bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature Dependence of Soil Water Retention Curves
Authors: Hopmans J. W. , Dane J. H. 
Published: July 2010

AbstractEffects of entrapped air volume and surface tension of soil solution are often regarded as the primary cause of temperature effects on the water retention curve. A procedure was developed to determine simultaneously the water characteristic curves and the volume of entrapped air for a glass beads medium and a Norfolk sandy loam (Typic Paleudults) at two temperatures. The volume change of entrapped air was determined from the change in volume of the free gas phase and the volume of water outflow from or inflow into a pressure cell. The results indicate a decrease in entrapped air volume with increasing temperature and suction. Surface tension values, calculated from capillary height measurements, showed the temperature coefficient of surface tension of soil solution to be smaller in magnitude than that of pure water. It was concluded that neither changes in entrapped air volume nor the temperature coefficient of surface tension of soil solution could account for the temperature effect on experimentally determined water characteristic curves of the two porous media.
Estimating Macroporosity in a Forest Watershed by use of a Tension Infiltrometer
Authors: Watson K. W. , Luxmoore R. J. 
Published: July 2010

AbstractThe ability to obtain sufficient field hydrologic data at reasonable cost can be an important limiting factor in applying transport models. A procedure is described for using ponded‐flow‐ and tension‐infiltration measurements to calculate transport parameters in a forest watershed. Thirty infiltration measurements were taken under ponded‐flow conditions and at 3, 6, and 15 cm (H2O) tension. It was assumed from capillarity theory that pores >0.1‐, 0.05‐, and 0.02‐cm diam, respectively, were excluded from the transport process during the tension infiltration measurements. Under ponded flow, 73% of the flux was conducted through macropores (i.e., pores >0.1‐cm diam.). An estimated 96% of the water flux was transmitted through only 0.32% of the soil volume. In general the larger the total water flux the larger the macropore contribution to total water flux. The Shapiro‐Wilk normality test indicated that water flux through both matrix pore space and macropores was log‐normally distributed in space.
Chemical Kinetics from a Thin Disc Flow System: Theory
Authors: Skopp J. , McCallister D. 
Published: July 2010

AbstractChemical kinetics information is difficult to obtain. Interpretation of data sets are subject to ambiguity both in regard to existing theory as well as in regard to the intrinsic chemical and physical processes. Clarification of these problems would aid in the understanding of time‐dependent reactions such as K release from soil. This study was undertaken to analyze a miscible displacement technique for obtaining chemical kinetics data. Theory is developed within the context of multiple working hypotheses where it is necessary to for‐mulate alternative empirical rate laws. Each rate law represents an alternative hypothesis, the consequences of which are deduced for a flow system. The appropriate differential equations are presented, and where possible, solved analytically. Solutions are presented for zero‐order, first‐order, and fractional‐order reaction terms. The investigation of complete kinetic formulations suggests that graphs of logarithm of concentration vs. time must be interpreted with care. Multiple line segments in a semilog graph may raise suspicions that multiple reaction mechanisms, multiple transport mechanisms, or backwards reactions may be significant. However, multiple line segments by themselves are not sufficient evidence to prove any of the possibilities.
Aggregate Structure and Carbon, Nitrogen, and Phosphorus in Native and Cultivated Soils
Authors: Elliott E. T. 
Published: July 2010

AbstractThis work corroborates the hierarchical conceptual model for soil aggregate structure presented by Tisdall and Oades (1982), extends it to North American grassland soils, and elaborates on the aspects relating to the influence of cultivation upon losses of soil organic matter. Aggregate size distributions observed for our soils are very similar to those of Australian soils, indicating that the microaggregate‐macroaggregate model may hold for a wide array of grassland soils from around the world. The use of two wetting treatments prior to sieving demonstrated that the native sod soil had the same general structural characteristics as cultivated soil but the macroaggregates were more stable. When slaked, native and cultivated soil present in the microaggregate size classes had less organic C, N, and P than the soil remaining as macroaggregates, even when expressed on a sand‐free basis. Moreover, the C/N, C/P, and N/P ratios of microaggregates were narrower than those of macroaggregate size classes. Much more C and N was lost than P under the conditions of this study. Element‐specific differences in microbial catabolic processes vs. extracellular enzyme activity and its attendant feedback controls are postulated to account for this difference. When the macroaggregates were crushed to the size of microaggregates, mineralizable C as a percent of the total organic C was generally greater for macro‐ than microaggregates early in the incubation for the cultivated soil and throughout most of the incubation for the native sod soil. Mineralizable N as a percent of the total organic N was greatest in macroaggregates even when the macroaggregates were not crushed. The macroaggregate‐micraggregate conceptual model is applied to help explain accumulation of soil organic matter under native conditions and its loss upon cultivation.
Effect of Lime and Organic Matter on Soybean Seedlings Grown in Aluminum‐toxic Soil
Authors: Ahmad F. , Tan K. H. 
Published: July 2010

