bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil Erosion Has Limited Effect on Field Scale Crop Productivity in the Southern Piedmont
Authors: Daniels R. B. , Gilliam J. W. , Cassel D. K. , Nelson L. A.
Published: July 2010

Many studies show that slightly eroded soils outyield severely eroded soils. We believe the yield differences between slightly and severely eroded soils is in part a misinterpretation of the data based on the assumption that all parts of a field were equally productive before man‐induced erosion began. The purpose of this study was to quantify the effects of surface horizon variability on the productivity of a soil map unit. Yield data from farmer‐managed Piedmont fields show that all parts of a field or soil map unit are not equally productive, regardless of erosion class. When yields are compared across erosion classes by landscape position, slightly eroded soils usually outyield severely eroded soils, but the differences are small. Because the area of severely eroded soils in most fields is small, their impact on field production is slight. Our analysis shows that when landscape position and erosion class variables are combined with the area of each, the average economic loss resulting from lower crop yields of eroded Piedmont soils is only $4.44 ha−1 yr−1 at 1987 prices.
Effects of Different Urea Fertilizers on Soil and Trees in a Young Thinned Stand of Western Hemlock
Authors: Radwan M. A. , DeBell D. S.
Published: July 2010

Effects of three different urea fertilizers on selected chemical characteristics of soils and foliage, and on growth per tree of a 24‐yr‐old thinned stand of western hemlock [Tsuga heterophylla (Raf.) Sarg.] were compared at a site in coastal Oregon. Treatments were the following: untreated control (C), urea (U), urea treated with N‐Serve®1 [nitrapyrin, 2‐chloro‐6‐(trichloromethyl) pyridine] (U + NS), and sulfur‐coated urea (SCU). Fertilizers were uniformly applied by hand to 0.03‐ha plots in March at 224 kg N ha−1. Soil, to a depth of 20 cm, and current‐year foliage were sampled periodically for 2 yr. Height and diameter of 10 dominant or codominant trees per plot were measured annually for 6 yr. Treatment effects on soil pH varied by fertilizer and sampling date; throughout, pH was lower with U + NS than with U, and the smallest change in pH was associated with SCU. Effects of fertilizer on inorganic N in the soil and on foliar nutrients varied by fertilizer and sampling date. Initially, N‐Serve inhibited nitrification and produced the highest NH4‐N concentrations. In general, all fertilizers increased inorganic N in the soil and total N in the foliage. Fertilizers significantly reduced foliar concentrations of some other macronutrients, especially in the first year after fertilization; some depressions were significantly less with SCU than with the other two fertilizers. Height growth per tree was not significantly affected by any of the fertilizers. Basal‐area and volume growth per tree were significantly greater with the SCU treatment than with the control, U, or U + NS treatments. Beneficial effects of SCU seemed to be mostly due to the slow release of N from the fertilizer, although some positive effect of S cannot be ruled out.
Conditions for Formation of Allophane in Soils
Authors: Parfitt R. L. , Kimble J. M.
Published: July 2010

The Al/Si atomic ratio of allophane was obtained from analyses of soil horizons for a range of New Zealand soils and for a wide range of volcanic soils from around the world. Imogolite‐like allophane (Al/Si = 2) occurs very frequently in soil horizons with >1 or 2% allophane, suggesting that it is more stable, or is more readily formed, in soils than other allophanes. Generally, allophane forms from glass (at pH(H2O) 5 to 7), and feldspar and/or biotite (at pH about 5) in soils with udic moisture regimes and with good drainage. Under these conditions silicic acid and hydroxy‐aluminum cations react to give allophane. A pH >4.7 is required for allophane to precipitate. The Si‐rich allophanes are present in environments where Si in soil solution is likely to be high, and Al‐rich allophanes are present in acid soils where the Si in soil solution is likely to be low. Examples are given of some different types of soils that contain allophane.
Solubility and Phosphorus‐31 Magic Angle Spinning Nuclear Magnetic Resonance of Phosphorus in Sludge‐Amended Soils
Authors: Hinedi Zeina R. , Chang Andrew C.
Published: July 2010

The solubility of P in two sludge‐amended soils was studied. Solubility and activity ratio diagrams for P in sludge‐amended soils were constructed and were compared with those of selected Ca‐P, Fe‐P, and Al‐P minerals. The solid phase controlling P solubility in the sludge‐amended soils appeared to be a carbonated apatite formed through coprecipitation. The 31P magic angle spinning nuclear magnetic resonance (31P MAS NMR) examinations confirmed that P in the sludge‐amended soils was in form of calcium phosphate. The resonant peak [at isotropic chemical shift (δlso) = 3.1 ppm] is indicative of an apatitic calcium phosphate environment characterized by carbonate substitution. Additionally, pyrophosphate was detected by the presence of a peak at δlso = −9 ppm.
Flow‐Through Incubation System for Monitoring Aerobic Soil Nitric and Nitrous Oxide Emissions
Authors: Hutchinson G. L. , Andre C. E.
Published: July 2010

