bluuebunny/crossref_metadata_2025 huggingface dataset:
Anion Adsorption by Allophanic Tropical Soils: III. Phosphate Adsorption
Authors: Gebhardt H. , Coleman N. T.
Published: July 2010

Andepts from Mexico and Hawaii bound 30–70 mmole P/100 g air‐dry soil at pH 4.3–4.7 during a 1‐hour reaction with 0.05M mixed H3PO4‐NaH2PO4 solution. As much as 130 mmole P/100 g were taken up from H3PO4 at pH 2.4. A B‐horizon sample, San Gregorio from Michoacan, Mexico, adsorbed P from H3PO4 and consumed H in nearly equimolar amount, with 38 mmole/100 g of each removed from solution in bringing soil from an initial pH of 5.4 to 4.3. Larger additions of H3PO4 dissolved appreciable Al, gave pH < 4, and yielded solutions that were supersaturated with respect to variscite. An apparent adsorption maximum of 38 mmole/100 g compares with maxima of 27 and 30 mmole/100 g for Cl and sulfate, respectively. High‐affinity adsorption of P from H3PO4 appeared limited by the supply of H‐ions to protonate sites or react with displaced OH. San Gregorio B horizon took up phosphate from NaH2PO4, but with low affinity. Phosphate uptake from NaH2PO4 was accompanied by coadsorption of Na. At a given pH and level of tightly bound P established with H3PO4, addition of NaH2PO4 resulted in low‐affinity adsorption of P and coadsorption of Na. Around half of the P bound from NaH2PO4 was readily eluted with water. Phosphate bound from H3PO4 was virtually insoluble in water. Some P was eluted by 0.5M arsenate or selenite. The Andepts bound P through at least three mechanisms: high‐affinity adsorption on protonated sites; low‐affinity adsorption with co‐adsorption of Na; and formation of insoluble variscite‐like substances.
A Kinetic Study of Ammonium and Nitrite Oxidation in a Soil Field Plot
Authors: Ardakani M. S. , Schulz R. K. , McLaren A. D.
Published: July 2010

Disappearance of NH4+ from percolating solution in a 40 m2 plot is at first attributable to both oxidation and to adsorption by the soil. Once a steady state was established and exchangeable NH4+ was equilibrated with NH4+ in soil solution, oxidation alone accounted for disappearance of NH4+ — N in the top 2.5 cm of the soil. Concentration profiles of NO2‐ and NO3‐ are described by a modified Michaelis‐Menten equation. Rate constants for oxidation of NO2‐ → NO3‐ and NH4+ → NO2‐ are 0.6 × 10‐3 and 2.5 × 10‐3 ppm/hour·cm3 per bacterium, respectively. These rates are in good agreement with the values found under controlled laboratory conditions.

Growth and distribution in soil of Nitrobacter and Nitrosomonas sp. were followed by weekly estimates of their numbers at different depths. The former reached a maximum population of about 106/cm3 of soil but declined to a stable density of about 105 organisms/cm3; the latter approached a steady level of about 104 organisms/cm3. Both organisms showed higher densities near the soil surface where the concentrations of substrates were always highest.
Nitrogen Transformations in Soil During Leaching; I. Theoretical Considerations
Authors: Misra C. , Nielsen D. R. , Biggar J. W.
Published: July 2010

Transport equations describing the movement and simultaneous oxidation of NH4+ to NO3‐ and reduction of NO3‐ to N2 by microbial and/or chemical means were set up and solved both for leaching of a pulse and for a continuous application of NH4+ and/or NO3‐ salt at the soil surface. Both ionic adsorption owing to cation exchange and microbiological transformations have been considered and distinguished as reversible and irreversible processes, respectively. The possibilities of the model extended to a sequential transformation during transport of more than two nitrogen species have been examined.
Nitrogen Transformations in Soil During Leaching: II. Steady State Nitrification and Nitrate Reduction
Authors: Misra C. , Nielsen D. R. , Biggar J. W.
Published: July 2010

Nitrogen transformations were examined by means of a miscible displacement technique that permitted passage of air with different levels of oxygen through the soil. With the use of steady state solutions of equations describing the convective transport of NH4+ and NO3‐ ions in Columbia silt loam, first‐order reaction rate constants k1 and k2 were ascertained for NH4+‐oxidation and NO3‐‐reduction, respectively. Values of k1 were measured to be ten‐fold greater than those of k2. At an oxygen level of 0.5% in the gaseous phase, nitrification was apparently inhibited.
Isolation of Microorganisms from a Texas Soil Capable of Degrading Urea Derivative Herbicides
Authors: Lopez C. E. , Kirkwood James I.
Published: July 2010