AbstractOrganic matter is believed to be able to reduce Al toxicity in Ultisols. Since little information is available to substantiate this hypothesis, a greenhouse experiment was conducted to compare the effects of organic matter and lime on soybean [Glycine max (L.) Merr.] plants grown under increasing Al stress in a Bradson (Typic Hapludults) soil. Treatments, replicated three times, were 0, 25, 50, and 100 mg Al kg−1 pot−1, 0, 5, and 10% wheat (Triticum aestivum L.) straw, and the equivalent of 0, 1, and 2 Mg CaCO3 ha−1. After thorough mixing and incubation of the growth medium at field capacity for 20 d, five soybean seeds were germinated per pot and the five seeds allowed to grow for 30 d. The results indicated that shoot and root growth were severely affected by increased Al treatments. Aluminum toxicity started to seriously affect plant growth at 50 mg Al kg−1, and plants were hardly growing at 100 mg Al kg−1. However, plant growth in the Al‐toxic soil was improved substantially by the application of wheat straw or lime. The data suggest that treatments with wheat straw produced taller plants and greater dry weight contents of roots than was found in plants grown only with lime. Lime alone yielded good results, but lime in the presence of organic matter was more effective in reducing the effect of Al toxicity. The plants receiving wheat straw still contained relatively high levels of Al (3.7–7.4 mmol kg−1) in their shoots, but little damage could be detected. A tendency toward a decrease in N content was noticed in shoots of plants grown in the presence of wheat straw, but this was believed to have been caused by a temporary immobilization of N because of the application of straw. It was concluded that organic matter was as effective as lime in reducing Al toxicity.
Pedogenesis on the Edwards Plateau, Texas: III. New Model for the Formation of Petrocalcic Horizons
Authors: Rabenhorst M. C. , Wilding L. P. 
Published: July 2010

AbstractPetrocalcic horizons occur in a number of soils formed from Cretaceous limestone in central and west Texas (Edwards Plateau land resource area). Microfabric and stable C isotope analyses confirmed that the indurated carbonate zones are mostly of pedogenic origin. Multiple lines of evidence indicate that the petrocalcic horizons in these soils form through a process of limestone alteration by in situ dissolution and reprecipitation of carbonates. Evidence includes: (i) very low noncarbonate residue levels in petrocalcic horizons, which are comparable to levels in limestone bedrock; (ii) lithologic discontinuities between petrocalcic horizons and the overlying sola; (iii) presence, concentration, and particle size distribution of flourite in some petrocalcic horizons; (iv) presence of secondary silica within petrocalcic horizons indicating limited movement of components within this zone; and (v) microfabric analysis. This in situ process is in distinct contrast to commonly held models depicting translocation and accumulation of carbonates within a solum that was initially nonindurated. A model is proposed to describe the genesis of limestone‐derived petrocalcic horizons.
Goodness of Fit for Eight Water Infiltration Models
Authors: Davidoff B. , Selim H. M. 
Published: July 2010

