bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tillage Effects on Soil Temperature, Soil Water, and Wheat Growth in South Australia
Authors: Radke J. K. , Dexter A. R. , Devine O. J. 
Published: July 2010

AbstractPlots of an Urrbrae fine sandy loam (Rhodoxeralf) were tilled with either a scarifier (tine digger) or a rotary cultivator (rotovator), or left untilled as checks. Wheat (Triticum aestivum L. cv. Gabo) was planted 9 June 1981 on half of the tilled plots resulting in five treatments randomized over plots in each of three replicates. Soil temperatures at the 50‐mm depth and microclimate variables were measured every half hour in one replicate only. Soil water content in the surface 10 mm was measured at 0800 and 1600 h on work days in two replicates. Soil water profiles, plant heights, soil structure, and penetrometer resistances were determined at various times on selected plots and replicates during the growing season. June and July were unusually cool and wet and wheat growth was slow. After 12 August, wheat grown on rotovated plots was significantly taller and yielded more at harvest in December than wheat grown on scarified plots. Soil temperatures at 50 mm differed only slightly among treatments except for wheat vs. no‐crop where the wheat plots had lower daytime soil temperatures after 8 September. Soil water in the surface 10 mm tended to be greater for scarified treatments than for rotovated treatments until late August. It was concluded that differences in wheat plant height were related to soil structure and soil water but not to soil temperature.
Effect of Three Conservation Tillage Practices on Soil Temperature and Thermal Properties
Authors: Johnson M. D. , Lowery B. 
Published: July 2010

AbstractThree conservation tillage systems, chisel (CH), till‐plant (TP), and no‐till (NT), were compared to conventional (moldboard) tillage (CN) for differences in depth zone (5 cm) and upper profile (5–15 cm) soil temperatures and related soil thermal properties. In‐row spring soil temperatures were highest in CN, slightly lower in TP and CH, and lowest in NT. The maximum difference in daily average temperature observed between tillage treatments occurred on 2 May 1982 when the NT, CH, and TP treatments were 5.9, 2.3, and 1.8°C cooler than CN, respectively. Soil thermal diffusivity (K') in the 5‐ to 15‐cm zone was 20 to 25% higher in the NT treatment than in the CN and CH treatments, which were not significantly different. In 1 of 2 yr, K' was significantly higher in the TP treatment than in the CN and CH treatments. The reduction in soil temperatures observed with conservation tillage was attributed to differences in thermal admittance (µ), heat flux to deeper depth, and total heat inputs to the soil profile. The higher thermal admittance and heat flux in the NT treatment produced lower upper profile soil temperature.
Point and Line Infiltration—Calculation of the Wetted Soil Surface
Authors: Warrick A. W. 
Published: July 2010

AbstractFor water introduced at a point on the soil surface a finite‐sized area becomes wetted which is not exceeded for large times. Similarly, a wetted strip develops parallel to a surface line source. In this paper, relationships are derived to provide the limiting (steady‐state) extent of these wetted areas. The quasi‐linear assumption necessary for solution is that the unsaturated conductivity K is Ko exp(αh) with h the pressure head (matric potential as a length) and Ko and α constants. Results for the area around a point is in near agreement with Wooding's (1968) approximation Ko/α2q = (πα2ro2 + 4αro)−1 for a slightly different surface boundary condition (ro is the wetted radius and q is the volume of discharge per unit time). For the strip the dimensionless quantity Ko/αqL = (3.96 αxo/2 + 0.721)−1 is a valid approximation for αxo/2 <5 where qL is the rate of discharge per unit length and 2xo the wetted width. For larger αxo/2 the simpler one‐dimensional relationship Ko/αqL = 1/(2αxo) suffices. The results are relevant with respect to trickle (drip) irrigation.
The Spectrophotometric Determination of Dissolved Organic Carbon in Peat Waters
Authors: Moore T. R. 
Published: July 2010

AbstractBased on spectra of peat water samples representing a range of geochemical origin from minerotrophic fens to ombrotrophic bogs, dissolved organic carbon (DOC) was only weakly predicted (r2 = 0.710) by absorbance at 330 nm. Differences in molecular weight fractions in the dissolved organic matter apparently did not affect the correlation. Major improvement in the predictive power of absorbance at 330 nm was produced by inclusion of the Fe content of the peat water (r2 = 0.962), which can be determined simply as o‐phenanthroline reactive Fe. Dichromate‐oxidizable organic C was also predicted well from absorbance at 330 nm.
Effects of pH and Organic Acids on Orthophosphate Solubility in an Acidic, Montmorillonitic Soil
Authors: Traina Samuel J. , Sposito Garrison , Hesterberg Dean , Kafkafi U. 
Published: July 2010

