bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Phosphorus Efficiencies of Two Winter Wheat Cultivars
Authors: Gardiner D. T. , Christensen N. W.
Published: July 2010

‘Stephens’ and ‘Yamhill’ winter wheat (Triticum aestivum L.) cultivars respond differently to P fertilization on low‐P soils. The objective of this study was to determine the reason for greater P efficiency in Yamhill. The cultivars were grown in three growth‐chamber experiments to describe response to a factorial combination of P levels and soil fumigation, and to compare root growth rates, root hair formation, and tissue P concentrations. Cultivars did not differ in root growth rate, total P uptake, or response to fumigation. Root hair length was affected by an interaction between cultivars and P concentrations in the growth medium. At the 2 µM P level, Yamhill had significantly (P = 0.05) longer root hairs than Stephens. Yamhill produced significantly greater shoot dry weight per unit of P taken up (0.20 g mg−1) than Stephens (0.17 g mg−1). The greater P efficiency of Yamhill was attributed to greater P‐use efficiency rather than to differences in P uptake.
Clover Residue Effectiveness in Reducing Orthophosphate Sorption on Ferric Hydroxide Coated Soil
Authors: Easterwood G. W. , Sartain J. B.
Published: July 2010

In many tropical soil systems, secondary minerals are coated with sesquioxides, resulting in inherently low P availability to plants due to P‐fixation mechanisms. Research was conducted to determine the influence of hydroponically grown clover (Trifolium repens L.) residue pretreatment in reducing orthophosphate sorption on a fine‐loamy, siliceous, thermic Typic Paleudult (Orangeburg series) that had been coated with synthetically prepared amorphous Fe(OH)3. A 3 × 2 × 3 factorial experiment was conducted in split‐split‐plot design with P as the main plot, Fe(OH)3 as the subplot, and clover as the sub‐subplot. Throughout two cropping periods of 50 d each, to assess the initial and residual effect of clover pretreatment, corn (Zea mays L.) dry‐matter yield, P uptake, and Bray 2 extractable P levels were superior with clover pretreatment prior to P fertilizer addition. When fertilizers, but not clover, were again applied to experimental units for a third cropping period, clover pretreatment did not influence plant dry‐matter accumulation or P uptake. It did, however, substantially increase Bray 2 extractable P levels. Potentiometric titrations relating to surface charge were conducted on treatments with Fe(OH)3 that had been amended with P, clover, and P plus clover after the first cropping period. Results suggest that organic acids from clover decomposition bind to Fe(OH)3 surfaces and are able to complex Lewis acid cations to increase P availability.
Ammonia Volatilization from Nitrogen Fertilizer Surface Applied to Orchardgrass Sod
Authors: Lightner J. W. , Mengel D. B. , Rhykerd C. L.
Published: July 2010

If the N needs of the grass sward cannot be met with a compatible legume, then additional N inputs must come from other sources, such as urea, to sustain high yields. However, urea is difficult to incorporate in an established grass pasture, which can result in considerable inefficiencies in N utilization. One cause of this inefficiency is volatilization of NH3. Field measurements were made to determine the amount of NH3 lost through volatilization from urea‐based fertilizers surface broadcast onto an orchardgrass (Dactylis glomerata L.) sod on a Xenia silt loam soil (a fine‐silty, mixed, mesic Aquic Hapludalf). Nitrogen sources used were: urea applied as both a granular solid product and as a solution; cogranulated urea‐urea phosphate (UUP); ammonium nitrate (AN); and urea‐KCL and urea‐CaCl2 solutions at a cation/urea‐N equivalency of 0.50 KCl or 0.25 CaCl2·2H2O. Fertilizer N was applied at 200 kg N ha−1 in the spring and 100 kg N ha−1 in late summer. Measurable NH3 loss occurred within 12 to 24 h after N application. Rate of volatilization was greatest from mid‐morning to early afternoon. Highest NH3 losses were from solid urea, urea solution, and urea‐KCl solutions. Losses from these materials ranged from 27 to 41% of applied N in the spring and from 12 to 37% in the summer. No significant volatilization losses were observed with AN. Ammonia losses from UUP were significantly less than those from solid urea in the spring, and at least 40% less in the late summer. Relative to urea solution alone, mixing CaCl2 with urea lowered volatilization significantly in both 1983 studies. Finally, the concentration of KCl with urea in this study did not effectively reduce NH3 volatilization.
A Volume Recorder for Lysimeter Waters
Authors: Hazlett P. W. , Foster N. W. , English M. C.
Published: July 2010

Water moving through the soil can be sampled by a variety of lysimeters, but in many cases the volume of water exceeds the capacity of the collection vessel. The design of a simple and inexpensive volume recorder used to measure large volumes of soil water from individual lysimeters is presented. During tests in the field, the volume recorder provided good estimates of water volumes collected by tension‐free lysimeters. The compactness and easy portability of the unit makes it ideal for year‐round use at remote field locations to determine variability in the flow of soil water.
Phosphorus Chemistry and Mineralogy in Excessively Fertilized Soils: Descriptions of Phosphorus‐rich Particles
Authors: Pierzynski G. M. , Logan T. J. , Traina S. J. , Bigham J. M.
Published: July 2010

