bluuebunny/crossref_metadata_2025 huggingface dataset:
Microband Fabric in Seasonally Frozen Soils
Authors: Mermut A. R. , St. Arnaud R. J.
Published: July 2010

A distinctive type of banded fabric occurring in sandy, seasonally frozen soils is described. It consists of fine lenticular units < 1 mm thick and 1 to 3 mm long, exhibiting an accumulation of plasmic material in the upper part of the band or lens. The units are separated by planar voids oriented parallel to the soil surface. Such fabric differs from previously described forms of banded fabric recognized in eluvial soil horizons of grassland and forested soils within central Saskatchewan, Canada, inasmuch as the units are smaller, and it occurs at variable depth and in calcareous soil horizons. Although such structure is often almost imperceptible in the field, macro‐scopically it can sometimes be related to faint platy structure. Climatically, it occurs in a region subjected to a high freezethaw frequency and can be attributed to the effects of frost action. It is most pronounced in sandy soils of uniform, fine sand size, containing < 10% clay. Its presence and degree of expression are invariably related to texture and degree of water saturation within the profile.
Contribution of Magnetite to Oxalate‐Extractable Iron in Soils and Sediments from the Maumee River Basin of Ohio
Authors: Rhoton F. E. , Bigham J. M. , Norton L. D. , Smeck N. E.
Published: July 2010

Magnetic separations of whole soil and sediment samples from the Maumee River Basin (Ohio) commonly produced small but significant quantities of detrital magnetite. These magnetites were soluble in acid solutions of ammonium oxalate and were also more reactive than a standard magnetite sample of comparable particle size. Differential thermal analyses suggested that the enhanced reactivity of the soil and sediment magnetites may be due to altered grain surfaces. Since detrital magnetite is a common constituent of the sand and silt fractions of many soils and sediments, care should be exercised when evaluating “amorphous” iron data obtained by any of the popular oxalate procedures.
ATP Concentration and Soil Respiration at Reduced Water Potentials in Arid Soils
Authors: Knight W. G. , Skujins J.
Published: July 2010

Adenosine triphosphate (ATP) concentrations and soil respiration rates of two arid and one subalpine forest soil were evaluated as a function of water potential (ψw) in the range −2 to −100 bars. Water potential was determined by thermocouple psychrometry, CO2 release from soil by titrimetry; ATP was extracted from soil with cold sulfuric acid and assayed by luciferin‐luciferase methology. ATP concentrations increased in the ψw range −2 to −20 bars in the arid soils and was negatively correlated (r2 = 0.92) with exponential decreases in respiration rates for the same ψw range. In the subalpine forest soil, the highest ATP concentration was at the highest measured water potential (−2 bars) and decreased with decreasing respiration rates (r2 = 0.93) and decreasing ψw values. It was concluded that the soil microflora may exhibit diverse physiological responses to water and, consequently, to available carbon‐source induced stresses in soils from environmentally different areas.
Carbon Flux to Surface Mineral Soil After Nitrogen and Phosphorus Fertilization
Authors: Kelly J. M.
Published: July 2010

The movement of organic carbon into the mineral soil profile was increased by a factor of 2 to 3 following urea application to the forest floor. Approximately 74% of the organic carbon movement occurred during the first 3 months following treatment. Phosphorus treatment and the interaction of nitrogen and phosphorus did not produce a statistically significant response.
Cation Release from Sodium‐ and Calcium‐Saturated Clay‐Sized Soil Fractions
Authors: Suarez Donald L. , Frenkel Haim
Published: July 2010

The cation release of sodium‐ and calcium‐saturated clay fractions of two montmorillonitic and one vermiculitic aridland soils was compared with that of specimen Ca‐ and Na‐saturated montmorillonites. The clays were reacted with distilled water (0.25, 0.5, 1.0, and 2.5% wt/v) at 25°C. Hydrolysis rates of soil clays were roughly comparable to those of the specimen montmorillonites. Sodium hydrolysis exceeded calcium hydrolysis for soil clay fractions, whereas Na and Ca hydrolysis rates were about equal for the specimen montmorillonites, due to the dissolution of other silicates in the soil clays. Sodium kaolinite hydrolyzed so rapidly that it could not be prepared free of Cl without almost total loss of exchangeable Na. The suspensions were filtered after about 500 hours, and the solution compositions were used to determine ion activity products for the various montmorillonites and other silicate phases. Solutions were slightly supersaturated with respect to crystalline gibbsite. Most soil‐clay solutions were also supersaturated with respect to kaolinite, montmorillonite, K mica, and illite. Although the major cation chemistry of the Ca‐saturated soil clay suspensions was predominantly controlled by the surface hydrolysis reactions, the Na‐saturated suspensions were affected by dissolution of non‐smectite minerals. The weathering of less stable minerals also resulted in additional silica and aluminum release. This is consistent with feldspar undersaturation and montmorillonite supersaturation in the soil‐clay suspensions. The pure montmorillonites gave activity product values consistent with published montmorillonite stabilities.
Boron Adsorption by Soils Using a Phenomenological Adsorption Equation
Authors: Mezuman U. , Keren R.
Published: July 2010