Samples of Hockley fine sandy loam were perfused with 500 µg/ml concentrations of monuron 3‐(p‐chlorophenyl)‐1, 1‐dimethylurea or diuron 3‐(3,4‐dichlorophenyl)‐1, 1‐dimethylurea for 2 weeks to isolate microorganisms tolerant to these concentrations. A fungus of the genus Fusarium and two unidentified bacteria were isolated by plating out small samples of the treated soil on Czapek's solution agar without sugar with 20 ppm of both herbicides added. The three isolates were tested for their ability to grow in solid and liquid media with different concentrations of the herbicides as sources of carbon. The same optimal growth of the fungus on Czapek's solution agar without sugar with 1 g/liter concentration of yeast extract was attained at 10 and 20 ppm monuron. When the yeast extract was excluded, best growth was attained at 2 ppm monuron. In Czapek's solution agar without sugar, and with 50 mg/liter of yeast extract, the fungus produced the highest amount of dry mycelia with 20 ppm monuron.

Cultures of the three isolates in Czapek's solution agar without sugar containing 20 ppm diuron, including 0.5 ppm of carbonyl 14C‐diuron, were incubated for 2 weeks. The organisms grew profusely, but no breakdown products of diuron were detected from the extracts of these cultures as analyzed by TLC (thin layer chromatography) and strip scanning techniques. Approximately 3.5% of the added diuron was collected as 14CO2 from soil samples incubated for 80 days with carbonyl labeled 14C‐diuron and a mixture of the three isolates. Periodic analysis of soil samples from these experiments did not indicate any breakdown products of diuron apparently due to insensitivity of the instrumentation and procedures. However, data from the fungal growth and CO2 evolution experiments suggest that these organisms can use monuron and diuron as a source of carbon.
Nonuniform Phosphorus Distribution in the Root Zone of Corn: Growth and Phosphorus Uptake
Authors: Stryker R. B. , Gilliam J. W. , Jackson W. A.
Published: July 2010

The implications of nonuniform P distributions in the root zone of corn (Zea mays L.) on growth and P uptake were explored utilizing a split root system. Maximal dry matter accumulation occurred only when the entire root system was exposed to an external P supply. Reduction in shoot growth of nearly 20% was associated with those P distributions in which part of the root system was devoid of an external P supply. There was a concomitant decrease in root growth in “no P” zones such that shoot/root ratios remained constant regardless of whether all or part of the root system was exposed to P. The growth rate of roots dependent on an internal supply of P via translocation (roots in “no P” zones), as contrasted to that of roots with an external supply, is considered to have been limited by the rate at which inorganic P was supplied to the growing points.

These effects were not due to the lack of total P uptake for it was shown that a portion of the root system could take up high amounts of P if the external supply was sufficient.

For P distributions with one root zone devoid of an external P supply, significant differences in P concentrations, leaf widths, and dry weight occurred between opposite sides of some leaves. It is postulated that these nonuniform effects on leaves were the result of nonuniform P transport from the roots to leaves.
Distribution of Free Iron and Organic Carbon as Related to Available Water in Some Forested Sandy Soils
Authors: Shetron Stephen G.
Published: July 2010

The amount of available water (0.1–15 bar tension) in the B21 horizons of six sandy soil series increased as amount of free iron and organic carbon increased. Soils of the Typic Udipsamment subgroup had the lowest, and soils of the Typic Haplorthod subgroup the highest available water retention values. Retention of available water in the C horizons of these soils was positively correlated with free iron and specific surface. Cubic meter volume growth per hectare per annum for hardwood and pine stands increased as amounts of free iron, organic carbon, and available water increased.
Prediction of Water Loss from a Fallow Field Soil Based on Soil Water Flow Theory
Authors: Gardner H. R.
Published: July 2010

A simple technique based on soil water flow theory to predict evaporation from nonhomogeneous field soils is presented. From cumulative evaporation measurements on undisturbed cores of soil, a dimensionless curve is drawn relating fractional water loss to the square root of time divided by the amount of water available for evaporation. A procedure is described to account for the residual water left in the soil from one rainfall event to the next. Predictions of cumulative evaporation made by the use of the dimensionless curve were compared with 4 years' of lysimeter data on Rago silt loam. The system would work best in an area with high average potential evaporation and low rainfall such as the Great Plains.
Time‐Dependent Linearized Infiltration. I. Point Sources
Authors: Warrick A. W.
Published: July 2010

Water flow from a point source is analyzed using a linearized form of the moisture flow equation. Time‐dependence is assumed with the results simplifying to those of previous investigators for steady‐state conditions. Discrete time‐distributed inputs such as might occur for trickle or high frequency irrigation is amenable to the solution. Numerical simulations include (i) the advance of a wetting front during infiltration, (ii) moisture variation resulting from a cyclic input as during irrigation, and (iii) the matric flux potential field for a two‐source problem.
Soil Factors Affecting the Adsorption of 2,4,5‐T
Authors: O'Connor G. A. , Anderson J. U.
Published: July 2010