Data is limited on the mineralogical characteristics and formation mechanisms of P‐bearing solids that occur in soils due to P fertilization. This study was conducted to characterize, isolate, and infer formation mechanisms for P‐rich particles found in two excessively fertilized soils. Phosphorus‐rich particles were described in terms of morphology, elemental composition, and crystallinity using electron optical techniques. These particles were found in the <2.2 Mg/m3 density separates from the clay fractions of a Plainfield loamy sand (mixed, mesic Typic Udipsamment) and Blount silt loam (fine, illitic, mesic Aeric Ochraqualf) that had been excessively fertilized for more than 20 y. Particle morphologies indicated that the P‐rich materials exist as discrete particles as well as coatings on other particles. The elemental composition of the particles varied within as well as between particles. Phosphorus concentrations in the P‐rich materials ranged from 5.6 to 27.2% per mole of cation (mole cation%). Aluminum and Si were the dominant elements associated with P, while Ca, Fe, and Mn generally were present at low concentrations. The P‐rich materials were amorphous to electron diffraction and can generally be described as an amorphous mixed Al‐Si‐P substance. An analogy was made between the P‐rich materials, the amorphous analog of variscite, and allophane.
A Rapid Method for Total Nitrogen Analysis Using Microwave Digestion
Authors: He X. T. , Mulvaney R. L. , Banwart W. L.
Published: July 2010

A microwave digestion procedure recently proposed for total N analysis of soil using HF‐HCl, H3BO3, and H2O2 was found to give much lower values than conventional Kjeldahl digestion in analysis of soil and plant samples and simple organic N compounds. An alternative microwave procedure was developed that involves Kjeldahl digestion with concentrated H2SO4 and a K2SO4‐catalyst mixture. With this procedure, digestion of five samples can be accomplished in 30 min. Complete recovery (≥98%) of N was obtained in analysis of several organic N compounds. Total N analyses of plant materials by the microwave Kjeldahl method agreed closely with those by conventional Kjeldahl digestion using an Al block; the microwave method gave somewhat lower results than the conventional method for surface soils with a high content of total N. Precision of the analysis was comparable for both methods. Recovery of N added to soil as NO3 averaged 97% when the microwave procedure was modified to include a pretreatment with salicylic acid and sodium thiosulfate. Although much more rapid, the microwave Kjeldahl method is not necessarily more convenient than conventional digestion with an Al block because of the need for frequent loading and unloading of samples.
Locating Sampling Sites for Salinity Mapping
Authors: Rhoades J. D. , Lesch S. M. , Shouse P. J. , Alves W. J.
Published: July 2010

An evaluation of the suitability of a commercial long‐range navigation (LORAN‐C) method to locate and determine mapping coordinates of soil salinity sites was made in California field trials. The LORAN‐C‐determined position was within 16 m of the true position 90% of the time. This is sufficient accuracy to locate sampling areas identified with Système Probatoire d'Obervation de la Terre (SPOT) satellite imagery (pixel resolution of 30 m), but not for locating smaller sampling areas, such as those identified in low‐altitude photographs. The LORAN‐C method proved suitable for producing regional salinity maps that could resolve soil‐salinity differences on a scale of 200 m.
Estimation of Water‐Retention Function Using Scaling Theory and Soil Physical Properties
Authors: Daamen Carl C. , Robinson James A. , Xiao Zhenhua
Published: July 2010

Estimation or measurement of water‐retention functions is an important part of studies of water balance in soils. Characterization of a spatially variable water‐retention function, S(h), where S is degree of saturation, is demonstrated here with a data set from a 2‐ha watershed. The soil is classified as Shepparton fine sandy loam. Four common functional forms for S(h) were fitted to the data set using scaling theory and nonlinear regression. Initially, only one model parameter, associated with a scaling factor, was fitted independently to each core. This scaling approach accounts for most of the variability (e.g., r2 = 0.975) and an estimate of the residual in S is within the accuracy of field measurement. Using nonlinear regression and fitting both parameters independently does improve r2 (= 0.991), but only marginally. Using the scaling approach, an expression of soil physical properties was used in place of the independent parameter. The regression (r2 = 0.967) gives values to the coefficients of physical properties in this expression, allowing scale factors to be calculated directly from physical properties. A jack‐knife estimation technique was employed to show how well scale factors are calculated from physical properties alone. This methodology accounted for spatial variability adequately, offering a simple, computationally efficient representation in numerical simulation. Other data sets indicated that approach may be useful on a regional scale for clearly defined soil groups.
Soil Phosphate Diffusion Coefficients: Their Dependence on Phosphorus Concentration and Buffer Power
Authors: Bhadoria P. B. S. , Kaselowsky J. , Claassen N. , Jungk A.
Published: July 2010

Measured values of effective P diffusion coefficients, De, were compared with De values calculated on the basis that P only diffuses in the liquid phase. Two soil blocks differing in P content were placed into contact for 2 wk, then quick frozen and cut into slices of 0.2 mm with a refrigerated microtome. The slices were extracted with 4 M HCl to obtain a P concentration‐distance curve. An average diffusion coefficient, D̅e, was determined from the total amount of P that had diffused from the soil of high P concentration to that of low P concentration. Effective diffusion coefficients for a given soil P concentration, Dec, were obtained by analyzing the concentration‐distance curve. Phosphorus buffer curves were established by adsorption in the lower concentration range and by desorption in the higher concentration range, according to the process occurring during P diffusion in soil. The value of D̄e increased from 2.2 to 13.9 × 10−13 m2 s−1 when the average soil P concentration increased from 380 to 580 mg P kg−1 soil. The Dec values increased with increasing P concentration, although the relationship was not unique. For example, the same Dec value of 5 × 10−13 m2 s−1 was obtained at 340 mg P kg−1 when P was being adsorbed and at 600 mg P kg−1 when P was being desorbed during the process of diffusion. This result was related to different P‐buffer behavior of the soil during adsorption and desorption. The P diffusion coefficient in soil is, therefore, dependent not only on the buffer power, which is influenced by concentration, but also on whether P is being desorbed or adsorbed and on the time available for reaction. The value of De can be calculated if suitable values for the buffer power are used, and De for a wide P‐concentration range can be calculated if a weighted average buffer power is used.
Sampling Strategies for Assessing Hydraulic Conductivity and Water‐Conducting Voids in Saprolite
Authors: Vepraskas M. J. , Hoover M. T. , Bouma J.
Published: July 2010