A phenomenological equation was applied to boron adsorption by soils as a function of both pH and boron concentration. Experimental results obtained for four different soils were compared with results computed for each soil according to fitted adsorption parameters. The agreement between the calculated values and experimental results indicates that this model can be used to predict boron adsorption by soils. Experimental results of adsorbed boron by soils as a function of solution‐to‐soil ratio were compared with results computed according to the same fitted adsorption parameters. The agreement between the calculated and experimental results indicates that, within the tested range of solution‐to‐soil ratios, the water content does not affect the boron‐soil interaction.
Cadmium Adsorption by Soils and Uptake by Plants as Affected by Soil Chemical Properties
Authors: McBride M. B. , Tyler L. D. , Hovde D. A.
Published: July 2010

The quantity of Cd2+ adsorbed by soils from the northeastern USA was measured at a given equilibrium concentration (10−5M) of the metal in soil solution. This “retention capacity” was strongly related by a linear function to the exchangeable Ca2+ content of the soils. In addition, Cd2+ uptake by corn plants grown in these soils amended with 1‐µg Cd2+/g of soil was measured and found to be related to the retention capacity of the soil for Cd2+ by a curvilinear function. Although organic matter and clay in soil were able to limit Cd2+ uptake by the plants, the best soil indicators of Cd2+ availability were the retention capacity and exchangeable base (mainly Ca2+) content. The ability of exchangeable bases to account for most of the variability in Cd2+ adsorption by the soils as well as uptake by the plants is attributed to the important role of Cd2+‐Ca2+ exchange reactions in the soil.
Halloysite and Kaolinite Cesium Chloride‐Urea Intercalation Facilitated by a Trace of Water at Elevated Temperature
Authors: Higashi T. , Jackson M. L.
Published: July 2010

Addition of 75 µliters of H2O to a mixture of 50 mg of partially hydrated spherical and tubular halloysite or coarse kaolinite and 250 mg of CsCl at 80°C for 48 hours followed by two washings with 10% urea solution produces a complete CsCl‐urea intercalation at a 10.4–10.6å x‐ray diffraction spacing. Washing with 10% urea solution enhanced the 10.4–10.6å peak by removal of the excess CsCl. Fireclay and fine kaolinites require 1–4 min of grinding in CsCl for complete expansion to 10.4–10.6Å spacing. As a result of 3 min of grinding, an additional 8–23% of SiO2 + Al2O3 is dissolved from such kaolinites during 2.5 min of boiling in 0.5N NaOH.
Soil Sorption of Nickel: Influence of Solution Composition
Authors: Bowman R. S. , Essington M. E. , O'Connor G. A.
Published: July 2010

Sorption/desorption isotherms were used to evaluate the effects of solution composition on the retention of nickel (Ni) by soils of varying physical and chemical properties. Soils examined included agricultural soils of New Mexico, as well as soils from potential chemical waste disposal sites. Sorption of Ni from 0.01N CaCl2 was extensive for all samples: more than 99% of added Ni was sorbed in some cases. Desorption in 0.01N CaCl2 was slight (extreme hysteresis). Ability to extract sorbed Ni with diethlyenetriaminetetraacetate (DPTA), however, indicated that Ni sorption was not completely lrreversible. Increasing the CaCl2 concentration to 0.1N lowered Ni sorption by up to 40%. This was due primarily to direct sorption competition by Ca, rather than to increased Ni‐Cl complex formation, as shown by parallel experiments using Ca(ClO4)2. Presence of small amounts of ethylenediaminetetraacetate (EDTA) in the equilibrating solution lowered Ni sorption by up to 98%. The extent of the chelate effect depended upon whether EDTA was present in the Ni solution before or after contact with soil.
New Methods of Studying Soil Detachment due to Waterdrop Impact
Authors: Al‐Durrah M. , Bradford J. M.
Published: July 2010

An improved and inexpensive raindrop tower 8.9 m in height was designed so that a single drop will hit a soil target area 1.6 cm in diameter. The soil used in this study was taken from the surface 15 cm of an Ida silt loam (mesic Typic Udorthents). The surface shear strength was altered by remolding the soil to three bulk densities and by equilibrating the cores to matric potentials of −5, −19, −38, and −62 mbars. The weight of soil detached from the impact of single water‐drops 3.0, 4.6, and 5.6 mm in diameter was closely correlated with the undrained soil shear strength as measured by the Swedish fall‐cone device. A correlation coefficient of 0.97 was found between splash weight and a linear function of the ratio of waterdrop kinetic energy to the soil shear strength. The fall‐cone method of determining soil shearing strength is rapid, inexpensive, and could be easily adapted to field use.
The Calibration of the Richards Flow Equation for a Draining Column by Parameter Identification
Authors: Zachmann D. W. , DuChateau P. C. , Klute A.
Published: July 2010

Before the Richards equation can be used to simulate the flow of moisture through a soil it is necessary to estimate the water capacity and hydraulic conductivity functions which appear as coefficients. We present four parameter identification methods and one direct method for estimating these hydraulic properties. For the sample problem considered, the parameter identification method which used cumulative discharge data to estimate water capacity and hydraulic conductivity performed the best in predicting water content as a function of depth and time during drainage.
Hydraulic Gradients Across Simulated Rain‐Formed Soil Surface Seals
Authors: Sharma P. P. , Gantzer C. J. , Blake G. R.
Published: July 2010

Hydraulic potentials across surface seals on packed soil columns were measured with a tensiometer‐transducer‐data logger system. Matric potential drops during steady‐state infiltration across seals formed by simulated rainfall on 12 different soils ranged from 6.4 to 14.2 cm of water. The matric potential that developed just below the seal during steady‐state infiltration was nearly constant for a considerable depth range in the soil column. Cultural factors determining aggregate stability were found to be more significant than textural factors in influencing hydraulic properties of surface seals.
Effect of High Root Temperature and Rhizobium Strain on Nodulation, Nitrogen Fixation, and Growth of Soybeans
Authors: Munévar F. , Wollum A. G.
Published: July 2010

The effects of high root temperatures on nodulation, nitrogen (N) fixation, and dry matter production of ‘Lee’ soybean [Glycine max (L.) Merr.] plants inoculated with 13 different strains of Rhizobium japonicum were studied in the greenhouse. Plants were grown in vermiculite, and their root systems were submerged in thermostatically controlled water baths. A treatment without inoculation in which 12 mM of KNO3 was supplied with the nutrient solution was included.