AbstractThe effects of pH and organic acid addition on residual orthophosphate (o‐phosphate) solubility in an acidic, montmorillonitic soil separate suspended in 20 mol NaCl m−3 were investigated. In the absence of added organic acid, the solubility of residual o‐phosphate in the soil decreased as the pH value was increased from 4 to 7. With o‐phosphate additions that resulted in low aqueous‐solution o‐phosphate concentrations, the soil sorbed more o‐phosphate at pH 7 than at 5.5. The solubility data appeared consistent with the presence of an Al‐phosphate solid whose formation was initiated through the hydrolysis of exchangeable Al3+ and subsequent reaction of the hydrolytic product with o‐phosphate in aqueous solution. Additions of citric, tartaric, or formic acid at low concentrations (<0.1 mol m−3) produced a drop in residual o‐phosphate solubility at pH 5.5 and 7.0. In the case of citric acid, o‐phosphate solubility gradually returned to its value in the absence of organic ligand as the ligand concentration was increased to 0.6 mol m−3, whereas no such increase occurred in the case of tartaric or formic acid. This behavior was rationalized as the outcome principally of two competing reactions: (i) the reaction of adsorbed, polymeric hydroxy‐Al with organic ligand to form an exchangeable Al species that combined with o‐phosphate to reduce its solubility, and (ii) the complexation of adsorbed Al to form a soluble Al‐organic complex that did not subsequently combine with o‐phosphate. The latter reaction was important only for citric acid. The former reaction, favored by a large stability constant for Al‐organic acid adducts, produced o‐phosphate solubility decreases in the order citrate > tartrate > formate.
Ammonia Volatilization from Nitrogen Sources Applied to Rice Fields: I. Methodology, Ammonia Fluxes, and Nitrogen‐15 Loss
Authors: Fillery I. R. P. , De Datta S. K. 
Published: July 2010

AbstractThe extent of NH3 volatilization from (NH4)2SO4, urea, and urea amended with the urease inhibitor, phenyl phosphorodiamidate (PPD), was studied concurrently in flooded rice (Oryza sativa L.) by using nondisturbing micrometeorological techniques. Nitrogen‐15 balance techniques were used to estimate the total 15N loss and the relative contribution of NH3 volatilization and nitrification‐denitrification to the N loss. N sources were applied to the floodwater 18 d after the transplanting of rice seedlings (AT treatments). Ammonia volatilization proceeded rapidly after the application of (NH4)2SO4 and urea, although the pattern of NH3 loss differed between the N sources. Ammonia fluxes accounted for 38 and 36% of the N applied as (NH4)2SO4 or urea, respectively, in an 8‐d period. A lower rate of NH3 loss (22% N applied) occurred within the same period from a field amended with urea + PPD (1% wt/wt), primarily because NH3 fluxes were negligible for at least 3 d after urea was applied. The total 15N loss at the termination of the NH3 loss measurements accounted for 44 and 41% of the (NH4)2SO4 and urea N, respectively. A significantly (P ≦0.05) lower 15N loss (33% N applied) occurred when a nitrification inhibitor (nitrapyrin) was applied with urea. These results suggested that nitrification‐denitrification may have contributed slightly to the total N loss from urea. Nitrapyrin did not significantly (P <0.05) affect 15N loss from microplots amended with (NH4)2SO4. A simplified micrometeorological technique that used wind speed and atmospheric NH3 concentrations at a single predetermined height to measure NH3 fluxes accurately estimated fluxes (R2 = 0.99) that were determined by the horizontal flux or mass balance technique. An indirect estimate of NH3 loss based on the rate of 15N loss from nitrapyrin and urea amended microplots (33% N applied) was similar to the total NH3 loss computed with the mass balance micrometeorological technique (36% N applied). This finding confirms the reliability of the mass balance micrometeorological technique used in NH3 loss measurements.
Uptake of Nitrogen from Soil, Fertilizer, and Crop Residues by No‐till Corn and Soybean
Authors: Power J. F. , Doran J. W. , Wilhelm W. W. 
Published: July 2010