A saprolite's saturated hydraulic conductivity (Ksat) and types of water‐conducting voids must be known to assess its suitability for liquid waste disposal. This study determined optimum numbers of pits and numbers of samples per pit needed to estimate a saprolite's Ksat and volume percentages of water‐conducting macrovoids and groundmass (microvoids). Three pits were dug across a 5‐ha area to expose B horizons and saprolite (2‐m depth), and undisturbed cores were collected from each pit. The Ksat was measured for each core, and water‐conducting voids were dyed. Volume percentages of water‐conducting (dyed) macrovoids (e.g., root channels with diam. ≥0.1 mm) and water‐conducting groundmass were determined from thin sections. Mean values for saprolite Ksat and volume percentages of water‐conducting macrovoids and groundmass were 0.25 cm h−1 and 1.1 and 47.9%, respectively. In order to minimize both the variance of each mean value and the time required for analysis, it was most efficient to collect only one core per pit. The most efficient number of pits depended on the desired size of the confidence interval and the property of interest. A 95% confidence interval for saprolite Ksat that was within 10% of the true mean would require over 700 pits per 5 ha, while an estimate of the percentage of water‐conducting groundmass would require only 10 pits per 5 ha. Increasing the width of the 95% confidence intervals to be within 50% of the means reduced the required number of pits for these properties to 28 and 1, respectively.
Water Quality Effects on Soils and Alfalfa: I. Water Use, Yield, and Nutrient Concentration
Authors: Prunty Lyle , Montgomery B. R. , Sweeney M. D.
Published: July 2010

The detrimental effects of salt buildup in northern Great Plains soils need quantification. This study was conducted to evaluate effects of irrigation water quality on alfalfa (Medicago sativa L.) yield, water use, and nutrient concentration during a 21‐mo period. Irrigation waters of seven qualities, totaling 4400 mm in wet/dry cycles, were applied to 20 by 60 cm undisturbed soil columns under green‐house conditions. Four loam soils representing moderate to moderately slow permeable drainage classes were used. The soils were: Williams loam (fine‐loamy, mixed Typic Argiboroll), Barnes loam (fine‐loamy, mixed Udic Haploboroll), Svea loam (fine‐loamy, mixed Pachic Haploboroll), and Parshall loam (coarse‐loamy, mixed Pachic Haploboroll). Effects of soil, water quality, and time on yield and water use were highly significant (R2 = 0.94*** [*** denotes significance at P = 0.001] and 0.93***, respectively). In all soils and waters, yield and water use decreased 30 to 60% by the end of the experiment. Mean nutrient concentrations, with the exception of Na, remained within 10% of the original values. Irrigation water with sodium adsorption ratio (SAR) of 20 and ionic concentration of 20 mmolc L−1 increased the alfalfa Na concentration to 15 times that with distilled irrigation water. Total Na added accounted for 84%*** of variation in relative yield. One‐half of the salt‐induced yield reduction appeared in the first third of the experiment. This underscores the inadvisability of irrigating with poor‐quality water that might be available during drought periods.
Surface Sealing in Coastal Plains Loamy Sands
Authors: Radcliffe D. E. , West L. T. , Hubbard R. K. , Asmussen L. E.
Published: July 2010

Soil surface seals may consist of a dense surface skin seal and/or a washed‐in layer of dispersed clay just below the surface. Work in Israel has shown that when clay contents are below about 20%, the seals that form are relatively permeable. In Georgia, soils of the Piedmont region with clay contents above 10% can form low‐permeability seals. Our objective was to determine if the more sandy soils of the Coastal Plain region would form seals and, if so, to describe the morphology of these seals. Infiltration was measured using a rainfall simulator on bare and straw‐covered tilled soil at six sites on three loamy sands. The three soils used were Tifton (fine‐loamy, siliceous, thermic Plinthic Kandiudult), Carnegie (clayey, kaolinitic, thermic Plinthic Kandiudult), and Clarendon (fine‐loamy, siliceous, thermic Plinthaquic Paleudult). Final infiltration rates were significantly lower in the bare soil at all but one site, indicating that sealing occurred. Final infiltration rates were not as low as those observed in soils from the Piedmont region of Georgia, probably due to the lower clay content of the Coastal Plains soils. Thin‐section micrographs suggested that these seals formed due to surface disruption with raindrop impact. Although grains that had been stripped of clay and oxides were observed at the surface, no distinct zones of clay and oxide concentration (washed‐in layers) were observed. Size and spatial relationships of the areas of stripped grains suggested that they had been transported and redeposited rather than developed in place.
Oak Influence on Nutrient Availability in Pine Forests of Central Arizona
Authors: Klemmedson James O.
Published: July 2010

