bluuebunny/crossref_metadata_2025 huggingface dataset:
Transient‐ and Steady‐flow Experiments Testing Theory of Water Flow in Saturated Bentonite
Authors: Smiles D. E.
Published: July 2010

The theory of water flow in a saturated, swelling clay has recently been criticized. This criticism concerns possible effects on the material characteristics of particle re‐orientation during transient flow, as well as suggestions that the flux equation (Darcy's law) may be inappropriate to such systems.

This paper examines these problems by comparing data from transient‐ and steady‐flow experiments with bentonite.

The data from all experiments are mutually consistent within the experimental error. It is concluded that Darcy's law is valid for this material and that the conductivity/water content, and water content/suction relationships are well defined.
Retention of Cu2+, Ca2+, Mg2+, and Mn2+ by Amorphous Alumina
Authors: McBride Murray B.
Published: July 2010

The adsorption of Cu2+ at low pH on amorphous alumina gels was studied using electron spin resonance and specific ion electrode techniques. The results, when compared with the inability of alumina to retain Mn2+, Ca2+, and Mg2+, indicated that Cu2+ demonstrated a specific preference for alumina. Both Cu2+ and Mg2+ were found to coprecipitate readily with alumina; however, these ions opened the structure, increasing the noncrystallinity and adsorptive capacity of the alumina. The data indicated that the sites of adsorbed and coprecipitated Cu2+ in alumina were similar, suggesting that adsorption of metals capable of occupying octahedral sites in the structure involves the same mechanism as substitution of the metals into the structure during coprecipitation. In both cases, the Cu2+ ions appeared to be nonexchangeable and immobile as they entered structural positions.
Transport of Microorganisms in Sand Columns
Authors: Wollum A. G. , Cassel D. K.
Published: July 2010

Transport of streptomycete conidia through saturated columns of uniformly packed sand was studied using miscible displacement techniques. Autoclaved sand was uniformly packed to give sand columns 20.3 and 152 cm high. Mean pore water velocities ranged from 14.4 to 131 cm/hour. A pulse of sterile water containing from 104 to 106 conidia and tagged with 36Cl was displaced through each column with sterile water. Column effluent was collected and analyzed for conidia by serial dllution techniques utilizing starch‐casein agar. At the termination of each run, the column was sampled and analyzed for conidia distribution. For 20.3‐cm long columns, increasing the mean pore water velocity increased the maximum conidia concentration of the effluent and decreased the volume of effluent at which maximum conidia concentration was observed. Decreasing the mean pore water velocities also resulted in a broadening of the breakthrough peak and a greater volume of effluent was collected before the maximum conidia concentration was attained. Longer columns behaved as the shorter columns with the slower pore water velocities. Considerably more effluent was collected before maximum conidia concentration occurred and substantially fewer conidia were recovered from the effluent. A majority of the organisms recovered were present in the sand and a preponderance of organisms were retained near the soil surface.
Liming of Latosols and the Effect on Phosphorus Response
Authors: Mendez Jose , Kamprath E. J.
Published: July 2010

Studies were conducted with six Latosols from Panama to evaluate exchangeable Al as the criterion for determining lime rate and the effect of liming on P availability. Liming rates equivalent to exchangeable Al × 1.5 neutralized most of the exchangeable Al and adjusted pH to levels satisfactory for plant growth. Such liming rates were considerably less than those required to adjust the pH to 7.

At low rates of applied P, liming to neutralize Al significantly increased growth of millet (Pennisetum typhoides, var. Gahi 1), but had no beneficial effect if high rates of P were applied at < 60% Al saturation. However, liming significantly increased growth at all P rates if the Al saturation is > 60%.
An Evaluation of Mechanical Impedance for Three Tillage Treatments on Norfolk Sandy Loam
Authors: Cassel D. K. , Bowen H. D. , Nelson L. A.
Published: July 2010

The variability of in situ mechanical impedance in field soils hinders evaluation of impedance differences stemming from various tillage and soil management practices. Use of the penetrometer cone index (CI) is one method to measure mechanical impedance and many CI data have been treated statistically. This study was conducted to evaluate the mechanical impedance as measured by CI for Norfolk sandy loam for the following tillage treatments: (i) moldboard plowing to 22 to 25 cm followed by disking, (ii) chisel plowing to 27 cm, and (iii) subsoiling at 91‐cm intervals to a depth of 45 cm followed by bedding. Mechanical impedance was continuously recorded to a depth of 41 cm with a tractor mounted, hydraulically driven, constant rate descent penetrometer at seven positions spaced 15 cm apart on a transect normal to the soybean row. Measurements were taken four times during the year, representing a wide range in soil water content; replicated gravimetric water content measurements were taken as a function of depth at two of the seven positions at the time penetrometer readings were taken.

Analysis of variance showed significant differences in CI for tillage treatment, soil depth, position, and all two‐way interactions. Chisel plowing reduced impedance at all seven positions to values less than those measured for the moldboard plowing. Of the three treatments, the subsoiled plots generally had the lowest impedance only in or near the subsoil slit, but had the highest impedance in the trafficked interrow.

We recommend that future characterizations of mechanical impedance (and other soil physical properties which are induced or modified by tillage practices which introduce nonhomogeneity of these properties, i.e., mechanical impedance, water movement, etc.) include sufficient measurements to isolate not only tillage effects, but also position and depth effects.
A Mechanism of Phosphate Adsorption on Soil and Anion Exchange Resin Surfaces
Authors: Taylor Robert W. , Ellis Boyd G.
Published: July 2010

Langmuir plots of P adsorption isotherms of four soils were shown to fit two intersecting lines. The adsorption data were also found to fit the BET equation. The monolayer capacities computed from the BET equation corresponded closely with the adsorption maxima computed from the initial slopes of the Langmuir plots.