Factors expected to affect the adsorption of 2,4,5‐T (2,4,5‐trichlorophenoxyacetic acid) on four soils of the western USA were studied. The effects were examined by equilibrating solutions of 2,4,5‐T with soils in their natural condition, after Casaturation, and with samples of the same soils treated to remove soil constituents expected to affect adsorption. Organic matter was an important contributor to 2,4,5‐T adsorption, and, in some soils, was the only adsorbent of significance. Oxides of Fe and Al did not contribute much to adsorption in the soils studied although the pH of soils studied was only slightly acid to alkaline. Allophane was apparently an effective adsorbent when the Si/Al ratio of the allophane was high.
Splash Correction Factors for Soil Erosion Studies
Authors: Farrell D. A. , Moldenhauer W. C. , Larson W. E.
Published: July 2010

Many research workers in soil erosion have measured soil and sand splash from impacting water drops or raindrops. Size and shape of the soil containers have varied. A theoretical study was made to determine the possible effect of the geometric parameters on the measurement of soil splash. The results show that estimates of soil detachment by raindrop impact could be substantially affected by the size and shape of the container.
Determining Effective Soil Water Diffusivities from One‐Step Outflow Experiments
Authors: Gupta S. C. , Farrell D. A. , Larson W. E.
Published: July 2010

A method is developed whereby effective or weighted mean diffusivity, D̄, can be estimated by using outflow data. These estimates can further be analyzed for soil water diffusivity, D(θ), with the help of a step‐wise function and the relationship given by Crank (1956). The suggested procedure for estimating soil water diffusivity is more accurate than previous methods because no assumption of constant diffusivity either over the pressure increment or over the length of the soil core is required. Moreover the procedure does not use the early part of the outflow curve and thus reduces the effect of membrane impedance on the estimates of D(θ).

The method was tested by simulating outflow experiments on a digital computer, and using data obtained to calculate diffusivities. Our estimates of diffusivity were in better agreement with the actual diffusivities than those obtained with the earlier “one‐step” method.
Chloride and Tritiated Water Flow in Disturbed and Undisturbed Soil Cores
Authors: McMahon M. A. , Thomas G. W.
Published: July 2010

Columns of disturbed and undisturbed Eden, Maury, and Pembroke soils were eluted with CaCl2 in tritiated water. The chloride was used as a substitute for nitrate since it is not affected biologically. The experiments were carried out to investigate the effects of natural soil structure on the flow of water and chloride. In all three soils flow was less stable in the undisturbed cores judging from the shape of the curve and the points of initial tritiated water and chloride breakthrough. Chloride moved through the undisturbed Eden and Maury soils faster than through the disturbed columns. Both soils exclude anions to a significant extent. In the Pembroke soil, which adsorbs anions, the chloride was retarded in the undisturbed column as compared to the disturbed column. The results suggest that field movement of water and anions is not described very well by columns of disturbed, packed soils.
Sodium Amalgam Reductive Degradation of Fungal and Model Phenolic Polymers, Soil Humic Acids, and Simple Phenolic Compounds
Authors: Martin J. P. , Haider K. , Saiz‐Jimenez C.
Published: July 2010

Reductive degradation of fungal humic acid‐type compounds and model phenolase phenolic polymers with 5% Na‐amalgam under N2 yielded 4 to 32% simple phenols which could be separated by two‐dimensional thin‐layer chromatography. Yields from soil and peat humic acids were 3 to 6%. Phenols recovered from all three types of polymers in greatest concentration were resorcinol, orcinol, 2,6‐dihydroxytoluene, phloroglucinol, p‐cresol or m‐cresol and p‐hydroxybenzoic, p‐hydroxycinnamic, ferulic, vanillic, 3,5‐dihydroxybenzoic, and protocatechuic acids. Vanillic and ferulic acids were found in the fungal polymers only when the organisms were cultured on plant residues or the phenols were placed under the fungus pads. Many other phenols incorporated into the model polymers were recovered in relatively low concentrations or not at all. In general, the phenols recovered in greatest concentrations from the polymers were those least affected by the Na‐amalgam reaction. Some of the hydroxybenzoic acids were partially or completely decarboxylated to form the corresponding phenols. Less than half the reacted phloroglucinol, caffeic acid and several other phenols were recovered. Hydroxynaphthalenic compounds were destroyed by the reaction. N‐linked phenylglycine was not recovered by the procedure. Over 16 phenols separated upon Na‐amalgam reduction of the soil humic acid fraction after incubation with 14C glucose or wheat straw were radioactive.
An Inexpensive But Durable Thermal Conductivity Probe for Field Use
Authors: Fritton D. D. , Busscher W. J. , Alpert J. E.
Published: July 2010