Existing evidence suggests that Gambel oak (Quercus gambelii Nutt.) improves soil fertility of the ponderosa pine (Pinus ponderosa Dougl. ex Laws) forest of central Arizona. Greenhouse bioassays were conducted to determine if Gambel oak also influences nutrient availability in the 0‐ to 15‐cm mineral soil layer. Barley (Hordeum vulgare L. cu. Gustoe) and pine seedlings were grown to estimate availability of N, P, K, and S in soils from 15 pine stands with basal area of oak varying from 0 to 62% of the total basal area, but equivalent in all other site factors. Without supplemental nutrients, barley yield from soils with 50% oak was three times greater than from those with no oak. With addition of N, P, K, and S, barley yield increased 370% on soils without oak, but only a 50% yield increase occurred on soils from stands with 50% oak. Regression analysis of barley yields for each nutrient revealed that availabilities of N and S were significantly related to amount of oak present. Availabilities of P and K were not related to oak presence. The bioassay with pine seedlings confirmed that oak positively influenced N supply. This test, however, showed no effect on S supply. Contrasting results for barley and pine tests are attributed to greater sensitivity of barley and high variance in the pine test.
Net Erosion on a Sagebrush Steppe Landscape as Determined by Cesium‐137 Distribution
Authors: Coppinger K. D. , Reiners W. A. , Burke I. C. , Olson R. K.
Published: July 2010

Soil erosion plays a major role in structuring landscapes of semiarid regions. The purpose of this study was to examine patterns and assess transport mechanisms of soil erosion and deposition in a native sagebrush steppe landscape in south central Wyoming using 137Cs. Six landscape units were identified using a cluster analysis based on four landscape variables. Cesium‐137 values varied little among landscape units, suggesting that intermediate‐scale (approximately 100 m) fluvial and eolian soil transport is unimportant in this system during the time since bomb‐test 137Cs deposition occurred. In contrast, analysis of variance showed that, on windswept landscape positions, 137Cs was significantly higher under shrubs than between them. These differences suggest that wind‐driven redistribution has occurred at a small scale (0.5–10 m). Even though 137Cs data indicate that intermediate‐scale transport is not occurring, analysis of the soil fine fraction across the landscape shows net transport of fines downslope, suggesting that, in this sagebrush ecosystem, soil redistribution by fluvial erosion occurs too slowly to be determined by 137Cs.
Suspension Nebulization Analysis of Clays by Inductively Coupled Plasma‐Atomic Emission Spectroscopy
Authors: Laird D. A. , Dowdy R. H. , Munter R. C.
Published: July 2010

Use of suspension nebulization for elemental analysis of clays by inductively coupled plasma‐atomic emission spectroscopy (ICP‐AES) was evaluated to ascertain the effects of particle size and various experimental parameters on total recoveries. To do so, specimens of Grundite illite and Georgia kaolinite no. 3 were fractionated by centrifugation to prepare samples of the <0.2‐, 0.2‐ to 2‐, 2‐ to 10‐, and 10‐ to 45‐µm size fractions. Portions of these samples were dispersed in 1 M HNO3 or 0.1 M NaCl and analyzed by ICP‐AES using suspension nebulization. Other portions of the samples were digested with HF and analyzed by ICP‐AES using solution nebulization. Total recoveries were determined by comparing the sum of all oxides for the suspension‐ and solution‐nebulization analyses. Total recoveries ranged from 2 to 100% depending on particle size of the samples, design of the spray chamber, observation height, carrier Ar pressure, sample nebulization rate, and method of sample preparation. Incident power of the plasma did not substantially affect total recoveries. The highest total recoveries were obtained by sonicating samples for 10 min at 80 W in 0.1 M NaCl, and by maximizing sample nebulization rate (2.6 mL min−1), minimizing carrier Ar pressure (1.52 mPa), and using a conical spray chamber for the analyses. For the <0.2‐ and 0.2‐ to 2‐µm size fractions, these conditions yielded reproducible results with total recoveries >90%. Total recoveries for the 2‐ to 10‐ and 10‐ and 45‐µm size fractions, however, never exceeded 70 and 24%, respectively. Therefore, suspension nebulization is not recommended for use with samples containing particles larger than 2 µm. Use of suspension nebulization with ICP‐AES, however, is a rapid and reliable method for performing multielement analyses of clay (<2‐µm) samples.
A Unique Soil‐Carbonate Liberation Technique for Use with Carbon‐14‐Labeled Carbonate
Authors: Sheppard Marsha I. , Schwartz W. J.
Published: July 2010

A fast, inexpensive, and efficient method was developed to liberate 14C‐labeled CO3 from soil, and trap the evolved 14C‐CO2 in vials ready for liquid scintillation counting. The apparatus is fabricated with microanalytical materials that minimize the contact surfaces and total internal gas volume. Another advantage is that the trapped CO2 is directed immediately into the counting vial, ready for analysis. Recoveries of standard additions to soil were always >97% and usually 99.9%. Comparison of this method with a similar direct CO2‐absorption method, now being used to radiocarbon date hydrological and geological samples, proves this method gives results similar to the traditional methods. Recoveries from non‐carbonated and carbonated (6% CO3) soil cores, spiked to simulate entry of contaminated groundwater, support the usefulness of this method for 14C soil‐transport studies.
Modified Calibration Procedure for the Measurement of Microbial Sulfur in Soil
Authors: Castellano S. D. , Dick R. P.
Published: July 2010

