bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the Ammonium Bicarbonate‐DTPA Soil Test for Assessing Boron Availability to Alfalfa
Authors: Gestring W. D. , Soltanpour P. N.
Published: July 2010

The NH4HCO3‐DTPA (AB‐DTPA) soil test of Soltanpour and Schwab was developed to simultaneously extract plant‐available P, K, Zn, Fe, Cu, and Mn. The extractant consists of 1.0M NH4HCO3 and 0.005M DTPA adjusted to pH 7.6. Although the AB‐DTPA soil test was developed primarily to extract the previously mentioned nutrients, its use for determining plant availability of other nutrients may be feasible. The objective of this study was to evaluate the AB‐DTPA soil test for determining plant‐available B.

Seven soils from Colorado which varied in texture and organic matter content were treated with sodium borate (Na2B4O7·10H2O) at 0, 1, 3, 5, and 10 µg B/g soil. Alfalfa (Medicago sativa var. ‘Ladak’) was planted in the soils in the greenhouse and then cut three times at the 30% bloom stage. Plant tissue digests and soil extracts (AB‐DTPA, hot‐water, saturation) were analyzed for B using inductively coupled plasma atomic emission spectroscopy (ICP‐AES).

Saturation and AB‐DTPA extractable B levels were nearly identical while the hot water soil test extracted significantly (α = 0.05) higher amounts of B. Alfalfa yields were not significantly (α = 0.05) affected by increasing B application rates indicating B deficiency and toxicity conditions were not present.

Plant B was highly correlated to all three extractants for the individual soils; however, the coefficients of determination (r2) for plant B and soil B differed appreciably when the pooled soils were analyzed statistically: r2 = 0.51 for AB‐DTPA, r2 = 0.87 for hot water, r2 = 0.76 for saturation extract, indicating the superiority of the hot‐water extractant for B. Multiple linear regression analysis also indicated the superiority of the hot‐water extractant and denoted that NH4HCO3‐DPTA soil test required the addition of soil variables (soil pH, % OM, % clay) to be considered an effective test.
Sulfur Nutrition of Rapeseed: I. Influence of Fertilizer Nitrogen and Sulfur Rates
Authors: Janzen H. H. , Bettany J. R.
Published: July 2010

Both sulfur and nitrogen deficiencies have been observed in large acreages of western Canadian soils. These deficiencies prompted an investigation of the interactive effects of N and S on rapeseed (Brassica napus L.), a S‐sensitive crop that is extensively grown on these soils. Four rates of N (0, 50, 100, 300 mg N kg−1 soil) and four rates of S (0, 5, 15, 40 mg S kg−1 soil) were applied in all combinations to rapeseed grown in a pot culture experiment. Maximum seed yield responses to N and S were observed only when the availability of N and S was in approximate balance. Excessive N applications relative to S availability severely suppressed seed production. This effect was attributed to the accumulation of toxic levels of N metabolites. Excessive S applications relative to N availability produced excessive accumulation of S in the plant tissue. The leaves, and, to some extent, the stems, were the predominant sites of excess nutrient accumulation. Seed nutrient concentrations remained relatively stable over all fertilizer treatments. In most plant parts, the applications of one element reduced the concentrations of the other element by a “dilution” effect. The optimum ratio of available N to available S in the soil was estimated to be 7 to 1. Ratios below 7 resulted in inefficient utilization of the assimilated S, while ratios exceeding 7 resulted in reduced seed yields.
The Relationship of Present Topography to Pre‐Loess Deposition Topography in Eastcentral Ohio
Authors: Norton L. Darrell
Published: July 2010

Previous work in Ohio has shown that loess deposition over glacial till smoothed the underlying topography considerably, resulting in a highly variable loess thickness. In this study, loess thickness and other soil properties were measured on an erosional landscape system and were presented by contour maps and three‐dimensional diagrams. The shape of the modern surface was very similar to the shape of the paleolandscape, so the loess thickness did not smooth the old surface very much. The uniform thickness of the loess allowed the amount of soil material removed from the landscape units studied to be calculated. Depending on the assumed age of loess deposition, the rate of geological erosion ranged from 0.035 to 0.060 Mg ha−1 yr−1 for this summit and shoulder position. The thickness of the fragipan was highly correlated with slope position and was more strongly developed on the shoulder positions. Studies such as this one, where depth measurements of soil properties are made at many points in a landscape and where the data is represented in three‐dimensional diagrams will lead to a better understanding of processes, such as erosion, that depend greatly on landscape position.
Predicting Soil Temperature and Soil Heat Flux under Different Tillage‐Surface Residue Conditions
Authors: Gupta S. C. , Larson W. E. , Allmaras R. R.
Published: July 2010

Model descriptions for soil temperature utilizing readily available information are needed to project management effects of tillage. In many cases these model descriptions must cover periods of a month or more during the growing season. A procedure was developed to utilize daily maximum and minimum air temperature along with normalized root zone temperatures. Root zone temperatures were much more sensitive to the surface residue than the surface roughness (or other tilled layer property) characteristic of tillage‐residue cover combinations. However, root zone temperatures normalized with respect to daily maximum and minimum temperatures were of a similar shape for all tillage‐residue cover combinations. These normalized soil temperatures also afforded easy comparison among treatments and locations. A Fourier series analysis of daily normalized soil temperatures averaged over part of a growing season showed that the average value around which average normalized soil‐temperature curves (diurnal wave) oscillate varies with depth and season. Amplitudes and phase angles of the first two harmonics of the Fourier series were approximately the same for all treatments over four seasons.

