bluuebunny/crossref_metadata_2025_split huggingface dataset:
Controlled Wheel Traffic Effects on Soil Properties in Ridge Tillage
Authors: Liebig M. A. , Jones A. J. , Mielke L. N. , Doran J. W. 
Published: July 2010

AbstractRidge‐till is gaining widespread use on highly erodible land. Matched‐width equipment has allowed producers to establish permanent traffic lanes in ridge‐till. The establishment of permanent traffic lanes and a lack of preplant tillage has increased concern about soil compaction. The purpose of our study was to assess the effects of long‐term controlled tractor wheel traffic on soil properties of a ridge tillage system. This research was conducted on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) in southeastern Nebraska. A split‐split‐plot design was employed to evaluate differences in soil properties among corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] crops; row, trafficked interrow, and nontrafficked interrow positions; and depths of 0 to 7.5, 7.5 to 15, and 15 to 30 cm. Axle load of the tractor used on the plots was 4 mg. Sampling was conducted in the summer after ridging. Most variability in soil properties among positions was confined to the 0‐ to 7.5‐cm depth. Bulk density, soil strength, aggregate mean weight diameter (MWD), water content at field capacity (FC), and water content at wilting point (WP) tended to be highest in the trafficked interrow and least in the row. Saturated water content and gravitational water (GW) were generally highest in the row and least in the trafficked interrow. Soil strength in the trafficked interrow was 56% greater than the nontrafficked interrow and 104% greater than the row. Similar, but less pronounced differences among positions were also observed for bulk density. Aggregate mean weight diameter in the trafficked interrow indicated that wheel traffic resulted in larger aggregates while ridging resulted in smaller aggregates in the 0‐ to 7.5‐cm depth of the row. Mean saturated hydraulic conductivity (Ksat) in the trafficked interrow was approximately one‐quarter of the mean value for the nontrafficked interrow and row. Organic C and TN were greater in the row than the interrow positions. The influence of tractor wheel traffic on soil properties was largely dissipated by the 15‐ to 30‐cm depth. Because of the dissimilarity in soil properties among positions, ridge‐tilled fields should be conceptualized and managed as three distinct soil zones, not as a single unit.
Soil Burrowing and Mixing by a Crayfish
Authors: Stone E. L. 
Published: July 2010

AbstractObservation of rapid lateral water flow through, rather than over, the surface of a level, clayey, mixed, thermic Typic Albaquult (Bladen series) prompted study of the abundant burrows of a crayfish, Procambarus rogersi rogersi Hobbs. The area was a 20‐yr‐old experimental plantation of slash pine (Pinus elliottii Engelm. var. elliottii), with a wide range in tree growth, ground vegetation, and O‐horizon thickness. The objective was to better understand the elaborate macropore system and its consequences for mixing the surface layers of a very poorly drained soil where other burrowing animals were lacking. Excavation of burrows and burrow casts revealed galleries, 4 to 10 cm in diameter, > 1.5 m long, chiefly in the upper 30 cm of soil but with vertical shafts to >1 m in depth. Fifty to 80% of randomly located 0.1‐m2 subplots in well‐forested plots had from one to five openings through the mineral soil surface into surficial burrows, demonstrating widespread distribution of the latter. Bands of rock phosphate broadcast on the surface 20 yr previously provide a marker of cumulative mixing; almost one‐half of the residual P had been mixed into the 5‐ to 15‐cm depth by crayfish activity.
Controls on Soil Solution Chemistry in a Subalpine Forest in North‐Central Colorado
Authors: Arthur M. A. , Fahey T. J. 
Published: July 2010

