bluuebunny/crossref_metadata_2025 huggingface dataset:
A Field Study of Soil Water Depletion Patterns in Presence of Growing Soybean Roots: I. Determination of Hydraulic Properties of the Soil
Authors: Arya L. M. , Farrell D. A. , Blake G. R.
Published: July 2010

The hydraulic properties of a Waukegan loam profile were determined by field and laboratory procedures. Pressure‐water content relationships obtained in the laboratory were found to be variable at pressures above −100 cm of water. In this range field data were considered more reliable.

Hydraulic conductivity in the field was determined from flux and hydraulic‐head gradient data. Hydraulic‐head gradients were obtained from tensiometric measurements of pressure at various depths. In the soil profile that was subject to both evaporation and drainage, the position of a downward moving “zero flux” boundary was determined. Flux across any depth was obtained by integrating the rate of change of water content with time between the “zero flux” boundary and the depth in question.

A modified laboratory technique was used to determine the diffusivity of undisturbed soil cores. Water content vs. distance data were obtained subject to the conditions that evaporation was proportional to the square root of time and the soil core was effectively semi‐infinite. A diffusivity equation developed by Bruce and Klute (1956) was used to calculate diffusivity from the water content‐distance functions. Diffusivities were converted to conductivities.

The “zero flux” boundary technique greatly reduced the time needed by covered plot methods to obtain conductivities at high soil‐water pressures. The laboratory procedure required only about 30 min/sample and gave results that compared favourably to field results.

At high water contents and to a depth of 20 cm, field conductivities were slightly lower than laboratory estimates. Below the 20‐cm depth field data tended to be slightly higher.
The Effect of Soil Properties on Zinc Adsorption by Soils
Authors: Shuman L. M.
Published: July 2010

Solutions containing eight different concentrations of Zn were equilibrated with four soils sampled at two depths to determine whether Zn adsorption conformed to the Langmuir isotherm and to relate the Langmuir coefficients to soil properties. Zinc adsorption conformed to the Langmuir isotherm and two linear portions of the curve were found. The adsorption sites for the lower part had very high bonding energy coefficients and low adsorptive capacities compared with the adsorption sites of the part of the curve corresponding to higher Zn concentrations in the equilibrating solution. The CEC was related to the adsorptive capacity. The lower part was equivalent to 23% of the CEC and the upper part to 76% of the CEC. Soils high in clay or organic matter had higher adsorptive capacities and higher bonding energies for Zn than sandy soils low in organic matter. More differences in Zn adsorption were observed among soil types than between depths in each soil type. A study of the effect of pH on the adsorption of Zn revealed that low pH reduced Zn adsorption more for the sandy soils than for those high in colloidal‐size materials.
Validity of Soil‐Water Samples Collected with Porous Ceramic Cups
Authors: Hansen Edward A. , Harris Alfred Ray
Published: July 2010

Laboratory and field tests were made to determine if porous ceramic cups collect representative samples of nitrate and phosphate from soil water. Substantial bias and variability were found. Some of the sources of sample bias were sorption, leaching, diffusion, and screening of phosphate ions by the cup walls. Sample variability of nitrate ions was strongly influenced by sampler intake rate, plugging, sampler depth, and type of vacuum system (which simulated different sampler sizes). These factors affect timing of sample collection and, because nutrient concentration in soil water is continually changing, they in turn affect sample concentration. These factors produced as much as a 60% range in sample concentration from eight samplers installed in a small uniform plot. Added to this variability is an unknown amount of bias representing the difference between the sample concentration and the average drainable soil‐water concentration. The many factors affecting the sample concentration together with the demonstrated variability and unknown bias make interpretation of sampler data difficult. To reduce sample variability, group samplers by intake rate, and use short sampling intervals, uniform sampler lengths, and the same initial vacuum for all samplers.
Soil Bulk Densities after Thirty Years under Different Management Regimes
Authors: Northup M. L. , Boyle J. R.
Published: July 2010

Variability of soil bulk density must be known to convert accurately concentrations of nutrients in a soil to absolute quantities. This study shows that cultivation increases the bulk density of some soils and simultaneously lowers its variability. Establishment of prairie and pine (Pinus spp.) vegetation on cultivated soils has not created significant differences in this property between vegetation types in 30 years.
Hydraulic Conductivity Calculations for Unsaturated Steady‐State and Transient‐State Flow in Sand
Authors: Elzeftawy Atef , Mansell R. S.
Published: July 2010

Using a method employed by Green and Corey (1971), hydraulic conductivity was calculated as a function of water content for Lakeland fine sand. A gamma ray transmission method for measuring soil water content and a tensiometer‐pressure transducer arrangement for measuring soil water suction were also used to experimentally determine values of hydraulic conductivity for a similar range of soil water contents in undisturbed soil cores and hand‐packed soil columns. Measured and calculated values were in good agreement for steady flow.