Formation and escape of the gaseous products of aerobic soil N transformation processes such as nitrification are logically studied in the laboratory using an incubation system that neither interferes with the diffusive transport of gases within the soil nor allows accumulation and further reaction of gaseous intermediates after their escape through the soil surface. In addition to satisfying these criteria, our flow‐through incubation system provides for continuously monitoring soil emissions of nitric oxide, nitrous oxide, and carbon dioxide, while also permitting soil analysis as frequently as required to characterize changes in the pool sizes and transformation rates of precursors involved in the production of these gases. Treated soil is placed both in the bottom of each incubation jar and in the eight (maximum) sample vials contained therein. The former serves as a continuous, undisturbed source of the measured gases while the latter provides convenient, preweighed samples for periodic chemical or microbiological analysis. Other features of the incubation system include (i) provision for anaerobic and sterile treatments, and (ii) automated air analyses and data acquisition controlled by a programmable timer that provides the flexibility to quickly and easily tailor the system's sampling, analytical, and recording functions to meet the specific needs of each experiment. Because the yield and composition of gases produced during soil N transformation processes is sensitive to incubation conditions, we propose that important features of this system be adopted by other laboratories to facilitate the comparison of research results by eliminating differences due to methodology.
Elevated Carbon Dioxide and Solution Phosphorus in Soil with Vesicular‐Arbuscular Mycorrhizal Western Wheatgrass
Authors: Knight W. G. , Allen M. F. , Jurinak J. J. , Dudley L. M.
Published: July 2010

Plants infected by mycorrhizae may exhibit increased root/fungal respiration and elevated concentrations of CO2 in the root zone. Carbon dioxide is a thermodynamically viable calcium phosphate weathering agent in calcareous soils. The weathering of phosphate minerals in soils releases P to the soil solution. This study was conducted to determine if differences in soil atmosphere CO2, of consequence to plant P availability, may exist between mycorrhizal and nonmycorrhizal plants. Western wheatgrass (Agropyron smithii Rydb.) was inoculated with raw soil that contained propagules of Glomus spp. and grown in prefumigated soil columns in the greenhouse. Soil atmosphere CO2 levels for inoculated plants averaged twice those of noninoculated plants in two separate experiments. The mean concentrations of CO2 in the soil atmosphere, measured at discrete weekly intervals, ranged between 0.13 and 2.63 kPa for inoculated systems and was significantly higher in 10 of 19 sampling events than for noninoculated systems (range of 0.05 to 1.02 kPa). Total plant P uptake was also significantly higher for inoculated compared with noninoculated plants. Total solution P, measured monthly in saturation throughput from experimental columns, was significantly higher in three of seven sampling events for inoculated compared with noninoculated plant systems. In treatments where noninoculated plants were grown under an imposed soil CO2 regime, total solution P was highly correlated with CO2. In soil systems where P availability is governed by the solubility of Ca‐phosphate minerals, mycorrhizae may contribute to the P nutrition of host plants via a CO2‐enhanced mineral weathering mechanism.
Effect of Tillage Practices on Microbial Biomass Dynamics
Authors: Follett R. F. , Schimel D. S.
Published: July 2010

Changes in microbial biomass dynamics and N cycling were studied in soils from a site derived from native grassland in western Nebraska managed under three tillage systems: no‐till, stubble mulch, and moldboard plow (bare fallow). A treatment of native sod was maintained in each replication. The site was in native sod until 1970 when it was plowed and an alternate wheat (Triticum aestivum L.)‐fallow rotation established. After 16 yr of cultivation, total N concentration in the top 10 cm of soil had decreased to 73, 68, and 50% of native sod in the no‐till, stubble mulch, and plow treatments, respectively. Soil microbial biomass levels were decreased to 57, 52, and 36% for the corresponding tillage treatments as compared to the native sod. In laboratory incubation studies, CO2 respiration was proportional to microbial biomass. Nitrogen mineralization, however, was not proportional to microbial biomass. Immobilization of added 15N was highest for the native sod treatment and amounts of 15N extracted by KCl were inversely related to microbial biomass. Respiration rates per unit of mineralized N (r/Nmin ratio) increased in the order of plow, stubble mulch, no‐till, and sod treatments, suggesting that C availability for microbial growth declined with increased tillage intensity. In these tillage experiments, increased tillage intensity decreased the ability of soil to immobilize and conserve mineral N.
Antecedent Rainfall and Tillage Effects upon Infiltration
Authors: Freebairn D. M. , Gupta S. C. , Onstad C. A. , Rawls W. J.
Published: July 2010

Infiltration characteristics of a Port Byron (fine‐silty, mixed, mesic, Typic Hapludoll) silt loam soil located in the karst terrain of southeastern Minnesota were determined using both ponded water and simulated rainfall. Three tillage treatments, with and without surface cover, were studied to provide a range of soil physical conditions. Simulated rainfall was applied after various amounts of both natural and artificial rain had fallen since tillage. Large differences in infiltration characteristics were attributed to the development of a surface crust. In the absence of a crust, this soil was highly permeable (>200 mm h−1) while surface‐crusted infiltration rates were as low as 10 mm h−1. Infiltration characteristics were related to depth of rainfall since tillage, cover, and random roughness. Statistical analysis showed that >77% of variation in infiltration rate, Green and Ampt hydraulic conductivity, and curve number was explained by the depth of rainfall since tillage, surface cover, and random roughness. A procedure is suggested that describes the change in infiltration characteristics as a function of rainfall since tillage for various tillage conditions.
Slope and Phosphogypsum's Effects on Runoff and Erosion
Authors: Warrington D. , Shainberg I. , Agassi M. , Morin J.
Published: July 2010