Studies of P adsorption on the energetically homogeneous sites of the anion exchange resins Dowex 1 − X8 and Dowex 2 − X4 (Cl − forms) at 25°C, gave results similar to those obtained with soils. Measurements of Cl‐ released during adsorption indicated that initially 2 mmole of Cl‐ were released per mmole of P adsorbed, and this value decreased at higher equilibrium P concentrations approaching 1 mmole of Cl‐. Measurements of pH of the equilibrium P solutions suggested that there was deprotonation of the H2PO4‐ ion during the initial stages of adsorption. Similar results were obtained when the Dowex 1 − X8 was saturated with the IO3‐ ion and P adsorption on the resin studied.

The differential isosteric heat of adsorption, ­ΔH, of P adsorption on Dowex 1 − X8 was computed between 11°C and 25°C. ­ΔH decreased sharply over the first region of the isotherm and became almost constant over the second.

It was concluded that at low concentrations P was bonded by two points of attachment after deprotonation of the H2PO4‐ ion, followed by one point of attachment at higher P concentrations during adsorption on the resin surface. This resulted in the deviation from linearity predicted by the Langmuir equation. This hypothesis for the mechanism of adsorption is presented to explain the deviation observed on soil and pure soil mineral surfaces.
An Exotic Source of Extractable Potassium in Some Soils of Northern Utah
Authors: Southard Alvin R. , Kolesar Peter T.
Published: July 2010

High values of extractable potassium are characteristic of some soils formed on the tuffaceous member of the Salt Lake Formation in northern Utah. The apparent source of the K is a zeolite, clinoptilolite. The Blackrock soil, mapped on part of the Salt Lake Formation, is noncalcareous in the upper part as opposed to the strongly calcareous Wheelon soil mapped on other parts of the formation. No attempt was made to delineate the exact extent of the zeolite‐bearing strata.
An Inexpensive Precipitation Gauge
Authors: Buchanan B. A. , DeVelice R. L. , Urquhart N. S.
Published: July 2010

An inexpensive, yet accurate, precipitation gauge was developed from readily available materials. The gauge accurately estimated precipitation as measured by a standard Weather Bureau gauge for 35 precipitation events in a one‐year period. This inexpensive gauge has been used successfully int he field for two years.
Steady Infiltration from Single and Periodic Strip Sources
Authors: Batu Vedat
Published: July 2010

The matric flux potential and horizontal and vertical flux distributions were obtained using Fourier analysis techniques for single and periodic strip sources located on the soil surface. The theory is based on the assumption that the hydraulic conductivity is an exponential function of the soil water potential. The matric flux potential distributions were compared with the results obtained by Warrick and Lomen (1976) who used different mathematical techniques.
Water Harvesting for Afforestation: II. Survival and Growth of Trees
Authors: Kowsar A. , Mehdizadeh P. , Vaziri E. , Boersma L.
Published: July 2010

Alternative methods of afforestation which do not require irrigation must be developed for arid regions. One such method is to concentrate water received by a watershed without vegetation on a smaller area where trees are planted. This can be done by making portions of the surface of a watershed area impervious to water through application of asphalt. This principle was tested near Tehran, Iran, by constructing 2‐m wide terraces on contour lines at 5‐m intervals resulting in a watershed to spreading area ratio of 1.5. Asphalt was sprayed at the rate of 1 liter/m2 in December 1969. Seedlings of Robinia pseudacacia L., Cupressus arizonica G., and Fraxinus rotundifolia Mill., tree species commonly used in irrigated afforestation projects in Iran, were planted in March 1970 on the terraces. Runoff from asphalt‐treated areas did not significantly increase the survival of the tree seedlings. The 23.4 mm of rain in July 1970, completely overwhelmed treatment effects. This rain was a rare event for the Tehran area. The increases in growth of height, crown cover, and stem cross section due to the asphalt treatment at the end of a 5‐year period were 61.5, 60.9, and 53.0%, respectively, for Robinia pseudacacia L.; 14.6, 15.4, and 31.6%, respectively, for Cupressus arizonica G.; and 29.4, 79.6, and 23.9%, respectively, for Fraxinus rotundifolia Mill.

Regression equations were developed correlating growth with amount of water and age of trees. Amount of water received in April and May in any given year was found to determine growth of height and crown during the following year. Amount of water received in April through October was found to determine the growth of stem cross section during the following year.
Comparison of a Laboratory and Commercial Block Digester for Plant Analysis
Authors: Prasad M. , Spiers T. M.
Published: July 2010

The design of a block digester fabricated in the laboratory is presented. The digester was capable of attaining 380°C in about 1 hour. Variation of temperature in different parts of the block was about 2°C greater compared to the Technicon block digester (BD‐40) at 328°C. Nitrogen, P, and K, and Ca, Mg, Fe, Zn, Mn, and Cu values from either block were in good agreement for all crops studied using H2SO4 + Se digestion, and HNO3 + HCIO4 digestion. Precision was good from both blocks using either digestion method although the Technicon block generally gave a slightly higher precision for HNO3 + HCIO4 digestion. In addition, when one sample was placed in six or eight different positions on the block for the H2SO4 digestion in order to maximize differences between replicates, a slightly higher C. V. was recorded with our digester. The construction cost of the latter which has a somewhat smaller capacity and no automation was only about 20% of the purchase price of the Technicon digester.
Recovery of 15N‐Labeled Fertilizer from Manured and Sludge‐Amended Soil
Authors: Pomares‐Garcia F. , Pratt P. F.
Published: July 2010