During transient flow soil water content was observed to be a non‐unique function of suction for water desorption, but depended upon the state of flow. Higher water contents were found at a given pressure head during unsteady flow than during steady flow or static equilibrium (zero flow). Graphs of water content versus soil water suction were similar for cases of steady and no‐flow conditions. For transient flow, the soil‐water pressure depended upon the soil‐water content and rate of change of pressure head with time.
Micronutrient Levels in the Rice Plant Y Leaf as a Function of Soil Solution Concentration
Authors: Yoon S. K. , Gilmour J. T. , Wells B. R.
Published: July 2010

A field experiment was established to evaluate the rice plant (Oryza sativa L. var Bonnet 73) Y leaf Fe, Mn, and Zn content versus soil solution concentration as a function of time. Rice straw additions were made to provide variable submerged soil solution chemistry. Rice straw amendments facilitated Fe and Mn release to the soil solution. Bicarbonate, hydroxide, and possibly organic ligands from the rice straw appeared to lower soil solution Zn concentration. Rice plant Y leaf analyses suggested that the oxidative status of the rice root system exerted some control over Fe and Mn content. Zinc content in the rice plant Y leaf followed submerged soil solution levels.
Geomorphology of a Glaciated First‐Order Valley in South Central New York
Authors: Daugherty L. A. , Hanna W. E. , Arnold R. W.
Published: July 2010

A glaciated first‐order valley in south central New York was studied to determine the post‐glacial evolution of the landforms. Ninety‐seven profiles were sampled at depth intervals of approximately 30 cm to determine internal features of the landscape units. Particle size differences were the main indicators of lithologic discontinuities. Arithmetic mean of the fine earth particle size in conjunction with the relative amounts and orientation of coarse fragments were useful in determining strata of the summit, shoulder, backslope, footslope, toeslope and the high, intermediate, and low level terraces. Congeliturbate as much as 10 m deep was found in the basin at the head of the stream in foot‐ and toeslope areas. The downstream portion of these deposits has been deeply entrenched by the stream. During periglacial times congeliturbate in the downstream channel contributed to temporary base levels of the stream. Much of this congeliturbate remains as terraces. The alluvium resulting from the entrenchment of the congeliturbate occurs as a series of 92 terrace remnants and it is believed that their strata, relative elevation, and gradient contain clues to the complex sequence of erosional and depositional events.
Vehicle Perturbation Effects upon a Tundra Soil‐Plant System: I. Effects on Morphological and Physical Environmental Properties of the Soils
Authors: Gersper P. L. , Challinor J. L.
Published: July 2010

Changes obtaining in the soil abiotic physical environment due to tracked‐vehicle disturbance were determined in Tundra soils near Barrow, Alaska. The study was a contribution of the U.S.I.B.P., Tundra Biome Program.

Six years following the scarring of the tundra surface by several years of infrequent passage by tracked‐vehicles (Weasel), the soils within the track had higher bulk densities and temperatures, accelerated and deeper thaw, and lower moisture percentages than undisturbed soil. Soil morphology was little altered except for direct physical alteration of surface organic horizons and a slight increase in mottling of mineral horizons in all but the wetter portions of the track. The intensity of alteration and associated environmental changes were related to the degree of evident disturbance (the amount of visible damage to the vegetative cover and soil surface) which, in turn, were related to differences in the natural drainage of the soils along the tracks; disturbance being greater, the poorer the natural drainage.

The study indicated that a slight amount of disturbance to the tundra surface may be beneficial in terms of increased productivity and nutrient content of vegetation (see Part II of this paper). On the other hand, heavy disturbance can result in severe damage to the tundra system due to subsidence and erosion preventing the revegetation of the disturbed areas.
Water Flux and Electrical Potentials in Water‐Saturated Bentonite
Authors: Gairon S. , Swartzendruber D.
Published: July 2010

Electrical potential, water flux, and hydraulic gradient were studied for saturated water flow through plugs of sodium bentonite at concentrations ranging from 11.5 to 35.1% clay. A special permeameter with an adjustable piston allowed measurements to be taken with a given mass of clay, but with successively lower clay concentrations as the piston was shifted out to increase the water content of the clay‐water mixture. At the lowest clay content, both electrical potential and water flux increased less than proportionally with increasing hydraulic gradient. This less‐than‐proportional behavior decreased as clay concentration increased, and, at 28.4% clay, proportional response to hydraulic gradient was obtained for both electrical potential and water flux. A less‐than‐proportional relationship between electrical potential and hydraulic gradient did not cause the water flux to increase more than proportionally with increasing hydraulic gradient, in contrast with what has been reported for nonswelling quartz powder and would be inferred from the classical double‐layer theory of streaming potential and electroosmotic flow. The relationship between electrical and hydraulic properties may thus be different for swelling porous media than for nonswelling media. The only indication of a more‐than‐proportional flux‐gradient relationship was found for a 35.1% clay concentration, in the form of a linear relationship displaced to the right from the origin to yield a positive gradient intercept and a negative water flux at zero hydraulic gradient.
Nitrogen, Phosphorus, and Potassium Requirements in No‐Tillage and Conventionally Tilled Corn
Authors: Moschler W. W. , Martens D. C.
Published: July 2010