AbstractHigh‐elevation ecosystems in the western USA are potentially susceptible to increased inputs of strong acids. A long‐term research project was established to identify the processes controlling surface water chemistry and to evaluate the sensitivity of Loch Vale Watershed in Rocky Mountain National Park, Colorado, to acid precipitation. Using lysimeters, we estimated the concentration and flux of major solutes in the Oie and B horizons in an old‐grown Englemann spruce (Picea engelmannii Parry ex Engelm.) and subalpine fir [Abies lasiocarpa (Hook.) Nutt.] forest, and in an adjacent site disturbed by a snow avalanche. In the forested site, most solutes were highly concentrated in soil solutions during the initial stages of snowmelt, and concentrations declined rapidly to low levels in the first 4 to 6 wk of snowmelt. Surface water chemistry in Loch Vale Watershed is controlled principally by mineral weathering. During the early stages of snowmelt, however, the flushing of solutes, especially N, S, and C, from forest soils (which comprise only 6% of the study area) exerts an important influence. Rates of cationic denudation per unit area were 3.5 times higher in the forest (131 µmolc m−2 yr−1) than in the whole watershed (38 µmolc m−2 yr−1) probably because of H+ exudation from roots during nutrient uptake and the generation of organic acids in the forest soils. Rates of N mineralization and nitrification as well as concentrations of NO3 in the soil solution were higher in the second year after forest disturbance from a snow avalanche than immediately following the disturbance, indicating a delayed nitrification response. Significant amounts of NH4 and NO3 were temporarily stored in extractable forms in the soil during the first year after the disturbance. Although precipitation inputs and theoretical mineral weathering can explain the total annual solute flux from Loch Vale Watershed, the effects of forest soil solutes may be important during the initial stages of snowmelt and following large‐scale disturbance.
Errors Associated with the Combination Method for Estimating Soil Heat Flux
Authors: Massman W. J. 
Published: July 2010

AbstractErrors are common to all methods of measuring soil heat flux. This study examines some of the errors that result when estimating the heat storage term (employed by the combination method) from measurements of the time rate of change of soil temperatures. Based on analytical models of the vertical profiles of soil temperature, my results indicate that errors of ±3 to 10% in the estimate of soil beat flux can result from following recommended procedures. For homogenous soils, these errors can be reduced by about 67% using two soil thermometers with unequal weighting to estimate the heat storage term. However, minimizing these errors for inhomogeneous soils may not be possible without detailed information on the vertical structure of the soil thermal properties.
Phosphorus Sorption as Influenced by Added Urea in Two Eastern Canadian Soils
Authors: Fan M. X. , MacKenzie A. F. , O'Halloran I. P. 
Published: July 2010

AbstractThe interaction of urea with P in soil‐fertilizer microsites may have an important effect on P availability to crops. A laboratory study was conducted to evaluate the effect of urea on P reactions in two eastern Canadian soils (Typic Humaquepts). Phosphorus sorption was studied by equilihrating soil samples pretreated with four levels of urea for 24 h with six rates of P in either 0.01 M CaCl2 or 0.03 M KCl solutions. Phosphorus desorption was determined by sequentially extracting the residual soil with 0.01 M CaCl2 or 0.03 M KCl, and 0.5 M NaHCO3. Urea application increased the soil pH (0.01 M CaCl2) in the fertilizer microsites from 5.2 to 7.3 in the Ste Rosalie soil and from 5.9 to 7.4 in the Ormstown soil. These pH changes had variable effects on soil P sorption characteristics, depending on soil and electrolyte. Phosphorus sorption increased with increasing urea and pH when using CaCl2 as the electrolyte. Added urea and pH had little effect when KCl was used, indicating that the urea effect on P sorption was influenced by Ca content. The effect of urea was not significant at P rates <320 mg P kg−1 soil. The observed increase in P sorption and decrease in solution P with added urea was probably related to precipitation of Ca‐P compounds and the shift from H2PO−4 to HPO2−4 at higher pH values. Urea application increased 0.5 M NaHCO3 extractable P and reduced nonextractable P in both soils. For soils with high Ca content, urea application with P fertilizer could reduce P concentration in soil solution and P mobility because of the increase in P sorption and P buffer capacity, but increase available P as expressed by NaHCO3‐extractable P.
Organic Matter Role in Illitic Soil Colloids Flocculation: II. Surface Charge
Authors: Heil Dean , Sposito Garrison 
Published: July 2010