A thermal conductivity probe is described which is constructed from heat‐shrinkable tubing, stainless steel tubing, and thermocouple wire. The probe requires about $3 worth of material and 0.5 hours of labor for construction. An example of data used to calculate the thermal conductivity of dry quartz sand is given. The probe is currently being used to acquire data in the field.
Diurnal Soil‐Water Evaporation: Comparison of Measured and Calculated Soil‐Water Fluxes
Authors: Jackson R. D. , Reginato R. J. , Kimball B. A. , Nakayama F. S.
Published: July 2010

The Philip and DeVries theory and the “isothermal” theory were used to predict diurnal soil water fluxes near the soil surface. The predicted values were compared with those obtained by measurements of soil‐water content, soil temperature, and evaporation. Previously measured soil‐water diffusivities were used in the theoretical calculations. The thermal vapor diffusivities were calculated using both the “simple” and the “complete” theory of Philip and DeVries. Comparison of measured and calculated fluxes indicated that the theory of Philip and DeVries predicts the measured values better at intermediate water contents, but the “isothermal” theory predicts values better at high and very low water contents.
Unsteady, Unsaturated, n‐Dimensional Moisture Flow in Soil: A Computer Simulation Program
Authors: Van der Ploeg R. R. , Benecke P.
Published: July 2010

A computer simulation program for predicting n‐dimensional moisture flow in soils is simple to program and does not require extensive mathematical background. The programming was done with the computer program System/360 Continuous System Modeling Program (CSMP). For a number of selected problems the simulation results were compared with existing analytical and numerical solutions, and good agreement was found. Comparisons are made for 1‐dimensional adsorption, 3‐dimensional (spherical) absorption, 2‐dimensional infiltration from a line‐source, and 3‐dimensional infiltration from a point source.
A Method for Measuring First‐Stage Soil Water Evaporation in the Field
Authors: Arkin G. F. , Ritchie J. T. , Adams J. E.
Published: July 2010

An economical, automated method was developed for measuring soil water evaporation during first‐stage drying simultaneously at several locations in a field to evaluate the effectiveness of mulches and crop canopies in reducing soil water evaporation. The method also provides a reasonable procedure for separating soil water evaporation during first‐stage drying from transpiration, when the total evapotranspiration rate is accurately measured.

Water flow through a thin evaporation plate with a known surface area is measured and used as a direct indicator of the evaporation rate. Flow rates can be recorded manually or automatically.

Field tests of evaporation indicated that the resolution of the system was equal to that of a precision weighing lysimeter and that the system gave reasonable accuracy on an hourly basis. Mulch rates of 1,000, 4,000, and 10,000 kg ha‐1 reduced daily soil water evaporation measured with this method by 26, 59, and 78% of the bare soil evaporation. Cumulative daily soil water evaporation was reduced by 57 and 71% under plant canopies with 100‐ and 50‐cm row spacings and similar leaf area indices (3.0 and 2.7, respectively).
Biomass Production and Nitrogen Recovery after Fertilization of Young Loblolly Pines
Authors: Baker J. B. , Switzer G. L. , Nelson L. E.
Published: July 2010

Ammonium nitrate applied at rates of 112 and 224 kg of N/ha in successive years to different areas of a young loblolly pine (Pinus taeda L.) plantation increased aboveground biomass by 25% and N accumulation by 30%. Fertilization at plantation age 3 resulted in significantly greater biomass and N accumulations in the pine; fertilization at age 4 caused greater accumulations of biomass and N in the herbaceous fraction. These differences are related to changes in the composition of the herbaceous species. Fertilization had little effect on distribution of biomass or N within the pine component of the system. Comparable but generally small proportions of applied N were recovered in the aboveground vegetation in spite of two‐fold differences in quantities of applied N and threefold differences in biomass development. Nitrogen recovery was influenced only by the frequency of N application.
Comparative Efficiency of Soluble and Controlled‐Release Sulfur‐Coated Urea Nitrogen for Corn in Tropics
Authors: Dalal R. C.
Published: July 2010

The efficiency of the soluble‐N sources, ammonium sulphate (AS), urea‐ammonium phosphate (UAP) and urea and controlled‐release‐N sources, sulfur‐coated urea (SCU‐8.9, SCU‐1.1 and SCU‐0.9) of differing N‐release rates (applied at 50, 100, and 200 kg/ha of N to an acidic soil) were compared in terms of N uptake and grain yield of corn (Zea mays L.). The apparent N recovery of added N, calculated by uptake differences from the control plots, was evaluated from N uptake by the two successive crops, one in the wet season and the other in the following dry season. In general, N uptake, grain yield, and apparant N recovery were increased by added N in this order: SCU‐0.9 = SCU‐1.1>SCU‐8.9 = Urea>UAP = AS; which was opposite to the nitrification of these N sources except that the performance of urea was better than the other soluble‐N sources, primarily because it had a smaller effect on soil pH and exchangeable Al. The inclusion of microbicide in the S‐coatings of SCU had no influence on N efficiency or grain yield. More N was recovered from SCU with slower N‐release characteristics irrespective of coating weight. Apparent recovery of added N was almost complete from urea, SCU‐8.9, SCU‐1.1 and SCU‐0.9 when appplied at the rate of 50 kg/ha of N, although the recovery at 200 kg/ha of N was about 50%. The “priming effect” of soluble‐N sources on soil N was observed. It appeared that release of fixed NH4+‐N was primarily responsible for the priming effect on soil N.
Boron Availability as Influenced by Application of Fly Ash to Soil
Authors: Plank C. O. , Martens D. C.
Published: July 2010

