bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling Wheat Seedling Growth and Emergence: II. Comparison with Field Experiments
Authors: Bouaziz A. , Bruckler L. 
Published: July 2010

AbstractTo improve the understanding and prediction of wheat (Triticum aestivum L.) emergence under dry conditions, a model describing wheat emergence in field conditions is presented. The proposed approach separates three basic processes from sowing to seedling emergence: (i) seed imbibition and germination, (ii) root and seedling growth as influenced by soil water potential and temperature, and (iii) seedling emergence as affected by forces exerted by plant coleoptiles and soil surface structure. Previously developed models of each process were combined to predict seedling emergence. Field experiments consisting of irrigated and nonirrigated treatments and hand and mechanical seeding were used to validate the model. Model inputs included soil water content vs. time, mean air temperature (daily basis), dry bulk density, the soil water content/water potential relationship, and soil surface structure. Sensitivity analysis showed a high sensitivity of the model to geometrical characteristics (root and coleoptile tortuosities and root angle) of seedlings under field conditions. Model prediction of germination and emergence were generally satisfactory, although errors occurred after irrigation or rainfall. Discrepancies were explained by changes in the mechanical properties and increasing impedance of the soil surface after wetting and subsequent drying, or by changes in soil temperature after wetting. Finally, simulations of germination and emergence for three climatic conditions (wet, intermediate, and dry), two sowing techniques (hand and mechanical), and two soil surface structures (fine and coarse) demonstrated the effects of those factors on emergence. In the most favorable case, 95% emergence occurred 15 d after sowing. In the most unfavorable treatment, 41% emergence occurred after 29 d.
Optimum Application Parameters for Point Injection of Nitrogen in Winter Wheat
Authors: Janzen H. H. , Lindwall C. W. 
Published: July 2010

AbstractPoint injection may enhance N fertilizer use efficiency in winter wheat but optimum application parameters have not been identified. Three field experiments, employing 15N tracer techniques and manual injections on small plots, were established at two sites in southern Alberta, Canada, to identify optimum injection intervals and injection depth for spring point‐injection of urea‐ammonium nitrate solution (UAN). The optimum lateral (across‐row) injection interval was found to be the equivalent of two row spacings (40 cm). Higher intervals resulted in unacceptable variability in N availability because wheat in rows not directly adjacent to injections assimilated comparatively little fertilizer‐derived N. The optimum longitudinal injection interval was also approximately 40 cm. Analysis of fertilizer N distribution from the injection point demonstrated unacceptable variability when this interval was exceeded. Crop uptake of fertilizer N was reduced when the injection interval was increased from 40 to 60 cm. Adoption of smaller injection intervals in both dimensions, while not jeopardizing fertilizer use efficiency, would increase the cost of fertilizer application. The optimum injection depth was observed to be approximately 10 cm. Grain yield response and fertilizer N recovery in the crop increased four‐ and three‐fold, respectively, when injection depth was increased from 2.5 to 10 cm. This effect was attributed to the inaccessibility of fertilizer N residing in dry surface soil. Injection of fertilizer at 15 cm rather than 10 cm demonstrated no additional advantage.
Pedon Distribution of Minerals in Coastal Plain Paleudults
Authors: Harris W. G. , Hollien K. A. , Carlisle V. W. 
Published: July 2010

AbstractMineral distributions in three Florida Paleudults were investigated with respect to particle size, horizon, depth, and location within the soil matrix. Mineralogy of sand, silt, and clay was determined using optical microscopy, x‐ray diffraction, and thermal analysis. Also, mineralogy of sand‐grain coatings was compared with intergrain matrix material. Elemental‐oxide composition of siltsized phyllosilicate grains was determined by electron microprobe analysis. Sand fractions consisted mainly of quartz, with lesser amounts of feldspar and mica, which were more prevalent in lower horizons. Coarse‐ and medium‐silt fractions were also dominated by quartz, but contained appreciable feldspar and mica in B horizons. Kaolinite and hydroxy‐interlayered vermiculite (HIV) were most prevalent in fine‐silt and clay fractions. Abrupt changes in silt and clay mineralogy across the E‐ and B‐horizon boundary (E‐B) included a decrease in quartz and HIV and an increase in kaolinite. Relative amounts of HIV did not markedly change with depth in arenic epipedons, but decreased steadily below the E‐B boundary for all pedons. Sand‐grain coatings from Bt horizons contained more mica than did the intergrain matrix, whereas coatings in A and E horizons contained appreciably more HIV. Distribution of phyllosilicates in these pedons could be explained by a hypothetical sequence of processes which includes (i) illuviation of kaolinite formed from weathering or dispersed from clay lenses in the sediments, (ii) comminution of sand‐ and silt‐sized mica, (iii) incorporation of finegrained mica in sand‐grain coatings, and (iv) transformation of finegrained mica to HIV in highly permeable eluvial horizons.
Use of Civil Engineering Fabrics in Pedological Field Research
Authors: Darmody R. G. , Bicki T.J. 
Published: July 2010