To better estimate S biomass in soils, an alternative calibration technique for the measurement of microbial biomass S in soil was developed. Rather than using pure cultures of bacteria and fungi to determine the biomass‐S calibration constant (Ks), cultures of bacteria and fungi were grown using soil dilutions as primary inoculum. These microorganisms were harvested and washed, and dense suspensions of bacteria or fungi (in 0.15 M NaCl matrix solution) were prepared. The suspensions were used as inoculum for the calibration procedure, where bacteria or fungi were each grown at three S concentrations (1, 4, or 16 mg SO4‐S L−1) and subsequently added to soil and fumigated with CHCl3. The mean value of 39.3% was calculated for the proportion of microbial S extracted with calcium phosphate [8 mM Ca(H2PO4)2] from a Woodburn silt loam (a fine‐silty, mixed, mesic Aquultic Argixeroll) following CHCl3 fumigation. This procedure may better reflect the soil microbial biomass than using pure cultures, because soils have mixed microbial populations.
Field Study of Bromacil Transport under Continuous‐Flood Irrigation
Authors: Jaynes D. B.
Published: July 2010

The transport processes of sorbing chemicals in field soils are poorly understood. This study characterized the leaching behavior of the weakly sorbing herbicide bromacil (5‐bromo‐3‐sec‐butyl‐6‐methyluracil) in comparison to Br‐ during continuous‐flood irrigation of a small field plot. Twenty‐four solution samplers were used to periodically collect in situ samples from seven depths within four 1.83 by 1.83 m subplots. Estimates of the pore water velocity (vs) and dispersion coefficient (D) were made by fitting an analytical solution of the convection‐dispersion (CD) equation to the Br‐ data. Estimates of retardation (R) were made by fitting the CD equation to the bromacil data using the vs and D estimates from the Br‐ data and letting R be a fitting parameter. Estimates of R were also made from the results of batch equilibration studies using soil from seven depths. Best‐fit vs and D values exhibited considerable variability from sampler to sampler (CV = 1.25 and 1.30, respectively) and showed no significant trends with depth. Retardation values estimated from the CD equation averaged 1.88, but varied from 1.21 to 3.35 and also showed no significant trend with depth. In contrast, batch equilibration studies showed the absorption properties of the surface 0.6 m of soil to be significantly different than the 0.6‐ to 3‐m depth, with R values decreasing from 1.62 for the surface 0.6 m to 1.31 at 3 m. Although the two methods gave the same estimate of R in the surface soil, neither the lower R values at deeper depths nor the tendency to decrease with depth as predicted from the batch studies was apparent in the transport data. Using D as an additional fitting parameter to the bromacil data resulted in an average increase of 1.96 for this parameter, indicating more dispersion for the sorbing solute. Increased dispersion and increased tailing of the sorbed solute may be attributed to spatially variable adsorption and to a negative correlation between vs and R (r = −0.524).
Nitrogen and Nitrogen‐15 Analysis Using Automated Mass and Emission Spectrometers
Authors: Craswell E. T. , Eskew D. L.
Published: July 2010

Analysis of large numbers of samples has been a major limitation in the use of 15N. Two new instruments—an automatic N analyzer coupled to a mass spectrometer (ANA/MS), and a microprocessor‐controlled emission spectrometer (NOI‐6e)—were therefore compared with a longer established procedure of the International Atomic Energy Agency Laboratories involving 15N analysis with a Micromass (MM) 602E mass spectrometer. For 10‐mg plant samples ranging from natural abundance (NA) to 1.341 atom % 15N, the ANA/MS agreed with the MM 602E to within 0.002 atom %, and the NOI‐6e to within 0.014 atom %. In the range 1.895 to 2.398 atom %, data from the ANA/MS and the NOI‐6e agreed with the MM 602E within 0.022 and 0.093 atom %, respectively. Relative standard deviations (RSD) for six replications of a NA plant sample were: MM 602E, 0.22%; ANA/MS, 0.47%; NOI‐6e, 2.3%. For a plant sample with 2.398 atom % 15N the RSDs were: MM 602E, 0.03%; ANA/MS, 0.08%, and NOI‐6e, 0.3%. With finely ground soil samples (40 mg, 0.449 atom %) the RSD for 15N analysis with the ANA/MS was 0.30%. The ANA/MS was comparable to the Kjeldahl method (500‐mg samples) for plant N analyses and was found suitable for routine 15N analysis of plant and soil samples, but additional care in sample grinding was needed. The NOI‐6e analyzed 15N samples in one‐tenth the time required with previous emission spectrometers and its precision would be adequate for many agricultural experiments. The lower precision is a limitation, however, for measuring the 15N content in soil samples.
Wheat Stubble Management Affects Growth, Survival, and Yield of Winter Grain Legumes
Authors: Huggins D. R. , Pan W. L.
Published: July 2010

The adoption of no‐tillage systems in the Pacific Northwest will benefit from the development of crop rotations that complement winter wheat (Triticum aestivum L.). Experiments were conducted during 1986–1987 and 1988–1989 to determine the effects of wheat residue and fertility management on the growth, winter survival, and yield of ‘Glacier’ Austrian winter pea (Pisum sativum subsp. arvense L.) and winter lentil (Lens colinaris Medik.). No‐tillage (NT) and no‐tillage with reduced stubble (NT‐SR) enhanced soil moisture conservation and increased the early growth of Austrian winter pea (AWP), compared with conventional tillage (CT). Decreased shoot mass of winter lentil (WL) in NT, and elongated stems and reduced branching of AWP and WL in NT, were attributed to shading by stubble that reduced photosynthetically active radiation and red/farred ratios. Winter survival of AWP during 1986–1987 was reduced in NT (78%), compared with NT‐SR (91%) and CT (96%), but no differences occurred in 1988–1989. Less aboveground tissue necrosis of surviving AWP occurred in NT than in NT‐SR and CT for both years. Greater average yields in NT (3568 kg ha−1) and NT‐SR (3530 kg ha−1) than in CT (2700 kg ha−1) were correlated with greater fall growth and less winter injury. Residue management did not influence the yield of WL. Applied P and K did not have consistent effects on winter survival or yield. These results indicate that winter grain legumes can be used to complement wheat production in the design of no‐tillage rotations.
Modeling Tree Growth Sensitivity to Soil Sodicity with Spatially Correlated Observations
Authors: Samra J. S. , Stahel W. A. , Künsch H.
Published: July 2010