A model was developed to estimate soil temperatures for various tillage‐residue cover treatments with and without a crop cover for the northern Corn Belt states. The model utilizes the first two harmonics of the Fourier series and the relationships between the daily maximum and minimum soil surface temperatures vs. maximum and minimum air temperatures. Input needed for the model are: daily maximum and minimum air temperatures, thermal diffusivity of soil, and coefficients of the Fourier series fitted to average normalized soil temperatures. At one location in southern Minnesota the model predicted soil temperatures at 0.05 and 0.10‐m depths over 45 d during the spring of 1980 within an average difference of 2.0°C and a deviation of no more than 3.8°C 67% of the time.

A procedure to estimate hourly soil surface heat flux under different tillage and residue conditions is also presented. The procedure is based on the Fourier series soil temperature model. Inputs needed for the model are: (i) daily maximum and minimum air temperatures, (ii) thermal diffusivity, and (iii) volumetric heat capacity. Soil surface heat flux is often needed in the calculation of evaporation from the energy budget methods.
The Effects of Texture on the Resistance to Water Movement within the Rhizosphere
Authors: Bristow K. L. , Campbell G. S. , Calissendorff C.
Published: July 2010

A growth chamber study was designed to investigate the relative importance of the resistances involved in water movement within the rhizosphere. The components considered are the soil, the soil‐root interface, and the root itself. The plant species used was sunflower (Helianthus annus L.), grown in three soils of different texture. After several weeks of growth all water application was stopped and the soil allowed to dry by transpiration alone. Relevant destructive measurements were carried out during the course of the drying period, one pot being sacrificed for each set. Measurements included transpiration rate, soil and xylem water potential, rooting density, and hydraulic properties of the soils. As the soil dried, total resistance to water movement was found to increase most rapidly in the coarsest textured soil and least rapidly in the finest textured soil. A steady state model was used to partition the total resistance between the various resistive components. This enabled the root plus interfacial resistance to be quantified in terms of soil texture and water content.
Measurement of Inverted Electrical Conductivity Profiles Using Electromagnetic Induction
Authors: Corwin D. L. , Rhoades J. D.
Published: July 2010

Due to sharp discrepancies in the relative response of the horizontal and vertical coil configurations of the Geonics Limited EM‐38 electromagnetic induction soil conductivity meter for the top 15 cm of soil, the accuracy of measurement of bulk electrical conductivity for soil having a high surface electrical conductivity relative to deeper depths (i.e., an inverted electrical conductivity profile) has been unreliable. Two new approaches have been developed to compensate for these discrepancies, either through compensations in the vertical coil configuration response curve or the reestablishment of EM0,H adjustment curves utilizing data solely from inverted conductivity profiles. Both approaches yield more consistently reliable calculated bulk soil electrical conductivities when compared to measured electrical conductivities using the four‐electrode probe. The latter approach, however, appears to be more accurate.
Physical Transformations in a Vertical Soil‐Saprolite Sequence
Authors: O'Brien E. L. , Buol S. W.
Published: July 2010

A continuous vertical soil‐saprolite‐granitic gneiss profile was studied to determine its morphology, micromorphology, and physical properties. A clayey, kaolinitic, thermic Typic Hapludult formed in 4.5 m of saprolite derived from a granitic gneiss was sampled in 14 different levels from the surface to the consolidated rock to determine changes with depth. Morphologically, the Piedmont soil has a gravelly sandy loam surface over a red, clayey, moderately structured subsoil. The saprolite has a 1.15 m transitional sandy clay loam horizon over 3.35 m of a sandy loam saprolitic material with rock controlled structure overlying consolidated rock. Micromorphologically, content of skeletal grains increases with increasing depth in the subsoil and saprolite. Plasma and compound void volume decrease with increasing depth. Bulk density measurements of 0.95 Mg m−3 are found in the soil surface, 2.46 Mg m−3 in the rock, and about 1.3 Mg m−3 in the subsoil and saprolite. Pore size distribution as indicated by soil moisture release measurements shows 40% more macroporosity in the subsoil than the saprolite. Saturated hydraulic conductivity in the subsoil is 2.2 µm s−1—over twice the 1.1 µm s−1 found in the upper saprolitic horizon. Theoretically derived unsaturated hydraulic conductivities show little difference between the subsoil and saprolite. The significant physical changes accompanying the weathering of this saprolite to soil include: a weathering of sand‐sized weatherable minerals to clay‐sized minerals, an increase in structural strength of the Bt horizon, an accompanying increase in macroporosity in the Bt horizon, and higher saturated hydraulic conductivity in the Bt horizon than in the saprolite.
Temperature and Moisture Regimes in Soils Mulched with Transparent Polyethylene
Authors: Mahrer Ytzhaq , Naot Ofir , Rawitz Ernest , Katan Jaacov
Published: July 2010

A numerical one‐dimensional model was developed in order to study the effect of soil mulching with transparent polyethylene film upon the soil moisture and temperature regimes. Environmental conditions, soil physical characteristics, and optical properties of the cover are considered. Calculated moisture and temperature profiles were compared with observed ones in experimental field plots. It was shown that soil moisture and temperature distributions are significantly influenced by the polyethylene mulch. The results indicate that the numerical model accurately predicts the soil moisture and temperature regimes in two tested soils. In both a Rehovot sand soil and a light clay soil, experimental and calculated results showed that the temperature maxima of the soil increase with increasing soil moisture content. In the light clay soil both the experimental and numerical results showed that the tarping of the soil with transparent polyethylene caused a significant increase in soil moisture in the upper soil layer. At close to air‐dry moisture content, the maximum temperature of the light clay soil indicated a much higher value than the wettest mulched plot of the same soil. Physically based explanations are given for the measured and computed results.
Development and Calibration of an Irregular Hole Bulk Density Sampler
Authors: Flint Alan L. , Childs Stuart
Published: July 2010