A greenhouse pot experiment was conducted with various rates of manure (0, 20, 40, and 60 metric tons/ha) and sludge (0, 10, 20, and 30 metric tons/ha) combined factorially with 0, 50, 100, 150, and 200 mg N/kg soil as (NH4)2SO4 labeled with 15N, using barley and sudangrass as test crops. Most of the N from (NH4)2SO4 was recovered by the first cutting of barley forage (from 37.2 to 70.2%); the N from (NH4)2SO4 recovered by sudangrass, the last crop of the cropping sequence, ranged from 0.7 to 8.9%. No significant effect of both wastes and (NH4)2SO4 rates on the overall inorganic N fertilizer recovered by the crops was found. The difference method underestimated the (NH4)2SO4‐N recoveries by the crops under sludge treatments. The depression in the mineralization rate of sludge by the (NH4)2SO4 applied was proposed to account for these discrepancies.

A fertilizer N balance, in which the sum of (NH4)2SO4‐N removed by the crops plus the N accumulated in the soil was subtracted from the (NH4)2SO4‐N input, was used to estimate the fertilizer N losses. These losses were 7.8, 9.1, and 13.1%, respectively, for control (unamended), manure and sludge treatments.

With increasing rates of (NH4)2SO4, the nitrogen “A” values defined as the N available in the soil in terms of N from (NH4)2SO4, increased in the control, remained almost constant with manure, and decreased with sludge treatments.
Salt and Water Stress Influences Nitrogen Metabolism in Red Kidney Beans
Authors: Frota J. N. E. , Tucker T. C.
Published: July 2010

Both salinity and water deficit reduce yields of crop plants. This study was an attempt to provide a better understanding of these stress effects on N metabolism and the utilization of NH4‐N and NO3‐N.

Red kidney bean plants (Phaseolus vulgaris L.) were grown under salt stress (NaCl), water stress (carbowax), and in a normal nutrient solution (control). The 15N in NO3‐, NH4+, α‐amino acids, total soluble‐N, and protein‐N in plant shoots were analyzed after the plants received (15NH4)2SO4 and K15NO3 in nutrient solution for 6, 12, 24, and 48 hours. Sodium chloride and carbowax resulted in equal accumulations of NO3‐, NH4+, and free α‐amino acids in bean shoots. Protein synthesis was significantly reduced in bean shoots when the plants were subjected to NaCl salinity and carbowax, with either source of N, and the inhibition was more severe under salt stress than water stress.
Cation‐exchange Capacity of Clay‐rich Soils in Relation to Organic Matter, Mineral Composition, and Surface Area
Authors: Martel Y. A. , De Kimpe C. R. , Laverdière M. R.
Published: July 2010

Regression analyses were used to correlate organic matter, texture and surface area values to the cation‐exchange capacity (CEC) of clay‐rich soils in the lowlands of Quebec. The Ap, Bg and Cg horizons of 11 Gleysolic soils (Aqu‐Suborders) were analyzed for CEC, exchangeable bases and acidity, total and fine clay contents, organic matter, surface area and mineralogical composition. The soils contained illite, chlorite, smectite, and vermiculite in addition to quartz and feldspars. In the Ap horizon, total clay (r = 0.815**) and fine clay (r = 0.841**) contents were better related to CEC than organic matter (r = 0.566**) and surface area (r = 0.570**). In the Bg and Cg horizons, surface area (r = 0.918** and 0.814**) gave the best correlation with CEC. As calculated by multiple regression equations, CEC values of organic matter increased with depth from 56.5 to 223 meq/100 g, while CEC values of total clay decreased from 37.7 to 22.5 meq/100 g and that of fine clay decreased from 57.5 to 50.7 meq/100 g. Variations in the mineralogical composition, although small, were sufficient to explain nearly 50% of the variations in the CEC. Clay mineralogy is important to predict the CEC of such soils where the contribution of clay is 3.5 to 5 times greater than that of organic matter.
Hard Red Spring Wheat Straw Yields in Relation to Grain Yields
Authors: Bauer Armand , Zubriski Joseph C.
Published: July 2010

Residue management planning programmers utilize a constant straw/grain ratio to predict wheat (Triticum aestivum L.) straw yields. The efficacy of this approach was evaluated for conventional height and semidwarf hard red spring wheat cultivars. Functional relationships between grain yields and straw/grain ratios were determined from data obtained in the northern Great Plains. Straw/grain ratios ranged from 0.72 to 4.71. Single correlation coefficients, r, were −0.643** and −0.589** for semidwarf and conventional (n = 117 and 72) over a grain yield range of 240 to 5,850 kg/ha. “Best fit” regression (n = 189) was Y = 3.152 − 0.000753X + 0.0000000655X2 (Y = straw/grain ratio). About 78% of 49 observations fell within the 0.05 confidence limits at >3,000 kg/ha grain yield, but <30% at lower yields. Straw yields predicted by regression were within ±1,000 kg/ha in 74, 51, and 84% of the observations at grain yields of <1,600, 1,600 to 3,000, and >3,000 kg/ha, respectively. A single, constant straw/grain ratio will predict straw yields with less accuracy than ratios obtained from regression.
The Nitrogen‐15 Abundance in a Wide Variety of Soils
Authors: Shearer Georgia , Kohl Daniel H. , Chien Sen‐Hsiung
Published: July 2010