Revegetation of degraded sites with an ecologically suitable tree species is an important environmental concern. Adequate evaluation of the salt tolerance of deep‐rooted perennials using pot or small‐plot culture investigations is often difficult. The natural soil heterogeneity found in field experiments provided a means to study the dependence of tree growth on soil variables such as sodicity. In such studies, the random errors of a regression model will usually show spatial correlations, and adjustments of statistical methods are, therefore, necessary. Tree height monitored for 3 yr was related to the root‐zone soil sodicity that was measured in four layers of a fine loamy Natric Haplustalf using a depth increment of 0.3 m. Sodium adsorption ratio was a better predictor of tree height variation than pH and DTPA‐extractable Na. Inclusion of DTPA‐P and ‐K in the regression model did not add to the information. The predictive power of the 0‐ to 0.6‐m layer alone was as good as that of all the four depths (up to 1.2 m) considered simultaneously. Neighboring residuals of ordinary regression of height on soil properties were correlated. Generalized least squares returned narrower confidence intervals of the sensitivity curves than corrected ordinary least squares. Consideration of pH as covariate to the log of the sodium adsorption ratio reduced confidence bands by 5 to 10%, which was roughly equivalent to 10 to 20% more observations.
Relative Efficiency of Broadcast and Banded Phosphorus for Sweet Corn Produced on Histosols
Authors: Sanchez C. A. , Porter P. S. , Ulloa M. F.
Published: July 2010

Histosols used extensively for crop production are often hydrologically linked to environmentally sensitive wetlands, making it imperative that management strategies be developed to improve the efficiency of fertilizer P. Furthermore, sweet corn (Zea mays L.) produced on Florida Histosols is grown in rotation with sugarcane (Saccharum spp.), which responds negatively to high P. Reduction of the P rates applied to sweet corn would increase the compatibility of this common crop rotation. Studies were conducted across six site‐seasons during 1988 and 1989 to evaluate the relative efficiency of broadcast and banded P for sweet corn. Broadcast and banded P rates were 0, 25, 50, 75, and 100 kg P ha−1. Broadcast P was surface applied and disked into the soil before planting. Banded P was applied ≈3 cm below the corn seeds in bands mixed with soil in an approximate diameter of 5 cm. Sweet corn responded to P when soiltest P levels were below 1.2 g m−3. Total marketable yields, yield of U.S. Fancy, and quality parameters of sweet corn ears were increased by P rate and affected by placement in four of the six site‐seasons. Band placement reduced the amount of P required for a specified sweet corn yield and also appeared to result in higher total yield. The relative efficiency of banded to broadcast P depended on soiltest P level. The relative efficiency was greater than 3:1 (band/broadcast) when soil‐test P was <0.2 g m−3 but approached 1:1 as soil‐test P increased to 1.2 g m−3. Overall, results indicate that banding P is, indeed, a viable strategy to reduce the amount of P used for sweet corn production on Histosols.
Comparison of Denitrification in Two Riparian Soils
Authors: Ambus Per , Lowrance Richard
Published: July 2010

The factors controlling NO3 removal in riparian buffer systems are poorly understood. We measured denitrification rates for two Coastal Plain, forested riparian zone soils: Kinston fine loamy sand (fine‐loamy, siliceous, acid, thermic Typic Fluvaquent) and Alapaha loamy sand (loamy, siliceous, thermic Arenic Plinthic Paleaquult). Kinston soils are more poorly drained and have higher organic matter than Alapaha soils. Surface soil and shallow aquifer samples were treated with solutions that contained chloramphenicol with either distilled water, NO3‐N, glucose‐C, or NO3 plus glucose. Denitrification potentials (N2O production in the presence of acetylene) were significantly higher in Kinston soil for both depths. Surface samples from both soils showed significant responses to NO3 additions but no response to C additions without NO3. Subsurface samples, taken from the top of the aquifer, showed no significant response to either NO3 or C treatments for either soil. Both soils showed a high degree of stratification within the top 10 cm, with 88 and 68% of denitrification potential in the top 2 cm for Alapaha and Kinston soils, respectively. Denitrification rates in cores were much lower than in slurries but rates in cores with NO3 or NO3‐plus‐glucose additions were significantly higher than unamended or C‐amended cores for the Kinston soil. Although both soils respond to NO3 additions, Kinston soils are better able to reduce incoming NO3. These results indicate that denitrification in the shallow aquifer is a more important NO3 removal mechanism at the Kinston site than at the Alapaha site.
Field Crop Recovery and Modeling of Nitrogen Mineralized from Labeled Sorghum Residues
Authors: Vigil M. F. , Kissel D. E. , Smith S. J.
Published: July 2010

