bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Knifed Vs. Broadcast Fertilizer Placement on Yield and Nutrient Uptake by Tall Fescue
Authors: Lamond R. E. , Moyer J. L. 
Published: July 2010

AbstractField studies were conducted from 1979 to 1981 to evaluate two fertilizer application techniques for established tall fescue (Festuca arundinacea Schreb.). Fertilizer solutions were formulated from urea‐ammonium nitrate solution (UAN, 28‐0‐0) and potassium tripolyphosphate (0‐11‐21) or ammonium polyphosphate (10‐15‐0) and potassium chloride (0‐0‐50) to supply various rates of N, P, and K. These fertilizer solutions were either surface‐broadcast through flat fan‐spray nozzles or injected (knifed) 15 to 20 cm deep behind shanks on 38‐cm spacings. The knifed method could be called a subsurface band application that places the fertilizer directly in the root zone.In Experiment I, N was applied at 56, 112, and 168 kg per ha with or without 20 kg of P/ha and 37 kg K/ha. In Experiment II, rates were 13, 112, and 168 kg N/ha; 0 and 20 kg P/ha; and 0 and 37 kg K/ha. All experiments were conducted on Parsons silt loam soils (Mollic Albaqualf, fine, mixed, thermic) that tested low to medium in available P and K. Total yields and N concentrations of forage generally increased with N rates up to 168 kg N/ha. Phosphorus fertilization increased forage yields, P concentrations, and P uptake. Forage yields were not significantly increased by K fertilization, but on low‐K soil, adding K tended to increase yields when N and P were supplied. Fertilization with K increased forage K concentrations, but had little influence on other forage constituents. Knifed fertilization was superior to broadcast applications of fertilizer and significantly increased forage yields, N content, N uptake, K uptake, and sometimes K concentrations and P uptake. The superiority of the knifed application was due mainly to better N utilization.
Behavior of Bromacil and Napropamide in Soils: I. Adsorption and Degradation
Authors: Gerstl Z. , Yaron B. 
Published: July 2010

AbstractThe adsorption and degradation of napropamide [2‐(α‐naphthoxy)‐N,‐N‐diethyl propionamide] and bromacil (5‐bromo‐3‐sec‐butyl‐6‐methyluracil) was studied in a number of Israeli soils with various properties. The adsorption of napropamide by soils was moderate, with Kd (adsorption coefficients) values ranging from 0.27 to 2.96 mL/g. Bromacil was adsorbed only slightly with Kd values of 0.03 to 0.39 mL/g. Adsorption was only slightly correlated with the soil clay content but was highly correlated with soil organic matter content, giving KOC (the adsorption per unit weight of organic carbon) values of 34 and 336 mL/g organic carbon for bromacil and napropamide, respectively. Use of the aqueous solubility of the compounds to predict adsorption gave values with considerable error in comparison with those measured, but by using the octanol/water partition coefficient (KOW) predictions were improved considerably. Degradation was studied at several moisture contents, temperatures, and initial concentrations. For the soils studied temperature and moisture content affected degradation more than did soil type or initial concentration. Degradation fit first‐order kinetics, with half lives of 17 to 1,643 d for napropamide and 14 to 1,494 d for bromacil.
Acid Tolerance of Rhizobium Trifolii in Culture Media
Authors: Thornton Frank C. , Davey C. B. 
Published: July 2010

AbstractTolerance to acidity (pH 4.2 to 4.6), low P (1 to 6 µM) and high Al (15 to 40 µM) for 100 strains of Rhizobium trifolii was assessed in liquid culture media in the laboratory. Response to acidity and Al varied among strains as evidenced by lower maximum cell densities and reduced growth rates, most preceded by a lag phase. Tolerance to acidity did not imply tolerance to Al in all cases. Strains were capable of tolerating higher levels of Al if acidity were reduced. Limitations in rhizobial growth due to low P concentrations were not as severe a stress as high acidity or high Al concentration.
The DTPA‐Extractable Iron, Manganese, Copper, and Zinc from Neutral and Calcareous Soils Dried Under Different Conditions
Authors: Leggett G. E. , Argyle D. P. 
Published: July 2010