AbstractSoil pits are the pedologist's preferred means of examining and sampling soils. On occasion, pedologists, whether for pedagogic or research reasons, many need to re‐examine a pedon from a backfilled pit. This may be difficult especially if a backhoe is used. The backfilled materials and the in‐place soil materials comprising the pit walls can be difficult to separate, and consequently the backhoe could damage the pedon. A simple method of lining a soil pit with a civil engineering fabric prior to backfilling solves this problem. The fabric is nonbiodegradable, permeable to water but not to soil material, and strong. It has also proven to be quite useful for keeping buried equipment clean and allowing for its easy exhumation.
Penetration Model Parameter Estimation from Dynamic Permeability Measurements
Authors: Ravi Varadhan , Jennings Aaron A. 
Published: July 2010

AbstractSeveral discrete interface‐penetration models have been proposed to quantify the permeability impacts of strong soil/solute interactions. Although it has been demonstrated that these models are capable of reproducing many of the response patterns observed in laboratory studies, their nonlinear, piecewise differentiable, implicit time boundary structure compounds efforts at formal parameter estimation. A modified Levenberg‐Marquardt algorithm is presented to resolve the constrained optimization problem of penetration‐model calibration. Examples are also presented to demonstrate that optimum parameter sets may be extracted from typical laboratory data, and to illustrate how results may be used to infer proper modeling strategies.
Laboratory Tests of a Theory of Fingering during Infiltration into Layered Soils
Authors: Baker Ralph S. , Hillel Daniel 
Published: July 2010

AbstractA theory has recently been presented by Hillel and Baker to explain and predict the occurrence of fingering and the fractional wetted volume during infiltration into layered soils in terms of measurable hydraulic properties. When the conductivity of a coarse‐textured sublayer at its effective water‐entry suction is greater than the rate of transmission through a finer‐textured top layer, the flow velocity increases across the interlayer plane. Thereupon, a spatially‐distributed flow field in the top layer will tend to constrict, forming spatially separated streams (fingers) in the sublayer. To test the hypothesis, ponded infiltration experiments were conducted in transparent laboratory chambers packed with air‐dry sands. The hydraulic properties of the media were determined by equilibrium capillary rise, parameter estimation, and horizontal absorption experiments. Dynamic measurements of flux and suction at the interlayer plane during infiltration revealed that the effective water‐entry suction is characteristic of the predominant pore size in the sublayer and can be predicted from its median particle size (r2 = 0.99). Predictions regarding the onset of fingering and the wetted fractional volume of fingers were both validated for the monodisperse and polydisperse sublayers studied.
Aluminum Complexation by Protocatechuic and Caffeic Acids as Determined by Ultraviolet Spectrophotometry
Authors: Sikora F. J. , McBride M. B. 
Published: July 2010

AbstractUltraviolet (UV) spectrophotometry was used to study the complexation of Al by protocatechuic and caffeic acids at pH 3.8 to 4.5. The stoichiometry of the Al‐organic acid complex was found to be 1:1 through Job's method of continuous variation in the pH range studied. Increased pH and Al concentrations resulted in bathochromic shifts in the UV spectra of the organic acids due to the formation of an Al‐organic complex absorbing UV radiation differently than the free organic. Aluminum was concluded to be chelated by the ortho‐hydroxy group of the organic acids, as opposed to carboxyl‐group binding. The deprotonation of the carboxyl group in the free organic and Al‐organic complex had to be considered in the calculation of association constants. Association constants of 1015.33 and 1015.06 for protocatechuic and caffeic acids, respectively, were determined by Al titrations. Calculated absorbance as a function of pH agreed well with experimental titrations. Application of the determined association constants to a simplified model of a forest soil solution is presented.
Phosphate Sorption Implications on Phosphate Soil Tests and Uptake by Corn
Authors: Kuo S. 
Published: July 2010