AbstractThe relative availability of nitrogen (N) from indigenous soil organic N, immobilized fertilizer N, currently applied fertilizer N, and crop residues is largely unknown. A nonirrigated experiment was conducted on a silty clay loam at Lincoln, NE, with both continuous soybean [Glycine max (L.) Merr.] and corn (Zea mays L.), in which crops were produced with no tillage after surface application of 0, 0.5, 1.0, or 1.5 times the quantity of aboveground crop residue produced the previous year. In 1980 and 1981, depleted 15N NH4NO3 (at 45 kg N ha−1) and crop residues were managed so that labeled isotope taken up in the 1981 crop could be separated into that from crop residues, from 1st‐yr fertilizer that had become immobilized, from fertilizer N applied the 2nd yr, and from indigenous soil N (plus fixed N for soybean).Grain and straw (stover) production of both crops in 1981 were increased 2000 to 3000 kg ha−1 by increasing crop residue rate. Almost all the N in soybean residues was mineralized and taken up by the second crop, with most of this uptake occurring after mid‐July. Uptake by soybean of labeled N immobilized in soil organic matter the previous year increased from about 2 to 6 kg N ha−1 as residue rate increased, possibly originating mainly from N temporarily immobilized in microbial biomass. Uptake by soybean of current‐year fertilizer N also increased slightly with residue rate. The fraction of total N in soybean derived from indigenous soil (plus fixed) N decreased with increased residue rate from about 85% for no residues to 55% for the 1.5 residue rate. For corn, essentially none of the N immobilized in corn residues was recovered by the next crop at any residue rate. Uptake of labeled N immobilized in soil organic matter was not affected by residue rate, but uptake from 1981 fertilizer treatment increased about 6 kg ha−1 with increased residue rate. Over 80% of the total N uptake by corn in 1981 came from indigenous soil N, regardless of residue rate.
Coastal Plain Soils of Southeastern Nigeria: II. Forms of Extractable Iron, Aluminum, and Phosphorus
Authors: Lekwa G. , Whiteside E. P. 
Published: July 2010

AbstractThe distribution of citrate dithionite and ammonium‐oxalate extractable Fe2O3 and Al2O3 were determined in nine Coastal Plain pedons of southeastern Nigeria. Distribution of available, organic, and active inorganic forms of P, plus the P fixation and available water holding capacities of these soils were also studied. The dithionite extractable Fe2O3 and Al2O3 generally increased with depth and clay contents in each of the six, loamy, well drained pedons studied. The active Fe ratio usually decreased with depth, suggesting that higher proportions of Fe2O3 were generally present in more crystalline forms in the lower horizons of the well drained soils. The active Al ratio usually increased with depth, but it was high throughout in the more poorly drained, loamy aquic pedons. The well drained ustic pedons contained larger amounts of Fe2O3‐d than did the well drained udic pedons. They also contained more Fe2O3‐d than Al2O3‐d, and the active Fe ratios were higher (≧ 3). The loamy udic pedons and the loamy aquic pedons contained larger amounts of Al2O3‐d than Fe2O3‐d, particularly in the latter. The sandy Aquod was very low in dithionite and oxalate Fe2O3 and Al2O3, except that the spodic horizon had maxima of dithionite and oxalate Fe2O3. Available and total active P contents of the studied soils were generally low. The relative abundance of the extractable inorganic P forms was generally in the order of Fe‐P > Al‐P > Ca‐P in the well‐drained loamy pedons. Organic P in all the pedons was relatively high in the surface horizons and constitutes the most abundant form of P measured in these soils. Phosphorus fixation increased with depth and showed close positive correlations with free iron oxide and clay contents.
Formation of Ferrihydrite by Inhibition of Green Rust Structures in the Presence of Silicon
Authors: Karim Zahurul 
Published: July 2010

AbstractThe initial phase formed during neutralization and partial oxidation of ferrous chloride solutions, with XRD reflections at 0.258 and 0.155 nm, is a close‐packed oxygen/hydroxyl sheet. The presence or absence of Si determines, apparently, what happens to the initial phase as oxidation proceeds. In the absence of Si, the initial phase further reacts to form green rust, presumably a double hydroxide of ferrous and ferric Fe which ultimately forms lepidocrocite. In the presence of Si, the formation of green rust structure from the initial phase is inhibited, as evidenced by symmetrical basal and asymmetrical hk x‐ray diffraction (XRD) lines, and ferrihydrite is the ultimate oxidation product.
Soil Equilibration with Minimal Solution Loss
Authors: Hooper Ginger K. , Kittrick J.A. 
Published: July 2010