AbstractDTPA (diethylenetriaminepentaacetic acid)‐extractable Fe, Mn, Cu, and Zn were determined on several neutral and calcareous soils dried at various temperatures. Extractable Fe increased linearly over the drying temperature range 22 to 100°C, whereas Mn increased in an irregular manner. Values for Cu and Zn changed only slightly over this temperature range. Extractability of all four elements increased when field‐moist samples were air dried; Fe by a factor of 2 to 3, and Mn, Cu, and Zn by a factor of about 1.3 to 1.5. The increases in extractable Fe and Mn appear to result from separate temperature and dehydration effects and are only partially reversible with rehydration and moist incubation. The results of this study indicate that sample handling be standardized for calibration and routine tests before DTPA‐extractable Fe and Mn can be used as reliable diagnostic tests for these elements. Close control of drying conditions for Zn and Cu analysis may be desirable but is not as critical as for Fe and Mn.
Structure of a Tilled Soil as Influenced by Tillage, Wheat Cropping, and Rainfall
Authors: Dexter A. R. , Radke J. K. , Hewitt J. S. 
Published: July 2010

AbstractTillage with a tined cultivator (scarifier) and a rotary cultivator was done on Urrbrae fine sandy loam in South Australia. One‐half of the plots were kept bare, while the other one‐half were cropped with wheat (Triticum aestivum L.). Soil macrostructure (voids and aggregates > 0.5 mm) was observed on sections sawed from blocks of the tilled soil which had been impregnated with epoxy resin. Macrostructure was quantified statistically along linear transects on the sections at 0.25, 0.5, and 0.75 of the depth of tillage at the time of tillage and on three subsequent dates when there had been 10, 135, and 395 mm of natural rainfall, respectively. Soil structures are compared and differences between them are presented. Initial differences in soil structure between the tillage treatments had largely disappeared by the second sampling date. Differences in structure due to the presence of the wheat crop were not significant until the final sampling date when the crop was at 0.66 of its final height. Multiple regression equations are presented for the soil macrostructure parameters as functions of cumulative rainfall after tillage and depth in the tilled soil layer.
The Soil Water Diffusivity Near Saturation
Authors: Clothier B. E. , Wooding R. A. 
Published: July 2010

AbstractMany laboratory porous materials are considered to have a zone of tension‐saturation in their water retentivity curve near saturation. This implies that the soil water diffusivity, D, is infinite in such a region. Here three new methods of measuring the diffusivity near saturation are presented. Experiments were carried out on a fine sand and all methods found D to be finite, yet large, having a value of approximately 1 to 2 × 10−3 m2 s−1. Since the near‐saturated conductivity of the sand is of the order 10−5 m s−1 this implies that the water retentivity curve near saturation has a finite but large slope of order 102 m. This was compatible with the measured retentivity data. The theory of one‐dimensional absorption implies that the slope of the Boltzmann variable with respect to volumetric water content near saturation equals twice D divided by the sorptivity. The slope calculated this way was compatible with that found in absorption experiments.
The Effect of Exchangeable Cations on Soil Mineral Weathering
Authors: Frenkel H. , Amrhein C. , Jurinak J. J. 
Published: July 2010

AbstractThe kinetics of dissolution of soil minerals as a function of the ionic composition of the exchange phase were studied using a calcareous soil and a noncalcareous soil. It was concluded that mineral dissolution occurred as a two‐step reaction when an exchanger phase is present. The initial fast reaction was completed in < 1 h and was linearly related to the amount of exchangeable sodium. The second slower reaction was independent of the exchangeable cation but dependent on the total mineral surface (soil‐to‐water ratio) available for weathering. The kinetics of dissolution for the second reaction was diffusion controlled.
A Mathematical Model of Soil Erosion and Deposition Processes: II. Application to Data from an Arid‐Zone Catchment
Authors: Rose C. W. , Williams J. R. , Sander G. C. , Barry D. A. 
Published: July 2010

AbstractMathematical theory for soil erosion and deposition processes on a plane land element was applied to data on runoff and sediment concentration as a function of time for nine runoff events from a small (1.3 ha) arid watershed in Arizona. Sediment concentration (and therefore sediment flux) vs. time measured at the exit to the watershed could be matched by the theory using particular values of two physically defined parameters. These two parameters are essentially the detachability of soil to rainfall, and the efficiency of sediment entrainment by overland flow. The first parameter had greatest effects on sediment concentration early in any runoff event, and the second parameter dominated later concentrations, thus allowing almost independent assessment of both parameters. The variation in soil detachability with mean depth of overland flow derived from the field data bore similarities to controlled laboratory observations.
A Simplified Model for Solute Movement Through Soils
Authors: Amoozegar‐Fard A. , Warrick A. W. , Fuller W. H. 
Published: July 2010