AbstractEight infiltration models were investigated for their capability to describe water infiltration into soils. The models were; Philip's, Modified Philip's, Kostiakov's, Talsma and Parlange's, Horton's, and Lewis and Milne's. Field measurements of water infiltration were made using single ring infiltrometers on field plots established on a Norwood soil (Typic Udifluvents) with four long‐term (27 yr) winter cover crop treatments followed by cotton (Gossypium hirsutum L.) each year. The four treatments were; (i) common vetch (Vicia sativa), (ii) wheat (Triticum aestivum L.) + 60 kg/ha N; (iii) 60 kg/ha N, and (iv) check (no fertilizer or winter cover). Measured infiltration rates for the winter cover treatments were significantly higher than for the check plots. With the exception of Lewis and Milne's, all models showed good agreement with measured infiltration. Model parameters obtained by best fit of measured data, were significantly different among the winter cover treatments. Based on R2 values, Horton, Kostiakov and Philip equations provided best predictions over all other models. Soil bulk density and saturated hydraulic conductivity for two soil depths were not affected by the winter cover treatments.
Wheat Residue Management Effects on Soil Water Storage and Corn Production
Authors: Unger Paul W. 
Published: July 2010

AbstractCorn (Zea mays L.) grown in the semiarid southern Great Plains usually is irrigated fully because yields decline if water stress occurs at any time during the growing season, but the groundwater supply for irrigation is being depleted. To decrease the dependence of corn production on the declining groundwater supply, practices must be developed to improve the storage and use of precipitation. This study was conducted to determine the effects of residue management practices after wheat (Triticum aestivum L.) on precipitation (and preplant irrigation) storage during fallow; corn growth, yield, and seed quality; and water use and use efficiency by corn. The soil was Pullman clay loam (fine, mixed, thermic Torrertic Paleustolls). Because of high initial water contents at the start of fallow in 1982, relatively little water was stored from precipitation during the 1982 to 1983 fallow. For the 1983 to 1984 fallow, water storage was higher with disk and sweep tillage than with no‐tillage because the disk and sweep plots received a preplant irrigation to wet the tillage‐loosened soil. Water use by corn was not affected significantly by tillage in 1983, but was significantly lower with no‐tillage than with disk or sweep tillage in 1984. Corn grain yields were lowest with a no‐tillage standing residue treatment in 1983 due to N deficiency. In 1984, yields were not affected significantly by tillage, but avg 0.29 Mg/ha higher on fertilized than on nonfertilized low‐residue plots and 2.0 Mg/ha higher on fertilized than on nonfertilized high‐residue plots. Kernel weight (mg/kernel) and kernel test weight were affected significantly by tillage in 1983, but not in 1984. The study showed that crop residues can be managed to use a greater proportion of precipitation for producing corn, thus reducing the dependence on irrigation. However, soil fertility must be adequate for obtaining high yields, especially on high‐residue plots.
Effect of Soil Properties on Hydraulic Conductivity‐Moisture Relationships
Authors: Schuh W. M. , Bauder J. W. 
Published: July 2010

AbstractA field study was initiated to examine relationships between in situ hydraulic conductivity, soil‐water suction, and soil physical and chemical properties. Data from the study were used to describe relationships between soil properties and slopes of hydraulic conductivity‐soil water suction curves, i.e., In K vs. In S curve slopes (N). Soil particle size distribution and soil moisture desorption slopes were also evaluated. Sand to silt ratio (SA/SI), geometric mean particle diameter (GMD), and an index of geometric mean standard deviation (GMSD) were strongly related to slope of the In K vs. In S curves. These same parameters were also functionally related to observed differences between slopes of In K vs. In S curves and slopes of soil moisture desorption curves. Particle statistical indices and sand to silt ratio (SA/SI) were better predictors of curve slopes than were particle size percentages alone. An attempt was made to determine any correlations between K(S) and these soil properties and to estimate K(S), using selected soil physical properties. Using “best fit” predictive models, estimated K(S) values varied from measured values by a factor of 2 to 3 at the 60% confidence interval and by a factor of 7 to 12 at the 95% confidence interval.
A Microlysimeter Field Study of Solute Transport through a Structured Sandy Loam Soil
Authors: Richter Goetz , Jury William A. 
Published: July 2010