One hundred thirty‐nine soil samples from 20 states were analyzed for 15N abundance. Soil characteristics and environmental conditions at the sampling sites varied widely. The total N of surface soil samples had a mean δ15N value (per mill 15N excess) slightly but significantly higher than the mean value for soils collected from deeper layers, although the relationship between δ15N and soil depth was not consistent from location to location. Differences among mean δ15N values for the total N of soil samples collected from cropland, pasture, uncultivated land (with native herbs), and forest were not striking. There was no systematic effect of variation in the rate of application of N fertilizer on the δ15N of the total N of soils. The mean δ15N value of surface soils, with respect to atmospheric N, was +9.22 and the standard deviation was 2.10 δ15N units. The range within which 90% of the samples fell was +5.1 to +12.3 δ15N units. Less than half of the variation among the soils in δ15N of the total N could be accounted for by differences in environmental variables or soil characteristics.
Elemental Distribution in the Light Mineral Isolate of Soil Separates
Authors: Drees L. R. , Wilding L. P.
Published: July 2010

The light mineral isolate (specific gravity < 2.89) was quantitatively separated from the 50–250µm, 20–50µm, and 5–20µm fractions of selected A and B soil horizons derived from loess and outwash deposits. Elemental Ti, Zr, Fe, K, and Ca were determined by X‐ray spectroscopy both on total and light mineral isolates. More than 75% of Ti, Zr, Fe, and Ca occurs in the light mineral isolates of the 5–20µm fraction while the 50–250µm light mineral isolate contains 25 to 70% of these elements. With the exception of K, there is a progressive concentration of above elements as particle‐size decreases. Essentially 100% of the K occurs in the light mineral isolate independent of particle‐size. The concentration of Ti and Zr is greater than can be accounted for by mineral grain counts in the light isolate. Little or no co‐association of Fe with Ti, Zr, Ca, or K could be established in secondary Fe‐oxide grain coatings. It is concluded that much of the Ti, Zr, and Fe concentrated in the light mineral isolates occurs as micro‐inclusions of accessory minerals within primary host minerals such as quartz and feldspars. Caution must be exercised in allocating elemental percentages of a given size fraction to specific detrital minerals.
Reactions of Ammonium Ortho‐ and Polyphosphate Fertilizers in Soil: III. Effects of Associated Cations
Authors: Sample E. C. , Khasawneh F. E. , Hashimoto I.
Published: July 2010

Diammonium phosphate (DAP), triammonium pyrophosphate monohydrate (TPP), and ammonium polyphosphate (APP) were surface applied on columns of Hartsells fine sandy loam, a Typic Hapludult, and the influence of these three salts on movement, distribution, and precipitation of soil and fertilizer cations was investigated.

In general, the NH4+ ions derived from the fertilizer salts moved in association with the phosphate anions in the form of salt diffusion, and also moved by counter diffusion in exchange for some of the exchangeable soil cations. This latter mode of transport resulted in movement of NH4+ a few millimeters beyond the limits reached by phosphates.

Exchangeabe Ca in the first 6 mm of soil contacted by the fertilizer solution from DAP was replaced by NH4+, and the displaced Ca2+ was precipitated in place by phosphates. Displaced Ca was transported in the fertilizer solution of TPP and APP for 6 to 8 mm before it was precipitated. Reactions of phosphates with displaced Ca2+ caused its activity in these soil zones to drop sharply and created a Ca gradient opposite to that of the phosphates. Consequently, Ca moved from soil on the farther side of the phosphate front into a Ca phosphate sink. This movement of Ca was partly in exchange for NH4+ (counter cation diffusion) and partly following hydrolysis from exchange sites.

Depletion of exchangeable cations, especially at or just beyond the fertilizer solution front, caused soil pH to drop as much as 1 pH unit below the initial soil value. Within the soil zone affected by phosphates, pH was about 7.5 with DAP and 6.7 to 7.2 with APP and TPP. Differences in pH between soil in the outer zones reached by phosphates and the inner layers ranged from 1.7 to 2.7 pH units.

Soil Al was influenced greatly by all three fertilizer solution. With DAP, the reaction products simply reprecipitated in place without undergoing any movement. Increased acid extractability was the only evidence of the presence of fresh precipitates involving Al. In addition to such a reaction, however, movement of Al occurred with TPP and APP, and there was evidence of rather‐well‐defined zones of precipitation involving Al pyro‐ or polyphosphates. There was no evidence to implicate Fe in reactions similar to those described for Al.
Studies in Soil Manganese: I. Factors Affecting Manganese Extractability
Authors: Salcedo I. H. , Warncke D. D.
Published: July 2010

Effects of 12 solution/soil ratio‐shaking time combinations upon Mn extracted by 0.1N HCl, 0.1N H3PO4, 0.005M DTPA, and 1N NH4OAc from 12 Michigan and Indiana soils were studied. A solution/soil ratio of 25 with 120 min of shaking maximized extractable Mn by the four extractants. However, with 0.005M DTPA and 1N NH4OAc shaking time and solution/soil ratio had little effect on extractable Mn. When results were correlated with Mn uptake by soybeans [Glycine max (L.) merr.], the best correlation was obtained with a solution/soil ratio of 5 and 120 min of shaking for 0.1N HCl and 0.1N H3PO4. Correlation of plant Mn uptake with DTPA‐ and NH4OAc‐extractable Mn was relatively independent of solution/soil ratio‐shaking time combinations used.
Effect of Chisel Versus Moldboard Plowing on Soil Erosion by Water
Authors: Johnson C. B. , Moldenhauer W. C.
Published: July 2010

We conducted an experiment using simulated rainfall on a field that was chisel plowed annually for 13 years before the experiment to compare erosion from this condition with moldboard plowing in the same field. One treatment was fall moldboard plowed, a second fall chiselled with some residue left on the surface, and a third was untilled in the fall with all residue removed in the spring. All three treatments were disked lightly in the spring. After the initial experiment was completed, residue was added so that all treatments had about 20% surface cover.