The effect of slope on runoff and erosion has been studied mainly in stable soils. Loamy soils from semiarid regions have unstable structures and tend to seal during a rainstorm. The permeability of the seal is sensitive to water quality. The effect of slope angle (5–30%) and addition of phosphogypsum (PG), which changes the water quality, on the infiltration rate (IR), runoff and erosion from an unstable sandy loam soil material (Typic Rhodoxeralf) was studied using a rain simulator. Increasing the slope slightly reduced the amount of runoff and increased the final infiltration rate. The increase in final IR was due to seal erosion. The PG application increased the permeability of the seal, tripled the final IR of the soil sample and decreased the volume of runoff by 50%. Phosphogypsum application also reduced erosion by 60% at the gentlest slope angle. Change in slope angle from 5 to 25% doubled soil loss in the PG‐treated soil samples but increased by seven‐fold soil loss from the untreated soil samples. Gypsum treatment releases electrolytes into the percolating and runoff water. Its effect on soil erosion is due to decreasing the fraction of runoff water, stabilizing the soil structure at the soil surface, and increasing the rate of sediment deposition. The dramatic effect of PG in reducing erosion from steep slopes may be used in stabilizing soil structures on steep slopes.
Root Zone Physical and Chemical Characteristics in Southeastern Spruce‐Fir Stands
Authors: Kelly J. M. , Mays P. A.
Published: July 2010

Because of their remote location and relatively limited extent, soils in the southeastern spruce‐fir zone have not been extensively characterized either physically or chemically. The objective of this study was to describe and characterize the soils found in most of the major spruce‐fir areas in the Southeast as a first step in evaluating potential growth changes in the region. Fifty‐two soil profiles, randomly distributed within the spruce‐fir cover type, were described and samples were collected for physical and chemical analysis. Soils sampled were classified into the following taxonomic subgroups: Lithic Borofolists, Umbric Dystrochrepts, Lithic Haplumbrepts, Typic Haplumbrepts, Pachic Haplumbrepts, and Lithic Haplorthods. The data set was further condensed by focusing only on the rooting zone as defined for each pit by field measurements. Mean rooting depths ranged from 17 to 39 cm. All profiles were strongly to extremely acid (pH 3.6–4.6), with CECs in the 28 to 39 cmol kg−1 range and base saturation less than 4%. Considerable variability was seen among soils in organic matter (132–312 g kg−1) and total Kjeldahl N (TKN) content (5.4–11.0 g kg−1). Statistically significant (P = 0.05) differences also occurred in exchangeable base cations, while total cations exhibited less variability among groups. Extractable P varied little among these subgroups with only the Pachic Haplumbrepts having significantly higher concentrations. Total P exhibited more variability in concentration. Acetate‐soluble SO4‐S ranged in concentration from 0.08 to 0.67 g kg−1. Extractable and exchangeable Al concentrations were generally lowest in the Lithic Borofolists and highest in the Lithic Haplumbrepts. Observed variations are attributed primarily to differences in organic matter accumulation and to the impact of soil creep/soil mixing due to general slope instability.
Modeling and Field Measurements of the Effect of Nitrogen Source on Nitrification
Authors: McInnes K. J. , Fillery I.R.P.
Published: July 2010

The movement of N in relation to water movement and plant uptake is, in part, determined by the rate of nitrification. Nitrifying bacteria are known to be inhibited by low pH. A laboratory incubation and a field experiment were conducted to study nitrification of NH4 supplied by ammonium sulfate (AS), diammonium phosphate (DAP), and urea, N sources that produce environments with different pH, particularly when applied to moderately acidic, poorly pH‐buffered soil. The field site was located on a texture contrast soil (sandy, thermic Natric Durixeralf) at Merredin, Western Australia. The incubations were performed on a sample of the surface 100 mm of this soil. The initial pH and the pH‐buffer capacity of the sample were 5.4 and 4 mmol kg−1 (pH unit)−1, respectively. Nitrification rates were found to vary with the inherent alkalinity of the N source, viz., urea > DAP > AS. The nitrification process was modeled taking into account the effect of pH on nitrifier growth and activity. A linear relation in the model between pH, and both the specific growth rate and activity of the nitrifiers accounted for most of the variability between N sources. In the field experiment, 15N remained largely in nonnitrate form for the first month after application, presumably because of low temperatures, but after 53 d production of NO3 was greater with urea than AS. With the slow rate of nitrification, the leaching of NO3 was minimal.
Adsorption Isotherms of Polyanions on Soils Using Tritium Labeled Compounds
Authors: Nadler Arie , Letey J.
Published: July 2010

Although the effects of polymers on various soil physical properties have been investigated, adsorption of polymers by soils has not been extensively studied. Adsorption isotherms were determined by the batch technique for three tritium‐labeled polyanions on one soil which received various pretreatments. Two polyacrylamide (PAM) compounds in which the NH2 was substituted with OH at 2% (2J) and 21% (21J), rendering them negatively charged, were used. Additionally, a guar compound (4246) used in the study was negatively charged and had a lower molecular weight than PAM. The soil was used without pretreatment and also with pretreatment to create a Ca soil, Na soil, organic matter‐depleted soil, and high‐pH soil. Polyanion type had a relatively greater effect than did soil pretreatment on adsorption, except for the Na soil, which had very low adsorption as compared to the other soil pretreatments. The more negatively charged polyanions (21J and 4246) had linear adsorption isotherms except for 21J on the Na soil. The 2J had adsorption isotherms that plateaued at higher concentrations. The amount of adsorption was in the general order 21J > 4246 > 2J. The exception was for the Na soil in which adsorption for all polymers was low and in the order 4246 > 2J > 21J. Aggregate stability was determined by wet sieving on all the samples. No direct association between the amount of adsorption and aggregate stability was found. The general effectiveness of the polyanions for improving aggregate stability of the natural soil was in the order 2J > 21J > 4246. The reverse trend was observed for the Na soil.
Cultivated and Adjacent Virgin Soils in Northcentral South Dakota: I. Chemical and Physical Comparisons
Authors: Blank R. R. , Fosberg M. A.
Published: July 2010