AbstractA 49‐d field experiment monitoring water and solute movement through a structured sandy loam is reported. Two field plots, each 15 by 30 m2 in area were instrumented with a 3 by 6 grid of small lysimeters containing undisturbed soil. Each lysimeter was weighed before and after irrigation and had effluent concentrations and drainage volumes recovered periodically. At the beginning of the experiment a pulse of KBr was added to the field and lysimeters with a mechanical lawn spreader and was leached into the soil with three water irrigations per week. Each plot received the same amount of water per irrigation but at intensities of 5.5 and 9.5 mm/h. Effluent breakthrough curves were constructed for each lysimeter. Substantial indication of preferential flow through part of the wetted pore space was observed in each lysimeter and the average breakthrough curves reflected substantial bypass. A statistical analysis of the drainage concentrations as a function of time showed the two fieldwide breakthrough curves to be identical. This not only showed that no intensity effect was apparent for solute movement on these plots but also indicated that the plot areas were large enough to incorporate all of the field scale variability within them. A calculation of solute flux from each lysimeter showed no correlation between instantaneous drainage and instantaneous solute concentration. As a consequence, we were able to show that the traditional method of estimating field scale solute flux as the product of average drainage and average concentration was adequate to describe solute leaching below the fields. Thirty‐six soil cores were taken in the two plots at the conclusion of the experiment. The average concentration depth patterns were similar for the two treatments and showed evidence of movement to at least 1.2 m during the lifetime of the experiment, implying that preferential flow continued to occur to greater depths.
Straw Decomposition in Irrigated Soil: Comparison of Twenty‐three Cereal Straws
Authors: Smith J. H. , Peckenpaugh R. E. 
Published: July 2010

AbstractThe objective of this research was to evaluate field decomposition of 23 cereal grain straws. Straw samples of ‘Fieldwin’ and ‘Owens’ soft white spring wheats (Triticum aestivum L.); ‘Borah’ and ‘McKay’ hard red spring wheat; ‘Nugaines’, ‘Daws’, ‘Lewjain’, ‘Stephens’, and ‘Hill 81’ soft white winter wheats; ‘Weston’, ‘Manning’, ‘Neeley’ hard red winter wheats; ‘Advance’, ‘Steptoe’, ‘Lud’, ‘Pirolene’, and ‘Klages’ spring barleys (Hordeum vulgare L.); ‘Kamiak’, ‘Boyer’, and ‘Schuyler’ winter barleys; Waid durham wheat (Triticum durum Desf.); and ‘Flora’ and ‘Palouse’ triticales (Triticale hexaploide Lart.); were buried in field plots. The straw bags were removed at intervals during 1 yr and analyzed for the amount of decomposition, and C and N contents. Final decomposition ranged from 54% for the Borah wheat straw to 75% for the Lud barley straw with about half of the straws decomposing 64 or 65%. The hard red spring wheat and triticale straws decomposed the slowest and two spring barley straws decomposed most rapidly, but no completely systematic differences were observed for different genera of straws. The original straw N concentrations ranged from 2.2 to 12.5 g/kg. Nine straws lost N during the incubation period from September to November while eight increased in N concentration during this time. In the next three incubation periods, from November to the following October, nearly every straw sample increased in N concentration. The total N weight in the straw increased to the May sampling and then decreased thereafter. This pattern indicates that the straw was releasing N as it was mineralized and became available for utilization by the growing corn crop. Carbon/N ratios ranged widely in the initial straw samples, becoming more nearly uniform as the decomposition process developed. The C/N ratios remained fairly high avg 41 for the final sampling even though the straw in every case had released N into the soil during the last sampling period. Regression analysis of total decomposition and change in weight of N in the wheat straw samples for the first 67‐d incubation in the field showed a linear relationship with decomposition during the year, decreasing with increasing N loss in the early stage.
Disposition of Fertilizer Phosphorus Applied to Winter Wheat
Authors: Sharpley A. N. 
Published: July 2010