During the initial rain application with no residue added, soil losses from the third treatment without surface residue were the same as those from the chisel plowed and disked surface with some surface residue. Both these treatments had only 23% of the soil loss of the moldboard plowed and disked treatment. During succeeding simulated rainfall under wet and very wet soil conditions, soil loss from the disked only treatment was up to 80% of that for the moldboard‐plowed treatment. When residue was added to all treatments, soil loss from the chisel‐plowed treatment was less than one‐half that from the moldboard‐plowed treatment.
Effects of Reduction and pH Changes on Phosphate Sorption and Mobility in an Acid Soil
Authors: Holford I. C. R. , Patrick W. H.
Published: July 2010

Suspensions of a silt loam in 0.01M CaCl2 (1:6) were incubated at redox potentials of 500, 280, 65, and −150 mV for 26 ± 2 days in factorial combination with pH treatments of 5.0, 6.5, and 8.0. Samples were then removed and equilibrated with graded concentrations of KH2PO4 under O2‐free conditions. Isotopically‐exchangeable P was measured on the zero treatment and P sorption on the other treatments after 24 hours equilibration. Sorption properties of the soil were determined by application of the Langmuir equation.

The largest changes occurred in the most reduced treatment (−150 mV) and at pH 8.0. At pH 5.0, an unnaturally low pH for an anaerobic soil, reduction to −150 mV decreased P sorption at solution P concentrations below 20 ppm because of the reduction and dissolution of ferric hydrous oxides. At higher concentrations sorption was increased by ferrous phosphate precipitation due to the very high concentrations of soluble Fe. At pH 6.5, reduction caused a very large increase in P sorption apparently because of increased adsorption on freshly precipitated amorphous ferrous hydroxides. At pH 8.0, P sorption was deceased at P concentrations below 2 ppm, probably because of increased surface negative charge, but increased at higher P concentrations due to precipitation of Ca phosphates. At all pH values, reduction increased the concentration of native P in solution. At pH 6.5 this was caused by an increase in labile P due to the release of P occluded and precipitated in ferric compounds. At pH 5.0 and 8.0 it was caused by a decrease in P bonding energy. Reduction to −150 mV caused the largest increase in soluble P and the smallest increase in P sorption capacity at pH 5.
Effect of Limestone Variables on Amendment of Acid Soils and Production of Corn and Coastal Bermudagrass
Authors: Haby V. A. , Anderson W. B. , Welch C. D.
Published: July 2010

Three particle size ranges of calcitic and dolomitic limestones were applied at 4.5, 9, and 13.5 metric tons/ha. Evaluations were designed to determine the most efficient treatment for neutralizing soil acidity, and increasing crop production in Katy fine sandy loam (pH 5.2) and Boy loamy fine sand (pH 5.4). Liming effects were evaluated by soil and plant analyses. Efficiency rating (ER) was used to describe the limestone particle size ranges. Finer limestone particles were assigned higher relative efficiency values. The sum of the products of particle size percentage ranges multiplied by the relative efficiency assigned those ranges, times the neutralizing value of that limestone is the ER.

Increases in soil pH were proportional to limestone ER and application rate. Calcitic limestone neutralized soil acidity more rapidly than did dolomitic. We found a statistically significant increase in calcium (Ca) in the 30‐ to 46‐cm depth of Boy loamy fine sand at the 13.5 metric ton/ha rate of ER 110 calcitic limestone. This was probably due to 689 kg of N/ha applied as NH4NO3 the first year following limestone treatment. Magnesium (Mg) increased in the 30‐ to 46‐cm depth due to all dolomitic treatments.

Limestone did not increase the yield of corn (Zea mays L.) or Coastal bermudagrass (Cynodon Dactylon L. Pers.) in the harvest year.

All treatments of calcitic limestone significantly increased the Ca percentage in corn. All dolomitic limestone treatments except the ER 26 material applied at 4.5 metric tons/ha increased Mg concentration in corn leaves and Coastal bermuda‐grass. Manganese toxicity occurred in corn plants growing in nonlimed plots the third season following treatment. Soil acidity and reducing conditions contributed to the toxicity.
Nitrate‐Nitrogen Leaching Following Urea Fertilization and Irrigation
Authors: Bauder J. W. , Schneider R. P.
Published: July 2010

Wheat (Triticum aestivum) was grown in undisturbed columns of Gardena silt loam, a coarse‐silty, mixed Pachic Udic Haploboroll, to evaluate NO3‐‐N leaching from urea under irrigation. Optimum and excessive irrigation rates and 135 kg N/ha (as urea in single application vs. three increments applied during the growing period) were compared in factorial combination. Chloride was added to all columns for comparison with NO3‐‐N. Leachate samples were collected throughout the study and analyzed for NO3‐‐N, NH4+‐N and Cl‐. Columns were dismantled at crop maturity and sampled for residual NO3‐‐N. Total N was determined in wheat at maturity.