Evaluation of the effects of cultivation on soil properties in Ustic Mollisols has generally been limited to surface horizons. To examine the effects of cultivation on both surface and subsurface horizons, six paired virgin and cultivated pedons of Williams soil (fineloamy, mixed Typic Argiboroll) or variants of Williams from northcentral South Dakota were compared for differences in various chemical and physical properties. When similar horizons were compared, chemical differences between cultivated and virgin pedons averaged as follows: (i) organic C content was 26% less in Ap horizons; (ii) water‐soluble Si was 49, 46, and 21% greater in A, Bt, and Btk horizons of cultivated pedons, respectively; (iii) water‐soluble Mg, Na, and K were 42, 32, and 18% lower in C horizons of cultivated pedons, respectively; (iv) oxalate‐extractable Fe was 28 and 56% higher in Ap and Bt horizons of cultivated pedons, respectively. When similar horizons were compared, physical differences between cultivated and virgin pedons averaged as follows: (i) bulk density was 18% greater in Ap horizons; (ii) Ap horizons contained 38% more very fine sand and 10% less silt; (iii) A and Btk horizons of virgin pedons possessed greater wet aggregate stability; and (iv) A horizons of virgin pedons average 30% more water retained at 0 MPa tension.
Spring Wheat Plant Parameters as Affected by Fallow Methods in the Northern Great Plains
Authors: Tanaka D. L.
Published: July 2010

Conservation tillage and no‐tillage practices for wheat (Triticum aestivum L.) production reduce soil erosion, conserve soil water, and alter crop environments. A study was conducted on a Williams loam (Typic Argiboroll) to determine the influences of stubble mulch, reduced tillage, and chemical fallow on grain yield and yield components, N and P concentrations in grain, water‐use efficiency, and straw production in a spring wheat‐fallow rotation. Average quantity of surface resldue prior to seeding spring wheat on chemical fallow plots (1371 kg/ha) was about three times the quantity on stubble‐mulch plots (399 kg/ha) and two times the quantity on reduced tillage (703 kg/ha) averaged over the 4‐yr study. The greater quantity of surface residue on chemical fallow plots in 1985 and 1986 resulted in significantly greater stored soil water to 1.70‐m depth when compared to stubble‐mulch plots. However, greater stored soil water did not result in significantly higher grain yield, although straw production for chemical fallow plots (2831 kg/ha) was significantly higher than for stubble‐mulch plots (2036 kg/ha) in 1985. Results of this study suggest that during years of crop stress resulting from limited soil water and above normal early spring temperatures, chemical fallow may produce more spring wheat than stubble‐mulch fallow. However, with limited water or temperature stress, stubble‐mulch fallow may produce more spring wheat than chemical fallow. Grain N concentrations were similar for all years except 1983 when N concentrations were greater for stubble‐mulch plots than chemical fallow plots. Fallow method did not influence grain P concentration. Grain water‐use efficiency was greater for wheat grown on stubble‐mulch plots than on chemical fallow plots.
Surface Hydrologic Response of Soils to No‐Tillage
Authors: Dick W. A. , Roseberg R. J. , McCoy E. L. , Haghiri F. , Edwards W. M.
Published: July 2010

No‐tillage (NT) crop production is practiced on approximately 5% of the total cropland in the USA. The effect of NT on soil surface hydrology is not well understood. In a 0.5‐ha watershed containing Rayne silt loam (Typic Hapludult) of 9% slope to which NT had been continuously applied for 16 or more years, storms with 1‐min intensities >76 mm h−1 were required before surface runoff could be generated. Approximately 96% of the annual surface runoff occurred as a result of these intense storms. To provide more detailed and statistically relevant information of NT effects on surface soil hydrology, a study was conducted using undisturbed lysimeters (4.8 by 1.7 m) containing a Canfield silt loam soil (Aquic Fragiudalf). During the 6 yr of the study, the amount of water that percolated through the soil and left the lysimeters as leachate was two times greater under NT as compared to conventional tillage (CT). Leachate equaled 55% of the precipitation input for the NT lysimeters and 24% for the CT lysimeters, with the greatest amounts leaving the lysimeters during the winter and spring seasons. The amount of leachate, expressed as a percentage of total water (sum of runoff plus leachate), leaving the lysimeters was 88% for the NT treatments and 60% for the CT treatments. Amounts of surface runoff were two times greater under CT than NT. Cross correlation analysis indicated a similar temporal pattern between leachate production and precipitation for both tillage treatments. A stronger temporal relationship existed between precipitation and runoff for the CT than for the NT treatment, however. The effect of NT on surface soil hydrology was clearly evident only 3 yr after the last tillage operation.
Urea Phosphate Effects on Infiltration and Sodium Parameters of a Calcareous Sodic Soil
Authors: Ryan John , Tabbara Hadi
Published: July 2010

