaHCO3‐P was high. In such areas, the covariate HCl‐P had little effect on the interpolated value but still added a component to the estimation variance. Co‐kriging could not be used to interpolate values for extreme locations where there were no NaHCO3‐P samples within the radius of the kriging neighborhood. Despite local improvement in estimation precision the full benefits of co‐kriging interpolation are not universally obtained from nongeometric variate‐covariate sampling patterns.
Distribution of Slope Steepness in the Palouse Region of Washington
Authors: Mulla David J. 
Published: July 2010

AbstractSlope steepness on eight slope aspects in four 930‐ha study areas of the Palouse region of southeastern Washington were obtained from elevations digitized from the Garfield, La Crosse, Thornton, and Wilcox 7.5‐min topographic quadrangle maps. A statistical analysis showed that slope steepness in these study areas could be described in terms of Gaussian frequency distributions after applying either a log‐normal or square root transformation to the data. In the Garfield and La Crosse study areas, slope steepness was best described using a log‐normal transformation and the Gaussian frequency distribution. The mean slope steepnesses in the Garfield and La Crosse study areas were 8.8 and 9.2%, respectively. In the Thornton and Wilcox study areas, a square root transformation of slope steepness was fit to a Gaussian frequency distribution. Mean slope steepnesses in the Thornton and Wilcox study areas were 12.5 and 12.5%, respectively. To characterize slope steepness distributions for the eight slope aspects studied within each area, from two to five Gaussian models having statistically distinct parameters were required. The quantitative analysis of topography conducted in this paper shows that considerable spatial variability of slope steepness occurs between differing slope aspects of large areas in the Palouse. This information could be used in developing improved runoff and erosion prediction models that account for spatial variability of topography over large areas.
A Model of Competition for Ammonium Among Heterotrophs, Nitrifiers, and Roots
Authors: Riha Susan J. , Campbell Gaylon S. , Wolfe Joe 
Published: July 2010

AbstractThe purpose of this study was to predict the fate of ammonium nitrogen in soils. Ammonium, either from mineralization of native organic material or from applied fertilizer, is taken up by roots, heterotrophs, and nitrifiers. The density of roots in the soil is assumed to remain constant for time periods which are long relative to microorganism response times. It is assumed that heterotroph populations are generally controlled by some substrate other than N. Ammonium levels in soil are shown to be controlled by nitrifiers except for short periods of time following perturbation of the system. Nitrifier populations are controlled by the flow of NH+4 to the substrate pool. Predicted steady state NH+4 concentrations and nitrifier populations agree well with values which are commonly measured in the field. When the system is perturbed, its return to equilibrium is shown to be described by a simple damped oscillation in NH+4 concentration and nitrifier population. The period and time constant of this damped oscillation appear to agree with published values. Careful measurement of steady‐state concentrations and characteristics of the oscillation may allow determination of several important microbe parameters.
Boundary Location from Texture, Soil Moisture, and Infiltration Data
Authors: Hendrickx J. M. H. , Wierenga P. J. , Nash M. S. , Nielsen D. R. 
Published: July 2010

AbstractThe objective was to ascertain how well different soil physical properties or parameters could be used to identify boundary locations along a soil transect. A transect was established with 91 positions, 1 m apart. The infiltration rate was measured along the transect with small (0.3‐m diam) and large (1.0‐m diam) infiltration rings. Thereafter, 91 soil samples were taken at a depth of 0.3 m for texture analysis. Also, 91 neutron access tubes and tensiometers were installed in two parallel lines 0.3 m apart. Soil‐water content was measured 16 times at the 0.3‐m depth before and after flooding the transect. Soil‐water tension was measured 13 times after flooding. The moving split window technique was used as a numerical procedure for boundary location. Boundaries detected—based on soil texture, water content, and water tension data—nearly coincided. Under dry conditions, one set of water content measurements resulted in almost the same boundaries as detected with soil texture data. Under moist conditions, several sets of measurements were needed to detect boundaries. Boundary detection with infiltration data was less satisfactory. Window width had little effect on detection of boundaries. The moving split window technique appears to be a useful tool for establishing boundaries along transects, based on water content and tension data, or in combination with soil texture data.
Evaluation of Green Ash Root Responses as a Soil Wetness Indicator
Authors: Good Billy J. , Faulkner Stephen P. , Patrick William H. 
Published: July 2010

AbstractGreen ash (Fraxinus pennsylvanica Marsh.) seedlings were transplanted to plots along four bottomland hardwood transects in Louisiana which represent a wide range of soil‐moisture and flooding regimes, and include the following soil series: Arkabulta (Aeric Fluvaquents, Rosebloom (Typic Fluvaquents), Norwood (Typic Udifluvents), Moreland (Vertic Hapludolls), Tensas (Vertic Ochraqualfs), Kobel (Vertic Haplaquepts), Goldman (Aquic Hapludalfs) and Fausse (Typic Fluvaquents). Each plot was classified as “wet” or “mesic” based on soil wetness data. Root‐coating constituents (Al, As, Ca, Fe, K, Mn, Ni, P, and Zn) and alcohol dehydrogenase (ADH) activity of the seedlings were assayed after 1.5 yr. A two‐group discriminant analysis function was developed in order to determine how well the seedling root data would predict the predetermined site‐wetness category of each seedling's plot. The deposition of rootcoating constituents and anaerobic respiration were distinct enough between the seedlings of the wet and mesic sites to be useful in the development of a fairly reliable model for site‐wetness classification. The percentages of seedlings correctly grouped into the mesic and wet categories were 88.9 and 92.0, respectively. The variables chosen for inclusion in the discriminant analysis function, in descending order of predictive power, were K, Fe/Mn, Ni, Mg, ADH, and Mn.
Concentration of Iron Oxides from Soil Clays by Density Gradient Centrifugation
Authors: Jaynes W. F. , Bigham J. M. 
Published: July 2010