Leaching fractions (LF) differed significantly between optimum and excessive irrigation but were not affected by applied urea. Cl‐ moved with the wetting front. Leaching patterns for NO3‐‐N and Cl‐ were similar, but a slight lag in NO3‐‐N was observed. Concentration of NO3‐‐N in drainage water from all columns was initially similar (30 ppm NO3‐‐N), but then decreased as leaching volume changed. Maximum NO3‐‐N leaching occurred with split urea and excess irrigation. Minimum leaching occurred with optimum irrigation and split urea. Total NO3‐‐N leachate load was directly correlated with leachate volume. Soil solution concentrations at crop maturity were as much as 170 µg NO3‐‐N/ml. Residual NO3‐‐N varied among treatments and revealed as many as three peaks in NO3‐‐N concentration in the profile, indicating that N leaching occurred following each urea application. The results indicate marked NO3‐‐N movement from urea under excessive irrigation.
Effect of Nitrogen Source and Management on Ammonia Volatilization Losses from Flooded Rice‐Soil Systems
Authors: Vlek P. L. G. , Craswell E. T.
Published: July 2010

Ammonia volatilization was studied by equipping capped greenhouse pots with a forced‐draft system with external acid trap or by placement of open pots in a closed gas‐lysimeter (allowing plant growth) with internal acid traps. In both systems air turbulence was optimized to simulate undisturbed open systems. Flooded soils were fertilized with approximately 50 or 100 kg N/ha of granular urea (GU), ammonium sulfate (AS), and two modified urea products—sulfur‐coated urea (SCU) and urea supergranule (USG). The first three materials were broadcast and incorporated, whereas the last was placed at a depth of 8 cm.

Ammonia volatilization from urea proceeded rapidly following hydrolysis of urea in the floodwater, leading to losses of up to 50% of the applied urea within 2 to 3 weeks. Ammonia loss from (NH4)2SO4 occurred to a lesser extent due to a lack of alkalinity and occurred at a nearly constant rate, accumulating to ∼15% loss in 3 weeks. Ammonia losses from the modified urea materials were negligible.

Soil pH had little effect on the pH of the floodwater and, thus, on the ammonia volatilization process. However, ammonia volatilization losses were generally reduced by factors that reduced the level of ammoniacal N in the floodwater, such as increasing soil CEC and reduced N application.

Daily ammonia volatilization losses correlated well (r = 0.92) with the NH3(aq) concentration of the floodwater sampled between 1000 and 1100 hours each day. This observation holds promise for the development of a simple technique for assessing ammonia volatization losses from flooded soils based on simple physical and chemical parameters of the floodwater.
Morphology of a Paralithic Contact in a Soil Over Soft Sandstone
Authors: Schafer W. M. , Nielsen G. A. , Nettleton W. D.
Published: July 2010

Root distribution was studied in a soil having a paralithic contact in southeastern Montana. An abrupt change in root abundance was the most useful criterion for locating the paralithic contact. The soft rock below the contact is part of the Tongue River member of the Ft. Union formation. The soft rock is indistinguishable from the overlying soil in texture, color, structure, and water‐holding capacity, but has a bulk density of 1.50 g/cm3 and is hard whereas the soil has a bulk density of only 1.35 g/cm3 and is soft when dry. The soil, which has a paralithic contact within 50 cm, supplied 86% as much water to plants during the 1976 growing season as a nearby, texturally similar, deep soil. The difference was less than expected. Removal of water from the soft rock apparently occurred through a few roots which follow widely spaced, vertical pockets of soil deep into the soft rock. Roots from the pockets proliferate horizontally along natural laminations and planes of weakness in the soft rock. Water is removed from as deep as 30 cm below the paralithic contact during the growing season.

Present interpretation of paralithic contacts is discussed as it relates to this research. Proposed revisions to the definition are considered and further research is suggested.
Physical Model of the Hydrology of Sloping Heterogeneous Fields
Authors: Hillel D. , Hornberger G. M.
Published: July 2010

A model simulating water flow and storage in a 2‐dimensional section of a sloping field, in which surface runoff, infiltration, evaporation, unsaturated soil moisture movement and ground‐water flow are represented as a series of interacting 1‐dimensional processes, was adapted to cases of horizontally heterogeneous fields. The model is illustrated in a series of simulation trials with variously constituted hypothetical fields of loam and clay soils, subjected to a 108‐mm rainstorm. Runoff was found to depend on the fraction of the slope occupied by clay, and on the relative location of the clay (whether upslope or downslope with respect to the loam). Ground‐water recharge was found to be greater in the loam, as was the rate of lateral drainage. The capability of the model is discussed.
Solute Dispersion in Unsaturated Heterogeneous Soil at Field Scale: I. Theory
Authors: Dagan Gedeon , Bresler Eshel
Published: July 2010

In a heterogenous field whose hydraulic properties vary from point to point the transport of solute also differs from profile to profile. In this paper solute concentration on the field scale was treated as a random variable. The field heterogeneity was described in terms of the statistical distribution of the hydraulic parameters, which implies a corresponding distribution of the concentration. Equations for computing this distribution, as well as its average and variance, in a heterogeneous field were derived explicitly for a simple, but representative case, of leaching under random recharge distribution on the surface. The water and solute flow in unsaturated soil was assumed to be vertical and steady. The randomness of the hydraulic properties was reduced to that of the saturated hydraulic conductivity by adopting a scaling hypothesis and a log normal distribution.
Conservation Bench Terraces for Rice in a Subhumid Climate
Authors: Bhushan L. S.
Published: July 2010

Rain‐fed crops in northern India produce less than the potential maximum due to moisture stress at crucial stages of plant development. Research was initiated on a conservation bench terrace (CBT) system to evaluate its potential to increase water supply for increasing and stabilizing rice production on 2.5% sloping land in the subhumid climate. The width ratios of the contributing area to the collection area (terrace benches) were 0:1, 1:1, 2:1, and 3:1. The contributing area was cropped with corn planted on the contour.