The response of corn (Zea mays L.) to four rates each of N, and P, and three rates of K fertilizer was determined under no‐tillage and conventional tillage culture. The soil type was Jefferson silt loam, an infertile, acid soil. The experiments were conducted during 3 years of above‐average rainfall for the location. In conventional tillage culture the fertilizer was broadcast on turnplowed soil and disked in, while in no‐tillage culture it was broadcast and left on the soil surface. The objective was to clarify the relative fertilizer requirements of corn grown by the two tillage methods. Yield, nutrient element removal by the crop, and residual levels of nutrient elements were used to evaluate results. Results obtained by yield and nutrient removal criteria agreed with each other except at the higher rates of P, and K. In these cases considerable P, and K were absorbed without corresponding yield increase. Corn maturity was hastened by no‐tillage. It was concluded that at the highest rate of N, and all rates of P, and K tested, no‐tillage culture increased the efficiency of the applied fertilizers. The highest yield producing 3‐year total rates of N, P, and K tested with no‐tillage were 470.8, 67.3, and 215.2 kg/ha, respectively. At these rates the grain yield increases over conventional tillage receiving the same rates were 19.1, 18.3, and 14.6%, respectively. These increases in fertiliezr efficiency are of special value in times of food and fertilizer shortages, such as presently exist.
Local Soil‐landscape Relationships in Western Iowa: II. Quantification of Pedologic and Geologic Effects
Authors: Huddleston J. H. , Walsh J. A. , Jowett D. , Riecken F. F.
Published: July 2010

The soil‐landscape system consists of contiguous units of noncalcareous loess, calcareous loess, and alluvium. Soil data from each unit were subjected to a principal components analysis. The objective was to identify specific pedologic and geologic processes that have contributed to soil formation and to quantify the separate effects of each process. Factors generated by the analysis were interpreted as representing (i) processes of parent material formation, whose effects are inherited; (ii) processes of pedogenesis that modify initial‐state distributions; (iii) processes of loess stratification; (iv) processes of hillslope erosion and footslope sedimentation; (v) processes of nutrient concentration; and (vi) processes of nitrate mobility. The percentage variance removed by each factor indicates the relative strength of each process. Parent material effects dominate in calcareous loess, but pedogenic profile modifications dominate in noncalcareous loess. In both materials, the effects inherited from geologic processes of loess stratification could also be identified. Two processes in alluvium express effects of erosion‐sedimentation and of nutrient concentration in the waterway center. Pedogenesis is of tertiary importance to soil formation in alluvium.
Toposequence Relationships of Dystrandepts in Costa Rica
Authors: Alvarado A. , Buol S. W.
Published: July 2010

Three Typic Dystrandepts; medial, isothermic, profiles located on a slightly convex position, a concave position, and a 20% slope were studied. The horizontal distance between adjacent profiles was approximately 100 m.

The soils were characterized by chemical, mineralogical, micromorphological and physical methods to establish the nature of the differences among them, and to develop hypotheses of their genesis.

The genesis of these soils appears to be controlled by composition and age of the parent material and only slightly influenced by the relief. Periodic additions of pyroclastic materials build up thick A horizons rich in plagioclases and pyroxenes. Halloysite was evident in the deeper and older underlying materials where it was also observed in sand‐sized aggregates. The B horizons in the convex and sloping topographic positions were slightly more enriched with iron, which seemed to be translocated from the A horizons, than was the profile in the concave position.

Differences due to topographic position did not affect taxonomic placement of the profiles in the family category.
Trials with Sulfur‐Coated Urea and Other Nitrogenous Fertilizers on Pinus radiata in New Zealand
Authors: Mead D. J. , Ballard R. , Mackenzie M.
Published: July 2010

Sulfur‐coated urea fertilizers were included in six experiments with seedlings of Pinus radiata D.Don. The fertilizers were applied in notches alongside seedlings about 2 months after planting, and tree growth was measured for 2 or 3 years. After slash burning on a strongly weathered clay soil, slow‐release nitrogen fertilizers, including three formulations of S‐coated urea, proved more effective than urea. On a more fertile pumice soil, on both slash burnt and unburnt sites, no response to N fertilizers was detected. However, where the topsoil of this soil type had been either completely or partially removed (a log landing and a windrowed area, respectively) a response to N occurred. In these two disturbed areas S‐coated urea showed no advantage over conventional soluble NH4‐N fertilizers. There were no differences between the effectiveness of the three formulations of S‐coated urea at any of the experimental sites.
The Growth of Disturbances in Unstable Infiltration Flows
Authors: Philip J. R.
Published: July 2010

The stability analysis of the delta‐function model of infiltration yields a maximum wave‐number for unstable disturbances, Mcrit, and a wave‐number for maximum amplification, M*. The “column effect,” i.e. the suppression of instability in laboratory columns, depends on Mcrit; and the dimensions of fingers in unstable flows can be expected to depend on M*. When instability is induced by a sudden jump of G, the water pressure gradient behind the wetting front, Mcrit and M* may be evaluated simply and directly. When, on the other hand, instability emerges during gradual increase of G, it is necessary to study the amplification of disturbances during the whole course of increase of G through positive values.