Increasing root temperatures from 28 to 40°C had a detrimental effect on the number of nodules, the specific nitrogenase activity, the N content, and the dry weight of tops and roots of inoculated plants. The magnitude of this effect was highly dependent on the rhizobial strain.

For some strains, higher nodule weights and higher total nitrogenase (C2H2 reduction) activity were found at 33 than at 28°C, whereas for other strains, these variables declined with increasing temperatures. It appeared that, with increasing temperatures, the processes determining nodule initiation became susceptible at lower temperatures than those associated with nodule growth.

When plants formed nodules under nonlimiting temperatures and then were transferred to stressing root temperatures, appearance of additional nodules, N fixation, and plant growth were restricted by high root temperature. These results indicate that the detrimental effect of increasing root temperatures on inoculated plants is due in part to the reduction in number of nodules formed and also to limitations imposed on other processes of the soybean‐Rhizobium association.

The growth of plants supplied with combined N was also adversely affected by continuous high root temperatures. However, while a temperature of 34°C restricted the growth of plants depending on N fixation, it was stimulatory for the growth of plants supplied with combined N. Therefore, the effect of temperatures near 34°C on the growth of nodulated plants without combined N was due mainly to the effect on the symbiotic system and not on other physiological processes of the plant.

The response of different Rhizobium strains in symbiosis with soybean plants to increasing temperature was related to their response to temperature in pure culture and modified the adverse effect of temperature on plant development. Therefore, pure culture screening of R. japonicum may be a useful tool to aid in the selection of strains better suited for soil environments where high temperature is a limiting factor for the symbiosis.
Response of Phaseolus vulgaris L. to Molybdenum Under Acid Conditions
Authors: Franco A. A. , Munns D. N.
Published: July 2010

Common beans (Phaseolus vulgaris L.) have been found not to respond to molybdenum (Mo) when grown on deficient soils that were also very acid (< pH 5.2).

Greenhouse and growth chamber experiments in soil and solution culture were done to (i) test whether soil acidity prevents Mo response in bean by interferring with Mo uptake or translocation to nodules; (ii) establish relationships between Mo concentrations in nodules and in other plant parts; and (iii) assess cultivar differences in Mo uptake.

In the six cultivars studied, plant Mo concentrations were little influenced by pH in the range 4.8 to 5.8. In more detailed experiments with the cultivar Venezuela 350, neither pH (4.8 to 6.3) nor temperature (21 to 31°C) affected Mo concentration or distribution over a wide range of Mo supply in soil and solution culture.

Nodule Mo concentration varied less than shoot Mo in response to varied external supply. It correlated with Mo in stems better than in leaves or roots. Root Mo related closely to external Mo. Leaves appeared to act as sinks for Mo disposal at high Mo levels.

One bean cultivar accumulated more Mo in stem and seed than five other cultivars. It was also noted that Mo was 10 times higher in seeds produced at Davis, Calif., (on an Entisol) than at Goiana, Brazil (on an Oxisol). These data confirm that genetic and environmental controls on seed Mo can be manipulated to help control Mo deficiency.
Soil Carbon, Nitrogen, and Bulk Density Comparisons in Two Cropland Tillage Systems after 25 Years and in Virgin Grassland
Authors: Bauer Armand , Black A. L.
Published: July 2010

Stubble mulching is advocated as a desirable soil management practice, but no data are available for the northern Great Plains showing the effect of its long‐term use on soil properties. Neither have any comparisons been made of organic carbon (C) levels in cropland and virgin grassland in this region since 1947.

Four farm field sites, each of moderately coarse‐, medium‐, and fine‐textured soils under conventional tillage, stubble mulch tillage, and virgin grassland (never cultivated) were sampled at 0 to 7.6, 7.6 to 15.2, 15.2 to 30.5, and 30.5 to 45.7 cm to measure organic C, total nitrogen (N), and bulk density.

Average organic C and total N to a depth of 45.7 cm, % by weight, were significantly higher under stubble mulch than conventional tillage management. Organic C concentration in moderately coarse‐ and fine‐textured soils was 44 and 13% higher, respectively, under stubble mulch than conventional management, but it did not differ between the two management systems in medium‐textured soils.

The percentage loss of C and N from the 0‐ to 7.6‐ and 7.6‐ to 15.2‐cm soil zones due to cropping as compared to virgin grassland was no greater than the percentage loss found in 1947 at field stations after nearly 40 years of cropping. In another comparison considering only medium‐textured soils on farm fields, percentage loss of organic C after about 70 years of cropping, using 1979 virgin grasslands as a reference, was no greater than loss after about 40 years of cropping, using 1950 virgin grasslands. Continued cultivation of dryland soils, especially with stuhble mulching, has maintained organic C and total N at higher levels than was projected from earlier research.