AbstractThe disposition of fall‐applied fertilizer P (30 kg P ha−1) to winter wheat (Triticum aestivum L.) on four Southern Plains soils was investigated over a 4‐yr period under field conditions, using 32P as a tracer. Wheat was harvested 70 d after planting and P fertilization. An average increase in wheat dry‐matter yield (0.86‐1.94 Mg ha−1) and Bray‐1 P content of 0‐ 50‐mm surface soil (8.4‐34.4 mg kg−1) was observed following each fertilizer P application over the 4 yr. The major proportion of applied fertilizer P at wheat harvest remained in the soil as inorganic P (60‐76%) with little conversion to organic P (8‐15%). The proportion as Bray‐1 P ranged from 17 to 51%, decreasing with an increase in P sorption capacity of the soil. With consecutive fertilizer applications the proportion of fertilizer P as Bray‐1 P increased. Little movement of fertilizer P was observed below the 50‐mm depth (3‐7%). Recovery of fertilizer P by winter wheat decreased with consecutive fertilizer applications, ranging from 23 to 9% of that applied. The recovery was inversely related to the residual Bray‐1 P content of surface soil (Bray‐1 P content prior to each fertilizer application). Thus, although dry‐matter yield of winter wheat increased with consecutive fertilizer applications, fertilizer P recovery decreased as residual P made an increasing contribution to uptake of P by winter wheat. Consideration of residual soil P levels may, thus, reduce costly maintenance fertilizer P applications.
Ammonia Loss from Applications of Urea‐Ammonium Nitrate Solution to Straw Residue
Authors: McInnes K. J. , Ferguson R. B. , Kissel D. E. , Kanemasu E. T. 
Published: July 2010

AbstractThe increased use of urea and urea‐based N fertilizers along with an increase in crops under no‐ or reduced‐tillage practices may require changes in fertilizer management practices. Surface application of urea‐based fertilizer risks the loss of some N by volatilization of NH3. Our objectives were to assess the loss of NH3 and to simultaneously observe the associated N transformations and movements in the field following broadcast application of urea‐ammonium nitrate solution at a rate of 200 kg N ha−1 to soil with wheat (Triticum aestivum L.) straw residue cover. Also, we wanted to characterize the factors associated with the residue that might affect loss. A micrometeorological mass‐balance method was used to measure NH3 loss during two sequential field studies with different amounts of precipitation and irrigation. Volatilization losses showed diurnal patterns coinciding with fluctuations in residue temperature, residue water content, and wind speed. Cumulative NH3‐N losses were 7.6 and 16.6% of the N applied, respectively. The rate of urea hydrolysis and NH3 loss were quite sensitive to the availability of water. Simulated rainfalls with 2.5‐mm sprinkler irrigation increased NH3 loss. In both studies, peak volatilization rates came the 1st d after irrigation. The maximum measured rate of NH3 loss was 51 µg m−2 s−1 (1.5 kg N ha−1 h−1). Rainfalls of near 30 mm in both studies moved much of the remaining fertilizer below the 40‐mm soil depth. Wheat straw was found to have a urease activity of about 1830 mg urea kg−1 h−1, a pH near 8, and a H‐ion buffering capacity of 53 mmol kg−1 (pH unit)−1. These factors undoubtedly contributed to NH3 loss.
Phenolic Compounds in Soils of Hydrosequences and Developmental Sequences of Spodosols
Authors: Vance G. F. , Mokma D. L. , Boyd S. A. 
Published: July 2010

AbstractThe extraction of low molecular weight phenolic compounds from pedons of two hydrosequences and two developmental sequences was investigated. Seven phenolic compounds were identified in Na4P2O7 extracts: three benzoic acids—protocatechuic, p‐hydroxybenzoic, and vanillic acids; two aldehydes—p‐hydroxybenzaldehyde and vanillin; and two cinnamic acids—trans p‐coumaric and ferulic acids. Identification of the compounds was by cochromatography with authentic standards. In general, the total phenolic content increased going from the somewhat excessively drained to the somewhat poorlydrained members of the hydrosequences and from the least‐developed to the most‐developed members of the Spodosol developmental sequences. The substituted benzoic acids accounted for most of the phenolic compounds in all horizons. While p‐hydroxybenzoic and vanillic acids dominated in the surface horizons, protocatechuic acid was found in higher concentrations in the spodic horizons. Aluminum and Fe maxima also occurred within horizons that had protocatechuic acid as the prevalent phenolic compound. The results suggest that Al and Fe chelate complexes with protocatechuic acid may play a role in the formation of spodic horizons.