Existing methods for measuring soil density and rock fragment content are often imprecise or difficult to use on steep slopes and in skeletal soils. A portable device was developed for measuring these physical properties using an irregular hole technique. The method employs a direct volume measurement using lightweight 3‐ to 6‐mm diameter epoxy spheres. A sample volume of 1.5 × 10−2 m3 can be measured and rock fragments up to 85 mm in diameter can be sampled. The combination of direct volume measurement and surface calibration before measurement allows determination of sample volume to 1% accuracy. Measurements made with the new device compare well with sand cone and core sample measurements under conditions considered favorable for all methods. The device is particularly useful on steep slopes and where rock fragment contents greater than 15% limit the standard methods.
Denitrification and Nitrous Oxide Production in Successional and Old‐Growth Michigan Forests
Authors: Robertson G. Philip , Tiedje James M.
Published: July 2010

Soils from 12 successional and old‐growth forests in Michigan were examined for N2O production under each of three incubation conditions: without amendment, in a 20% (vol/vol) acetylene atmosphere, and in an acetylene‐amended atmosphere after a simulated rainfall. Intact cores were taken during the growing season and incubated in the laboratory for 90 to 180 min in a porespace‐recirculation system that sampled for N2O and CO2 at 10‐min intervals. Measurable rates of N2O production occurred in cores from all sites and under all incubation conditions; in general but not always, rates were higher in the presence of C2H2 than in its absence, and increased upon simulated rainfall. Under acetylene‐ and water‐amended conditions, mean production was highest in an old‐growth and a late‐successional hardwood site and in a recent clearcut (30 to 80 mg N2O‐N m−2 d−1); intermediate rates (2 to 3 mg N2O‐N m−2 d−1) were observed in soils from a midsuccessional hardwood stand and from two old‐field communities, and low rates (<0.6 mg N2O‐N m−2 d−1) occurred in soils from a young sand dune community, from a midsuccessional and a late‐successional hardwood stand, and from a managed, a midsuccessional, and an old‐growth conifer community. Nitrate production, CO2 production and water content could explain 65% of the variation in rates of N2O production among sites under acetylene‐amended conditions. Nitrate pool sizes and pH differed substantially among sites but were not well correlated with N2O production. The presence of a class of cores that produced N2O only in the absence of acetylene suggests that sources of N2O other than denitrifiers may be important in some sites.
Potassium Chloride for Improved Urea Fertilizer Efficiency
Authors: Rappaport B. D. , Axley J. H.
Published: July 2010

Muriate of potash (KCl), a major source of fertilizer K, can be applied in combination with urea [(NH2)2CO] to reduce ammonia (NH3) volatilization. Addition of KCl in combination with urea to fertilize field crops should not increase fertilizer costs.

Laboratory investigations with a Klej loamy sand (Aquic Quartzipsamments) showed that a combination of 1 part urea with 1 part or greater of KCl (by weight) as a fertilizer solution reduced ammonia losses from 42% to 4.6% or less.

Application of 1 part of KCl to 1 part urea in a liquid fertilizer increased sorghum‐sudan grass (Sorghum sudanese L.) hay yields over that of urea alone by 85 g m−2 in field studies on a Galestown sandy loam (Psammentic Hapludults). Also, 0.77 parts of KCl to 1 part of urea was equally beneficial. Yield of field corn (Zea mays) on a Hagerstown silt loam (Typic Hapludalfs) was increased by urea in combination with potassium chloride over urea alone by 113 g m−2.
Contour‐Lined Photobase Maps for Soil Mapping
Authors: Hodges Robert L. , Baker James C. , Darling Dennis
Published: July 2010

Contour‐lined photobase maps have proved advantageous to soil scientists making soil surveys in the wooded areas of the Coastal Plain of Virginia. On conventional, unlined aerial photographs, dense vegetative regrowth of cut over woodlands appear as uniform tones. This restricts photo interpretation, making accurate depiction of soil boundaries difficult. Contour‐lined photobase maps allow the soil scientist to maintain location within the accuracy of the topographic map, resulting in increased accuracy in soil boundary placement. In the Coastal Plain of Virginia, contour‐lined photobase maps have facilitated an increase in the mapping rate.
Boron Adsorption by Montmorillonite as Affected by Particle Size
Authors: Keren R. , Talpaz H.
Published: July 2010

The effect of clay particle size on B adsorption by the Na and Ca forms of montmorillonite was determined at two pH levels. Boron adsorption by the smaller clay particles of both Na and Ca forms was much greater than by the larger clay particles at both pH levels. The increase in B adsorption in the smaller clay particle systems was related to the increase in the edges' surface area of the clay platelets. Data from batch experiments were compared with results computed according to fitted adsorption coefficients (maximum B adsorption and affinity coefficients which related to the binding energy). The agreement between calculated values and experimental results indicates that the adsorption model can be used to predict B adsorption by Na‐ and Ca‐montmorillonite at various particle sizes.
Amendment of Mine Spoil to Increase the Number and Activity of Microorganisms
Authors: Lindemann W. C. , Lindsey D. L. , Fresquez P. R.
Published: July 2010