Such a study is made for one example of instability induced by air compression and for one where it is induced by increase of conductivity with depth. Both exhibit qualitatively similar patterns of amplification: disturbances of small M (wave‐number) begin to be amplified sooner, but are ultimately overtaken by some disturbances of larger M starting later. Definite values of M* are found, and the results discussed with special reference to fingering and to the column effect.
On the Differential Equation for the Equilibrium Moisture Profile in Swelling Soil
Authors: Sposito Garrison
Published: July 2010

Differential equations which describe the equilibrium vertical distribution of moisture in swelling soil have been derived previously using both thermodynamic and fluid‐mechanical methods. A fundamental disagreement exists between these expressions which is resolved in this paper through a detailed thermodynamic analysis of the equilibrium state of water in a swelling soil. The correct differential equation for the moisture profile is found and the discrepancy between previous results is shown to have been caused either by introduction of extrathermodynamic variables or by an incorrect handling of the effect of overburden pressure on the soil water.
Soil Potassium Relationships as Indicated by Solution Equilibrations and Plant Uptake
Authors: Munn D. A. , McLean E. O.
Published: July 2010

Four Ohio soils of wide range in K release capability were initially K‐treated (0, 100, 200, 800 ppm) and successively cropped three times with corn in a growth chamber. Aliquots of the soils with and without K added and before and after cropping were assayed by extraction, equilibration, and plant uptake techniques for the effects of cropping and K‐treatment. Uptake of K by the corn was closely related to the K release capabilities of the soils. Exchangeable K increased as rate of K increased. Initial cropping decreased the exchangeable K in all soils eliminating the effect of K treatments on exchangeable K. However, after initial cropping where no K was added, exchangeable K varied sixfold from the lowest to the highest. Nonexchangeable K removed with H2SO4 initially reflected K additions, but after the first crop, the values decreased progressively as K release capabilities of the soils increased. Parameters from Q/I isotherms of the soils gave correlations with percentage and total K contents of assay crops less satisfactory than for exchangeable and H2SO4 extractable K. There was a tendency for prior cropping to increase the fixation and reduce the plant recovery of subsequently applied K in the two soils high in clay and total K.
Initial Release of Nitrogen from Ureaform Under Field Conditions
Authors: Hadas Aviva , Kafkafi U. , Peled A.
Published: July 2010

The mineralization of ureaform in the soil has been observed during the three weeks following application in a small plot of a banana (Musa Cavendishii, var. Cavendish) plantation at two different seasons of the year. In the cooler season ammonium and nitrite accumulated and persisted for 2 weeks. In the warmer season, only ammonium accumulated during 2 days. The rate of mineralization, calculated as a first‐order reaction, was greater at the higher temperature, but the rate constants were about 10 times greater in the field than in previous laboratory experiments. The reasons for this are probably changes in microbiological activity and mineralization of nitrogen from sources other than the fertilizer.
Clay Mineralogy, Physical, and Chemical Properties of Some Soils in Arid Regions of Iran
Authors: Mahjoory Ramez A.
Published: July 2010

Coarse, medium, and fine‐textured soils were studied in three different arid regions of Iran, namely Gazvin, Karaj, and Kooshkak alluvial plains, respectively. Six representative pedons including 33 samples were tested.

X‐ray analyses indicated the clay mineral components of soils consist of some discrete vermiculite, chlorite, clay mica (illite), kaolinite, and interstratified clay mica‐vermiculite or chlorite.

Quantitatively, vermiculite and clay mica are the major clay mineral components in these soils. The average vermiculite contents of coarse, medium, and fine‐textured soils are calculated as 41.7, 41.4, 42.4%; clay mica contents are 26.3, 38.0, and 20.0%, respectively. The amount of clay mica decreases significantly with depth in most of the soils studied.

Physico‐chemical determinations revealed the soils are calcareous throughout and the carbonates increase from coarse‐ to fine‐textured soils. The morphogenetic sequences of carbonate accumulation are divided into three morphogenetypes. Most organic matter contents are < 1%. They decrease with depth but increase from coarse‐ to fine‐textured soils.

Soils with poor structural development contain > 20% CaCO3, and have considerable amounts of vermiculite but lower amounts of clay mica. The slight accumulation of silt, clay, and carbonates at the surface of some soils may indicate the influence of atmospheric addition in the genesis of the soils studied. Two of the soils are classified Typic Camborthids, two of them Xerollic Camborthids, and the other two, Xerollic Calciorthids.
Thick Bh Horizons in the North Carolina Coastal Plain: I. Morphology and Relation to Texture and Soil Ground Water
Authors: Daniels R. B. , Gamble E. E. , Holzhey C. S.
Published: July 2010

Spodosols in North Carolina have thick, vertically continuous Bh horizons wherever the parent material is a sand or loamy sand texture that has a high water table and a downward flow of ground water. These Bh horizons are 5–9 m thick, and their lower boundaries are always a few centimeters above a less permeable layer or a bed of greenish‐gray sand. Pollen counts and the general morphology indicate that the thick Bh horizons are post depositional features. Percolating organics, monitored by shallow wells, move from the surface downward in quantities greater than necessary to account for the whole Bh horizon thickness.
Crop Production Function Determinations as Influenced by Irrigation and Nitrogen Fertilization Using a Continuous Variable Design
Authors: Bauder J. W. , Hanks R. J. , James D. W.
Published: July 2010

Continuous variable (CVD) and randomized block, split plot (RBSD) designs were used to produce data from which production functions were developed relating corn yield to soil water and nitrogen fertilizer. Data were collected at Logan, Utah in 1972 and Farmington, Utah in 1973.