Cropland bulk densities to 30.5 cm ranged from 7 to 20% higher than on grassland but did not differ between conventional and stubble mulch tillage management.
Agricultural Erosion Indicated by 137Cs Redistribution: II. Estimates of Erosion Rates
Authors: Brown R. B. , Kling G. F. , Cutshall N. H.
Published: July 2010

Erosion rates were estimated for 6‐ and 12.9‐ha nested agricultural watersheds in the western Willamette Valley, Oreg., using 137Cs activity levels and two different approaches, termed “volumetric” and “gravimetric.” The volumetric approach involved calculation of the volume and mass of sediment currently residing in depositional zones, based on areal extent of the zone and depth of occurrence of 137Cs in the zone. This sediment was assumed to have come from the uplands (sideslopes plus ridgetops) by erosion during the period of fallout (since 1954). Reasonable ranges of watershed sediment delivery ratios and lengths of record were assumed. It was estimated by this technique that modern erosion rates in the uplands had been between 3 and 14 metric tons ha−1 yr−1.

The gravimetric approach involved algebraic manipulation of areal concentrations of 137Cs activities in depositional and upland zones to obtain estimates of erosion loss of 137Cs from the uplands. Estimated 137Cs losses were converted to estimated soil losses, which ranged from 6 to 27 metric tons ha−1yr−1.

Considering the imprecision of these markedly different means of estimating soil loss rates, the volumetric and gravimetric estimates agree reasonably well. Together, they provide good evidence that the rate of modern erosion at the study site has been within and very possibly above the range of erosion rates normally thought of as tolerable.
Influence of Intensive Cultivation and Irrigation on Soil Properties in the Jordan Valley, Israel: Recrystallization of Carbonate Minerals
Authors: Magaritz Mordeckai , Amiel Abraham J.
Published: July 2010

This is part of a study regarding the effect of intensive cultivation on the soil properties in the Jordan Valley in an area where a decline of crop yield was detected. The high pCO2 values in the cultivated soil (−1.3 Atm) and the large amount of irrigation water applied enhanced the processes occurring in the CaCO3 − HCO3‐ − CO2 system. The largest difference in the amount of dissolution and recrystallization between the cultivated and undisturbed soils was found in the lower part of the profile (horizon BCa and B3). The total amount of CaCO3 leached from the cultivated soil was about 7% of the total carbonate (about 500 metric tons/ha). Most of this loss was from the finer‐grained fraction. An even larger effect was found on the amount of recrystallized carbonate in the soil (about 11% of the total carbonate). A decrease was observed in the bulk density of the upper soil horizons in the cultivated soil relative to the undisturbed soil. The highest bulk density of the cultivated soil was found at a depth of about 1 m compared to the maximum in the 0‐ to 15‐cm depth in undisturbed soil.
Dissolution of Oxides of Manganese and Iron by Root Exudate Components
Authors: Jauregui Mario A. , Reisenauer H. M.
Published: July 2010

The reactions of malic acid, an important constituent of root exudates, with the hydrous oxides of manganese (Mn) and iron (Fe) were studied to further our understanding of the processes controlling the solubility and plant intake of these elements. The reaction of malate with δ‐MnO2 followed either of two pathways depending on the pH‐controlled adsorption of carboxylates on the oxide surface. In acid systems, the first product of the oxidation of malate (oxaloacetate) is adsorbed on δ‐MnO2 surfaces and hydrolyzed to a molecule each of formate and malonate. These products are further oxidized to carbon dioxide (CO2) and water, and 6 mol of Mn2+ are released; the malonate is oxidized via tartronate, formate, and oxalate, and the formate is oxidized directly. Oxaloacetate not adsorbed by the δ‐MnO2 is rapidly decarboxylated to pyruvate, which is subsequently oxidized to acetate and CO2, and only 2 mol of Mn2+ are released. Although favored by acid conditions, adsorption of oxaloacetate by MnO2 is still significant at the pH of calcareous systems; thus, the reduction of MnO2 can proceed via both pathways in agricultural soils.

The reduction of Fe(OH)3 by malate was less than that of δ‐MnO2 and was enhanced by acidity and addition to low levels of δ‐MnO2. Higher levels of added δ‐MnO2 diminished soluble Fe due to adsorption and reoxidation of Fe2+ by the δ‐MnO2.
Residual Available Phosphorus in Near‐Neutral and Alkaline Soils: I. Solubility and Capacity Relationships
Authors: Fixen P. E. , Ludwick A. E.
Published: July 2010

A continuous cropping greenhouse study of 28 Colorado soils with phosphorus (P) rates of 0 and 30 ppm was conducted. The objective was to investigate the nature and solubility of residual available P in near‐neutral and calcareous soils.

Solubility and capacity factor comparisons indicate that octacalcium phosphate was not likely an important residue in 27 of the 28 soils. One of the soils which had a history of heavy barnyard manure applications appeared to be buffered in the vicinity of the octacalcium phosphate isotherm. Tricalcium phosphate or a mineral similar in composition and solubility may have accounted for at least a portion of the fertilizer residues. The plant availability of tricalcium phosphate is apparently quite low since seven of the nine calcareous soils initially plotting on or near this isotherm responded to P fertilization.
Residual Available Phosphorus in Near‐Neutral and Alkaline Soils: II. Persistence and Quantitative Estimation
Authors: Fixen P. E. , Ludwick A. E.
Published: July 2010

A continuous cropping greenhouse study of 28 Colorado soils with phosphorus (P) rates of 0 and 30 ppm was conducted. The objectives were to (i) evaluate the persistence of residual available P in near‐neutral and calcareous soils and (ii) to predict its quantity. Residual available P was defined as the amount of P removed fron soil by plant uptake until the NaHCO3‐P level dropped to 10 ppm.