If mine spoil areas are not topsoiled in spoil reclamation, microbial numbers and activities may need stimulation. The objectives of this study were to determine the effect of spoil amendment on microbial parameters and mycorrhizal infection of grass species in the field. Spoil on the San Juan coal mine near Farmington, New Mexico was amended with hay, sludge, or topsoil inoculum, or was covered with 30 cm of topsoil as normally practiced. Microbial parameters measured in both the rhizosphere and nonrhizosphere included numbers of bacteria, Streptomyces, ammonium oxidizers, Azotobacter, dehydrogenase enzyme activity and fungal genera distribution. Mycorrhizal inoculum (roots and soil containing Glomus mosseae and G. fasciculatum) was also applied and plants were examined for percentage mycorrhizal roots. The addition of either sludge or hay or topsoiling increased the number of microorganisms, enzyme activity and fungal genera distribution in nonrhizosphere spoil. Topsoil added as an inoculum had little or no effect on these biological factors. Only the number of Azotobacter was significantly increased in the rhizosphere by spoil amendment. Providing an available carbon source was more critical in stimulating an active and varied microflora than was a topsoil inoculum. Mycorrhizal infection was poor in all treatments. Amendments had no or little effect on percentage mycorrhizal roots. Covering the spoil with 30 cm of topsoil provided the greatest amount of mycorrhizal infection.
Fate of Labeled Nitrogen Fertilizer Applied to Winter Wheat for Five Years
Authors: Olson R. V. , Swallow C. W.
Published: July 2010

To assess the effect of time and rate of fertilizer N applications on fate of the applied N, a 5‐yr field experiment was conducted with winter wheat (Triticum aestivum L.). Microplots confined in metal frames to a depth of 1.42 m received annual applications of (NH4)2SO4 containing 7.65 atom %15N. Treatments, replicated four times, consisted of 50 and 100 kg N/ha applied in fall and spring on a Pachic Argiustoll soil. In four of the years, spring applications gave better fertilizer use efficiency than fall treatments, probably because of greater immobilization of fall‐applied N. After 5 yr, 27 to 33% of the applied fertilizer N had been removed by the grain. Soil N use was increased by fertilizer in some years and in those cases was correlated highly with increased growth, suggesting that the cause was larger root systems rather than a priming effect. Amounts of fertilizer N in the 1.8‐m soil profiles increased each year and at the end of the experiment averaged 54% of that applied during the 5 yr for 50‐kg treatments and 47% for 100‐kg treatment. From 71 to 77% of the surface‐applied fertilizer N remaining in the profiles was in the 0‐ to 0.1‐m soil layers. Most of the residual fertilizer N was immobilized in organic forms, but late applications and dry conditions in 1980 greatly reduced both nitrification and immobilization. There was good agreement between 15N and difference measurements of crop removal of fertilizer N for the 5‐year period, although difference measurements were more variable and did not agree well with 15N measurements in individual years.
Ultrasonic Dispersion of Soil Aggregates Stabilized by Polyvinyl Alcohol and T403‐Glyoxal Polymers
Authors: Moen D. E. , Richardson J. L.
Published: July 2010

Aggregate and structural analysis of soils treated with polymeric soil conditioners has proved to be a problem and prompted this study utilizing an ultrasonic dispersion method. Two Red River Valley soils, a Glyndon loam and a Fargo silty clay were tested along with a mine spoil material from near Zap, North Dakota. The Fargo and Glyndon soils were treated in the laboratory with T403‐glyoxal, a newly developed two‐phased amine‐aldehyde polymer, and polyvinyl alcohol (PVA). The dispersion created by an ultrasonic power input of 37.5 W for 30 to 400 s was determined by pipette analysis. The percent clay remaining undispersed decreased exponentially with increased time of exposure to ultrasound. Stability of sample aggregates was determined by the initial dispersion value and strength of aggregates by the rate of dispersion (slope). Tests using a sodium‐affected minespoil material resulted in low values for both stability on wetting and aggregate strength thus supporting the methods used. Polymer treatments resulted in 50% increases in stability on wetting and large increases in aggregate strength. Samples treated with 1% PVA or 5% T403‐glyoxal were made effectively coarser because of the extreme strength of microaggregates. Polyvinyl alcohol was much more effective per unit weight than T403‐glyoxal, but the latter was effective in creating very strong microaggregates (<0.25 mm), which effectively reduced plasticity of the soils.
Formation of Ferric Oxyhydroxides from Ferrous and Ferric Perchlorate in Stirred Calcareous Systems
Authors: Loeppert R. H. , Hossner L. R. , Amin P. K.
Published: July 2010

Reactions between Fe salts and CaCO3 are important in influencing the nutrient availability of Fe in calcareous soils and are also important in soil pedogenic processes. The objective of this study was to investigate the reaction between Fe2+ or Fe3+ and CaCO3, especially with regard to influence of CaCO3 surface area and PCO2 on rate of reaction and Fe oxide product. Ferrous or ferric perchlorate, 0.01M, was reacted with calcite in stirred aqueous suspensions while bubbling vigorously with an oxidizing purge gas. Redox potential and pH were monitored continuously during the reactions. Upon addition of Fe(ClO4)2 to an aqueous calcite suspension, pH was initially controlled by the solution phase Fe at approximately 5.0 to 6.0; however, as the Fe salt was completely precipitated there was a rapid rise in pH to the equilibrium pH of calcite. In all cases, pH and redox endpoints corresponded closely. Rate of reaction was strongly dependent on CaCO3 surface area. With the Fe(ClO4)2 system and with air as the purge gas, rate of reaction was linearly related to calcium carbonate surface area. Increased PCO2 resulted in reduced rates of reaction and deviation from the linear relationship between surface area and rate of reaction. With the Fe(ClO4)2 system, mineralogy of the Fe oxide product as determined by x‐ray diffraction was influenced by PCO2. Lepidocrocite and goethite were the dominant products formed in the presence of air and 20% CO2 (balance air), respectively. With the Fe(ClO4)3 system, poorly crystalline ferrihydrite was the only product obtained.
Macroporosity to Characterize Spatial Variability of Hydraulic Conductivity and Effects of Land Management
Authors: Ahuja L. R. , Naney J. W. , Green R. E. , Nielsen D. R.
Published: July 2010