AbstractSolute movement through soil can be described by a variety of mathematical models whose unknown parameters (often three or more) must be estimated accurately and efficiently. In many cases, the movement of an ion can be described by a breakthrough curve at a given depth. Such a curve resulting from a step input of solute is often of sigmoidal shape. In this paper, an error function model that fits such a breakthrough curve is presented with two unknown parameters. The parameters can be estimated explicitly by a small calculator. Although chosen by least square differences, the parameters can be interpreted on the basis of sound physical principles.
Effect of Soluble Species Released from Soil Sources on the Composition of Soil and Drainage Solutions
Authors: Levy Rachel , Shainberg I. , Mazouz Rachel , Eisenberg Henrietta 
Published: July 2010

AbstractTwo soils differing in the amounts of calcium and magnesium released during dissolution of soil minerals, cation exchange capacity (CEC), lime content, and water‐holding capacity were irrigated under the same conditions with four synthetic waters. Two of the waters contained only chloride, and the other two contained both chloride and bicarbonate anions. Sodium adsorption ratios of the two chloride and two bicarbonate waters were either 10 or 20. Following every 10 wetting and drying cycles the two soils were leached with about 10% excess water. Five such leachates were collected and analyzed. Soil analysis was performed after 20 and 40 irrigation cycles. A significant difference was found between the chemical composition of the drainage and soil solutions of the two soils. To evaluate this diversity, the law of mass conservation was used to calculate the amount of calcium and magnesium released by dissolution in the absence and presence of carbonate precipitation. Two assumptions were used in these calculations: (i) during irrigation with the chloride waters no precipitation of carbonates occurred, and (ii) during irrigation with the bicarbonate waters no dissolution took place. These assumptions proved valid only for the soil that released small amounts of salt by dissolution. The two soils released almost equal amounts of calcium and magnesium from exchange sites, although there was a significant difference in CEC. It was concluded that the primary source that induced the differences in chemical composition of the drainage and soil solutions was the amount of calcium and magnesium released by mineral dissolution.
Multifactor Kinetics of Phosphate Reactions with Minerals in Acid Soils: II. Experimental Curve Fitting
Authors: Lin Chenfang , Motto H. L. , Douglas L. A. , Busscher W. J. 
Published: July 2010

AbstractA kinetic model of phosphate reactions with minerals in acidic soils was used to simulate experimental results obtained under a variety of conditions based on three factors—solution pH, solution concentration, and mineral specific surface area. Three minerals with different reactivity (kaolinite, gibbsite, goethite) were studied to check the adaptability of the model and show the effect of mineral properties on reaction with phosphate. The experimental data as well as the kinetic models showed that high pH values, low concentrations of the phosphorus in the reacting solution, and small specific surface area will reduce retention of phosphate. Any other change of the three factors increases the retention capability. The model shows its flexibility in simulating phosphate reactions with different minerals. The results show promise for the miltifactor approximation of phosphate reactions with soil minerals in acid to neutral soils.
pH‐Dependent Boron Adsorption by Montmorillonite Hydroxy‐Aluminum Complexes
Authors: Keren R. , Gast R. G. 
Published: July 2010

AbstractBoron adsorption by hydroxy aluminum and by hydroxy aluminum montmorillonite complexes was determined as a function of pH and boron concentration in solution. Data from both experiments were compared with results computed according to the fitted adsorption coefficient. The agreement between calculated values and experimental results indicates that the phenomenological equation suggested by Keren et al. (1981) can be used in a modified form to predict boron adsorption on hydroxy aluminum as a function of both the boron concentration and the pH. Boron adsorption by both the physical and chemical mixtures (hydroxy aluminum and montmorillonite) was greater than by montmorillonite alone, with the physical mixture adsorbing the largest amount of boron.
Effect of Tillage, Cropping, and Fertilizer Management on Soil Nitrogen Mineralization Potential
Authors: El‐Haris M. K. , Cochran V. L. , Elliott L. F. , Bezdicek D. F. 
Published: July 2010