There are potential advantages to using acidic fertilizers, especially in irrigation systems. Such materials improve water infiltration and permeability in soils whose structure is adversely affected by excess Na. A laboratory study evaluated urea phosphate (0–20 g kg−1 solutions), which contains H3PO4, with respect to initial infiltration of the urea phosphate (UP) solution and subsequently with water alone. A calcareous clay soil was equilibrated in columns with saline solutions [electrical conductivity (EC), 1.5 dS m−1] with sodium adsorption ratios (SAR) of 5, 10, 20, 40 and 60, to give varying exchangeable sodium percentages (ESP). Initial infiltration rates (IR) were enhanced only with the dilute UP solutions, i.e., 1.0 and 2.5 g kg−1, while all UP solutions improved subsequent infiltration with water alone. As the UP concentration of the infiltration solution increased, decreases occurred in soluble Na from the saturation extract and exchangeable Na, and estimated SAR. The improvement in IR was probably due to H3PO4 solubilizing CaCO3 for exchange reactions of Ca2+ with soil Na+. Urea phosphate may therefore enhance water use efficiency in some irrigated soils as well as serving as an effective source of N and P.
Water‐Drop Kinetic Energy Effect on Water Infiltration in Calcium and Magnesium Soils
Authors: Keren R.
Published: July 2010

The effect of adsorbed Mg and Ca ions on the infiltration rate (IR) of two montmorillonitic soils (Calcic Haploxeralf and Typic Rhodoxeralf) at several kinetic energies of water drops was studied. The kinetic energy of the water drops, the type of adsorbed ion and the electrolyte concentration in the applied solution all have a strong effect on the IR of the soils saturated by Mg or Ca ions. The higher IR values of the soils exposed to electrolyte solution suggests that clay dispersion takes place in Mg and Ca soils exposed to deionized water from simulated rainfall. The IR of the soils decreased with increasing kinetic energy and the values were always lower for Mg soils than for Ca soils. This difference was attributed to the higher width of the hydration shell of the adsorbed Mg than the Ca ion. Breakdown of the soil aggregates and clay dispersion are the two mechanisms that appear to be operative in seal formation when soils are saturated by either Ca or Mg ions exposed to deionized water. Magnesium adsorbed by montmorillonitic soils has a specific effect on IR, whether the soils contain CaCO3 or not.
Herbicide Reactivity of Soil Organic Matter Fractions in No‐Tilled and Tilled Cotton
Authors: Stearman G. K. , Lewis R. J. , Tyler D. D. , Tortorelli L. J.
Published: July 2010

Because of the increased use of herbicides in no‐tilled soils and the difference in organic C distribution between tilled and no‐tilled soils, it is important to compare herbicide activity in different tillage systems. Soil humus fractions and characteristics were determined on surface Lexington silt loam soil (fine, silty, mixed, thermic Typic Paleudalf) samples of no‐tilled and tilled cotton field plots in West Tennessee. Soil humic and fulvic acid were extracted by standard methods. Total C ranged from 9.9 g kg−1 in the tilled soil to 13.5, 16.6 and 23.5 g kg−1 in the no‐tilled soils, with rye (Secale cereale L.), vetch (Vicia villosa Roth) and crimson clover (Trifolium incarnatum L.) cover crops, respectively. The tilled soil had the largest fraction of extractable C and fulvic acid, relative to total soil C. Humic acid was characterized by 13C‐NMR (nuclear magnetic resonance spectroscopy), titration of functional groups, and elemental analysis. Carboxyl groups determined by 13C‐NMR ranged from 6.1 to 7.7 mol kg−1 humic acid and compared more closely with total acidity than with carboxyl‐group determinations by titration. A greenhouse herbicide bioassay was conducted and sorghum [Sorghum bicolor (L.) Moench] growth was measured to indicate soil organic‐matter effects on the phytotoxicity of two herbicides. Herbicide activity was inversely related to soil C, extractable C, carboxyl groups of humic acid, and fulvic‐acid C. Fulvic‐acid C correlated best with herbicide activity. Decreased herbicide activity in tilled (no cover crop) soil was largely attributed to the C in tilled soil being in a more reactive state than C in no‐till (cover cropped) soil.
Solid‐state Carbon‐13 Nuclear Magnetic Resonance and Infrared Spectroscopy of Composted Organic Matter
Authors: Inbar Y. , Chen Y. , Hadar Y.
Published: July 2010