The CVD water and nitrogen treatments, respectively, were sequential or continuous and not randomized. The design is compact but has some statistical uncertainty. The CVD had 7 or 8 soil water (W) levels and 22 or 24 nitrogen (N) levels compared to 4 W and 5 N levels for RBSD. The area used for the RBSD was 3 or 4× that used for the CVD.

The data analyzed for the CVD led to the same conclusions as the analysis of the RBSD. The production function (regression equation) at Logan was different from that at Farmington except when comparisons were made on a relative basis.
Nitrate Movement and its Distribution in the Soil Profile of Differentially Fertilized Corn Watersheds
Authors: Schuman G. E. , McCalla T. M. , Saxton K. E. , Knox H. T.
Published: July 2010

Nitrate movement within the 6.1‐m soil profile of a watershed in southwestern Iowa, fertilized at 448 kg N/ha per yr, resulted in a 720‐kg/ha increase in NO3‐N below the corn root zone during the 3‐year study. The NO3‐N concentration of the baseflow from the watershed increased during this period, indicating that some of the leached NO3‐N reached the ground water. The watershed fertilized at the recommended N rate (168 kg/ha per yr) did not increase the quantity of NO3‐N below the corn root zone; however, some NO3‐N leaching did occur.

Between April 1971 and April 1974, the accumulation of NO3‐N in the profile of the excessively fertilized watershed moved from the 1.0‐ to 3.1‐m depth. Three‐fourths of NO3‐N movement occurred between June 1972 and April 1973 when 80 cm of precipitation caused 21 cm of percolation below the corn root zone (183 cm). The watershed fertilized with 168 kg N/ha per yr did not show any zones of significant NO3‐N accumulation in the soil profile at any of the sampling dates.

The depth to the water table on the lowest contour sampled on the excessively fertilized watershed was 4.6 and 4.9 m in April 1973 and April 1974, respectively. The average NO3‐N concentration for these two sampling dates at the water table depth increased from 3.7 to 12.9 ppm. The average NO3‐N concentration at the water table depth on the normally fertilized watershed was 2.0 and 4.5 ppm in April 1973 and April 1974, respectively, with a water table depth of 3.0 m.
Solubility and Solubility Product of Dicalcium Phosphate Dihydrate in Aqueous Solutions and Soil Solutions
Authors: Bennett A. C. , Adams Fred
Published: July 2010

The solubility product (Ca2+)(HPO42‐) of CaHPO4 · 2H2O was determined in several aqueous solutions containing ions common to soil solutions. Extrapolation of analytical Ca and P concentrations to zero ionic strength yielded pKSD values ranging from 6.54 to 6.59 and averaging 6.57 for 10 aqueous salt solutions. A method of successive approximation that computed ionic activity was used to determine the pKSD for three concentrations of 15 different aqueous salt solutions saturated with CaHPO4 · 2H2O. Calculated pKsp values ranged from 6.44 to 6.63; the average was 6.55. Eight soil samples that varied widely in pH and soil‐test P were treated with CaHPO4 · 2H2O at rates of 600 to 3,000 ppm P. Soil solutions were displaced, analyzed, and (Ca2+)(HPO42‐) was calculated. Eight of the 20 samples of soil were considered to be saturated with CaHPO4 · 2H2O because their (Ca2+)(HPO42‐) values were approximately the same as that for similar aqueous salt solutions. It was concluded that the presence of excess CaHPO4 · 2H2O in soil could be inferred by ion‐activity products of displaced soil solutions.
Degradation of a Nonionic Surfactant in Soils and Peat
Authors: Valoras N. , Letey J. , Martin J. P. , Osborn J.
Published: July 2010

Nonionic surfactants are used to improve water movement into water‐repellent soils. The effective longevity of treatment and potential water pollution are affected by surfactant degradation. Degradation of 14C‐labeled Soil Penetrant 3685, a nonionic surfactant, was measured in incubation studies in the laboratory. Three soils and one peat, numerous surfactant concentrations, and two soil‐moisture levels were used as experimental variables. Plots of degradation percentage versus time produced “S” type curves. Increasing the concentration increased the lag period prior to most rapid degradation. The most rapid and highest percentage of degradation were generally associated with soil materials having the lowest adsorptive capacity for the surfacant. From about 75 to 85% of the added 14C was evolved as 14CO2 in 1 year for the most favorable conditions for degradation. Degradation rate was decreased by decreasing the soil‐moisture content. Degradation of soil organic matter was not greatly affected by surfactant applications—< about 10,000 ppm, but progressively decreased with higher surfactant concentrations.
Effects of Vegetation on the Distribution of Carbon, Iron, and Aluminum in the B Horizons of Northern Appalachian Spodosols
Authors: De Kimpe C. R. , Martel Y. A.
Published: July 2010

The effects of coniferous and deciduous vegetation on the distribution of C, Fe, and Al oxides in the B horizons of 10 Podzolic (Spodic) soils of the Northern Appalachian Mountains were investigated. Organic C was extracted with 0.5N NaOH. Iron and aluminum oxides were extracted with pyrophosphate and with dithionite‐citrate‐bicarbonate. Significantly more Fe and Al was found under conifers than under deciduous trees in the upper part of the B horizon. Aluminum content was also higher in the lower part of the B horizon.