AbstractPhosphate sorption greatly affects P availability in soils. This greenhouse study was conducted to determine the influence of the quantity of P added and P sorption capacity on P soil tests and P accumulation by corn (Zea mays L.). Seven soils with varying contents of amorphous Al oxide were treated with 0 to 4 mmol P kg−1, incubated for 9 wk, and planted with corn in pot culture after uniform fertilization with N and K. Corn plants were harvested 4 wk after sowing. The dry‐matter yields, P concentration in the plants, as well as sodium bicarbonate extractable P (NaHCO3‐P) and sodium acetate extractable P (NaOAc‐P) were determined. The P‐sorption capacities of the soils were closely related to their amorphous Al oxide contents, and the average affinity coefficient was close to the intrinsic equilibrium constant for the formation of neutral surface species. While increasing in proportion to the amounts of P added, the concentration of NaHCO3‐P and NaOAc‐P decreased as the P‐sorption capacities of the soils increased. Both soil tests were a function of the fraction of P coverage on soil surfaces (Θ), defined as the ratio of the amount of P sorbed to the P‐sorption capacity. As with the soil tests, the plant P concentration and P uptake were all highly correlated with Θ. The quantity of P added and P‐sorption capacities of the soils affected the plant P concentration, dry‐matter yield, and P uptake in the same manner as they did the soil tests. As a single measurement, Θ was more successful than the two soil tests in predicting P accumulation and P uptake by the plants.
Salt Distribution and Hardpans at Dryland Saline Seeps in Southern Alberta
Authors: Sommerfeldt T. G. , Chang C. , Lamond B. J. 
Published: July 2010

AbstractHardpans at 30‐ to 60‐cm depth were found at three dryland saline‐seep sites in southern Alberta. The soils were sampled for analyses at 0.3‐m depth intervals to 1.2 m along two parallel transects across the sites. Of the acid‐extractable salts, CaCO3 was the most abundant. Shallow hardpans were found only in the saline, waterlogged, CO3‐rich soil in the discharge areas, generally at the depth where the 1:25 acid‐extractable Ca and CO3 contents exceeded 0.6 mol kg−1 of soil. Similar contents were also found in the recharge areas, where there was no detectable hardpan. Conditions in the discharge areas apparently were suitable for the precipitation and cementation necessary to form the hardpans. Further research is needed to characterize the hardpans and to study conditions, mechanisms, and causes for their formation and their relationships with saline seeps.
Rates of Change in Soil Structural Stability under Forages and Corn
Authors: Perfect E. , Kay B. D. , van Loon W. K. P. , Sheard R. W. , Pojasok T. 
Published: July 2010

AbstractData on rates of change in soil structural stability under different cropping systems are scarce. Field measurements of changes in dispersible clay (DC) and wet aggregate stability (WAS) were made during 3 yr in six forage treatments and conventional and zero‐till corn (Zea mays L.). The study was conducted on a silt loam soil (fine‐silty, mixed, mesic Typic Haplaquept intergrading to fine‐silty, mixed, mesic Typic Eutrochrept) near Elora, ON, Canada. The DC and WAS changed exponentially with soil water content at time of sampling and were adjusted for this parameter before calculating changes with time. No increases in structural stability occurred during the 3‐yr time period within the corn treatments. In contrast, all of the forage treatments resulted in highly significant rates of structural improvement. A half‐life parameter was used to quantify these changes. Calculated half lives for the different forages were similar in magnitude, being approximately 2.7 and 5.4 yr for DC and WAS, respectively. Across the treatments, highly significant correlations were found between rates of structural stabilization and mean root length (r = −0.57 for WAS, significant at P = 0.01), mean root weight (r = −0.56 for DC and −0.65 for WAS, significant at P = 0.01) and the coefficient of variation for soil water content (r = −0.64 for DC and −0.56 for WAS, significant at P = 0.01). Forages may promote structural improvement through their influence on the amplitude of wetting and drying cycles. In addition, large increases in stability were observed over the intervening winter months, suggesting a freeze‐thaw effect.
Cropping Frequencies to Sustain Long‐Term Conservation Tillage Systems
Authors: Langdale G. W. , Bruce R. R. , Wilson R. L. 
Published: July 2010