Use of stabilized composts as horticultural container media has been a fruitful and desirable alternative in utilization of agricultural wastes. We prepared compost from cattle manure and investigated the products at various stages of the composting process. The objectives of this work were to measure, quantify and correlate changes in the organic constituents of separated cattle manure (CSM—the solid fraction obtained by centrifugal separators from a slurry of cattle manure) during composting by using both chemical and spectroscopical analytical methods. This research should provide the information necessary for the establishment of maturity indexes for CSM. Carbon‐13 NMR spectra acquired with Cross‐Polarization Magic Angle Spinning (CPMAS) and infrared spectra measured with a Fourier‐Transform InfraRed spectrophotometer (FTIR) were applied to bulk CSM samples without extraction. Both methods confirmed the presence of appreciable amounts of carbohydrates throughout the composting process. During the process the level of carbohydrates decreased while levels of alkyl C, aromatic C, and carboxyl groups increased. The higher rate of decomposition of the carbohydrates resulted in the accumulation of modified lignin. Changes in FTIR absorbance ratios of several distinct peaks were linearly and significantly correlated with various parameters of compost maturity. Crude fiber analyses showed lower concentrations of soluble organic matter, hemicellulose and cellulose while that of lignin increased. Cation exchange capacity increased from 63 to 181 cmol/kg OM, and humic substances content increased markedly from 38 to 71% of the organic matter, while the C/N ratio decreased from 27.1:1 to 8.7:1 during the 147‐d composting process. The proposed spectrometric procedures using CPMAS 13C‐NMR and FTIR measurements directly on decomposing organic matter without extraction, provide information exhibiting significant correlations with more conventional chemical parameters of compost maturity.
Bradyrhizobium japonicum Inoculation and Seed Priming for Fluid‐Drilled Soybean
Authors: Berg R. K. , Jawson M. D. , Franzluebbers A. J. , Kubik K. K.
Published: July 2010

Microbial inoculation coupled with seed priming has potential application in fluid‐drilled cropping systems. The feasibility of applying Bradyrhizobium japonicum during seed priming and at planting using cellulose‐based gels was evaluated with soybean, Glycine max (L.) Merr. A greenhouse study evaluated whether exposure to Strain USDA 110SK or 123SR for 24 h during seed priming increased soybean nodulation by those strains compared to a subsequently applied gel‐carried strain. Well‐nodulated soybeans resulted when inoculation occurred only during seed priming. However, whenever gel inoculation was used, soybean nodules were almost exclusively occupied by the strain applied with the gel, regardless of whether the root radicle had or had not emerged prior to inoculation at seed priming. Differences in condition of seedbeds and soils at planting, and between fluid and conventional planting systems, influenced results from two field sites in eastern Nebraska. Strain 123SR occupied 5 to 10% of nodules at a Sharpsburg‐soil (fine, montmorillonitic, mesic Typic Argiudoll) site when carried in a cellulose‐based fluid gel at planting. Inoculation during solid‐matrix seed priming had little effect on nodule occupancy and Strain 123SR was not recovered when peat was used as a carrier. In contrast, 123SR was rarely recovered, regardless of treatment, from a Kennebec soil (finesilty, mixed, mesic Cumulic Hapludoll). Fewer nodules formed on Kennebec‐ than Sharpsburg‐soil soybeans (17 vs. 31 nodules/plant). Increased grain yields were observed at the Kennebec site (2.87 vs. 2.24 Mg/ha) when fluid‐drilled soybean seed was solid‐matrix primed. Seed priming apparently aided soybean establishment under dry soil conditions. Field delivery of viable bradyrhizobia in gel was shown to be feasible for fluid‐drilled soybean. Short‐term exposure to Bradyrhizobium inocula during seed priming did not increase soybean nodulation by that strain.
Statistical Relationships among Selected Properties of Northern Cameroon Vertisols and Associated Alfisols
Authors: Yerima B. P. K. , Wilding L. P. , Hallmark C. T. , Calhoun F. G.
Published: July 2010

Six Usterts and one Ustalf developed from lacustrine sediments and Precambrian schists in northern Cameroon were characterized for physical, chemical, and mineralogical properties. Correlative statistical relationships were established among physical and chemical properties including surface area (SAT), shrink‐swell (COLE), cation exchange capacity (CEC), percent total clay (PCL), percent coarse clay (PCCL), percent fine clay (PFCL), water retention at 33 kPa (WAT), organic carbon (OC), calcium carbonate equivalent (CCE), pH, and exchangeable sodium percent (ESP). In general, upland soils, developed from Precambrian schists and sandstones, yielded lower correlation coefficients among these properties than lowland soils developed from Quaternary fluvial deposits. For the lowland soils, COLE was highly correlated with SAT, PCL, and WAT; simple coefficients of determination (r2) were 0.91, 0.80, and 0.74, respectively. Similar correlations were obtained for COLE for upland soils, but neither CCE for these soils, nor ESP for either upland or lowland soils were significantly correlated with COLE. The CEC of soils studied was highly correlated with SAT and PCL; r2 values ranged from 0.59 to 0.91. The SAT of Usterts in lowlands was very highly correlated with PCL, PFCL, PCCL, CEC, and COLE; these independent variables generally accounted for greater than 90% of the variance in SAT. For Usterts and Ustalfs of uplands, the SAT was not so closely correlated with these parameters, especially PFCL and PCCL, which varied in amount and clay mineralogy with depth. Multiple linear regressions did not generally improve predictive abilities for COLE, CEC, and SAT over simple linear relationships. Regression relationships developed constitute useful predictive indices for estimating engineering and agronomic properties from existing physical and chemical data and soil survey reports of northern Cameroon.
Mapping Depth to Bedrock on a Glaciated Landscape with Ground‐Penetrating Radar
Authors: Collins M. E. , Doolittle J. A. , Rourke R. V.
Published: July 2010