After fractionation of the organic matter, fulvic acids appeared as the most important fraction. They contained on the average 52% of the C and > 90% of the Fe and Al involved in organo‐metallic complexes. These were found in significantly greater amounts in the upper part of the B horizons of soils developed under conifers.

The content of sesquioxides in organo‐metallic complexes is a criterion for the classification of the Spodic or Podzolic B horizon in both the US and Canadian systems of soil classification. Variations in sesquioxides due to vegetation type may exclude some Podzolic soils of the Northern Appalachian Mountains developed in fine‐textured material of being classified as Spodosols in the US system.
Salt and Water Balance in Imperial Valley, California
Authors: Kaddah M. T. , Rhoades J. D.
Published: July 2010

Salt balance (SB = Veff.w · Ceff.w − Vinf.w · Cinf.w) of the Imperial Valley (IV) has been determined annually since 1943 by the Imperial Irrigation District. Salinity trends in the valley are assessed from biweekly measurements of the volume, V, and concentration, C, of influent, inf.w, and effluent, eff.w, waters. In this paper we summarize the SB data, evaluate their significance, and suggest approaches for assessing salinity trends in the soils of the valley.

The SB data reflected the cropping and water use patterns in the valley. However, the data were insufficient to distinguish origin of water and salt in effluent waters or to provide information about changes in root zone salinity. In 1973 total evapotranspiration (ET) by crops in the valley was estimated to be 229 × 103 ha‐m, equivalent to 70% of the water delivered to the farmers. Deductions as to Cl‐ composition of influent and effluent during 1973 suggest that the Cl‐ load in the effluent water was contributed as follows: 54.7% from ground water, 35.0% from root zone drainage water, and 10.3% from tail water (runoff).

A more definitive interpretation of the salt balance data would require more accurate evaluation of volume of tail and consumptive use waters and volume and concentration of root zone percolate. If this information cannot be obtained on a valley‐wide basis, then an alternative approach is to establish a representative number of soil salinity monitoring plots through the valley and assess their root zone salinity periodically.
Stabilizing Soil Aggregates with Phosphoric Acid
Authors: Thien Steve J.
Published: July 2010

Four P‐containing fertilizer materials (H3PO4, liquid and dry ammonium polyphosphate, and triple superphosphate) were compared for ability to increase water stability of aggregates in an acid soil. Only agricultural‐grade H3PO4 significantly increased aggregate stability—from 6.2% in the untreated samples to 45.2% in samples treated with 228 kg P/ha. The induced stability lasted through at least five wetting and drying cycles, each cycle consisting of 1.8 cm of water applied over a 1‐hour period followed by 2 weeks of air drying. Water stability of soil aggregates treated with H3PO4 increased as H3PO4 was increased to 228 kg P/ha (maximum tested). Exchangeable Al increased from 0.2 ppm Al in untreated soil to 2.55 and 2.85 ppm Al in soil layers receiving 112 and 224 kg P/ha, respectively. While the highest P concentrations tested caused soil pH to temporarily drop approximately one unit, pH returned to the pretreated value after four wetting cycles. Scanning electron microscope photos showed more fine particles present in the treated aggregates than in the untreated samples. Phosphoric acid apparently modifies the soil physical environment by preserving the fine‐particle content of aggregates which in turn increases their water stability.
Plinthite Characterization in Selected Southern Coastal Plain Soils
Authors: Wood B. W. , Perkins H. F.
Published: July 2010

Samples of plinthic horizons from five soil series were collected in the Southern Coastal Plains Province of Georgia. Plinthite and various colors of soil material in each horizon were separated and analyzed for particle size distribution, Fe2O3 content, and mineralogy.

Iron segregation is greater in plinthic than nonplinthic soil formations in subsurface horizons. In the upper part of B2t horizons where plinthite is nearest the surface, Fe is present as amorphous hydrated oxides and goethite giving the soil matrix a brownish‐yellow color. In the plinthite, there is a higher Fe content than in surrounding non‐plinthic soil and the Fe is present as the dehydrated oxide hematite in addition to the amorphous hydrated oxides and goethite. The lower part of the B2t horizon is composed of three color phases in which the Fe content as well as the form of Fe differs. In the pale‐colored soil (white, pale yellow), total Fe is relatively low. Iron occurs in greater amounts in the forms of goethite and amorphous compounds in the brownish yellow soil material. Plinthite has the highest Fe content which occurs as hematite, goethite, and amorphous hydrated oxides.

Particle size distribution varies within plinthic horizons. Nonplinthic soil materials have higher percentages of <2µm particles than was found in plinthite. Kaolinite in the clay fraction of plinthite is in a more disordered crystalline state than in the matrix soil. The silt fraction of the soil matrix contains quartz in the pale‐colored soil and quartz and goethite in the yellow soil. Silt fractions of plinthite contain quartz, hematite, and goethite. The coarser texture of the plinthic material appears to be a result of destruction of kaolinite and crystal growth of Fe compounds. The end product of this process is hardened ironstone nodules or septaria which contain quartz, hematite, goethite, and weakly crystalline kaolinite.
Correlation of Plant Manganese with Extractable Soil Manganese and Soil Factors
Authors: Randall G. W. , Schulte E. E. , Corey R. B.
Published: July 2010

The availability of Mn on 37 low and 20 high organic matter Wisconsin soils was determined by growing oats (Avena sativa L.) and ryegrass (Lolium perenne), respectively, in consecutive greenhouse studies. The Mn uptake values were used to develop prediction equations by means of multiple regression analysis with Mn extracted by various extracting solutions (18 extractants for the low and 13 for the high organic matter soils) plus various functions of soil pH and organic matter as the independent variables.