AbstractConservation tillage technologies are essential to develop long‐term alternative agriculture approaches to protect the nation's resources. This study was conducted to develop long‐term multiple cropping systems to sustain conservation crop production. Soybean [Glycine max (L.) Merrill] and grain sorghum [Sorghum bicolor (L.) Moench] cropping sequences following wheat (Triticum aestivum (L.) grain harvest were studied at three tillage‐intensity levels on a Cecil sandy loam (clayey, kaolinitic, thermic Typic Hapludult) soil. During the first 4‐yr crop rotation cycle, coulter in‐row chisel (MT) planted grain sorghum produced significantly more grain than either coulter (NT) or disk harrow (CT) planted (4.89 vs. 4.58 and 4.39 Mg ha−1), without a crop‐rotation response. In the second 4‐yr cycle, the sorghum grain yields declined NT > MT > CT (5.14 > 4.74 > 4.40 Mg ha−1) significantly with each increase in tillage‐intensity level. Soybean responded consistently and significantly to high‐frequency (1:1) rotation with grain sorghum. These responses to rotation with grain sorghum become less important to conservation tillage systems when favorable rainfall distributions permit grain yields that range between 2.00 and 3.50 Mg ha−1. Wheat yields increased significantly following soybean (first rotation cycle) until take‐all (Graeumannomyces graminis) became epidemic. Elucidation of significant grain sorghum responses to in‐row chisel and coulter conservation tillage during the first and second crop‐rotation cycles, respectively, requires additional research that focuses on characterization of temporal changes in the soil environment. Rotation of both cool‐ and warm‐season crops is necessary to sustain long‐term conservation tillage.
Nitrogen‐Fertilization Rate and Soil Nitrate Distribution for Microirrigated Sugarcane
Authors: Stanley C. D. , Green R. E. , Khan M. A. , Santo L. T. 
Published: July 2010

AbstractConcern continues to grow over the fate of chemicals used in agricultural production and the associated potential for groundwater contamination. Management practices can directly influence the efficiency of inorganic fertilizer use by crops, and can affect the amount that moves away from the root zone. A field study was conducted to investigate the effect of three N‐fertilization rates (17.8, 9.1, and 6.0 kg ha−1 wk−1) on NO3 distribution and movement for the first 24 wk of growth of microirrigated sugarcane (Saccharum officinarum L.) grown on a Wahiawa silty clay (clayey, kaolinitic, isohyperthermic Tropeptic Eutrustox). One uncropped treatment receiving 9.1 kg ha−1 wk−1 was included for evaluation without crop uptake. The plots received irrigation daily, with N being applied once weekly. Clusters of soil‐solution extraction tubes were installed at depths of 15, 45, and 75 cm from the soil surface and 0, 30.5, 61, 91.5, and 122 cm away from microirrigation emitters to determine NO3 distribution patterns on a weekly basis. Soil water potential was monitored with tensiometers placed at similar locations. Results showed that all N levels were applied excessively early in the season and exhibited NO3 leaching beyond the root zone. Data collected at 22 wk after planting showed that the 6.0 kg ha−1 wk−1 rate had low NO3 concentrations through the soil profile, indicating a N‐rate closer to crop requirements. Daily irrigation applications were probably excessive and may have contributed to loss of NO3 from the root zone for all treatments. This study demonstrated that a dynamic approach to fertilization and irrigation needs to be developed to minimize water and nutrient losses from the crop root zone.
Douglas Fir Growth and Foliar Nutrient Responses to Nitrogen and Sulfur Fertilization
Authors: Blake John I. , Chappell H. N. , Bennett W. S. , Gessel S. P. , Webster S. R. 
Published: July 2010