Six years of research have shown that levelled benches received 0.25, 0.50, and 0.76 m3/m2 of estimated runoff from the 1:1, 2:1, and 3:1 ratios, respectively. Consequently, measured soil water in the level benches was greater than the storage in level benches without a contributing area at the time of panicle emergence. The rice yields in the level benches with contributing areas were 21, 47, and 88%, respectively, greater on three ratios than yields on the level check without a contributing area. The 84% increase in rice grain yield on the 3:1 CBT was attributed to increased soil water content at panicle emergence.

A major advantage of the CBT system was that chances of crop failure were reduced. The probability of obtaining rice yields of < 1,400 kg/ha was decreased from 50% on level bench to 16% in level benches with a 3:1 ratio. Similarly, the probability of achieving yields > 3,500 kg/ha was 50% in the 3:1 CBT system and 0% in the level bench (NW). Total dry matter production for the 3:1 CBT system was 1.7 times greater than the level check.
Particle Shape and Size of Two Sodium Calcium Montmorillonite Clays
Authors: Dufey Joseph E. , Banin Amos
Published: July 2010

Viscosity measurements of Na‐Ca montmorillonite suspensions (Wyoming and Camp‐Berteau) were performed at five temperatures (11 to 35°C). At a given composition of the surface phase, discontinuous variations of intrinsic viscosity were observed with changing temperature. According to similar observations from the literature, variations would be due to structural modifications of water layers surrounding the clay particles.

By combining those results with optical density spectra, we have pointed out different characteristics for the Wyoming and Camp‐Berteau clays. The single plates of Camp‐Berteau montmorillonite are smaller than those of Wyoming. At high Ca‐loading, the formation of thicker particles by parallel condensation of single plates does not involve any marked increase of average major axis in the case of the Wyoming clay. On the other hand, the Camp‐Berteau plates are likely to overlap when they condense; that results in an increasing major axis with increasing Ca‐loading, leading to similar shapes for both pure Ca‐clays. Those results were confirmed by measurements of water content in clay sediments.
Aluminum Organic Matter in Acid Soils: Salt‐Extractable Aluminum
Authors: Bloom P. R. , McBride M. B. , Weaver R. M.
Published: July 2010

Sample horizons of an acid Inceptisol from New York, an Oxisol from Brazil, and an aluminum‐peat complex containing 1 mole of Al per mole of peat carboxyl groups were extracted with 1N KCl and 1N LaCl3. For all three materials, LaCl3 extracted significantly more Al. The quantity of Al extracted expressed as a fraction of the BaCl2‐TEA acidity was greater for the peat than the soils. It was concluded that the fraction of Al bound by organic matter is important in determining the quantity of Al extracted from surface soils by neutral salts and that “exchangeable aluminum” and “effective cation exchange capacity” are defined by the cation and concentration of the extracting salt.
Water Vapor Movement in Soil: Reconciliation of Theory and Experiment
Authors: Jury W. A. , Letey J.
Published: July 2010

A large number of separate experimental studies of water vapor movement in response to thermal gradients are shown to be independent of water content over a wide range of water contents. Two models, proposed by J. R. Philip and D. A. de Vries (1957) and J. W. Cary (1963), are rewritten in a compatible form and compared to the data. The phenomenological model of Cary describes the data if the phenomenological coefficient β has a value between 1.0 and 3.5, whereas the mechanistic theory of Philip and de Vries underpredicts the vapor transport observed in the experiments in all cases.

A modification of the theory of Philip and de Vries is proposed which increases the influence of liquid water on vapor transport. In the new formulation the experimental information is adequately described and both models are rendered compatible. Both experimental and theoretical results suggest that water vapor movement may be described by a simple expression which is a known function of temperature, and is independent of water content over a wide range of saturation. Even without calibration it is suggested that this expression can describe water vapor flux to within a factor of 2.
Diffusion of a Biodegradable Pesticide: I. In a Biologically Inactive Soil
Authors: Gerstl Z. , Yaron B. , Nye P. H.
Published: July 2010

The diffusion of parathion (O,O‐diethyl O‐p‐nitrophenyl phosphorothioate) in a biologically inert (“sterile”) loamy soil (Gilat − Israel) was investigated. It was found that the diffusion coefficient (D) of parathion in Gilat soil over a large range of moisture contents varies between 0.66 × 10−7 and 3.39 × 10−7 cm2/sec. The main factors affecting the diffusion of parathion in a “sterile” soil are the adsorption coefficient of the compound on the soil surfaces (K), the moisture content, and the impedance factor (f). The variables K and f were measured independently and the experimental values of D were compared with the theoretical values. Only a small fraction of adsorbed parathion was undergoing diffusion, the mobile fraction of the adsorbed molecules being about 10% of the total adsorbed parathion.
Diffusion of a Biodegradable Pesticide: II. As Affected by Microbial Decomposition
Authors: Gerstl Z. , Nye P. H. , Yaron B.
Published: July 2010