On the low organic matter soils (O.M. < 6%), using only the Mn test, the best prediction values with uptake were obtained with total Mn, and with the 0.1N H3PO4 and 0.01M EDTA in 1N NH4OAc extractants (R2 = 57, 50 and 49%, respectively). Inclusion of soil pH and organic matter with the soil test values resulted in Mn uptake being predicted best by the 0.01M and 0.05M EDTA extractants (R2 = 68% for both). The contribution of the soil test in the prediction equation was strongest when the 0.1N H3PO4, 0.01M EDTA in 1N NH4OAc, 0.05M EDTA or DTPA (pH 7.3) extractants were used.

On the high organic matter soils (4.2 to 78.5% OM), a regression equation with soil pH, organic matter and their cross‐product as the independent variables accounted for 70% of the Mn uptake variability. By including test × pH and test × organic matter for the 0.01M EDTA in 0.1M (NH4)2CO3 or DPTA (pH 10.7) extractants, the R2 values were increased to 80%. Soil test Mn or its squared value did not contribute significantly to any of the prediction equations; whereas, soil organic matter and the pH × organic matter cross‐product contributed to all.
A Nomograph for Hydrometer Method of Particle Size Analysis
Authors: Sur Hardip. S. , Singh N. T.
Published: July 2010

The hydrometer method for particle size analysis in soils involves calculations of size of particle (d) settling in a suspension at a given time (t) from the hydrometer reading (R). A parabolic relation described by θ = m(a‐bR)1/2 exists between (θ) and R. A nomograph based on relationships between different parameters of the hydrometer method has been developed and its use is explained.
Influence of Hysteresis on Moisture Flow in an Undisturbed Soil Monolith
Authors: Beese F. , van der Ploeg R. R.
Published: July 2010

The moisture dynamics of an undisturbed soil monolith were studied during a lysimeter experiment. Daily measurements were made of the soil suction at 10 depths. Also daily measured were the precipitation, the seepage, and the evaporation from the monolith during a 3‐year period. For selected periods, a drying (desorption) curve and a wetting (sorption) curve of the soil moisture characteristic were determined from field data. Also the capillary conductivity was determined with use of daily monolith observations. With use of these hydraulic functions, the unsaturated soil moisture flow equation was solved numerically for one‐dimensional vertical flow. In order to determine the effect of hysteresis on the suction distribution in the monolith, calculations were performed either with the desorption curve or with the sorption curve without scanning between these curves. Neither of the two curves leads to complete agreement between observed and calculated soil suction values; the desorption curve usually gives too high values, the sorption curve too low values.
Response of Potted Slash Pine Seedlings on Imperfectly Drained Coastal Plain Soil to Additions of Zinc
Authors: McKee W. H.
Published: July 2010

In a greenhouse study, seedling dry weights and uptake of Zn, K, Mg, and Ca were increased by applying 1 ppm of Zn to Caddo silt loam soil fertilized with 123 ppm of N, 0.31 meq of K/100 g, and varying amounts of P and lime. Zinc interacted with P and lime to alter N uptake. Zinc uptake rose with increasing amounts of Zn and available P in the soil at harvest, but declined with increasing levels of exchangeable Mg, K, and Ca.
Long‐term Evaluation of Slow‐release Nitrogen Sources on Turfgrass
Authors: Waddington D. V. , Moberg E. L. , Duich J. M. , Watschke T. L.
Published: July 2010

Short‐term studies with slow‐release nitrogen sources have not provided information on the changes in response that may occur with continued use of a given material. In this study eight nitrogen sources were used to fertilize ‘Merion’ Kentucky bluegrass (Poa pratensis L.) for 7 consecutive years to obtain long‐term results. Fertilizers used were urea, Uramite (ureaform), IBDU (isobutylidene diurea), Urex (urea‐paraffin matrix), ADM (plastic coated urea), Milorganite (activated sewage sludge), and two complete (NPK) fertilizers, with two‐thirds of the nitrogen from ureaform or IBDU and the remainder soluble. Urea was applied every other week and the other fertilizers were applied one, two, or three times per season to obtain total N of 1.46 or 2.44 kg/100 m2. Weekly clipping yields and color ratings were used to evaluate turfgrass response to the fertilizer treatments. Milorganite, Uramite, and IBDU produced more uniform growth than Urex, ADM, and the complete fertilizers. Response to Urex, ADM, and the complete fertilizer with IBDU was similar, and was often characterized by excessive growth after application. The greatest increase in response with continued use occurred with Uramite, which was the least efficient fertilizer in the first two years. At the end of the 7‐year period, determinations of yield, color, and total soil N indicated that Uramite had the greatest residual effect.
An Evaporation Chamber with Constant Suction
Authors: O'Connor G. A. , Cull C.
Published: July 2010