AbstractNitrogen‐fertilizer response in conifer stands of the Pacific Northwest has been related to soil and foliar S, and growth has occasionally been enhanced by the addition of S. In order to test the effect of soil SO4‐S concentrations on N response, five stands of Douglas fir, Pseudotsuga menziesii (Mirb.) Franco, with low to moderate quantities of SO4‐S in the mineral soil horizon were treated with N and with N plus S. Sulfate‐S concentrations varied among soils from 6.0 to 19.2 mg S kg−1 in the surface soil and from 6.0 to 78.7 mg S kg−1 in the subsoil. Three treatments were applied: control, 224 kg N ha−1 as urea, and 224 kg N ha−1 plus 112 kg S ha−1 as a mixture of urea and (NH4)2SO4. Adjusted gross volume growth responses to N alone averaged −1.63 to 6.26 m3 ha−1 yr−1 after 3 to 4 yr; average volume growth gains from application of N with S over application of N alone varied from 0.73 to 4.5 m3 ha−1 yr−1 at four locations. At one location, the N‐alone effect was greater than that from N with S. Foliar N concentrations in the N‐with‐S treatments were generally higher than in the N‐alone treatments. Little change in foliar‐S content occurred in the N‐with‐S plots. Mean treatment effects were unrelated to foliar N/S, total S, or foliar SO4‐S on the controls, and the relationship between soil SO4‐S and the differential growth response between N and N with S was highly variable. Treatments were reapplied at a rate of 448 kg N ha−1, 224 kg S ha−1, and 9 kg B ha−1. Four‐year growth effects were similar to the first period except at one location where N responses appeared greatly improved by B. Periodic annual growth response to N over the entire study period was inversely related to site index and directly related to foliar N content. Prescriptions involving S will require more efficient S sources and a better assessment of S uptake and S reactions in these soils.
Adsorption of Heavy Metals by Silicon and Aluminum Oxide Surfaces on Clay Minerals
Authors: Schulthess C. P. , Huang C. P. 
Published: July 2010

AbstractThe pH value of an adsorption edge (i.e., the pH value where a change occurs in the amount of aqueous ions adsorbed by a solid phase) is dependent on the surface‐metal bonding strength and, consequently, on the type of adsorption site involved. The metal‐adsorption sites of natural (untreated) kaolinite, montmorillonite, and synthetic mordenite were elucidated by comparing the pH values of their adsorption edges with those of Si and Al oxides. Cation adsorption by these clays is strongly influenced by the Si/Al surfacesite ratio, steric effects of interlayers or channels, Lewis acid strength of the metal, and pH of the medium. Using Ni, kaolinite showed additive adsorption behavior by the Si and Al oxide surfaces with well‐defined boundaries. The adsorption edge of Ni by mordenite occurred at low pH values and was attributed to the increased Ni‐binding stability inside the channels of the zeolite structure. Several heavy metals (Ni, Zn, Cd, and Pb) were used to properly identify the various adsorption edges on montmorillonite. The adsorption of Ni by montmorillonite was similar to the Si and Al oxide surfaces but with an additional adsorption edge observed at low pH values, which was attributed to the interlayer structure of the clay. The presumed pH‐independent cation‐adsorption behavior below pH 6 by 2:1 clay minerals is probably due to pH‐dependent adsorption on amorphous Si oxide sites that can induce ion‐exchange reactions at much lower pH values than previously assumed.
Determination of Boron in Soils Containing Inorganic and Organic Boron Sources
Authors: Kaplan D. I. , Adriano D. C. , Mills G. L. , Sajwan K. S. , Burkman W. G. 
Published: July 2010

AbstractLaboratory experiments were conducted to evaluate the potential interference of organoborates with the commonly used azomethine‐H method of determining B in soils. In addition, an alternative method, the cold‐water‐extractable B (CWE‐B) method, was developed and compared with the commonly used hot‐water‐extractable B (HWE‐B) method on soils containing organoborates. In a solution study, the organoborate sodium tetraphenyl‐boron (NaTPB) interfered more than its hydrolysis by‐product diphenylboric acid (DPBA) with the colorimetric detection of B by the azomethine‐H method. The interference was enhanced by boiling these compounds under conditions similar to those required by the HWE‐B method. However, passing these organoborate solutions through C18 cartridges (an octadecyl‐silane bond phase packing that adsorbs many organic compounds) prior to boiling alleviated the interference. Furthermore, the C18 cartridges had little effect on inorganic B levels. A study measuring indigenous B levels of 31 diverse soils collected from throughout the USA revealed that the CWE‐B method extracted less B, though its values were highly correlated (r = 0.84; P ≤ 0.01) to the HWE‐B values. In addition, these HWE‐B and CWE‐B values were almost identically correlated to the same soil properties: pH and exchangeable Ca. The use of C18 cartridges in conjunction with the CWE‐B method was satisfactory for determining inorganic B levels in soils containing organoborates.