The relationships between fly ash application to soil and B availability under field conditions were studied over a 3‐year period. The two fly ash samples studied contained 232 and 370 ppm of total B. Incorporation of one application in 1971 of either fly ash sample into a Tatum silt loam increased alfalfa (Medicago sativa L.) yield over a 3‐year period. Yield increases were attributed to an alleviation of B deficiency. Boron uptake data indicated that B in the fly ash samples was readily available initially but decreased with time. Results of correlation and regression analyses suggested that hot‐water‐soluble B extractions could be used to predict plant availability of B in fly ash‐soil mixtures.
Soil‐Water Pressure During Intermittent Simulated Rain Application Measured with a New Rapid‐Response Tensiometric Technique
Authors: Sloneker L. L. , Olson T. C. , Moldenhauer W. C.
Published: July 2010

A method is described for measuring instantaneous changes in soil‐water pressure in soil beds during intermittent application of simulated rainfall. Differences in soil‐water pressure do occur in soil beds, depending on nozzle off time. Intermittent off periods between nozzle on times affected soil‐water pressure which influenced the accumulated rainfall energy required to initiate runoff.
Supersaturation Phenomena and the Formation of Fluorapatite in Aqueous Suspensions of Phosphate Rock
Authors: Chien S. H. , Wier D. R. , Black C. A.
Published: July 2010

Dilute HCl solutions equilibrated with Florida phosphate rock and Tennessee brown phosphate rock in the presence of solid fluorite (CaF2) developed a condition of supersaturation with respect to fluorapatite at 25C. In suspensions boiled before equilibration at 25C, however, the solutions were in equilibrium with fluorapatite, as evidenced by ion‐activity products for fluorapatite in the solutions. The pH and concentrations of calcium and phosphorus in solution decreased due to boiling a suspension of Florida phosphate rock, as expected if fluorapatite had been precipitated. A condition of supersaturation with respect to fluorapatite redeveloped upon long‐continued equilibration of boiled suspensions of Florida and Tennessee phosphate rocks at 25C. Dilute HCl solutions equilibrated with phosphate rock or with phosphate rock plus solid fluorite became supersaturated with respect to fluorite at low pH values (about pH 3) where considerable calcium and fluoride were released from the phosphate rock, and the supersaturation persisted until the end of the equilibration period of 47 days at 25C. At pH values above about 4, the solutions became saturated with fluorite if solid fluorite was present but remained unsaturated where only phosphate rock was present as the solid phase.
Kinetics of Fixation of Iron and Zinc Applied as FeEDTA, FeHDDHA and ZnEDTA in the Soil
Authors: Lahav N. , Hochberg M.
Published: July 2010

The disappearance of zinc and iron from soil solution after their addition as soluble metal chelates is attributed to adsorption and fixation. The value of the adsorption coefficient, Kd, was estimated from a batch experiment but because of the inaccuracy involved they were evaluated from the breakthrough curves of column experiments using Rehovot sand. FeEDDHA was neither adsorbed nor was its iron fixed by the soil to any significant extent.

The fixation of iron applied as FeEDTA was found to be a first order reaction. Assuming that the fixation reaction kinetics is similar in both the solution and the solid phase, then the reaction rate constant can be expressed as k = (k1θ + k2ρKd)/(θ + ρKd), where k1 and k2 are the reaction rate constants in the liquid and solid phases, respectively. θ is the volumetric water content and ρ is the bulk density. By using 5 different soil/water ratios, the values of k1 and k2 were found to be 0.0096 h‐1 and 0.087 h‐1, respectively. The value of k was also estimated from the breakthrough curve in a column experiment by using the relative effluent concentration under steady state condition (C/Co)s.