To develop simplified methods of hydraulic characterization of field soils and effects of management, frequency distribution of macroporosity (or effective porosity) in a soil is investigated as a measure of its saturated hydraulic conductivity distribution. The effective porosity (φe) of a soil is related to its saturated hydraulic conductivity (Ks) by a generalized Kozeny‐Carman equation. The exponent of this relationship is assumed to vary within a narrow range (value of 4 or 5). The equation is then combined with scaling theory to derive the frequency distribution of Ks scaling factors from the φe distribution. These concepts are tested on experimental data for two widely different soils, a mollisol and an oxisol. The φe is defined as total porosity minus soil water content at −33 kPa pressure head. The exponent of the Ks‐φe relationship is found to be nearly 4 for the soil‐core data of both soils, while for a smaller set of in‐situ field data for oxisol, which was within a narrow range of φe, the value of the exponent was smaller. There was a considerable scatter in the relationships. However, with the exponent set equal to 4 or 5 the distribution of Ks scaling factors derived from φe distribution closely matched the experimental Ks‐derived distribution. The approach has a promise for large‐scale applications.
Hydraulic Conductivity and Water Retention of Clay Soils Containing Coarse Fragments
Authors: Ravina Israela , Magier Joshua
Published: July 2010

Field observations show that clay soils with medium to high coarse fragment contents are less compacted, have a more favorable structure and provide better physical condition for tree growth than similar soils containing small amounts of coarse fragments. The effect of coarse fragments on soil compaction, hydraulic conductivity, and moisture retention at low suctions was investigated. Increasing coarse fragment content increased resistance to compaction and consequently preserved lower soil bulk density. Larger volumes of large pores were found after compaction of soil with increasing coarse fragment content. In compacted soils of increasing coarse fragment content, hydraulic conductivity was higher. Aerated porosity of soils between fragments increased with increasing fragment content. It was concluded that coarse fragments contribute to improved physical conditions by acting as a “skeleton,” which resists soil compaction.
Aerobic and Anaerobic Microbial Populations in No‐till and Plowed Soils
Authors: Linn D. M. , Doran J. W.
Published: July 2010

Surface soils from long‐term tillage comparison experiments at six U.S. locations were characterized for aerobic and anaerobic microbial populations and denitrification potential using an in situ acetylene blockage technique. Measurements of soil water content, bulk density, and relative differences in pH, NO‐3‐N, water‐soluble C, and total C and N contents between tillage treatments were also determined at the time of sampling. Numbers of aerobic and anaerobic microorganisms in surface (0–75 mm) no‐till soils averaged 1.35 to 1.41 and 1.27 to 1.31 times greater, respectively, than in surface‐plowed soils. Bulk density, volumetric water content, water‐filled pore space, and water‐soluble C and organic C and N values were similarly greater for surface no‐till soils compared to conventionally tilled soils. Deeper in the soil (75–300 mm), however, aerobic microbial populations were significantly greater in conventionally tilled soils. In contrast, below 150 mm, the numbers of anaerobic microorganisms differed little between tillage treatments. In no‐till soils, however, these organisms were found to comprise a greater proportion of the total bacterial population than in conventionally tilled soils. Measurements of the denitrification potential from soils at three locations generally followed the observed differences in anaerobic microbial populations. Denitrifying activity, after irrigation with 15 mm of water, was substantially greater in surface 0‐ to 75‐mm no‐till soils than in conventionally tilled soils at all locations. At the 75‐ to 150‐mm soil depth, however, the denitrification potential in conventionally tilled soils was the same or higher than that of no‐till soils. In surface no‐till soils, increased numbers of anaerobic microorganisms and a substantially greater denitrification potential, following irrigation, indicate the presence of less‐aerobic conditions in comparison to conventionally tilled soils. This condition appears to result from greater soil bulk densities and/or water contents of no‐till soils, which act to increase water‐filled porosity and the potential for water to act as a barrier to the diffusion of oxygen through the soil profile.
Soil Temperature Effects on Root Growth and Phosphorus Uptake by Corn
Authors: Mackay A. D. , Barber S. A.
Published: July 2010