AbstractNitrogen mineralization potentials (No) were determined on soil from a long‐term crop rotation tillage experiment on a Palouse silt loam (fine‐silty, mixed, mesic Pachic Ultic Haploxerolls). Crop rotations included continuous winter wheat (Triticum aestivum L.), alternate winter wheat and (pea Pisum sativum L.), alternate winter wheat and spring wheat, and pea‐alfalfa (Medicago sativa L.)‐green manure, followed by 5 y of alternate spring wheat and winter wheat. Tillage variables were moldboard plowing, chisel plowing, or no‐till. Long‐term N fertilizer rate plots were also studied on a Ritzville silt loam (coarse‐silty, mixed, mesic Calciorthidic Haploxerolls). The tillage plots were cropped annually, whereas the fertilization rate plots were alternately fallowed and cropped to winter wheat with and without spring supplemental irrigation. Moldboard plowing resulted in uniform No values throughout the top 15 cm of soil, but N mineralization potential (No) was greater for chisel plowing and no‐till than for moldboard plowing at the 0‐ to 5‐cm depth and less at the 5‐ to 10‐ and 10‐ to 15‐cm soil depths. The net result was that average No for 0 to 15 cm was unaffected by tillage or crop rotation in the fall sampling. In the spring sampling, average No for either chisel plowing or no‐till was significantly higher than for moldboard plowing. Also, peas‐alfalfa‐green manure followed by alternate spring wheat‐winter wheat had a significantly higher No averge than both continuous winter wheat and winter wheat‐pea but was not different from winter wheat‐spring wheat. The No of the tillage and the crop rotation management treatments were significantly greater with samples obtained in the fall than from those obtained in the spring. Nitrogen mineralization potentials increased linearly with increased N rate on both the dryland and supplemental irrigated treatments. However, supplemental irrigation uniformly increased No compared with the corresponding nonirrigated treatments.
Eolian Influence on Development and Weathering of Some Soils of Point Reyes Peninsula, California
Authors: Crawford T. W. , Whittig L. D. , Begg E. L. , Huntington G. L. 
Published: July 2010

AbstractWind‐deposited sands have influenced characteristics of soils on Tomales Point at the northern end of Point Reyes Peninsula in California. The distribution of eolian materials, the interface between eolian and residual granitic parent materials, and mineral weathering were investigated in five pedons along a transect from near the edge of a wave‐cut bluff fronting on the Pacific Ocean to near the crest of a stabilized dune. Based upon distinct textural discontinuities, proportions of rounded and angular sands, organic carbon, and phyllosilicate species in silt and clay fractions, nonconforming zones of eolian materials over granitic residuum were clearly distinguished. The soils along the transect include members of coarseloamy, mixed, isomesic Pachic Haplustolls, coarse‐loamy, mixed, isomesic “Entic” Dystropepts, sandy, mixed, isomesic ustic Dystropepts, and mixed, isomesic Typic Ustipsamment families. A mineral weathering sequence involving the transformation biotite → vermiculite → smectite is evident within the buried granitic residuum along the transect.
Composition and Acidic Functional Group Chemistry of an Aqueous Chestnut Leaf Litter Extract
Authors: Blaser P. , Sposito Garrison , Holtzclaw Kenneth M. 
Published: July 2010

AbstractThe elemental composition, amino acid distribution, infrared spectrum, and carboxyl group content of a chestnut leaf (Castanea sativa L.) litter extract were determined. Proton titration data also were obtained by both continuous and discontinuous titrations. The overall titration endpoint could be identified directly by conductometric titration. Proton formation functions for the extract were computed from the two sets of titration data. In order to explain protonation during titration, the data were fitted to a simple chemical model by nonlinear regression analysis. From this calculation, the acidic properties of the litter extract could be modeled assuming three classes of acidic functional groups, with logarithms of the conditional protonation constants in the ranges: 4.00–4.25, 6.00–6.75, and 8.7–9.0.
Diffusion of Radon through Soils: A Pore Distribution Model
Authors: Nielson K. K. , Rogers V. C. , Gee G. W. 
Published: July 2010