Efficient use of fertilizer N requires an assessment of the N contribution from decomposing crop residues. The objectives of this study were to quantify and model the amount of mineralized N recovered by a growing crop from 15N‐labeled sorghum (Sorghum bicolor [L.] Moench) residues of variable N concentration and composition. The residues were incorporated into the surface soil of field microplots. The microplots were double‐cropped with sorghum and wheat (Triticum aestivum L.) for a 3‐yr period. The 15N tag in the crop residue was used to distinguish between residue‐derived N and that from soil organic matter. Between 4.5 and 25% of the residue N applied (36–83 kg N ha−1 was applied as crop residue N) was recovered by a sorghum crop 110 d after incorporation. This constituted 56 to 77% of the total N recovered during a 3‐yr period. Accumulated N recovered over time was described by modified first‐order models. Regression analysis indicated that 93% of the variability in N recovered by 110 d could be explained using the C/N ratio and acid‐detergent fiber contents of the residues. Measurements of N mineralized, using the method described above, were compared with predicted N mineralized, using MINIMO (a subroutine of the CERES‐Maize model). After adjusting MINIMO parameters using data collected 110 d after residue incorporation, the slope and intercept of a linear fit between measured and MINIMO‐predicted N mineralized 1097 d after residue incorporation were not different from one and zero, respectively.
Iron Oxidation at the Surfaces of Slash Pine Roots from Saturated Soils
Authors: Fisher H. M. , Stone E. L.
Published: July 2010

Root aeration in saturated gleyed soils is indicated by Fe oxide coatings on live‐root surfaces. Oxygen diffusing through gas‐permeable tissues, from the atmosphere to submerged roots, ultimately diffuses into and oxidizes the rhizosphere. The objectives of this study were to: (i) characterize the oxidizing conditions of slash pine (Pinus elliottii Engelm. var. elliottii) roots growing in saturated conditions, and (ii) test the hypothesis that submerged taproot systems are internally aerated. One study examined Fe‐oxide deposits on the roots of six saplings grown outdoors in drums filled with saturated, Fe‐amended peat. Another study examined roots of two mature slash pines growing naturally on a poorly drained Paleaquult. Orange Fe‐oxide precipitates coasted cortical tissue of sapling taproots and root branches growing in saturated peat. Iron concentrations in these roots were 6 to 96 times greater than in the surrounding peat. In gleyed horizons of the Paleaquult, Fe‐rich precipitates cemented sand to the surfaces of large‐diameter roots and entirely ensheathed fine roots of pine and pine cypress (Taxodium ascendens Brogn.). Prominent mottles, all neoferrans, surrounded fine pores, remnants of decayed‐root channels. Despite the anoxic growing conditions, all of the examined slash pine root systems oxidized and accumulated Fe, supporting other evidence that the taproot systems of slash pine growing in wet soils are internally aerated.
Iron Oxides in Selected Brazilian Oxisols: II. Mössbauer Studies
Authors: Fontes M. P. F. , Bowen L. H. , Weed S. B.
Published: July 2010

Clay fractions (<2 µm) of Oxisols derived from four different parent materials, all from the Triangulo Mineiro Region, Minas Gerais, Brazil, were analyzed using Mössbauer spectroscopy to provide insight into their Fe mineralogy. As little as 0.5% Fe as hematite in the total clay was quantitatively determined by this technique. Aluminum substitution in the Fe oxides resulted in lowering of the field of maximum probability (H max) and this Al substitution affected the magnetic ordering of goethite more strongly than did poor crystallinity. However, Al substitution estimated from Hmax showed some inconsistencies with varying temperature of Mössbauer analysis as well as with values obtained from chemical analysis. Apparently, the currently available Mössbauer calibration curves, obtained from synthetic samples of hematite and goethite, are not readily applicable to soil samples. Little difference in goethite content was found among the soils developed on parent material from mafic rocks. The data suggest that, in the presence of high levels of Fe in an ustic environment, the amount of goethite formed is not strongly correlated with organic matter. The values of the lower half‐width (LHW) of the hyperfine field distribution at room temperature showed some hematites to consist of very fine particles (broad LHW), whereas other hematites were better crystallized (sharper LHW).
Relation between Vertical Soil Movements and Water‐Content Changes in Cracking Clays
Authors: Bronswijk J. J. B.
Published: July 2010

Field studies on swelling and shrinkage in clay soils are scarce, due to the lack of sound experimental methods and suitable mathematical equations. This study was aimed at developing such methods and equations. Disks were positioned at various depths in the soil in order to measure vertical movements in undisturbed soil. Newly developed equations were applied to convert these vertical soil movements into three‐dimensional volume changes and crack volume and to relate them to water‐content changes. These equations are unique in that they are valid for water loss in the structural‐, normal‐, residual‐, and zero‐shrinkage phases, and for both isotropic and anisotropic shrinkage. Methods and equations were successfully tested in a 1‐yr field experiment in a heavy marine clay soil in the Netherlands. The use of seven rotating disks for measuring soil volume changes was about 10% more accurate than two other less laborious methods. An interesting application of this method and equations is the determination of soil water‐content changes by measuring vertical soil movements.
Changes in Soil Water Tables Following Phosphorus Fertilization of Young Slash Pine
Authors: McCarthy J.W. , Stone E.L.
Published: July 2010