The adsorption of ZnEDTA was negligible under the present experimental conditions. Thus k = k1 and is independent of the water content and bulk density. This was shown by comparing the results of the two experimental techniques. The value of k1 thus found was 0.084 h‐1. The first order model of the fixation reaction of zinc applied as ZnEDTA is applicable for time periods up to 8 to 10 hours.
Landform‐Soil‐Vegetation‐Water Chemistry Relationships, Wrigley Area, N.W.T.: II. Chemical, Physical, and Mineralogical Determinations and Relationships
Authors: Walmsley M. E. , Lavkulich L. M.
Published: July 2010

The relationship among five landforms in terms of chemical, physical, mineralogical, and water chemistry of lakes and the through flowing streams is presented. The landforms occur as a catenary sequence (toposequence) in the intermittent permafrost region of the Mackenzie Valley, N.W.T., Canada. The five landforms are identified as an alpine meadow, an area of stone stripe and stone ring formation, a colluvial slope, an area of coalescing fans and an area of polygonal bog formation. Information collected on the chemical quality of a stream flowing through the area included pH, O2, Ca, Mg, Na, K, Cl, F and NO3. Chemical, physical, and mineralogical analyses of the soils occurring on these landforms illustrated the effect of climate on soil genesis. Cryoturbic action is the dominant process occurring in the stone stripe area while ice segregation is predominant in the area of polygonal bog formation. The limited decomposition of the soil organic matter is related to the harsh climate. Subdued pedogenic development of soils in the coalescing fan area is evident by their youthful profile differentiation. Water chemistry demonstrated the functional and integrated effect between dissolved load in the water and the landform through which the stream has flown.
Nonerodible Aggregates and Concentration of Fats, Waxes, and Oils in Soils as Related to Wheat Straw Mulch
Authors: Smika D. E. , Greb B. W.
Published: July 2010

Nonerodible (>0.84 mm) soil aggregates and concentration of fats, waxes and oils in the surface 5‐cm depth were determined as related to (i) rates of initial straw mulch, (ii) date of initial fallow tillage, (iii) removal of straw, and (iv) nitrogen fertilization. Nonerodible soil aggregates were also determined as affected by tillage implements commonly used in fallow with residue removed by burning and with residue present.

Increasing the amount of wheat (Triticum aestivum L.) straw mulch from 1,680 to 3,360 kg/ha on the soil surface at the start of fallow increased nonerodible aggregation by 5% and fats, waxes, and oils in the soil by 0.019 mg/g of soil. Delaying initial fallow tillage after harvest until spring increased nonerodible aggregates by 3% and fats, waxes, and oils in the soil by 0.052 mg/g of soil. Without N, mulched soil contained 7% more nonerodible aggregates and 0.010 mg more fats, waxes, and oils/g of soil than did bare soil.

All implements tested, except the oneway disk, increased initial nonerodible aggregation by 2 to 7% when wheat stubble had been removed prior to the tillage operation. The oneway disk decreased nonerodible aggregation 4%. During subsequent tillage, all implements decreased nonerodible aggregation except the chisel. Successive operation with the oneway disk decreased aggregation the most at 9%/operation.

Nonerodible soil aggregates at time of winter wheat seeding (Sept.) and the following spring were highest with a fallow tillage sequence of tandem disk, blade twice, and rodweed with flat chisel points twice. This sequence destroyed 67% of the initial residue. Nonerodible aggregation was lowest when the tandem disk was used three times, followed by rodweeder with flat chisel points twice. These operations destroyed 90% of the original residue. Overwinter decrease in nonerodible aggregation was smallest when only the blade and rodweeder with flat chisel points were used.
Minimal Leaching with Varying Root Depths of Alfalfa
Authors: Bernstein Leon , Francois L. E. , Clark R. A.
Published: July 2010

Alfalfa (Medicago sativa L. cv. ‘Sonora’) was grown in greenhouse lysimeters with soil depths of 60, 120, and 180 cm to determine whether rooting depth affected tolerance to the low leaching percentage of 6.25. Salinities of the drainage waters averaged about 6 mmho/cm for the controls irrigated with 0.4 mmho/cm water, and 26 mmho/cm for lysimeters irrigated with 2.0 mmho/cm water. Steady‐state salinity profiles were maintained for 3 years. Yields with the more saline water averaged 23% less than those of the controls, in good agreement with previous findings, but were not significantly affected by lysimeter depth. Water requirements and uptake of chloride and sodium were only slightly affected by lysimeter depth. Salinity profiles with maximum salinities of 26 mmho/cm in the soil water can, therefore, be compressed into as little as a 60‐cm depth with no greater effects on yield or salt uptake by the crop than those obtained with salinity profiles extended over 120 or 180 cm.
A New Ceramic Cup Soil‐Water Sampler
Authors: Harris Alfred Ray , Hansen Edward A.
Published: July 2010

A newly designed soil‐water sampler utilizing a miniature porous ceramic cup is suitable for either collecting large samples or for microtechniques. It eliminates sample transfer in the field and contamination from water channeling along sampler, and can be enclosed to discourage vandalism. It also permits immediate preservation of the collected sample.
Two‐Dimensional Similarity Solution: Theory and Application to the Determination of Soil‐Water Diffusivity
Authors: Turner Neil C. , Parlange Jean‐Yves
Published: July 2010

The Bruce and Klute methods (1956) to measure the soil‐water diffusivity (D) relies on the existence of a similarity solution for the one‐dimensional movement of water when the soil‐water potential is maintained constant at one end of a horizontal column of soil. If the flux is kept constant along a line‐source, a similarity solution exists also in two‐dimensions and an exact equation for this case is derived:
urn:x-wiley:03615995:saj2sssaj197503615995003900030013x:equation:saj2sssaj197503615995003900030013x-math-0001 where θo is the initial moisture content, θ is the moisture content after time, t, and ψ is the similarity variable.