The diffusion of parathion (O,O‐diethyl O‐p‐nitrophenyl phosphorothioate) was investigated and a model which involves treating microbial activity in the diffusion system was developed. The kinetics of parathion degradation during 7 days of incubation at three moisture content (θ = 0.14, 0.24, and 0.34) was determined and compared with the calculated values. It was found that the rate of parathion decomposition rises with increasing water content. The amount of parathion decomposed at any time increased with the increase in the initial concentration. The calculated course of decomposition of parathion fits the experimental results obtained over 7 days, which was the longest period in the diffusion. The experimental results and predicted distribution of parathion and of the metabolite formed (diethylthiophosphate) are presented as affected by time and soil moisture content. The proposed model—which considers the rate of decomposition at any distance and time, and depends on the local concentration of parathion and on the microbial activity—satisfactorily fits the experimental results.
Biomass Response of Loblolly Pine to Selected Cultural Treatments
Authors: Haines Sharon G. , Davey C. B.
Published: July 2010

The effects of site preparation and other cultural treatments on the biomass of 1‐ and 2‐year‐old loblolly pine (Pinus taeda L.) seedlings were examined. Treatments included various combinations of disking, applying herbicides, fertilizing, subsoiling, fumigating the soil, irrigating, and mowing. Oven‐dry weights of stems, needles, roots, and branches were determined. Root collar diameter was significantly affected by treatment after both 1 and 2 growing seasons and was as effective an indicator of treatment response as other variables singly or in combination.
Measured and Approximate Flux‐Concentration Relations for Absorption of Water by Soil
Authors: White I.
Published: July 2010

The flux‐concentration relation of Philip (1973) is calculated using moisture profiles measured during absorption of water by a fine sand when water was supplied at both constant hydraulic potential and constant rate. The general behavior of the measured flux‐concentration relations was found to be consistent with those of the model soils calculated by Philip. Within the accuracy of the measurements, no significant time‐dependence of the relation was found for the constant flux boundary condition over a large time span. Measurements of the time‐averaged flux‐concentration relation, however, suggest some significant time‐dependence for short times. Simple approximations for the flux‐concentration relation, based on these observations, are suggested. These approximations enable easily evaluated predictions to be made of the salient features of constant rate application of water to soil, which are sufficiently accurate for most practical purposes.
Use of Selective Agents for Recovery of Rhizobium meliloti from Soil
Authors: Barber Lynn E.
Published: July 2010

This study was planned to develop a useful selective medium for differentiating Rhizobium meliloti in soils or inocula. The objective was to define a medium which will permit growth of rhizobia and restrain growth of other microorganisms which might inhibit or mask growth of the desired strains of Rhizobium. A yeast mannitol agar medium reinforced with 500 µg/ml pentachloronitrobenzene, 1.5 µg/ml brilliant green, 1.0 µg/ml sodium azide, and 25 µg/ml Congo red proved to be very effective in differentiating R. meliloti from other species of rhizobia as well as other forms of soil microorganisms native to Oregon. Antibiotic resistance as a marker can also be used in association with the selective medium to study the ecology of rhizobia in soil or other environments. However, antibiotic resistance is apparently not a stable character and deserves frequent testing, particularly in long‐term studies.
Variability of Minesoils and Natural Soils in Southeastern Montana
Authors: Schafer William M.
Published: July 2010

A study of minesoil variability near Colstrip, Montana, showed that different kinds of soils exist within mine areas, and that individual soil bodies are large enough to map at a scale of >1:10,000. Minesoils were more variable than natural soils at the local scale (0–10 m lateral spacing), while natural soils were more variable at the landscape scale (>500 m lateral spacing). Fourteen soil families were recognized in a 300‐ha natural landscape while only two soil families were found on mined land. Variation in natural soil properties was correlated with geomorphic variables while minesoil variability was related to mining and reclamation methods. Problems were encountered while attempting to classify soils according to Soil Taxonomy.
Influence of a Compact Zone on Solute Transport During Infiltration of Water
Authors: Hira G. S. , Singh N. T.
Published: July 2010

In most soils, continuous plowing results in the formation of a compact zone below the plowing depth. Laboratory studies were conducted to examine the effect of such a zone on the displacement of chloride (Cl‐) during infiltration of water. A compact zone of 4‐ or 8‐cm thickness of 1.62 g/cm3 or 1.80 g/cm3 bulk density was created at a depth of 8 cm in soil columns. A surface‐applied slug of calcium chloride was leached with 4 or 6 cm of distilled water. The presence of a compact zone in the soil profile pushed the Cl‐ peak deeper, dispersed the ions in a narrower region, and increased the peak Cl‐ concentration. Increasing bulk density and thickness of a compact zone increased the depth of the peak Cl‐ concentration.
The Gapon Coefficient and the Exchangeable Sodium Percentage‐Sodium Adsorption Ratio Relation
Authors: Oster J. D. , Sposito Garrison
Published: July 2010

A recent, corrected thermodynamic equation for the Gapon cation exchange selectivity coefficient produces a relation between the exchangeable sodium ratio (ESR) and the sodium adsorption ratio (SAR) that is indistinguishable from the widely used, empirical ESR‐SAR relation when SAR ≤ 40. In this sense, the thermodynamic theory of cation exchange is consistent with the empirical ESR‐SAR relation over the range of SAR values that has practical importance in the management of sodium‐affected soils.