A residual effect of the fertilizer treatment persisted beyond six greenhouse crops for nearly one‐half of the 28 soils. Recovery of applied fertilizer ranged from 47 to 119% and averaged 74%. The following equation was developed to predict the quantity of residual available P in soils: Residual P, mg/2 kg soil = −17.02 + 2.062 (NaHCO3‐P, ppm) + 0.058 (NaHCO3‐P × clay, %) − 0.187 (lime, % × clay). R2 = 0.90; 55 soil treatment combinations.
Corn Root Development in Constructed Soils on Surface‐mined Land in Western Illinois
Authors: Fehrenbacher D. J. , Jansen I. J. , Fehrenbacher J. B.
Published: July 2010

The effect of B horizon replacement on corn root development in the reclamation of surface‐mined land was studied in a highly productive soil area of western Illinois. Two constructed soils, one with 55 cm of A horizon over 77 cm of replaced B horizon, and the other with 55 cm of A horizon replaced directly over graded dragline spoil, and a third, representative, undisturbed soil, Clarksdale silt loam, were studied. Placement of B horizon material was done without allowing any scraper traffic on the plots, a more careful procedure than would be possible over the entire post‐mine surface under current technology. Corn roots were sampled in 1979 directly under one plant using a 10‐ by 30‐ by 183‐cm soil root monolith. Corn was the first crop planted on the constructed soils following reclamation.

The A horizons were similar on all soils. In the replaced B many soil peds were intact and the bulk density was 1.5 g/cm3 throughout, similar to the undisturbed B of Clarksdale. The bulk density of the graded spoil was 1.7 g/cm3 at 54 cm and increased to 1.9 g/cm3 at 102 cm. Depth of root penetration was 163 cm in Clarksdale, 120 cm in A/B, and 74 cm in A/spoil. Root length densities were significantly greater in replaced B than in graded spoil. Below 113 cm, root length densities were significantly greater in Clarksdale than in replaced B.

The data suggest that Clarksdale B horizon material, when placed with minimal compaction, is a more favorable rooting medium than the newly placed dragline spoil. Corn yields in 1979, the first year after reclamation, did not substantiate this. However, in 1980 corn yields were significantly higher (1,800 kg/ha higher) on A/B than on A/spoil. Corn yields on undisturbed Clarksdale were about 10% greater than on A over B in 1980.
Chemical and Morphological Soil Characteristics in a New England Drainage‐toposequence
Authors: Veneman P. L. M. , Bodine S. M.
Published: July 2010

Chemical, physical, and morphological properties of soils in a representative drainage‐toposequence in central Massachusetts were determined. The soils reflect the acid character of the glacial till derived from granitic materials by the low cation exchange capacity (CEC) and base saturation values, although some effect of past liming is evident. Within a depth of 70 cm most catena members are underlain by a hardpan. This appears to be mainly of geogenetic origin but also exhibits pedogenetic influences in the occurrence of free grain and channel argillans in the upper 25 cm of the pan, especially in well‐ and moderately well‐drained profiles. Depth to the hardpan varies between 45 and 120 cm and in general is somewhat less in soils on the steeper slopes than those on the more level areas.

The slowly permeable pan severely restricts vertical drainage of excess soil water and causes increased lateral flow. This results in wetter soil conditions downslope as is evident from the presence of mottling in B horizons. The hardpan is characterized by low chroma ped interiors and bright, high chroma ped ferrans indicative of prolonged wet, but unsaturated, soil conditions. The somewhat poorly and poorly drained catena members have B horizons with relatively low chroma matrix colors and high chroma channel neoferrans which reflect a generally wet soil environment with relatively short, drier periods.

Dithionite‐citrate and sodium pyrophosphate‐extractable iron and aluminum contents were determined in B horizons of selected profiles along the catena to evaluate the performance of present U.S. soil taxonomic criteria for spodic horizons since the well‐ and moderately well‐drained soils were classified as Brown Podzolic soils until the 1975 revision. Current chemical criteria effectively exclude these soils from spodic horizon qualification.
Deficit, High‐frequency Sprinkler Irrigation of Wheat
Authors: Miller D. E. , Hang An N.
Published: July 2010

The effect of daily deficit sprinkler irrigation on the yield and quality of wheat (Triticum aestivum L.) was evaluated using the line source technique. Studies were conducted on sandy and loam soils with much different water‐holding characteristics. Irrigation rate variables were initiated at about the time of full cover (pre‐ to early‐boot) when the soils were near the upper limit of available water. Evapotranspiration (ET) rates were estimated from evaporation pan (Ep) data as ET = 0.95 Ep. On the sand, the yield and quality of wheat increased with increased application of water, up to about 100% estimated ET. On the loam soil, daily irrigations which equalled or exceeded 40% estimated ET produced similar yields. On this soil, the total water used, including water depleted from the soil, also varied over a wide range without affecting yields.
Measuring the Hydraulic Conductivity of Soil Horizons with Continuous Macropores
Authors: Bouma J.
Published: July 2010