AbstractThe ability to predict the effect of various factors on soil flocculation depends on a knowledge of the mechanisms by which those factors operate. The purpose of this study was to investigate the mechanisms that control the effects of organic matter content, pH, and bivalent cation type on soil flocculation. The electrophoretic mobility of an illitic soil before and after treatment with H2O2 was measured at a soluble Ca or Mg charge fraction of 0.0 to 0.9 at pH 6, and at pH 4 to 9 and a soluble Ca charge fraction of 0.0 or 0.5 The change in the net particle charge as pH was increased from 6 to 8 at a soluble Ca concentration of 0.65 and 2.26 mol m−3 was determined from proton and Ca ion titrations. Electrophoretic mobility was independent of both Ca vs. Mg and organic matter content, which suggests that the influence of these factors on flocculation was caused by steric effects. The effect of pH on soil flocculation and electrophoretic mobility in the presence or absence of organic matter, on the other hand, was consistent with an electrostatic mechanism. The change in net particle charge from pH 6 to 8 became more positive as the soluble Ca concentration was increased, and this result was modeled in terms of competitive binding of H+ and Ca2+ by soil functional groups.
Interaction of Mugineic Acid with Synthetically Produced Iron Oxides
Authors: Inoue K. , Hiradate S. , Takagi S. 
Published: July 2010

AbstractInteractions between mugineic acid (MA) purified from root washings of Fe‐deficient barley (Hordeum vulgare L., cv. Minorimugi) and synthetically produced Fe oxides (goethite, hematite, lepidocrocite, and ferrihydrite) were studied in the equilibrium pH range of 3 to 11. The amount of MA adsorbed on Fe oxides was related to their specific surface area and followed the order: ferrihydrite > > goethite ≥ lepidocrocite ≥ hematite. The adsorption of MA on Fe oxides also decreased with increasing equilibrium pH and increased with increasing MA concentration. The MAFe complexes were also adsorbed on Fe oxides, especially on ferrihydrite and goethite, at pH 3 to 7. At pH > 10, however, MAFe complexes were decomposed to MA and Fe(OH)3 colloids. The amount of Fe dissolved from Fe oxides by MA was in the following order: ferrihydrite > > lepidocrocite ≥ hematite = goethite. The Fe dissolution from Fe oxides by MA was related to their crystallinity and the maximum amount of Fe dissolved by MA was in the pH range of 7 to 8. The amounts of MA adsorbed on Fe oxides and Fe dissolved by MA from Fe oxides depended on MA concentration, pH, and the type and the amount of Fe oxides added in the system. The Fe dissolution processes from Fe oxides by MA could involve two factors, namely (i) the complexation of MA with Fe exposed on the surface of Fe oxides by ligand exchange; and (ii) the release of MAFe complexes from adsorption sites on Fe oxides by nucleophilic substitution. Our data further clarify the chemistry of Fe nutrition of graminaceous plants in Fe‐deficiency‐causing soils.
Ammonia Volatilization from Liquid Hog Manure: Influence of Aeration and Trapping Systems
Authors: O'Halloran I. P. 
Published: July 2010

AbstractMeasurements of N loss from manures may reflect differences in the types of manures and methodologies used. This study's objective was to test the suitability of 0.32 M H3BO3 and 0.9 M H2SO4 for trapping NH3 volatilized from liquid hog manure (LHM) under various experimental conditions. Samples of LHM were incubated for 15 d in containers with aeration outlets positioned above, at the middle, or at the bottom of the LHM. Lowering the position of the aeration outlet increased both the pH of the LHM and the amount of NH3 volatilized. More NH3 was trapped in H2SO4 than H3BO3, and the difference in trapping efficiency of the two acids increased with their NH3 concentrations. Neither the amount of NH3 trapped nor the exponential relationship between the NH+4 concentrations of two H3BO3 traps in series was influenced by changing the bubble path length through the acid. Regression analysis indicated that >95% trapping efficiency was obtained only when the NH3 concentration of H3BO3 was below 0.42 mg N mL−1, much lower than the 0.9 mg N mL−1 reported to be the limit for using H3BO3 in the Kjeldahl method. Even when using two traps in series, H3BO3 appeared to trap less NH3 than H2SO4. Amending LHM with sucrose lowered the pH of H3BO3 used to trap volatilized NH3, thereby interfering with NH3 determination and rendering H3BO3 unsuitable for determining NH3 volatilization. Investigators who use H3BO3 to measure NH3 volatilization in other systems must ensure that similar interferences do not occur and that NH3 concentrations do not exceed 0.42 mg N mL−1.
Fractal Description of Soil Fragmentation for Various Tillage Methods and Crop Sequences
Authors: Eghball Bahman , Mielke Lloyd N. , Calvo Guillermo A. , Wilhelm W. W. 
Published: July 2010