In many upland areas on glaciated landscapes, it is difficult to examine soil profiles and determine the depth to bedrock. Glacial rock fragments and irregular or weathered bedrock surfaces limit the effectiveness of auger techniques. While general trends can be inferred from the landscape, depth to bedrock or thickness of till cannot be accurately predicted from landscape position alone. Therefore, ground‐penetrating radar (GPR) was used to map the depth to bedrock for two study sites in Maine. Data were used to (i) determine the variability of the depth to bedrock in similar delineated areas of a map unit, (ii) compare the accuracy of GPR with auger methods, and (iii) evaluate the performance of GPR on a glaciated landscape in Maine. Results were confirmed by studying a trench excavated to bedrock. These results indicated that GPR techniques were more reliable and effective than conventional auger techniques for determining the depth to bedrock, and thus for determining the composition of map units that are based on soil‐depth criteria. Additionally, the screw auger was shown to be an unreliable tool for determining soil depths in moderately coarse‐textured tills having large amounts of coarse fragments.
Impact of Crop Production on the Physical Status of a Typic Albaqualf
Authors: Scott H. D. , Wood L. S.
Published: July 2010

Extensive tillage during long periods of time affects soil productivity by altering soil properties. Quantitative measurements were made to determine the combined effects of duration of tillage and production of soybean [Glycine max. (L.)] and rice (Oryza sativa) on selected physical and chemical properties of a Crowley silt loam (fine, montmorillonitic, thermic Typic Albaqualf). Four adjacent fields were sampled which included a virgin prairie and three fields in cultivation for 1, 12, and 30 yr. Undisturbed soil cores were taken at 0.05‐m depth intervals to 0.15 m and analyzed for soil water retention at 10, 30, 50, 80, 100, 500, and 1500 kPa, bulk density and saturated hydraulic conductivity. Organic matter content, pH, and particle size were determined on disturbed samples. Compared with the cultivated soils, the prairie had higher organic matter contents. The 12‐yr and 30‐yr fields in cultivation had higher pH values and bulk densities but lower water retained at a given pressure than the prairie and 1‐yr field in cultivation. No differences were found with respect to particle‐size distribution. For a given soil property, values of CV were affected by time in production but not by depth. The CV was low in the prairie, increased in the 1‐ and 12‐yr fields and in the 30‐yr field was similar to values found in the prairie. The greatest changes in organic matter and bulk density occurred in the initial 12 yr of cultivation. The temporal variability of organic matter contents in the surface 0 to 0.05‐m interval was mathematically modeled with both constant and variable rate equations.
Wheat Residue Loss from Fields under No‐till Management
Authors: Stott D. E. , Stroo H. F. , Elliott L. F. , Papendick R. I. , Unger P. W.
Published: July 2010

To successfully implement no‐till crop management systems for winter wheat (Triticum aestivum L.), knowledge is needed on how rapidly large residue fragments are lost. At five sites in Washington, Texas, and Indiana, losses of surface‐managed winter wheat residues were measured over time. Sites were sampled periodically by using grab samples to determine weight loss per unit area. Thirty weeks after harvest, residue weight losses ranged from 35 to 42% and, after an additional 5 wk, losses ranged from 38 to 55%. Snow cover provided insulation for residues, allowing decomposition to continue during winter when sufficient moisture was present. On chemical fallow plots, there was a 50 to 80% loss after a year. On plots seeded with a no‐till spring crop, residue losses ranged from 81 to 88% by harvest time. Contributions of various sources of residue mass loss are discussed. Effect of residue loading rate was also determined; the highest residue loading rate exhibited the smallest losses. After a year, there was 75, 72, and 50% residue weight loss from the 1680, 3360, and 6720 kg ha−1 plots, respectively. At three sites, changes in the surface area covered by the decomposing residues was measured. Initial coverage from harvest ranged from 93 to 99%. Coverage declined to between 85 and 95% after winter.
Tillage and Fertilizer Effects on Water Infiltration
Authors: Zuzel J. F. , Pikul J. L. , Rasmussen P. E.
Published: July 2010

Tillage techniques have been linked to the formation of tillage pans, which cause reduced infiltration capacity and increased runoff and erosion. Reduced infiltration is especially detrimental on steeply sloping agricultural lands, which are common in many areas of the Pacific Northwest and elsewhere. Infiltration rates in three long‐term tillage treatments with two fertilizer levels were measured using a rainfall simulator. Tillage treatments were plow, disk, and sweep, and have been continuous since 1940. Nitrogen fertilizer has been applied at 45 or 180 kg/ha since 1962. Final infiltration rates for the plow, disk, and sweep treatments averaged 17, 14, and 16 mm/h, respectively. The final rate for the high‐N treatment averaged 22 mm/h vs. 9 mm/h for the low‐N treatment. Results also indicate that surface sealing by raindrop impact and soil frost are probably more important than the tillage pan in controlling the infiltration capacity. Analysis of the infiltration‐rate curves strongly indicates that, if surface sealing is prevented by a complete residue cover, the type of tillage does not have a significant effect on infiltration and is not a major factor in reducing the infiltration capacity of this soil. Conversely, fertility level is an important determinant of infiltration capacity, apparently because of the additional biomass produced by the crop.
Soil Source, Seed Source, and Organic‐Matter Content Effects on Douglas‐Fir Seedling Growth
Authors: Page‐Dumroese D. S. , Graham R. T. , Harvey A. E. , Loewenstein H.
Published: July 2010