AbstractHigh speed centrifugation with a large‐scale zonal rotor and a linear, tetrabromoethane‐ethanol density gradient (1.0–2.8 Mg m−3) was utilized to fractionate the <0.2µm clay materials from three soils with differing Fe‐oxide mineralogy. Hematite, goethite, and lepidocrocite were concentrated 4‐ to 10‐fold in the high density range (>2.4 Mg m−3) while the low density fractions (<2.2 Mg m−3) were depleted in reductant‐soluble Fe. Density gradient centrifugation also produced useful mineralogical separations of the soil phyllosilicates. In particular, smectite was concentrated in the 1.8 to 2.1 Mg m−3 density range whereas the 2.1 to 2.3 Mg m−3 density range was enriched with kaolinite, vermiculite, and clay mica. Electron microscopy and x‐ray diffraction analyses indicated that Fe‐oxides were present in the materials studied as discrete particles rather than as “coatings” on associated minerals.
Diffusion of Nitrogen‐15 Kjeldahl Digests for Isotope Analysis
Authors: MacKown C. T. , Brooks P. D. , Smith M. S. 
Published: July 2010

AbstractSteam distillation methods are commonly used to prepare Kjeldahl digests for N stable isotope analysis. Steam distillation requires skilled operation of specialized equipment as well as considerable operator time, and is subject to sample cross contamination unless precautionary washing procedures (which further increase sample preparation time) are adopted. A simple, inexpensive, labor saving diffusion method for Kjeldahl digests using disposable polypropylene specimen containers (128 mL) with threaded lids was devised to overcome problems with steam distillation. Diffused ammonia was collected in a disposable test tube (12 by 75 mm) containing an acid trap. Fractionation of N stable isotopes was <1% for diffused diluted simulated Kjeldahl digests, even when <20% of the initial NH3 present was diffused. As diffusion becomes more complete isotope fractionation decreases. Direct comparison of aliquots of the same plant tissue Kjeldahl digest by steam distillation and diffusion over a wide range of 15N enrichments (0.36‐43.3 atom %) indicated that deviation of the two methods was about 1%. The 15N enrichment of diffused samples was consistently slightly less than that of steam distilled samples. The method is recommended for research using 15N enriched or depleted sources, but not for research measuring natural variation in 15N abundance, unless complete diffusion is assured.
Effect of Growth Rate on the Growth of Bacteria in Freshly Moistened Soil
Authors: Hartel Peter G. , Alexander Martin 
Published: July 2010

AbstractA study was conducted to determine the significance of growth rate on the ability of six bacterial strains to grow in soil immediately following moistening of air‐dry soil and to determine if growth in soil solution could be used as a predictor of bacterial growth in soil. The generation times of the six bacterial strains in soil solution extracted from unincubated Eel silt loam that was air‐dried and moistened immediately before inoculation, and the extent of growth was directly correlated with the rate of growth of the bacteria, except for one species. The six bacteria did not increase in number in Eel silt loam that had been previously incubated for 14 d after moistening. However, addition of glutamate to this soil increased the numbers of the bacteria that grew most rapidly and had essentially no influence on the two slowest growing strains. Similar results were obtained with strains of Pseudomonas and Bradyrhizobium in two other soils or soil solutions obtained from them. The data indicate that growth in soil solution was a good indicator of the ability of bacteria to grow in nonsterile soil when the soil was inoculated immediately following moistening of air‐dry soil and that slow growth, the absence of available C, or both, limit bacterial proliferation.
Simulation of Nitrogen‐15 Immobilization by the Model NCSOIL
Authors: Hadas Aviva , Molina J. A. E. , Feigenbaum Sala , Clapp C. E. 
Published: July 2010

AbstractThe computer model NCSOIL computes the dynamics of C and N transformations in soil. In its original version, the microbial biomass assimilated organic N from the decay of organic pools, and inorganic N was immobilized only when decomposed organics were deficient in N with respect to biomass needs for growth (NCSOIL—direct version). A new version was presented in which it was assumed that microbial biomass immobilized N only from the inorganic pool, while the decay of organic N always resulted in N mineralization (NCSOIL‐MIT version). NCSOIL‐MIT was calibrated and tested for the incorporation of inorganic 15N in the organic soil N against experimental data and compared with the direct version. Net N mineralization was highly sensitive to the microbial efficiency of soil decomposable organic C incorporation. An efficiency of 0.2 gave a good account of net N mineralization for soils unamended with organic substances. NCSOIL‐MIT simulated the incorporation of 15N, added as NH4, into the organic soil pools. The kinetics of 15N immobilization was sensitive to microbial efficiency as well as to other parameters that control soil N turnover. NCSOIL—direct version required the decomposition of polysaccharide‐like material in order to obtain 15N incorporation in the soil organic pools, and the kinetics of 15N immobilization depended on the rate of polysaccharide decomposition.