Temperature affects each of the mechanisms involved in P uptake by corn. The extent to which each reduces P uptake, however, has not been resolved. The objective of this study was to determine the effect of temperature on each of the parameters used in a mechanistic mathematical model that predicts P uptake and then to use the model in a sensitivity analysis to evaluate the temperature dependency of parameters critical for predicting P uptake by corn. The effect of soil temperature, 18 and 25°C, and soil P status on root growth and P uptake by corn (Zea mays L.) was investigated in a series of pot experiments in a controlled climate chamber. Total yield of corn was 4‐ to 6.4‐fold, root growth 2.6‐ to 5.1‐fold, and P uptake 2‐ to 4‐fold greater at 25°C than at 18°C. Increasing air temperature to 25°C while holding soil temperature at 18°C resulted in a 2.7‐fold increase in root growth and a 2.2‐fold increase in P uptake. Predicted P uptake calculated with a mechanistic mathematical model by corn grown for 8, 15, and 21 d agreed with observed P uptake at both 18°C (y = 0.97x + 3.64, r = 0.99**) and 25°C (y = 1.07 x − 1.86, r = 0.99**). In the sensitivity analysis the parameters used to calculate P uptake at 18°C were changed individually to those measured at 25°C and then P uptake was again predicted. Rate of root growth, which increased 4.97‐fold when temperature increased from 18 to 25°C, had the most pronounced effect on calculated P uptake, indicating that this was the primary reason low temperature reduced P uptake by corn. The parameters describing the movement of P to the root surface and P uptake at the root surface appear to play only a minor role in causing reduced P uptake by corn at low temperature.
Effects of Desurfacing of Alfisols and Ultisols in Southern Nigeria: I. Crop Performance
Authors: Mbagwu J. S. C. , Lal R. , Scott T. W.
Published: July 2010

The widespread incidence of soil erosion in the tropics has been reported but few studies have dealt with the specific problem of decline in crop productivity associated with the soil loss. An understanding of the effect of topsoil loss on crop yield is needed in order to develop some management practices for restoring productivity on eroded soils. The effects of topsoil removal on maize (Zea mays L.) and cowpea (Vigna unguiculata L.) grain yields and their response to N and P rates were investigated in one double cropping sequence on an Ultisol at Onne in southeast Nigeria, and two Alfisols at Ikenne and Ilora in southwest Nigeria. In comparison with unfertilized uncut control, maize grain yield was reduced by 95.4, 95.4, and 100% at Onne, 30.5, 73.6, and 93.5% at Ikenne, and 72.5, 82.6, and 99.5% at Ilora for 5‐, 10‐, and 20‐cm soil depths removed, respectively. Cowpea yield reductions were 62.7, 70.6, and 68.3% at Onne, 1.5, 59.1, and 65.1% at Ikenne and 42.6, 33.1, and 80.5% at Ilora for 5, 10, and 20 cm of soil removal, respectively. None of the fertilizer combinations used was an effective substitute for topsoil removed at Onne during the two seasons and at Ilora during the second season. The rate of 60 and 120 kg N ha−1 in combination with 30 kg P ha−1 restored maize yield at Ikenne equivalent to or within 4% of the control for 5 cm soil removed. At Ilora combinations of 60 and 120 kg N ha−1 and 15 and 30 kg P ha−1 produced maize grain yields equivalent to or within 43% of control where 5 cm soil was removed.
Effect of Exchangeable Sodium and Phosphogypsum on Crust Structure—Scanning Electron Microscope Observations
Authors: Gal M. , Arcan L. , Shainberg I. , Keren R.
Published: July 2010

The effect of soil sodicity and phosphogypsum treatment on the structure of the crust of two soils (sandy loam and clay soil) was studied using a scanning electron microscope (SEM). The crust of the sandy loam with ESP 1.0, and the two soils at all levels of sodicity when treated with phosphogypsum, consisted of a compacted skin seal attributed to the mechanical impact of raindrops. Little clay movement or development of a “washed in” layer was observed under these conditions. Conversely, when the ESP > 1.6 (in the two soils) the crust consisted of naked sand and silt grains over a dense “washed in” layer. The compacted layer of disintegrated aggregates is not stable when soil and water conditions are favorable for clay dispersion (sodic soils and low electrolyte soil solutions). In soils with no exchangeable sodium, aggregate breakdown and surface compaction by raindrops are the dominant mechanisms for crust formation. In soils with ESP values above 1.5, chemical dispersion of the soil clays (enhanced by the sodicity of the soil, the low electrolyte concentration in the rain, and the stirring effect of the raindrops) and the downward movement of the clays into the “washed in” layer clogging the pores in this layer were the dominant mechanisms in crust formation. Soils with a “washed in” layer had a very low infiltration rate.
Konyaite in Salt Efflorescence from a Tertiary Marine Deposit near Geelong, Victoria, Australia
Authors: Shayan A. , Lancucki C. J.
Published: July 2010

Konyaite [Na2Mg(SO4)2·5H2O] was identified for the first time in Australia in salt efflorescences from a Tertiary marine deposit below exposed basalt flows at a quarry near Geelong, Victoria. Other soluble salts in the efflorescence were epsomite (MgSO4·7H2O), gypsum (CaSO4·2H2O), and halite (NaCl). Heating at 110°C converted the konyaite to a mixture of bloedite [Na2Mg(SO4)2·4H2O], loeweite [Na4Mg2(SO4)4·5H2O], and thenardite (Na2SO4). Recrystallization at 23°C of the efflorescence dissolved in varying amounts of water indicated that epsomite and thenardite form from dilute solutions, whereas increasing amounts of konyaite recrystallize from the more concentrated solutions under faster evaporative conditions. The salts are transported to the basalt quarry site in river seepage or ground water from the neighboring marine deposits and are left on the exposed surfaces by evaporation.
Routine Procedure for Rapid Determination of Soil Carbonates
Authors: Loeppert R. H. , Hallmark C. T. , Koshy M. M.
Published: July 2010

