bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crop Species, Amendment, and Water Quality Effects on Selected Soil Physical Properties
Authors: Bauder J. W. , Brock T. A. 
Published: July 2010

AbstractSaline and sodic soils have developed in some irrigated areas of Montana. Cropping systems that promote maximum efficacy of surface‐applied amendments for reclamation need to be identified. Effects of crop species, amendment, and water quality on alteration of selected physical properties of a Haverson silty clay (fine‐loamy, mixed [calcareous], mesic Ustic Torrifluvent) were compared. Crops grown in lysimeters and compared with a noncropped control were alfalfa (Medicago sativa L.), barley (Hordeum vulgare L.), and sorghum‐sundangrass [Sorghum bicolor (L.) Moench‐ S. × drummondii (Steudel) Millsp. & Chase], commonly referred to as sordan. Soil amendments included a check, gypsum (CaSO4·2H2O), phosphogypsum (CaSO4·2H2O with <1% [w/w] P), and MgCl2. Lysimeters were irrigated with water having either a total dissolved solids (TDS) concentration of 0.75 g L−1 and a sodium adsorption ratio (SAR) of 1.15 or TDS of 1.65 g L−1 and SAR of 7.01 until three barely crops were successively grown. The presence of a crop caused a significant increase in bulk density in all lysimeters and a significant decrease in total porosity, compared with the uncropped control treatments. Barley caused the greatest decrease in total porosity, followed by alfalfa, then sordan. Total porosity decreased nearly 0.1 m3 m−3. The result was a significant increase in number of micropores (<0.149 × 10−2 mm radius) and a disproportionately greater decrease in number of macropores (>1.49 × 10−2 mm radius). Soil water release characteristics differed among the different crop treatments. Neither amendment treatment nor irrigation water quality had a significant effect on either porosity, pore‐size distribution, or bulk density. Results of this study indicate that crop selection and rotation may affect the significance of surface‐applied amendments used for reclamation and leaching of Na‐ and salt‐affected soils.
Dynamic Oxygen and Carbon Dioxide Exchange between Soil and Atmosphere: II. Model Simulations
Authors: Ouyang Y. , Boersma L. 
Published: July 2010

AbstractAn important general objective for modeling gaseous transport through unsaturated soils is to provide better understanding of gas exchange between the terrestrial ecosystem and the atmosphere. A more specific objective is the evaluation of problems of soil aeration. We present sensitivity analyses of a mathematical model developed for the dynamic exchange of O2 and CO2 between soil and atmosphere. We also present simulations to evaluate changes in concentrations during cycles of infiltration, evaporation, and redistribution during which simultaneous transport of water, heat, O2, and CO2 was involved. Simulation was also used to evaluate possible effects of O2 and CO2 concentrations on the rate of root growth; effects of a compacted layer on the simultaneous transport of water, O2, and CO2; effect of the presence of a crop canopy on concentrations of O2 and CO2 in the soil; and an evaluation of possible nonideal behavior of CO2 molecules in the gas phase of the soil. Results emphasize the important effects of rainfall, evaporation, and root respiration on O2 and CO2 concentrations in the soil. Simulations show that root growth below a compacted soil layer may be restricted by low O2 concentrations resulting from limited diffusion through the compacted layer. The presence of a crop canopy has a decisive effect on concentrations of O2 and CO2 at the soil surface, thereby affecting the concentrations of those gases in the root zone.
Transport of Imazethapyr in Undisturbed Soil Columns
Authors: O'Dell J. David , Wolt Jeff D. , Jardine Philip M. 
Published: July 2010