AbstractSoil structure has been difficult to quantify and, at best, has been studied semiquantitatively. Fractal representation of soil fragmentation can provide an indication of soil structure. The purpose of our study was to use fractal analysis to quantify soil fragmentation under various tillage and crop sequence treatments at different times during the growing season. We collected soil samples from four tillage treatments (established 10 yr earlier) of chisel, disk, no‐till, and moldboard plow in factorial arrangement with two crop sequences of corn (Zea may L.)‐soybean [Glycine max (L.) Merr.]‐corn (C‐S‐C), and soybean‐corn‐soybean, (S‐C‐S) on a Sharpsburg (fine, montmorillonitic, mesic Typic Argiudoll) soil. Aggregate‐size distribution was used to calculate fractal dimension (D) for each treatment. Higher D values indicate greater soil fragmentation and a soil dominated by smaller aggregates. The opposite is true for lower D values. Differences in soil fragmentation observed for tillage treatments after autumn tillage became even greater over winter. Soil fragmentation increased over autumn and winter, with D increasing in the order of plow > chisel > disk > no‐till. Formation of larger soil aggregates increased during the growing season for all tillage systems. The D values for C‐S‐C were smaller than S‐C‐S in the no‐till, indicating that the previous year's corn in C‐S‐C provided more large aggregates. Soybean appears to have negative effects on large‐aggregate formation in no‐till. Aggregate densities, averaged across tillage and crop sequence, increased from 1.25 to 1.77 Mg m−3 as the aggregate diameter decreased from 6.38 to 0.162 mm. Fractal analysis was found to be useful in determining soil fragmentation differences due to different tillage methods and crop sequences.
Erosion Processes on Arid Minespoil Slopes
Authors: Sidle Roy C. , Brown R. W. , Williams B. D. 
Published: July 2010

AbstractSurface wash and dry ravel erosion rates from minespoil were measured for 4.7 yr after initial reclamation at a site in western Nevada. Average annual total erosion from all 15 plots ranged from 0.48 to 1.10 Mg ha−1. Neither mulching treatment nor slope gradient (3:1 vs. 2:1) significantly affected surface wash from reclaimed minespoils. About 70% of the total wash load from the entire study period occurred during two midsummer to autumn periods (1989 and 1990) in which the most intense storms occurred. Southwest‐facing slopes (windward) had significantly higher surface erosion compared with northeast‐facing slopes (leeward). The higher surface roughness encountered on 2:1 slopes appeared to more effectively control surface wash than gentler (3:1) slope gradients or early‐stage vegetative cover. Straw mulch significantly reduced ravel erosion from the relatively smooth 3:1 slopes. Mulch treatment was not effective in reducing ravel erosion from rougher, 2:1 slopes. Windward (southwest‐facing) slopes had significantly higher ravel erosion than northeast‐facing slopes. Ravel rates were not as directly affected by rainfall intensity as were surface wash rates. Regressions of surface wash with EI (rainfall energy‐intensity factor) were best with short‐term intensities (i.e., EI5, R2 = 0.94); regressions of ravel with EI were best using longer term intensities (EI30; R2 = 0.83). Except for very dry collection periods (including autumn to spring), surface wash exceeded ravel.
Agroecosystem Approach to Soil and Crop Management Research
Authors: Peterson G. A. , Westfall D. G. , Cole C. V. 
Published: July 2010