A procedure is presented for the routine determination of soil carbonates based on the following reaction: CaCO3 + 2 HC2H3O2 → Ca2+ + 2 C2H3O2‐ + H2O + CO2 (g) A known quantity of acetic acid is added to a known quantity of soil. The pH of the reaction mixture is then determined following complete dissolution of CaCO3. Calcium carbonate content is determined empirically from a standard curve relating pH to known CaCO3 content according to the equation: pH = K + n log [CaCO3/(T − CaCO3)], in which T equals the total amount of calcium carbonate which could be completely dissolved by the acetic acid added to the system, and K and n are constants. Several possible sources of error exist in the procedure; however, potential errors may be minimized by the maintenance of optimum working conditions. Results obtained by the acetic acid procedure compared favorably with results obtained by the Chittick procedure. The proposed procedure has the advantage of simplicity and offers a rapid alternative for routine determination of soil carbonates.
Nitrogen Mineralization Potential and Nitrogen Transformations of Sludge‐Amended Soil
Authors: Lindemann W. C. , Cardenas M.
Published: July 2010

An experiment was conducted to determine values for the mineralization potential (No), rate constant (k), and rate of mineralization for soils freshly amended with sewage sludge, and to determine the influence of soil type and sludge rate on these values. A secondary objective was to determine if the sum of two exponential functions could better model N mineralization than a single exponential functions, as is normally used. A clayey soil (Glendale, a Typic Torrifluvent) and a sandy soil (Latene, a Typic Calciorthid) were amended with three rates (0, 15, and 30 g kg−1) of gamma irradiated, dried, anaerobically digested sewage sludge. The Glendale soil was mixed with sand (1:1 by weight) to increase aeration. Triplicate 80‐g samples of each soil mixture were incubated aerobically for 32 weeks at 0.01 MPa moisture tension and 35°C. Before incubation and periodically during incubation, the soils were leached with 0.01M CaCl2 and the leachate analyzed for NH+4, NO‐2, and NO‐3. No and k were estimated by a nonlinear least squares iterative statistical method. Cumulative (NO‐3 + NO‐2)‐N at the end of 32 weeks was dependent on sludge rate, but not on soil type or the soil type‐sludge rate interaction. Cumulative (NO‐3 + NO‐2)‐N for the 0, 15, and 30 g kg−1 treatments were 60.9, 137.4, and 182.6 mg (NO‐3 + NO‐2)‐N kg−1, respectively. Mineralization rates decreased rapidly the first two weeks, followed by a slower decrease with time. Rates were higher in sludge‐amended soil than in unamended soil and averaged 0.6, 1.8, and 2.2 mg (NO‐3 + NO‐2)‐N kg−1 week−1 for the 0, 15, and 30 g kg−1 treatments, respectively, after 32 weeks. Several methods of estimating No and k were attempted. The best estimates for sludge‐amended soil were obtained by modelling N mineralization as the sum of two exponentials. Total N mineralization (organic N loss, x̄ (mean) = 63%) was more than twice that of net N mineralization (NO‐3 + NO‐2‐N accumulated, x̄ = 27%). Total and net mineralization were greater in the Glendale soil (x̄ = 68% and 30%, respectively) than in the Latene soil (x̄ = 58% and 24%, respectively). Total mineralization increased with sludge addition, but net mineralization decreased with sludge addition. Denitrification losses probably accounted for the discrepancies between total and net mineralization. Denitrification increased with sludge addition and was greater in the Glendale than the Latene soil.
Relationships among Anaerobically Mineralized Nitrogen, Chemical Indexes, and Nitrogen Availability to Corn
Authors: Fox Richard H. , Piekielek William P.
Published: July 2010

An accurate method for predicting the N supplying capability of a soil must be available in order to increase N fertilizer efficiency in humid areas with a mixed agriculture that includes N inputs from livestock manure and forage legumes. Previous work had shown that a number of chemical N availability tests were not well correlated (r < 0.4) with the soil N available to field grown corn (Zea mays L.) in 67 experiments throughout Pennsylvania over a 6‐y period. Soils from these same sites were anaerobically incubated for 7 d to determine if the N mineralized during this period would be better correlated with field‐measured N availability than the chemical indexes. The anaerobically mineralized N was no better correlated with field N availability than were the chemical indexes. Anaerobically mineralized N was most closely correlated with total soil N content (r = 0.79) and boiling 0.01M CaCl2 extractable N (r = 0.74). By restricting the experimental sites to well‐drained soils where a legume (primarily alfalfa) had not been growing in either of the 2 years preceding the experiment, the correlation coefficients between two of the indexes, the UV absorbance of a boiling 0.01M CaCl2 extract and NO3 content of the surface 40 cm of soil at planting, and the field estimate of N availability were increased to 0.65 and 0.59, respectively. A stepwise multiple regression analysis using field N availability selected these two estimates with a resulting coefficient of determination (R2) of 0.50. These results are encouraging but are not high enough to use in a routine soil testing laboratory. Restricting the soils as described did not improve the correlation between anaerobically mineralized N and field‐measured N availability. Nitrogen fertilizer recommendations for corn based on current Pennsylvania guidelines that consider crop yield goals and management history were on the average 41 kg/ha (SD = 53 kg/ha) higher than would have been needed to achieve economic optimum yields in these experiments. This is much less precise than desired, but recommendations in effect prior to changes induced by results from these N fertilizer response experiments would have been 94 kg/ha (SD = 53 kg/ha) more than needed for economically optimum yields.
Characteristics and Geomorphic Relationships of Some Representative Aridisols in Southern Iran
Authors: Gharaee Hossein A. , Mahjoory Ramez A.
Published: July 2010