AbstractThe disappearance of imazethapyr [(±)‐2‐[4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazole‐2‐yl]‐5‐ethyl‐3‐pyridinecarboxylic acid] from soil solution was investigated to evaluate the transport of imazethapyr in undisturbed soil columns. Soil treated with imazethapyr was incubated for 0.15, 1, 2, 4, 8, and 16 d, at which times soil solution was obtained by vacuum displacement. Bromide and imazethapyr were then applied to the surface of undisturbed soil columns followed by application of deionized water at approximately 3 cm d−1. The removal of imazethapyr from solution (i.e., sorption) exhibited biphasic kinetics and was well described (R2 = 0.99) by two simultaneous first‐order reactions. The initial reaction was essentially instantaneous and the secondary reaction was time dependent. The classical convective‐dispersive (CD) equation was used to describe solute transport through undisturbed soil columns. Bromide and imazethapyr breakthrough curves (BTCs) were displaced to the left of one pore volume and showed considerable tailing, with imazethapyr BTCs retarded in relation to Br‐. This was indicative of preferential solute mobility in the soil. Imazethapyr BTCs were similar to model simulations using transport parameters determined from Br‐ BTCs, kinetic parameters from the imazethapyr solution concentration decay curves, and retardation factors calculated from the distribution coefficient at the 1‐d incubation time. Model simulations using retardation factors from later times predicted increasingly delayed imazethapyr breakthrough with lower peak concentrations than measured. Preferential flow paths apparently reduced attenuation of imazethapyr as predicted from equilibrium adsorption measurements.
Predicting Calcium and Magnesium Precipitation in Saline Solutions following Evaporation
Authors: Miyamoto S. , Pingitore N. E. 
Published: July 2010

AbstractSalt precipitation associated with water evaporation from saline water is a fundamental process occurring in irrigation and drainage waters and aquaculture ponds. This study examined five different methods of predicting Ca and Mg precipitation in saline solutions following evaporation: (i) Ca precipitation as calcite; (ii) Ca precipitation as metastable CaCO3, such as vaterite; (iii) CaCO3 plus Mg precipitation as magnesite or nesquehonite; (iv) formation of homogeneous magnesian calcite and resulting changes in solubility; and (v) formation of heterogeneous magnesian calcite particles having various levels of Mg substitution and solubility. Computed results were then compared with laboratory data in which 10 saline solutions simulating irrigation waters were concentrated up to 30‐fold through evaporation at 25 °C. Precipitated salts from selected cases were also analyzed by x‐ray diffraction and an electron probe. Results indicated that Ca precipitation is extensive, and that Mg precipitation or substitution is minimal, except when HCO3 concentrations greatly exceed Ca concentrations. The presence of Mg reduced the rate of precipitation in evaporating solutions, and provided quasi‐stable dissolved Ca concentrations following evaporation, which were significantly higher than calcite solubility. X‐ray diffraction analyses indicated the formation of magnesian calcite with a Mg molar content up to 7% with some aragonite. Electron probe microanalyses supported a theoretical prediction (based on Method v) that magnesian calcite particles are heterogeneous, having higher Mg contents toward the particle surface. Calcium and Mg concentrations in the saline solutions following evaporation were best estimated by Method v, which incorporated the coevolution of the composition of solution and solid phases.
Light‐Fraction Organic Matter in Soils from Long‐Term Crop Rotations
Authors: Janzen H. H. , Campbell C. A. , Brandt S. A. , Lafond G. P. , Townley‐Smith L. 
Published: July 2010

AbstractLight‐fraction (LF) material, comprised largely of incompletely decomposed organic residues, may provide a sensitive indicator of the effects of cropping practices on soil organic matter. The objective of our study was to determine the influence of agronomic variables on soil LF content, and to evaluate the LF as a measure of labile organic matter. Soils from three long‐term crop rotation studies in Saskatchewan, Canada, were analyzed for LF content and composition. The experiments, established at Indian Head (Udic Boroll), Melfort (Udic Boroll), and Scott (Typic Boroll), included wheat (Triticum aestivum L.) based rotations varying in fertilizer application, frequency of summer fallow, and cropping sequence. The LF of the surface soil (0–7.5 cm) accounted for 2.0 to 5.4%, 3.3 to 7.1%, and 7.1 to 17.5% of the organic C at Indian Head, Melfort, and Scott, respectively. Within each site, the LF content was generally highest in treatments with continuous cropping or perennial forages and lowest in those with a high frequency of summer fallow. Fertilizer application generally favored LF accumulation. Differences in LF content among sites and treatments were attributed to variable residue inputs and rates of substrate decomposition. The respiration rate and microbial N content of soils was strongly correlated with the LF content, suggesting that the LF is a useful indicator of labile organic matter. Nitrogen mineralization was also correlated with LF content, though the relationship was less consistent, presumably because the high C/N ratio of the LF induced temporary N immobilization. The LF content is a sensitive indicator of the effects of cropping on soil organic matter content and composition but, because of its transient nature, probably reflects primarily short‐term effects.
Soil‐Based Irrigation and Salinity Management Model: I. Plant Water Uptake Calculations
Authors: Cardon G. E. , Letey J. 
Published: July 2010