The application of this equation in measuring the soil‐water diffusivity of a sandy soil is shown.
Specific Adsorption of Trace Amounts of Calcium and Strontium by Hydrous Oxides of Iron and Aluminum
Authors: Kinniburgh D. G. , Syers J. K. , Jackson M. L.
Published: July 2010

Freshly prepared Fe and Al hydrous oxide gels and the amorphous product of heating gibbsite selectively adsorbed traces of Ca and Sr from solutions containing a large excess (∼1M) of NaNO3. The fraction of the added Ca (Sr) adsorbed depended principally on the suspension pH, the amount of solid present, and to a lesser extent on the NaNO3 concentration. Significant Ca and Sr adsorption occurred on the Fe and Al gels, and heated gibbsite, at pH values below the points of zero charge (8.1, 9.4, and 8.3±0.1, respectively), indicating specific adsorption. The pH (± 0.10) at which 50% of the Ca was adsorbed (pH50) occurred at pH 7.15 for the Fe gel (0.093M Fe), 8.35 for the Al gel (0.093M Al), and 6.70 for the heated gibbsite (0.181M Al); for Sr, the pH50 values were 7.10, 9.00, and 6.45, respectively. For the Fe gel and heated gibbsite, an empirical model based on the law of mass action described the pH dependence of adsorption reasonably well and suggested that for each Ca or Sr fraction adsorbed, approximately one proton was released. Failure of the Al gel to fit this model may have resulted from its rapid aging.
Infrared Study of the Sorption of Phenol and p‐Nitrophenol by Montmorillonite
Authors: Saltzman S. , Yariv S.
Published: July 2010

The sorption of phenol and p‐nitrophenol by montmorillonite saturated with different cations was studied by IR and X‐ray spectroscopy. Various associations between interlayer cations, water, and phenols were proven. Depending on the nature of the cation, phenol can act either as a proton donor or acceptor. The electrophylic NO2 substituent of the ring increases the acidic strength of the phenol group: therefore, p‐nitrophenol tends to behave mainly as a proton donor. The nitro‐group acts as an electron donor and, depending on the hydration status of the clay, either accepts protons from water coordinated to cations, or directly coordinates to the metallic cations.
Sulfuric Acid for the Treatment of Ammoniated Irrigation Water: I. Reducing Ammonia Volatilization
Authors: Miyamoto S. , Ryan J. , Stroehlein J. L.
Published: July 2010

Effects of sulfuric acid applied to ammoniated irrigation waters on ammonia volatile losses are analyzed theoretically and evaluated by laboratory and field experiments. Volatile loss of ammonia from irrigation waters is directly related to the concentration of NH4OH. Sulfuric acid application reduces the concentration of NH4OH relative to the total N applied as anhydrous or aqua ammonia, principally by lowering pH. This consequently reduces ammonia volatile loss, e.g., by as much as 50% when acid is applied at rates equivalent to ammonia. The reduction of ammonia loss by sulfuric acid application through forming NH4SO4‐ is nil. Simultaneous application of acid and ammonia may serve as a practical means of controlling ammonia loss as well as disposing of large quantities of projected surplus acid without reducing pH of irrigation water.
Potassium‐Calcium Equilibria in Sandy Soils Containing Interstratified Micaceous Clay
Authors: Murthy A. S. P. , Dixon J. B. , Kunze G. W.
Published: July 2010

Neutral to alkaline soils from several climatic and physiographic locations were studied. The clay mineralogy of these soils was characterized by interstratified mixtures of mica, montmorillonite and little vermiculite. X‐ray diffraction patterns for the most abundant clay fraction, < 0.2 µm, were composed of weak diffuse reflections for mica‐expansible components when they were Mg‐saturated and glycolated. Sand and silt fractions contained K‐feldspar and mica as possible sources of K+.