The morphology, genesis, and classification of three soils, each located on different physiographic positions, were investigated in southern Iran. These soils were: pedon 1, Beyza series on the Piedmont Alluvial Plain; pedon 2, Takht‐E‐Jamshid (Persepolis) series on the Upland Alluvial Plain; and pedon 3, Kooshkak (Jamalabad) series on the Lowland Alluvial Plain. These series represent 57% of the total study area (77 000 ha). The soils are calcareous throughout with carbonate concretions, nodules, and powdery pockets present in pedons 2 and 3. Clay skins are indicated in the B horizons of pedon 2. Soil pH rises from the Piedmont to the Lowland Alluvial Plain whereas organic matter decreases. Electrical conductivity does not show a regular trend from the Piedmont to the Lowland Alluvial Plain. Results of X‐ray diffraction analyses of < 2 µm clay indicate that the soils contain regularly interstratified smectite‐vermiculite and/or chlorite, clay mica‐vermiculite or chlorite, and some discrete vermiculite, chlorite, clay mica, kaolinite, and quartz. Evidence for attapulgite is also suggested. Tentatively, pedon 1 is classified as a Fluventic or Xerollic Camborthid; pedon 2a Xerollic or Typic Calciorthid; and pedon 3 a Xerollic Haplargid or Calciorthid.
Susceptibility of Agricultural Soils to Interrill Erosion
Authors: Meyer L. D. , Harmon W. C.
Published: July 2010

Soil losses from crop row sideslopes were evaluated for 18 soils in a bare, tilled condition to determine their relative susceptibilities to interrill erosion. Erodibilities varied by a ratio of > 10:1 for the initial run and by 4:1 for succeeding runs. The poorly aggregated high‐silt soils were most erodible, and the high‐clay soils were least erodible. Simple correlations of interrill erosion with various soil properties were determined. Erosion was best correlated with clay (<2 µm) percentage, 1500 kPa water, exchangeable calcium, sum of exchangeable bases, cation exchange capacity, and organic matter content, all negatively. Interrill erosion was well correlated (positively) with the site specific K‐factor of the universal soil loss equation.
Comparing Soil Tests for a Forested Acid Sandy Soil Topdressed with Sewage Effluent
Authors: Fiskell J. G. A. , Rebertus R. , Comerford N. B. , Pritchett W. L.
Published: July 2010

Mobility of nutrients and heavy metals from mineralization of sewage sludge in acid soils is an environmental concern. Chemical properties of a forested acid sandy soil on flat terrain were examined at 6 and 30 months after ceasing multiple spray applications of sewage effluent. Total dry sludge applied was 5 and 26 Mg ha−1 on the treated 3‐ by 15‐m portion of 9‐ by 15 m plots. Less than 1.1 mg L−1 of either NO‐3‐N or PO3‐4‐P was found at the 24‐ to 90‐cm depth in soil solution extracted from the untreated bed adjacent to the planting area during 144 days. Treated areas were sharply defined by the growth of indigenous dog fennel (Eupatorium sp.) which was the dominant species. Mean soil pH was below 4.7 at 6 months and 5.1 at 30 months. Treated interbed Cd, Cu, and NH+4‐N were higher with depth at 30 months than 6 months while the reverse held for PO3‐4‐P. Untreated bed or interbed soils had lower soil test values than corresponding treated soils. Much higher metal values were found at the 7‐cm depth than deeper. Differences in metal extracted from treated and untreated soils were readily distinguished by DA (Mehlich I), DTPA‐TEA, and EDTA‐AA soil test methods. All three methods extracted from 25 to 75% of the metals applied in the sludge. Lack of more downward movement of N, P, and metals was attributed to slow mineralization of the sewage sludge.
Spatial Variability of Field‐Measured Denitrification Gas Fluxes
Authors: Folorunso O. A. , Rolston D. E.
Published: July 2010

The structure and magnitude of the spatial variability of N2O and N2O + N2 fluxes were investigated along 12 transects of a Yolo loam (Typic Xerorthents) field site. The field‐measured N2O and N2O + N2 fluxes were In‐normally distributed and exhibited large spatial variability. Calculated coefficients of variation ranged from 161 to 508% for the N2O + N2 fluxes and 282 to 379% for the N2O fluxes. Analysis of autocorrelograms and partial autocorrelograms showed that in only 1 transect out of the 12 did the N2O and N2O + N2 fluxes reveal any spatial dependence indicative of an autore‐gressive process. Thus, the denitrification flux values for this field site are considered to be spatially independent. With a knowledge of the frequency distribution and variances of the measured gas fluxes, it was calculated to require from 156 to 4117 N2O + N2 flux measurements and 350 N2O flux measurements to estimate the “true” mean flux within ±10% of the estimated mean on a 3 by 36 m experimental plot.
Sorption of Cadmium by Calcareous Soils: Influence of Solution Composition
Authors: O'Connor G. A. , O'Connor Candice , Cline G. R.
Published: July 2010

Cadmium sorption‐desorption by three Ca‐saturated, calcareous soils was studied in the presence of various Ca salts. Cadmium retention was extensive in all soil‐solution systems and was best characterized by a two‐part Freundlich relationship. Part I of the isotherm was interpreted to represent Cd retention by highly Cd‐specific adsorption sites, while part II of the isotherm represented a mixture of highly Cd‐specific and nonspecific adsorption sites. This interpretation was supported by desorption data. Differences in Cd sorption from various Ca solutions were at least partially rationalized by considering free Cd2+ activities as predicted by GEOCHEM. Additional consideration, however, must be given to complementary (competing) ion activities.