AbstractBoth gas exchange and moisture loss are important experimental variables influencing the attainment of equilibria in CO2‐dependent systems. The Kimble permeable membrane (PM) cap and perforated parafilm were tested for both CO2 flow across the membrane and moisture holding ability. Samples of calcite and calcite + soil were equilibrated in an open atmosphere (of known CO2 content). No significant difference in pH − 1/2pCa2+ − 1/2pCO2 was found between the PM cap and the parafilm, perforated to allow gas exchange. However, the moisture loss for perforated parafilm was 10 times greater than with the PM cap.
Calculation of Microbial Maintenance Rates and Net Nitrogen Mineralization in Soil at Steady‐state
Authors: Smith J. L. , McNeal B. L. , Cheng H. H. , Campbell G. S. 
Published: July 2010

AbstractProduct formation equations were used for the calculation of specific maintenance energy rates for soil microbial biomass and incorporated into a conceptual model for maintenance C flow. The model separates active and sustaining biomass and includes considerations for endogenous catabolism, cryptic growth, and microbial death. Coupling of the model with product formation equations enabled the calculation of specific maintenance rates for five soils, using data from a 60‐d incubation. Calculated maintenance rates were approximately half the values commonly reported for soils and used in ecosystem models. With the use of the calculated specific maintenance rates, the conceptual model and data from a 60‐d incubation, the net soil N mineralized during the steady‐state period could also be calculated. The resultant C/N ratio of the biomass formed during this period was 7.6. Calculations involving N provided verification of the maintenance rate calculations and of the validity of the conceptual model.
Organic Carbon and Nitrogen Changes in Soil Under Selected Cropping Systems
Authors: Zielke R. C. , Christenson D. R. 
Published: July 2010

AbstractThe use of different cropping systems is one means of conserving soil organic matter. This study was conducted to evaluate the effect of 9 yr of selected cropping systems on organic C (WBC), N levels (TKN), and N mineralization characteristics (BMN) of a Charity clay (Aeric Haplaquepts). The six cropping systems consisted of combinations of corn (Zea mays L.), oats (Avena sativa L.), alfalfa (Medicago sativa L.), sugarbeets (Beta vulgaris L.), and navy beans (Phaseolus vulgaris L.). Each crop in each system was fertilized at recommended rates. Cropping systems that contained corn had up to 10% more WBC and 7% more TKN at the time of sampling than systems that did not contain corn. Nitrogen mineralization characteristics correlated linearly with WBC and TKN using S81 soil samples but not with WBC, TKN, or N uptake in a greenhouse study using F81 soil samples. The uptake and response to applied N in the greenhouse indicated that 9 yr of cropping with a particular system had an effect on the N supplying capacity of the soil. Reduced uptake and larger responses to applied N were observed for systems that did not contain corn and that lost larger amounts of C and N over the 9‐yr cropping period.
Soil pH Effects on the Distribution and Plant Availability of Manganese, Copper, and Zinc
Authors: Sims J. Thomas 
Published: July 2010

AbstractCrop response to micronutrient fertilization on the poorly buffered coastal plain soils of Delaware has received renewed interest in recent years. Specifically, given the susceptibility of these soils to overliming and the widespread use of manures, questions have been raised concerning the influence of soil pH and micronutrient source on the distribution and plant availability of Mn, Cu, and Zn, Four soils that varied widely in organic matter content (16‐100 g/kg), texture, and cation exchange capacity (CEC) were studied. A fractionation scheme was utilized that partitioned Mn, Cu, and Zn into the exchangeable, organic, Mn‐oxide bound, amorphous Fe‐oxide bound, and crystalline Fe‐oxide bound forms. Micronutrient distribution among these fractions was studied over a pH range of 4.0 to 7.7 in the soils alone, and in the same soils amended with poultry manure (PM) or (MnSO4 + CuSO4 + ZnSO4). The various fractions of each element were then correlated with Mn, Cu, and Zn uptake by wheat (Triticum aestivum L.) in a greenhouse experiment. Soil pH markedly altered the distribution of Mn and Zn but had little effect on Cu. Although soil type did have some influence, exchangeable Mn and Zn were generally the dominant species of the elements below pH 5.2, while at higher pH values organically complexed and Fe‐oxide bound forms were dominant. The majority of soil Cu was in the organic fraction, but considerable percentages were found in the amorphous Fe‐oxide fraction. Significant source by pH interactions were observed only for exchangeable Mn and Zn. Organic ligands in the manure retained more Zn in a nonexchangeable form under acidic conditions, but had only minor effects on exchangeable Mn. Plant uptake of Mn and Zn was primarily related to the exchangeable fractions; however, predictive models were significantly enhanced by the inclusion of soil pH. Inconsistent correlations and low r2 values for all models involving Cu illustrate the difficulty in predicting crop response to native or added Cu.
Using Ground‐penetrating Radar to Study Changes in Soil Map Unit Composition in Selected Histosols
Authors: Collins M. E. , Schellentrager G. W. , Doolittle J. A. , Shih S. F. 
Published: July 2010