Laboratory chambers to aid in the evaporation of water from soil surface have been described by numerous authors, but few units have been described which allow simultaneous collection of drainage water. This note describes the components and performance of an evaporation chamber enclosing a rotating turntable which allows the application of constant suction to multiple soil columns. The chamber will not be appropriate to all studies involving soil water evaporation, but offers certain advantages over conventially described units, particularly if suction needs to be applied to soil columns as they evaporate on a revolving turntable. Total cost of the chamber, including professional labor, was < $700.00.
An Electrical Conductivity Probe for Determining Soil Salinity
Authors: Rhoades J. D. , van Schilfgaarde J.
Published: July 2010

An electrical conductivity probe for determining soil salinity is described with construction details. The probe's utility for measuring soil salinity within discrete soil depth intervals is illustrated with examples. Using the salinity probe, the Barnes method for estimating electrical conductivity profiles was shown to be accurate for soils that are reasonably homogeneous laterally.
Influence of Ionic Strength and Inorganic Complex Formation on the Sorption of Trace Amounts of Cd by Montmorillonite
Authors: Garcia‐Miragaya J. , Page A. L.
Published: July 2010

Cadmium sorption by montmorillonite from solutions in the 15 to 120 ppb range was studied in the presence of increasing concentrations of NaClO4, NaCl, and Na2SO4 solutions. The ionic strengths ranged from 0.01 to 1.00. Increasing ionic strengths decreased the amount of Cd sorbed on the clay surfaces. The percentage sorbed decreased from around 90% for I = 0.01 to about 50% for I = 1.00 in the ClO4 systems. The sorption of Cd in the chloride system was in the range between 25 to 50% less than the ClO4 systems for the same ionic strength. This was attributed to the presence of uncharged and negatively charged complexes of Cd with Cl ligands. This fact has some implications, especially in arid zone soils where high Cl concentrations in soil solutions are not unusual; there, Cd will behave mainly as a neutral species (CdCl20) and as an anion (CaCl3‐ and CdCl42‐), rather than as a cation (Cd2+).

The SO4 systems showed a moderate decrease in the amount of Cd sorbed with respect to the ClO4 systems for the same salt concentrations. This observation was interpreted as due to the presence of a fraction of Cd in solution as the CdSO40 species.
Soil Elastic Constants: I. Calculations from Sound Velocities
Authors: Briones A. A. , Uehara G.
Published: July 2010

Compressional and shear wave velocities were measured in remolded cylindrical‐shaped soil materials from a Vertisol and two Oxisols. The modulus of elasticity, shear modulus, and bulk modulus were computed from measured sound velocities. Compressional wave velocity increased with increasing water content, shear wave velocity decreased with increasing water content and both velocities increased with increasing soil density. The Vertisol with a high content of swelling clay underwent greater change in modulus of elasticity and shear modulus for a given change in water content than the Oxisols.
Soil Nitrate‐nitrogen Determined by Coring and Solution Extraction Techniques
Authors: Alberts E. E. , Burwell R. E. , Schuman G. E.
Published: July 2010

Soil‐coring and solution‐extraction sampling techniques were compared for determining the content of NO3‐N in the soil profile of a Monona silt loam (Typic Hapludoll) in southwestern Iowa. The NO3‐N content of the 3.05‐m profile, determined by solution extraction, was 28% lower in 1972, 8% higher in 1973, and 13% lower in 1974 than that determined by soil coring. The profile difference in NO3‐N content between the two sampling techniques was insignificant in 1973 and 1974 but was highly significant (1%) in 1972.
A Perspective on Two Centuries of Progress in Soil Fertility and Plant Nutrition
Authors: Viets Frank G.
Published: July 2010

In the American colonial period soil fertility management depended on the empirical practices learned on similar soils in Western Europe, many of them known since Roman times. There were no experiment stations, colleges of agriculture, or known principles on which to build better practices. Advances in chemistry, physics and plant physiology starting very late in the 18th century catalyzed the beginnings of soil science in the late 1890's and early 1900's.

The most rapid advances in discovery of principles and putting them into practice have occurred since World War II aided by new electronic instrumentation, development of statistical theory and designs for field research, and new fertilizer and pest control materials. Among the developments put to practical use have been extension of the list of essential elements, soil and plant tissue testing for better guidance of fertilizer useage, and theories on ion transport from the solid phase to the root surface, which help to explain fertilizer placement effects, “fixation,” residual availability, and fertilizer efficiency.

Our present high‐yielding agriculture depended on the development of systems with the timely combination of the best cultivars; soil, water and plant management alternatives; and plant protection. Soil fertility specialists have had a leading role in the development of these systems.

Although progress in development of soil fertility theory appears to have slowed, great challenges exist for making further progress using modern developments from engineering and other sciences. Among the problems are an ever‐growing need for more food and natural fiber. This need involves further intensification for higher yields and the expansion of agriculture onto kinds of soils having unprecedented soil fertility problems. The conservation of fossil fuel energy; the management of nitrogen to improve efficiency of uptake, and to minimize denitrification and ground water pollution; and finally the development of cultivars that tolerate adverse soil conditions uncorrectable economically with traditional fertilizers and amendments are also necessary developments. To apply with selectivity all of the knowledge now available from diverse sciences will require broader training of individuals and more refined field measurements of significant variables affecting plant growth during the season.