Measurement of Ksat of soil horizons with continuous macropores is discussed. Different fluxes at grad H = 1 cm cm−1 and zero pressure head ranged from 2,000 to 10 cm day−1 in the B21g (clay) of a Typic Fluvaquent with vertical worm channels and from 20 to 1 cm day−1 in the Clg (compact sandy loam) of a Plaggeptic Haplaquod. Fluxes were obtained using (i) large detached columns (Ksat entire soil), (ii) columns that were attached to the subsoil, and (iii) detached columns with light crusts on top [Ksat of the soil matrix, which is referred to as K(sat)].
Ionic Activity Products and Crystal Forms of Calcium and Magnesium Carbonates Precipitated from Calcium‐Magnesium Bentonites
Authors: Levy Rachel , Whittig L. D. , Tanji K. K.
Published: July 2010

A series of laboratory experiments were conducted to study quantities, mineral forms, and solubility of alkaline earth carbonates precipitated from Ca‐Mg‐bentonite systems. The effects of Mg on carbonate precipitation and solubility were assessed in isolation from other carbonate precipitation inhibitors commonly found in soils. Five bentonite systems were preconditioned by saturation with different proportions of exchangeable Ca and Mg. Calcium/magnesium ratios ranged from 99:1 to 8:92. Portions of each system were seeded with calcite, and both seeded and unseeded systems were equilibrated with deionized water or NaHCO3. Equilibrium solution concentrations of Ca, Mg, Na, HCO3, and Cl and also pH served as input data to the WATEQF solution chemistry computer program for calculations of ion strength, ion pairs, ion activities, and carbonate ionic activity products (IAP).

The data obtained from the series of experiments clearly demonstrated that solubility characteristics of calcium carbonate in the Ca‐Mg‐bentonite systems were influenced by incongruent properties of freshly precipitated carbonate surfaces. The data further show that Mg inhibited crystallization and increased solubility of calcium carbonate and that high concentrations of Mg in the NaHCO3‐bentonite precipitation medium induced crystallization of Mg calcite. In some systems, Mg was precipitated in forms which were not identified by either x‐ray diffraction analysis or IAP characteristics.
Enzyme Activity and Respiration in Minesoils
Authors: Stroo H. F. , Jencks E. M.
Published: July 2010

Microbial respiration and soil enzyme activity measurements were made in both native soils and in minesoils varying in age and vegetation in order to determine the levels of microbial activity during the initial stages of soil genesis. By all indices, microbial activity was lower on unfertilized minesoils than in native soils. Amylase and phosphatase activities increased with time, as did respiration rate, so that after 20 years, activity levels in the surface 10 cm approached those of native soils. Recovery was related to the accumulation of organic matter and nitrogen (N). Recent minesoils receiving high inputs of lime and fertilizers had the highest activity levels found, resulting in a depletion of organic matter and nitrogen which suggests that a self‐sustaining ecosystem has not yet developed on these sites.

Respiration rate, and amylase and phosphatase activities were all significantly correlated with each other. Oxidizable carbon (C) and total and mineralizable nitrogen were the soil factors most closely correlated with respiration rate, while clay content also affected amylase activity. Urease activity was not correlated with any of the other indices or soil factors studied.

No evidence for enzyme inhibition in minesoils was found, but phosphatase activities were lower in minesoils, suggesting that P mineralization may be slower on minesoils. Mineralizable N increased rapidly with age on unamended sites, but after 20 years it was only one‐half that found in native soils.

The presence of vegetation was critical for the recovery of microbial activity. Black locust (Robinia pseudoacacia) was similar to grasslegume vegetation in its effect on microbial activity and N accumulation. Compaction of the soil during reclamation caused slow organic matter and N accumulation, and thus low microbial activity.
Evaporative Flux from Wheat and Fallow in a Semiarid Climate
Authors: Aase J. K. , Siddoway F. H.
Published: July 2010

Daily evaporative flux and accompanying energy balance components were measured for land in summer fallow and in wheat (Triticum aestivum L.) located side by side in a typical strip‐crop farming area. The study was conducted on a Williams loam (fine‐loamy, mixed Typic Argiborolls) 11 km northwest of Sidney, Mont. Two precision‐weighing lysimeters were used, each situated in the middle of two adjacent 180‐ by 180‐m fields. The two fields, including the lysimeters, were alternately cropped and fallowed. ‘Olaf’ spring wheat was grown in 1978 and 1979 and ‘Roughrider’ winter wheat in 1979–1980. The three cropping seasons differed in that 33 cm of rain fell during the 1978 season and about 9 cm fell in each of the 1979 and 1980 seasons. However, because the root‐zone soil profile was near field capacity in the spring of 1979, the yield of about 4,000 kg/ha was comparable to that in 1978. In all 3 years, cropped and noncropped lysimeters lost almost identical amounts of water up to the time that tillering was completed. Thereafter, evapotranspiration from cropped surfaces was much higher than evaporation from noncropped surfaces. The fallowed lysimeter gained 12 cm of water in 1978 and lost 7 and 2.5 cm in 1979 and 1980, respectively. The cropped lysimeter lost 20 cm in 1978, 42 cm in 1979, and 14 cm in 1980. Rates of water use by the wheat were highest during the heading growth stage in 1978 and during flowering in 1979 and 1980. Differences in the growth stage duration among years seemed to have no relationship to degree days. As indicated by both energy balance and daily ratios of evaporative flux (LE) to net radiation (Rn), sensible heat transfer to the crop strongly influenced evapotranspiration, except in 1980 when the crop was stressed most of the season and contributed sensible heat downwind from the cropped area. For a crop to be energy efficient and also have water available for growth, water conservation practices must be followed consistently, and the crop must be protected as much as possible from stress conditions.
Dispersion of Clays on Graphite Supports for X‐Ray Microprobe Analysis
Authors: Berkheiser V. E. , Monsees M. B.
Published: July 2010