Douglas‐fir [Pseudotsuga menziesii var. glauca (Beissn.) Franco] seedling success on harvested areas in northern Idaho is often limited on harsh sites because of moisture and nutrient stress. This study was conducted to determine the importance of soil source, seed source, and organic matter on seedling growth and nutrition. Soil and seed were taken from both high‐ and low‐elevation sites at the Priest River Experimental Forest, Priest River, ID. In a greenhouse, seed was sown in both home‐source soil (taken from local seed‐collection zone) and nonsource soil (taken from opposite seed‐collection zone) mixes. Soil mixes included 100% organic, 50% organic/50% mineral, or 100% mineral soil. Seedlings were measured for height, bud length, root collar diameter, dry root and shoot weight, total N, total P, K, and number of ectomycorrhizal roots tips g−1 of dry root. Both soil and seed sources had similar nutrient and growth characteristics for each of the three soil mixes. One hundred percent organic soils, after only one growing season, produced seedlings that were significantly taller and had greater bud length, root collar diameter, and biomass than those growing in either mineral soil or the organic/mineral mix. Total N and P uptake was greater in the organic soil than in the mineral soil or the mix, but K uptake was greater in pure mineral soil. Low‐elevation seed‐source trees were always taller than their high‐elevation counterparts, an apparent result of adaptation to longer growing seasons. The best ectomy‐corrhizal colonization took place in the mineral soil mix. Ectomy‐corrhizae were most prolific on seedlings grown in nonsource soil when compared with those grown in home‐source soil. Regeneration success in the Inland Northwest will be substantially improved by maintaining the integrity of organic horizons on harvested areas and by adhering closely to seed‐transfer‐zone guidelines.
Ammonia Volatilization from Urea as Influenced by Soil Temperature, Soil Water Content, and Nitrification and Hydrolysis Inhibitors
Authors: Clay D. E. , Malzer G. L. , Anderson J. L.
Published: July 2010

Residue cover influences temperature and water gradients in the soil profile. Changes in the physical environment of the soil influence NH3 volatilization from urea‐containing fertilizers. Field and laboratory experiments were conducted to investigate the influence of residue‐cover‐induced changes in soil water and temperature on NH3 volatilization as impacted by urea treatment with a nitrification and urease inhibitor. Fertilizer treatments were urea, urea plus dicyandiamide (DCD), urea plus N‐(n‐butyl)thiophosphoric triamide (NBPT), and urea plus NBPT and DCD. Following fertilizer application, the soil was either left bare or covered with corn (Zea mays L.) residue. Every 3 h over a 4‐d period, water potential, soil temperature, CO2 production, and NH3 volatilization were measured. The influence of fertilizer treatments on soil pH was determined in a laboratory incubation experiment conducted over 8 d under controlled environmental conditions. Treatments were similar to the field experiment, with NH3 volatilization, pH, and CO2 production measured daily. The NH3‐volatilization rate in the field was highest 2 d after urea application at a time that corresponded with daily maximum soil temperature and decreasing soil water content. Residue cover reduced NH3 volatilization. Volatilization of NH3 as a result of urea application was not increased when urea was treated with DCD. Ammonia volatilization as a result of urea treatment with NBPT was reduced by 100 times over untreated urea. During an incubation experiment, soil pH increased from 6.5 to 7.2 in the urea‐NBPT, and from 6.5 to 9.0 in the urea and urea‐DCD treatments. Associated with the pH increase in the urea‐NBPT treatment was a reduction in CO2 production when compared with the untreated soil.
High‐Gradient Magnetic Concentration of Chlorite and Hydroxy‐Interlayered Minerals in Soil Clays
Authors: Weed S. B. , Bowen L. H.
Published: July 2010

Identification and characterization of chlorite and hydroxy‐interlayered layer‐silicate minerals (HIM) common to many soils of the Atlantic Coastal Plain would benefit if the minerals could be concentrated and isolated by a suitable technique that would not alter them chemically or mineralogically. High‐gradient magnetic separation (HGMS) meets these requirements and was used in this study as a pretreatment in the analysis of soil clays. Deferrated coarse clay (2–0.2 µm) of soil material from several Ultisols on the Coastal Plain of North Carolina was subjected to HGMS using magnetic fields ranging from 0.04 to 0.89 T. Resulting fractions were analyzed by x‐ray diffraction, differential thermal analysis, Mössbauer spectroscopy, and total chemical analysis. Iron‐substituted Ti oxides, including rutile, ilmenite, anatase, and pseudorutile were found in the fractions separated at low magnetic field; chlorite was found at higher field strengths; HIM was separated at medium to high fields; kaolin and quartz plus HIM were found in the tailings. Mössbauer spectroscopy showed the chlorite to contain Fe2+ indicating that it is inherited primary chlorite. The chlorite is trioctahedral and constitutes <10 g kg−1 of the coarse clay; the HIM is dioctahedral and appears to make up >650 g kg−1 of the coarse clay. Structural formula of the HIM calculated from total chemical analysis of Casaturated clay and assuming a negative charge of 49 per unit cell layer is (Ca0.07K0.26Na0.15)(Si7.38Al0.62) (Al2.87Fe0.63Mg0.50)O20(OH)4Al1.86(OH)5(H2O)0.58, suggesting a phengitic muscovite or celadonite precursor. The cation exchange capacity (CEC) based on Ca content in the total analysis is about 15 cmolc kg−1 of HIM. The HGMS was effective in simplifying the mineralogical composition of materials studied, based on Fe content of the components.