AbstractIntensive cultivation practices and subsidence of Histosols in Florida's Everglades Agricultural Area (EAA) has resulted in the need to reevaluate soils information gathered and published in the early 1970s as part of the National Cooperative Soil Survey Program. This study was initiated to determine the present range, thickness, distribution, and spatial variability of selected Histosol map units in the EAA using ground‐penetrating radar (GPR). Four consociations were selected for study. The thickness of the organic materials has decreased significantly when compared to the thickness in the published soil survey report. When compared with the GPR data, the proportions of areas mapped in the 1970s that have thick organic layers (>90 cm) had decreased with a corresponding increase of areas with thin organic layers (<90 cm). This shift represents approximately a 35% increase in lithic subgroups. Also, many areas previously mapped as consociations need to be recorrelated as complexes; only the Okeechobee muck map unit would remain a discrete consociation. Using the GPR increased sampling speed and enabled a continuous profile of organic thickness over bedrock to be obtained.
Effect of Periodic Burning on Soil Nitrogen Concentrations in Ponderosa Pine
Authors: Covington W. W. , Sackett S. S. 
Published: July 2010

AbstractTo determine the effects of different burning intervals on soil N status in substands of sapling‐, pole‐, and sawtimber‐sized ponderosa pine (Pinus ponderosa Laws.) we sampled plots burned at 1‐, 2‐, and 4‐yr intervals by three strata at two depths (0–5 and 5–15 cm). Generally, NH4+ and NO3‐ concentrations were higher on plots repeatedly burned than on unburned controls. However, plots not reburned for 4 to 5 yr had concentrations similar to controls. No significant difference in total (organically bound) N was found among treatments. We conclude that frequent periodic burning can be used to enhance N availability in southwestern ponderosa pine sites.
A Simple Barium Chloride Method for Determining Cation Exchange Capacity and Exchangeable Cations
Authors: Hendershot William H. , Duquette Martin 
Published: July 2010

AbstractSeventeen soil samples from acidic forest soils (Typic and Pergelic Cryorthods) and near‐neutral agricultural soils (Typic Haplaquepts) were used in an experiment to compare three methods of determining cation exchange capacity (CEC). The methods tested are the sum of cations displaced with 0.1 M BaCl2, and exchangeable Ba after saturation with BaCl2 and replacement with either MgSO4 (compulsive exchange) or MgCl2. The results show that when Al, Mn, and Fe are included with Ca, Mg, Na, and K in the sum of cations, this method gives the same result as do the other methods. It is recommended that this simple one‐step method be used in routine analysis of acidic soils, especially when nonagricultural lands are under investigation.
Effects of Ionic Strength, Calcium, and Citrate on Orthophosphate Solubility in an Acidic, Montmorillonitic Soil
Authors: Traina Samuel J. , Sposito Garrison , Hesterberg Dean , Kafkafi U. 
Published: July 2010

AbstractA recent study by the authors of the effects of pH and organic acids on residual orthophosphate solubility in an acidic, montmorillonitic soil (Typic Chromoxererts) was extended to include variations of ionic strength (NaCl background) and Ca2+ concentration at fixed ionic strength. The objective of the experiments was to elucidate further the mechanism of orthophosphate solubility in a montmorillonitic soil containing exchangeable Al(III) and added citric acid. At ionic strengths between 20 and 100 mol m−3 (NaCl) and Ca2+ concentrations between 1 and 5 mol m−3 at 20 mol m−3 ionic strength (NaCl background), additions of citric acid at low concentrations (<0.1 mol m−3) reduced orthophosphate solubility. The solubility then gradually returned to its value in the absence of added organic acid as the citric acid concentration was increased to 0.6 mol m−3. The only significant effect of increasing the ionic strength or the Ca2+ concentration was to decrease orthophosphate solubility at any level of citric acid addition. Orthophosphate‐citric acid interactions in the soil were influenced only quantitatively, probably through the displacement of exchangeable Al(III) by Na+ and/or Ca2+, by increasing the concentration of these two metal cations in the soil solution.