AbstractA new soil‐based model for irrigation and soil salinity management has been formulated to rectify deficiencies in existing soil‐based models with respect to mass balance, numerical stability, and the treatment of plant growth and water uptake dynamics. The advantages of the new model are: (i) the treatment of temporal variation in potential transpiration (TP) and rooting depth and distribution, (ii) the adjustment of TP based on feedback from simulated crop water uptake, (iii) the provision for treating growth‐stage‐specific crop tolerance to salinity and water stress, and (iv) the provision for multiseasonal simulation through the treatment of noncropped periods. A sensitivity test and a comparison of model calculations to experimental data were conducted. The model tended to overpredict relative crop yield from a field experiment based on relative crop water uptake calculations. The mean simulated relative yield was 7% higher than observed with a root squared error (RMSE) of 8.8% relative yield. Willmott's d index (a statistical index of agreement between measured and observed data) result was high 0.79 (perfect agreement = 1.0).
Crusting, Runoff, and Erosion Response to Soil Water Content and Successive Rainfalls
Authors: Bissonnais Yves Le , Singer Michael J. 
Published: July 2010

AbstractSoil crusts reduce the water infiltration rate and may induce the erosion process by increasing runoff. We investigated the effects of initial soil water content and successive rainfalls on soil crusting, subsequent runoff, and erosion. Surface samples of Capay silty clay loam (fine, montmorillonitic, thermic Typic Chromoxerert) and Solano silt loam (fine‐loamy, mixed, thermic Typic Natrixeralf) were packed into 0.37‐m2 plots inclined at 9% slopes and subjected to simulated rainfall applied at 40 mm h−1 as 3.2‐mm‐diam. drops falling 2.5 m. Three successive 1‐h rainfalls were applied to initially air dried or prewetted soils. Water splash, runoff, soil splash, and wash materials were collected at 5‐min intervals. Post‐rainfall photographs of crusted soil surfaces provided additional morphological evidence to support conclusions drawn from quantitative data. Prewetting reduced crust development, runoff, and erosion and the differences remained significant even during the third rainfall. For the initially air dry soils, erosion rates and runoff reached steady state after 25 mm of rain during the first rainfall, and were the same for the second and third rainfalls. For prewetted soils, runoff and erosion were lower, did not reach steady state during the first event, and increased during each subsequent rainfall. The infiltration rate for initially air dry soils was 20 times lower than for prewetted soils after 40 mm of the first rainfall, and remained 10 and 2 times lower after the second and third rain, respectively. The crust was still not completely developed on prewetted soils after 120 mm of cumulative rainfall.
Seed‐Zone Temperature and Moisture Conditions under Conventional and No‐Tillage in Alaska
Authors: Bidlake W. R. , Campbell G. S. , Papendick R. I. , Cullum R. F. 
Published: July 2010

AbstractIdentification of tillage and residue management options that favor crop production and promote soil conservation is an important research objective. A study was conducted to compare seed‐zone temperature and moisture conditions under conventional and no‐tillage regimes during stand establishment of spring barley (Hordeum vulgare L.) in interior Alaska. The approach was to monitor soil temperature and moisture conditions in a conventional tillage and a no‐tillage plot, and to develop and apply a mechanistic model of heat and moisture transport for partially frozen soil‐crop residue systems. The model simulates temperature and vapor density profiles and radiation transfer within the crop residue canopy and soil temperature and soil water matric potential. Both measured and simulated results indicated that the no‐tillage soil was cooler and wetter than the conventional tillage soil. The average daily difference between simulated temperature at the 6‐cm depth was 2.5°C during the 54‐d simulation period. Simulated matric potential of unfrozen soil at the 6‐cm depth varied between −12 and −45 J kg−1 for conventional tillage and between −3 and −5 J kg−1 for no‐tillage. Simulations indicated that the average difference in soil temperature at the planting depth was reduced by 31% when the no‐tillage planting depth was decreased to 3 cm, and this practice may be used to exploit the greater moisture availability under that management to obtain more favorable seed‐zone conditions.
Oxygen Concentration and Redox Potential Gradients in Unsaturated Model Soil Aggregates
Authors: Zausig Jörg , Stepniewski Witold , Horn Rainer 
Published: July 2010