AbstractResearch techniques that have greatly advanced agronomic science in the 20th century, and have enhanced our knowledge of cause and effect, have been accompanied by reductionism. As a result, much valuable research has been accomplished, but less synthesis of results has occurred that provides answers to landscape‐level research questions. We propose that a systems approach to the study of soil and crop management problems is a useful technique that tests our present research knowledge in a way that answers practical agricultural problems and simultaneously identifies gaps in basic research knowledge. We have used a problem common to the Great Plains to demonstrate the systems approach: minimizing the soil‐ and environment‐degrading practice of summer fallowing and simultaneously increasing farm profitability. Although much is known about summer fallow at specific locations, less is known about extrapolating this knowledge across soil and climatic gradients. We show that intensified crop sequences under no‐till techniques can replace summer fallow in many environments, and increase the productivity per unit of water received. Simultaneous reductions in the damaging factors of summer fallowing, in particular soil erosion and organic matter losses, also have occurred. We are researching the problem at a landscape level without losing the ability to detect causae and effect, and are able to simultaneously conduct basic research on soil nutrient cycling and water budgets. The approach also is being used effectively as an adult educational tool, thereby facilitating the transfer of technology from the researcher to the producer.
Flux‐Averaged Concentrations for Transport in Soils Having Nonuniform Initial Solute Distributions
Authors: Toride Nobuo , Leij Feike J. , van Genuchten Martinus Th. 
Published: July 2010

AbstractThe need to distinguish between volume‐averaged or resident concentrations (cr) and flux‐averaged or flowing concentrations (cf) is now widely accepted. Flux‐averaged concentrations associated with the convection‐dispersion equation (CDE) have been mostly used for solute transport problems involving uniform initial distributions. We present flux‐averaged concentrations for nonuniform initial distributions using analytical solution methods for a semi‐infinite soil system and numerical methods for a finite system. Mathematically, cf is equivalent to cr associated with a first‐type inlet condition (rather than a third‐type condition) only for semi‐infinite soil profiles having uniform initial conditions. We show that, for a stepwise initial distribution, cf can be both negative or much greater than the initial concentration of cr, especially during the early stages of solute displacement. This physically odd situation results from the fact that cf represents a solute flux rather than a directly measurable volumetric concentration. Flux‐averaged concentrations at the exit of a finite soil column with a uniform initial distribution are nearly identical to cf for a semi‐infinite system when the column Peclet number is greater than ≈ 5. However, if the initial distribution involves a high gradient in cr near the exit, cr values for finite and semi‐infinite systems at the exit can be very different, similarly as those for cr, because of the adoption of different outlet conditions.
Error Analysis of the Heat Pulse Method for Measuring Soil Volumetric Heat Capacity
Authors: Kluitenberg G. J. , Ham J. M. , Bristow K. L. 
Published: July 2010

AbstractA recently developed heat pulse method allows rapid, automated measurements of the volumetric heat capacity (ρc) of soil. Estimation of ρc is accomplished by using a model for the conduction of heat away from an instantaneously heated infinite line source (IHILS). This study was conducted to examine possible errors in the use of the IHILS theory by comparing the IHILS model with three other models that account for the following characteristics of the heat pulse apparatus: finite probe length, cylindrical heater geometry, and short‐duration (noninstantaneous) heating. For typical probe geometry and heating times, estimates of ρc obtained from the IHILS theory were within 1% of the estimates obtained by using the more rigorous models. The most significant error resulted from approximating short‐duration heating with instantaneous heating in the IHILS model. A generalized error analysis is presented that permits direct graphical estimation of errors for different probe geometries, different heating times, and different soil thermal properties. First‐order error analysis was also used to examine potential error in ρc as a result of errors in probe spacing (r), temperature maximum (Tm), and heat input (q), the measured quantities that are used in the IHILS model to estimate ρc. Relative errors of 1% in measuring q and Tm lead to relative errors of 1% in ρc, whereas a relative error of 1% in r resulted in a 2% error. Measurement error in r and Tm limits the precision achievable with this method.