This study was conducted in a 19‐yr‐old experimental planting of slash pine (Pinus elliottii Engelm. var. elliottii) on a level, very poorly drained Bladen soil (clayey, mixed, thermic Typic Albaquult) that was highly deficient in P. Phosphorus applied at planting at rates from 0 to 314 kg/ha in a randomized block design resulted in a concomitant range in stand basal areas from 3 to ≈ 38 m2/ha at 17 yr of age. Our objective was to quantify observed differences in height and duration of soil water tables associated with P treatment. Forty‐eight groundwater wells were measured weekly over a 1‐yr period. Drawdown of soil water tables during low rainfall periods was greater and more rapid in the high‐P plots, and the subsequent rise after rainfall was slower. These differences appeared only when the water‐table surface was deeper than about 0.5 m. Above that depth, rapid lateral movement through coarse macropores allowed equilibration among the 0.08‐ha plots, regardless of P treatment. In addition to overcoming acute P deficiency, the single applications of P fertilizers indirectly increased the depth and duration of aerated surface soil, and hence the opportunities for root exploitation.
Solution Chemistry in a Red Pine Plantation Thirty‐Nine Years after Potassium Fertilization
Authors: Shepard James P. , Mitchell Myron J.
Published: July 2010

Accelerated leaching of nutrient cations has been hypothesized as a potential effect of acidic deposition. Nutrient‐cation deficiencies resulting from accelerated cation leaching have been proposed as a contributing factor in forest decline in Europe. The objective of this study was to intensively characterize the solution chemistry of a forest ecosystem in order to assess the status of its nutrient‐cation losses. Precipitation, throughfall, stemflow, and soil solution chemistry were monitored for 3 yr in a red pine (Pinus resinosa Ait.) plantation established in 1930 at the Pack Forest in the Adirondack Mountains of New York. Plots fertilized with 0, 59, and 118 kg K ha−1 in 1948 (designated C, L, and H, respectively) were studied to compare K leaching in systems of different K status and to assess the longevity of K‐fertilization effects on solution chemistry. The concentration of K in throughfall and stemflow was higher in the two fertilized plots relative to the control although 39 yr had elapsed since K fertilization. Fertilized plots generally had higher K concentrations in soil solution in the 0‐ to 8‐ and 8‐ to 15‐cm depths, whereas no differences were found among plots in the 15‐ to 45‐cm depth. Input‐output budgets indicated that much less H, NO3, and SO4 were leached below the rooting zone (0–45 cm) than were received from atmospheric (including dry) deposition. Net losses were observed for K, Ca, and Mg of 64, 294 and 17 molc ha−1 yr−1 (15, 3, and 1% relative to the exchangeable pools), respectively. These losses were not large compared with other forests in the USA.
Carbon Dioxide Degassing Effects on the pH of Spodosol Soil Solutions
Authors: Zabowski D. , Sletten R. S.
Published: July 2010

High levels of CO2 in soil air can influence the composition of the soil solution according to carbonate equilibrium relationships. Carbon dioxide can lower soil solution pH by reacting with water to form aqueous carbonic acid (H2CO*3; the asterisk denotes hydrated carbon dioxide plus carbonic acid). Measurements of soil CO2 from a subalpine Spodosol showed concentrations as high as 12 000 µL L−1 (1.2%). Standard methods used to collect soil solutions can degas CO2 from soil solutions, resulting in elevated solution pH or decreased dissolved inorganic C (DIC). The objectives of this study were to determine whether degassing affected solution pH when solutions were collected from an acidic soil using two different techniques. Both collection methods, low‐tension lysimetry and centrifugation with double‐bottomed cups, were found to cause degassing of CO2 from soil solutions; however, pH was affected only in solutions from the lower B horizon and C horizon. The pH of the solutions from the upper horizons was not affected because high concentrations of soluble organic acids maintain these solutions at a pH <4.5. Carbonate equilibrium relationships suggest that the effect of CO2 degassing on soil solution pH should be negligible for forest soils with a solution pH <4.5 with soil‐air CO2 concentrations up to 6000 µL L−1.
Winter Wheat Phosphorus Fertilization as Influenced by Glacial Till and Loess Soils
Authors: Sander D. H. , Penas E. J. , Walters D. T.
Published: July 2010

Fertilizer P efficiency can be greatly affected by different methods of application. This study was conducted to determine the effect of different methods of P application on winter wheat (Triticum aestivium L.) grain yield, yield components, and fertilizer efficiency as influenced by different soils. Five loess‐derived soils and four till‐derived soils were selected that ranged from 4 to 9 mg P kg−1 (Bray and Kurtz P1). Methods of P application included knifed into the soil (dual placement) (KF), broadcast and incorporated (BF), and application with the seed (SF) at rates of 0, 10, 20, and 30 kg P ha−1. Results indicated that grain yield was increased differently by applied P on the soils studied. Grain yield increase from applied P was significantly greater on till‐derived soils than loess soils, although soil‐test P (Bray and Kurtz Pl) was similar. Till soils also required a higher P rate to maximize yield than did loess soils. Both KF and SF were consistently superior to BF on all soils but were especially superior on the till soils. Fertilizer efficiencies for BF averaged only 2% on the till soils, compared with 18% for KF and SF applications. Applied P increased head numbers on all soils. The primary reason for increased effectiveness of KF and SF applications was increased effectiveness of head production. As head numbers were increased by applied P, head size was decreased, especially for SF application, which increased head numbers more than KF or BF. Our study concluded that the soil test for P did not adequately determine the degree of P deficiency between loess‐ and glacial‐till‐derived soils for winter wheat production. Seed and knifed‐in methods of P application performed similarly on loess and glacial till soils, both being superior to broadcast application.