AbstractA mathematical model was developed for calculating radon diffusion coefficients from water contents and pore size distributions of soil materials. The model accounts for radon diffusion in the air‐filled and the water‐filled pore space, for radon solubility in water, and for Knudsen diffusion in extremely small air‐filled spaces. The model considers soil pores to be composed of all possible serial combinations of the size increments from a measured pore size distribution. Diffusion coefficients for the resulting composite pores are computed and then used to calculate the overall diffusion coefficient of the soil by assuming parallel diffusion through all of the pore combinations. The resulting diffusion coefficients increase with the median pore diameter, and decrease with increasing soil water contents and with increasing widths of the soil pore size distribution. The model diffusion coefficients compare well with measured coefficients and with empirical calculations and are useful in evaluating the required soil cover thickness for uranium mill tailings reclamation.
Effects of Mica Content on Engineering Properties of Sand
Authors: Harris W. G. , Parker J. C. , Zelazny L. W. 
Published: July 2010

AbstractSand mixtures with variable weight percentage of mica (Wm) in a quartz matrix were evaluated to isolate the effects of mica content on compacted density, compressibility, shear strength, and bearing capacity. Maximum compacted density decreased linearly with increasing Wm, reflecting the inhibitory effect of platy grains on close‐packing of spheroidal grains. The initial tangent axial compression modulus (Eo), a reciprocal index of undrained compressibility, decreased logarithmically with increasing Wm. The relative effect of Wm on Eo was greater at higher confining pressures. Shear strength (φ), bearing capacity (qoh), and California bearing ratio (CBR) also logarithmically decreased with increasing Wm. Curves for Eo, φ, qoh, and CBR showed shoulders marking diminishing effects of mica additions beyond mica weight percentages of 10 to 15%. A hypothesis that the curvilinear nature of parameter‐vs.‐Wm relationships is due to the sensitivity of these parameters to mica‐quartz interaction at particle contacts is supported by observed linearity between the parameters and mica cleavage face area (MFA). The latter is indexed by mica frequency per 100 grains (Fm) measured by petrographic grain count on a specific size fraction. If the range of mica grain thicknesses is small relative to the range of diameters, then Fm for a single size fraction effectively approximates the MFA for the mica over the whole particle size range. Mica effects on certain engineering properties may be indexed more effectively by Fm than by Wm.
Phosphate Sorption by Soils: II. Sorption Measurement Technique
Authors: van Riemsdijk W. H. , van der Linden A. M. A. 
Published: July 2010

AbstractA computer‐controlled apparatus has been developed for measurement of P sorption by soils. A solution containing P is constantly pumped from a vessel through a soil column and back to the vessel again. Phosphorus concentration in the vessel can be assessed and regulated; constant, increasing and decreasing concentration are optional. The method of pumping solution through a column is convenient for relatively slow reactions and for reactions in which a high soil/solution ratio is required. When a high pumping rate is used, the results are comparable with classical batch experiments. The proposed method, however, has many advantages, e.g., avoiding mechanical disturbance of the soil particles and separating solids from solution. Eight soil samples can be examined at one time. This makes the apparatus suitable for routine as well as research experiments. The analytical part of the apparatus can easily be replaced; other ions of interest (K+, Mg2+, trace elements) can then be studied in the same way.
Nonuniform Leaching from Nonuniform Steady Infiltration
Authors: Philip J. R. 
Published: July 2010

AbstractThe two‐dimensional quasilinear steady flow equation is solved exactly for arbitrary periodic distribution of surface source strength v0 (x) (x, horizontal coordinate), both for flow to infinite depth and to a water table at finite depth. Solutions are given both for the Kirchhoff variable ⊗ and the stream function φ. They are explored in detail for . For each solution emphasis is placed on determining the limits on v0 (x) which ensure that the moisture potential Ψ ⩽ 0, so that the quasilinear formulation is applicable. This essential precaution has sometimes been disregarded. The presence of a water table strongly influences ⊗, but has relatively little effect on φ. This makes possible important mathematical simplifications. Remarkably, simple exact solutions are found for travel times. They reveal singularities in the travel‐time functions overlooked in previous work using a finite difference method. For large times, the family of isochrones behaves like a travelling wave with shape and velocity constant. Streamlines and isochrones are compared for a coarse soil (parameter α = 25 m−1) and a fine one (α = 0.25 m−1). Surface velocity differentials persist much more strongly for the coarse soil, which exhibits much greater horizontal variation of travel times. By one measure, nonuniformity of leaching is 7.8 times greater in the coarse soil than the fine one. A previous study of problems of this class concluded incorrectly that leaching is more uniform for saturated than for unsaturated flow.