A method for dispersing clay suspensions on graphite planchets for x‐ray microprobe analysis (XMA) is described. Use of a fluorosurfactant produced separated clay particles, each of which could be analyzed by XMA, in contrast to large aggregates when dried from water. Further improvements in particle flatness and orientation were observed for Ca2+‐saturated Cheto montmorillonite dried at 97% relative humidity.
In‐situ Measurement of Near‐surface Soil Strength by the Fall‐cone Device
Authors: Bradford J. M. , Grossman R. B.
Published: July 2010

This study explored the use of the Swedish fall‐cone device for insitu measurements of shear strength near the surface of soils. A laboratory fall‐cone device was adapted for field use by replacing the original base and lengthening the cone stems. In‐situ strengths were measured on selected soils in southwestern Iowa and southeastern Nebraska. A small increase in water potential resulted in a large decrease in shear strength. A heavier cone gave a lower strength value than a lighter cone. The near‐surface strength of Sharpsburg soils in winter wheat fields was measured throughout the year. The strength immediately after fall planting was 10 to 20 kPa at about −3 kPa water potential. In the spring of 1980, largely because of consolidation from rainfall in the immediate post‐thaw period, the strength was 30 to 50 kPa. In contrast, the spring of 1981 was dry and consolidation did not occur; consequently, there was no increase in strength from that immediately after planting.
Characteristics of Soils in a Stone‐free Surficial Deposit in Central Utah
Authors: Queiroz João , Southard A. R. , Wooldridge G. L.
Published: July 2010

Particle‐size distribution, x‐ray diffraction, organic carbon, and calcium carbonate equivalent were measured on selected Calciorthids and Camborthids formed in stone‐free surficial deposits on a structural plain in east‐central Utah. Mylar balloons were tracked with theodolites to determine the circulation of prevailing winds over the mountain slopes and adjacent land forms. Particle‐size distributions (80% silt and very fine sand) and observed wind circulation patterns (strong westerly mesoscale with hydraulic jump) indicate that wind has had a strong influence on the soils and that wind is directly responsible for the complex soil distribution on the land form. Presence of cylindrical soil structure units at depths greater than normal for cicada activity suggests that these features are relict and that these cylindrical soil structure units have been buried. Variable depths over short horizontal distances to K horizons further suggest burial by wind.
Water Harvesting for Afforestation: III. Dependence of Tree Growth on Amount and Distribution of Precipitation
Authors: Kowsar Ahang
Published: July 2010

Irrigation of greenbelts being established around major Iranian cities constitutes an unnecessary burden on the overtaxed water supplies in this arid country. Water harvesting through surface application of asphalt is an answer to this pressing problem. Terraces, 2 m in width, were constructed on contour lines at 1.5‐m‐vertical intervals on a 30% slope. Hot, medium‐curing, cutback asphalt solution (MC2) was sprayed onto the soil surface between the terraces at the rate of 1 L/m2 in December 1969. Seedlings of Robinia pseudacacia L., Cupressus arizonica G., and Fraxinus rotundifolia Mill. were planted on the terraces in March 1970. The 509‐mm‐accumulated runoff from the treated microwatersheds in the 1970–1975 period did not substantially affect the survival of the tree seedlings but improved their growth significantly. The increases in height, crown cover, and stem cross section due to the runoff at the end of 1978 were 46.6, 46.2, and 54.4%, respectively, for R. pseudacacia L.; 16.4, 14.3, and 33.8%, respectively, for C. arizonica G.; and 17.6, 62.6, and 36.9%, respectively, for F. rotundifolia Mill.

Regression equations were developed correlating growth with amount of water and age of trees. Height and crown growth of R. pseudacacia L., height growth of C. arizonica G., and crown growth of F. rotundifolia Mill. were influenced by water received in April and May of the previous and current years. Amount of water received in April and May of a given year influenced crown growth of C. arizonica G. for that year and height growth of F. rotundifolia Mill. during the following year. Amount of water received in April through October of a given year influenced stem cross‐section growth of R. pseudacacia L. and F. rotundifolia Mill. during the following year and that of C. arizonica G. 2 years later.
Influence of Fertilizer Nitrogen Source on Soil Physical and Chemical Properties
Authors: Intrawech A. , Stone L. R. , Ellis R. , Whitney D. A.
Published: July 2010

The soil‐dispersing potential of ammonium (NH+4) has caused concern about the possible negative influence of anhydrous ammonia (NH3) use on soil structure. In the fall of 1978, we collected disturbed and undisturbed soil samples to evaluate the influence of 10 years of annual application of four nitrogen (N) sources [NH3, ammonium nitrate (NH4NO3), urea, and urea‐ammonium nitrate solution (UAN)] on soil physical and chemical properties. A no‐N check was included during the 10‐year field study.