AbstractAnoxic microsites in unsaturated soils are often discussed in the context of denitrification or favorable conditions for plant root growth. To verify the existence of such anoxic microsites in the center of aggregates in unsaturated soils, O2 partial pressure, and redox potential were studied in model soil aggregates of spherical shape with microelectrodes. Soil material was taken from six soil horizons varying in texture and content of organic C. The measurements showed significant changes of the aeration status of these soil aggregates (diameter of 23 mm) as a function of pore water pressure in the range of pm = −1 to −6 kPa. At pore water pressures less than −4 kPa, all aggregates exhibited oxic centers. At higher soil moisture contents, the radii of anoxic centers at different pore water pressures could be related to soil respiration as the sink for O2, with parameters such as air‐filled porosity and pore continuity controlling the O2 flux to the aggregate center. The values of diffusion constant covered the range from 4 × 10−16 to 40 × 10‐16 mol Pa−1 m−1 s−1 and were related closely to pore water pressure, but didn't show a close relation to air‐filled porosity. The occurrence of anoxic aggregate centers was not always accompanied by a decrease in redox potential. It was assumed that these effects are induced by different microbial activities as well as by a different redox buffering of the six soils investigated.
Pyrite Oxidation, Carbonate Weathering, and Gypsum Formation in a Drained Potential Acid Sulfate Soil
Authors: Ritsema C. J. , Groenenberg J. E. 
Published: July 2010

AbstractTo quantify the rate of pyrite oxidation, weathering of carbonates and the formation of gypsum in a potential acid sulfate soil exposed to drainage, a column experiment was executed for 175 d. During the experiment, 24 g of FeS2, of the originally present 1327 g, oxidized within 70 d. Weathering of carbonates prevented acidification; an estimated 21 g of CaCO3 and 17 g of CaMg(CO3)2 dissolved simultaneously within the first 70 d. Rising Ca2+ and SO2−4 concentrations initiated gypsum precipitation from around Day 70 until the end of the experiment. A numerical model was used to simulate the experimental results. Estimated and simulated quantities of pyrite oxidation and carbonate weathering, and measured and simulated soil solution concentrations appeared to agree well. Model simulations indicate the formation of 63 g CaSO4 between Days 70 and 175 in the upper 60 cm of the soil profile.
Automated Determination of Nitrogen‐15‐Labeled Dinitrogen and Nitrous Oxide by Mass Spectrometry
Authors: Stevens R. J. , Laughlin R. J. , Atkins G. J. , Prosser S. J. 
Published: July 2010

AbstractThe 15N content of N2 and N2O emitted from 15N‐enriched soils conveys information about their sources; such information can only be obtained by mass spectrometry. Conventional dual‐inlet isotoperatio mass spectrometry (IRMS) involve complex gas sampling and inlet systems, which limit the use of the technique. Continuous‐flow IRMS was evaluated for the automated analysis of 15N‐labeled N2 or N2O. A gas sample is flushed from a vial by a He carrier stream. Carbon dioxide, NO, and water are chemically removed prior to chromatographic separation of N2 from N2O. For N2 analysis, the carrier stream is passed through a Cu reduction column to remove O2. A triple‐collector isotope‐ratio mass spectrometer analyzes a portion of the carrier stream for N2 at m/z 28, 29, and 30. Accurate values for ratio (29/28 and 30/28) differences in normal and enriched atmospheres were obtained from enrichments up to 2 atom % 15N with coefficients of variation (CVs) ranging from 0.07 to 1.37%. The reduction column is bypassed for the analysis of N2O at m/z 44, 45, and 46. From the 45/44 ratios, the 15N content of the N2O could be determined accurately with enrichments up to 40 atom %. Precision depended on concentration and enrichment, with CVs ranging from 10% for 15 µL N2O L−1 at natural abundance to <1% for 100 µL N2O L−1 at 10 atom % 15N. The concentration of N2O could be quantified from the ion currents at m/z 44, 45, and 46 with a detection limit of 2.1 µL N2O L−1. A batch of 132 samples can be analyzed automatically for N2 or N2O at a rate of six determinations per hour. Automation of 15N determination in N2 and N2O should aid the study of the processes resulting in evolution of these gases from soil.
Decomposition of Nitrogen‐15‐Labeled Wheat and Cellulose in Soil: Modeling Tracer Dynamics
Authors: Hadas Aviva , Feigenbaum Sala , Sofer M. , Molina J. A. E. , Clapp C. E. 
Published: July 2010