Soil physical properties (saturated hydraulic conductivity, probe resistance at ‐⅓ bar soil water potential, core bulk density, water content at ‐⅓ and −15 bar soil water potential, particle‐size distribution, geometric mean diameter of water‐stable aggregates, and compactibility) were not significantly affected by fertilizer treatment. The application of all N sources reduced the soil pH significantly compared with the no‐N check. In the 6‐ to 14‐cm soil layer, the Zn concentration was significantly lower and the Mn concentration significantly higher in the N‐source plots than in the no‐N check. All treatments receiving fertilizer N yielded significantly more grain (1975 through 1977 mean) than the no‐N check, with no significant difference in grain yield among the four N sources.

Our study found that 10 years of annual application of four N sources (included NH3) have had no measurable influence on soil structure and soil compactibility, compared with a no‐N check.
Effects of Nutrient Accumulation by Aspen, Spruce, and Pine on Soil Properties
Authors: Alban David H.
Published: July 2010

Nutrient analysis was done for adjacent, 40‐year‐old stands of pure quaking aspen (Populus tremuloides Michx.), white spruce (Picea glauca Moench Voss), red pine (Pinus resinosa Ait.) and jack pine (Pinus banksiana Lamb.) on two soils in Minnesota to determine the effects of tree species on soil properties. On both soils, aspen and spruce stands accumulated more of most nutrients than did pine stands, and these species differences were reflected in the litterfall. The weight of the forest floor did not differ among species, but nutrient accumulation and pH were greatest under aspen and spruce. Calcium content was about twice as high under aspen and spruce as under the pines. In the mineral soil, phosphorus (P) and potassium (K) did not differ among species; organic matter and nitrogen (N) tended to be lowest under aspen, and calcium (Ca) was much lower under aspen and spruce than under the pines. Soil pH and cation exchange capacity were highest under the pines; this was directly related to soil Ca contents. Mineral soil differences related to species were most pronounced in the top 10 cm; few differences occurred below 25 cm.

The large species differences in the N, Ca, and Mg contents of vegetation, forest floor, and mineral soil show a redistribution of these nutrients, but their amounts in the entire ecosystem do not differ by species. In contrast, P and K in the ecosystem decrease in the order aspen>spruce>pines, and this is largely a reflection of their accumulation in the vegetation since their differences in the soil are minimal.
Influence of Soil Characteristics on the Survival of Rhizobium in Soils Undergoing Drying
Authors: Chao Wei‐Liang , Alexander Martin
Published: July 2010

A study was conducted to establish whether certain soil characteristics could be correlated with the extent of survival of Rhizobium as the soils underwent drying. The numbers of R. meliloti and R. phaseoli fell markedly as the soils dried, but their abundance declined slowly in the soils maintained in an air‐dry state. The number of surviving cells increased if these bacteria were added to sterile soil and allowed to grow before desiccation was extensive. Survival of both species was poor in soils of pH values below 5.7. The number of survivors of R. meliloti but not R. phaseoli decreased as the content of clay and of water at 15 bar suction increased. At organic matter levels below but not above 2 to 3%, the abundance of survivors of these rhizobia was related to the organic carbon content of the soil. Survival of R. phaseoli was inversely related to the content of total available aluminum in the soils, but the number of survivors of the two species was not correlated with the available phosphorus levels.
Nutrient Availability under Trickle Irrigation: I. Distribution of Water and Bray no. 1 Phosphate
Authors: Bacon P. E. , Davey B. G.
Published: July 2010

The distribution of water and Bray no. 1 phosphate was measured in the surface soil of a Chromic Luvisol that had been under trickle irrigation for 5 years. The region of the soil reaching field capacity after 8 to 12 h of irrigation extended horizontally to at least 65 and up to 90 cm from the outlet and was no deeper than 12 cm from the surface. After irrigation had ceased soil water decreased with time but usually did not become significantly different from field capacity until after about 24 h.

Where the soil had not been fertilized, Bray no. 1 phosphate decreased from 42 to 19 ppm over a 25‐cm depth immediately below the trickle outlet, while 65 cm away it decreased from 78 to 16 ppm. Banding fertilizer 50 to 80 cm from the outlet increased phosphate at the surface to 113 ppm but did not increase phosphate at depth. These results imply that trickle irrigation caused both horizontal and vertical movement of native soil phosphate near the outlet, and that phosphate fertilizer applied 50 to 80 cm away from the outlet remained near the soil surface and above the root zone.

Irrigation of an 8‐ to 12‐h duration usually increased the concentration of Bray no. 1 phosphate by an average of 63% in a region of radius 30 cm from the outlet and about 12 cm in depth. The phosphate concentration remained above pre‐irrigation levels for between 6 to 23 h after the end of irrigation but fell to pre‐irrigation levels as the soil dried out.

A series of linear regression equations of similar slope were found to describe the relationship between Bray no. 1 phosphate and soil water content for all 300 samples collected in the multicycle irrigation experiment. Differences in intercept values were related to the variable phosphate distribution with depth at various distances from the trickle outlet.

Phosphate release probably resulted from reduction of amorphous iron phosphates during the anaerobic phase of the irrigation cycle. These results suggest that trickle irrigation leads to cyclic release of both native and applied phosphate during each irrigation cycle. Leaf analysis showed that under these circumstances there was no significant response to applied phosphate fertilizers at rates up to 78 g of P as single superphosphate per plant. Over the period studied trickle irrigation appears to be an agricultural management system with a much lower requirement for the application of phosphate fertilizer when tree crops are grown.