AbstractThe decomposition of heterogeneous plant material could be described more generally if it were based on decomposition rates of defined materials. In this study, mineralization of 15N‐labeled wheat (Triticum aestivum L.) and 15N turnover linked with the decomposition of cellulose in soil were measured and compared with simulated kinetics computed by the model NCSOIL. Dried wheat shoots (2 g C kg−1) with a C/N ratio of 14.4, or cellulose with (15NH4)2SO4 at the same C rate and C/N ratio, were added to two soils and incubated for 32 wk at 30 °C and 60% water‐holding capacity. Inorganic and Kjeldahl N and 15N were measured and compared with simulated data. Cellulose induced net immobilization of 70 mg N kg−1 within 2 wk; thereafter, net N mineralization was greater than for untreated soils. The decomposition rate constant of cellulose, computed by optimization of the model, was 0.024 d−1. The model underestimated N immobilization, the subsequent rate of net N mineralization, and the isotopic dilution of inorganic N. These discrepancies probably resulted from slower turnover of microbial biomass than simulated. Wheat decomposition was divided into three stages, corresponding to soluble, cellulose‐like, and resistant fractions that decomposed with rate constants of 3.0, 0.024, and 4 × 10−8 d−1 and accounted for 19, 45, and 36%, respectively, of organic wheat N. The computed gross mineralization of wheat N after 32 wk totaled 64% of added organic N, whereas 15N recovery as inorganic N was 40 to 50%, depending on the soil. The difference was attributed to concurrent assimilation of labeled N by soil microbial biomass that depended partly on native soil N concentrations and should be considered in interpreting tracer experiments.
Radiocarbon Signatures of Turnover Rates in Active Soil Organic Carbon Pools
Authors: Hsieh Yuch‐Ping 
Published: July 2010

AbstractIdentifying turnover rates in active soil organic carbon (SOC) pools is a critical step toward the understanding of soil nutrient cycling and global C cycles. The mean residence times (MRT) of the dominating active SOC pools in surface soils are usually less than a few decades. This range of MRT is difficult to determine because it is too short for radiocarbon dating and too long for most tracer techniques. I developed a procedure to construct radiocarbon signatures for identifying MRT in active SOC pools based on the residue bomb 14C in the atmosphere. The radiocarbon signature is specific to the year when a soil sample is taken. The sensitivity of the radiocarbon signatures is a function of MRT and the time when a soil sample is taken. This method is sensitive to MRT of active SOC pools in a range from 1 to 80 yr at the present time. Using those radiocarbon signatures, the MRT of active SOC pools in the Morrow Plots (Urbana, IL) and Sanborn Field (Columbia, MO) were estimated at 67 and 34 yr, respectively.
Short‐ and Long‐Term Phosphorus Dynamics in a Fertilized Ultisol under Sugarcane
Authors: Ball‐Coelho B. , Tiessen H. , Stewart J. W. B. , Salcedo I. H. 
Published: July 2010

AbstractIn Brazilian sugarcane production systems, P fertilizer represents a substantial input cost, yet it is used with low efficiency. Furthermore, extractants currently used to estimate available P in highly weathered soils are not satisfactory. Understanding soil P transformations is a prerequisite to improving estimates of available P and fertilizer use efficiency. We used a sequential P fractionation procedure to examine short‐term dynamics of P from fertilizer, residue returns, and soil, and long‐term changes in forms and quantities of soil P as a result of fertilization. Mulch and burn systems of residue management were imposed as treatments in field‐grown sugarcane (Saccharum officinarum L.) in northeast Brazil. Both treatments had similar inputs of P from residues (8.7 kg ha−1) but, despite the higher “available” P content of the ashes, more of the added P was mobilized and taken up by the plant in the mulch system, probably due to the presence of roots within the decomposing litter and more intense root exploration of the topsoil as a result of an improved moisture regime. This improved moisture and P supply was reflected in a 45% higher ratoon yield in the mulch treatment. Fertilizer P applied in a furrow 20 cm deep with the plant crop was concentrated in the more labile fractions, and had a residual effect on the first ratoon of about 30%. Over the long term (10 yr) there was accumulation (about 144 kg ha−1) of fertilizer P in the top 30 cm (in both labile and stable fractions). Nearly one‐half of the increase was in the first 7.5 cm of soil, a reflection of limited mixing of broadcast applications and uptake from the 7.5‐ to 15‐cm layer.