The two most micaceous soils produced Q/I curves with a horizontal range indicating further K+ sorption ceased in spite of the increased K+/Ca2+ ratio. The amount of K+ in the labile pool determined by the Q/I method was correlated best with the amounts of mica in the whole soil (r2 = 0.89) suggesting that mica in coarse and fine fractions acted as a potential source of labile K+ in these soils. A multiple regression equation was developed that predicted the amount of K+ in the labile pool from the amounts of mica and feldspar in the soil (R2 = 0.96). The results of this study suggest that mica in these soils will contribute K+ to the labile pool. The multiple regression coefficient indicated that feldspar content was negatively related to labile K+.
Characterization of Mineral Forms in Andepts from Chile
Authors: Espinoza W. , Rust R. H. , Adams R. S.
Published: July 2010

The mineralogy of two undisturbed volcanic soils from Chile (Typic Dystrandepts) and of the sand and clay‐size particles of the soil residues was studied by using ultrasonic, scanning electron microscope, X‐ray diffraction, transmission electron microscope, infrared spectroscopy, differential thermal analysis, and electron microprobe techniques. The effects of removal of organic matter, free iron and aluminum oxides, and amorphous alumino‐silicates was evaluated in the X‐ray, DTA, and IR analyses. The soils are characterized by an amorphous inorganic matrix in a flocculated state with a sponge type structure. This matrix presents a high specific surface (225 m2/g), CEC of about 45 meq/100g at pH 7.0, low base saturation (< 20%) and bulk density of 0.9 to 1.1 (g/cm3) and SiO2/Al2O3 molar ratio of 2.0 to 4.0. Organic matter appeared in some well preserved structures, partially due to silica accumulation. The principal primary minerals are fresh volcanic glass and K‐feldspars and the principal secondary mineral is allophane or an amorphous analog. The removal of organic matter, free iron and aluminum oxides and amorphous alumino‐silicates did not alter the DTA, X‐ray and IR patterns.
Clay Mineralogy of Selected Soils in Southern Nigeria
Authors: Gallez A. , Juo A. S. R. , Herbillon A. J. , Moormann F. R.
Published: July 2010

Clay minerals in eight soil profiles from southern Nigeria were investigated by means of X‐ray diffraction, infrared spectroscopy, differential thermal analysis, and electron microscopy. These soils are derived from basement complex rocks, arenaceous sedimentary rocks and basalts.

Kaolinite is the most predominant clay mineral for all the soils studied. A pronounced variation in clay mineralogy was found in the soils derived from basement complex rocks sampled at various locations along a toposequence. Halloysite occurs in freshly weathered materials, while smectite is found in poorly drained, lower members of the toposequence.

Gibbsite occurs in soil derived from cretaceous arenaceous rocks in the high rainfall area. Among all soils studied, the highest amounts of amorphous Al silicate and extractable Fe and Al oxides were found in those derived from basalts. In all cases, Fe oxides exist predominantly in crystalline forms.
Decomposition of Specifically Carbon‐14 Labeled Benzoic and Cinnamic Acid Derivatives in Soil
Authors: Haider K. , Martin J. P.
Published: July 2010

Specifically 14C‐labeled benzoic, phenolcarboxylic, and hydroxycinnamic acids were synthesized. The loss of the labeled carbon as 14CO2 upon incubation at 100 and 1,000 ppm in a neutral soil with and without the addition of 2% freeze‐dried humic acid or 0.5% finely ground peach wood (Prunus persica) was followed over a 12‐week incubation period. Under the experimental conditions the phenolic compounds were readily degraded in the soil. Within 1 week about 90% of the COOH carbon of p‐hydroxybenzoic, syringic, vanillic, and anisic acids had evolved as CO2. After 12 weeks this had increased to about 95%. Loss of the 14COOH carbon of 6‐methylsalicylic acid was about 75% at 1 week and 87% after 12 weeks. About 42 to 85% of the side chain carbons of p‐hydroxycinnamic acid and caffeic acids evolved as CO2 and from 66 to 85% of the ring carbon of protocatechuic, benzoic, vanillic, veratric, and caffeic acids was lost over the incubation period. The addition of peach wood or humic acid exerted very little effect on the decomposition rate and total decomposition of the phenols and the phenols did not influence the decomposition rate or total decomposition of the peach wood. The percentage distribution of the residual activity from 3‐14C p‐hydroxycinnamic acid, ring‐14C benzoic acid, and O14CH3 syringic acid varied from 14 to 21, 17 to 32, and 23 to 59% for the humic acid, fulvic acid, and residual soil fractions, respectively. Linkage into model phenolase polymers greatly retarded decomposition rate. Loss of ring carbon varied from 3 to 6% and side chain and COOH carbons from 8 to 75%. The higher losses occurred from COOH groups of single hydroxybenzoic acids linked into model phenolase polymers from hydroxytoluenes and hydroxyphenols.
Fragipans in Pennsylvania Soils: Properties of Bleached Prism Face Materials
Authors: Ranney R. W. , Ciolkosz E. J. , Cunningham R. L. , Petersen G. W. , Matelski R. P.
Published: July 2010

Bleached prism faces are a common feature of soil fragipan horizons. Particle size and chemical and clay mineralogy data indicate these zones are areas of accumulation of material from horizons above. The data also indicates that two processes are active in the movement of material into the prism face area. These processes result in bimodal distribution of particle sizes in the prism face areas. The exact nature of the processes is unclear and may involve both deposition and some stripping.
Hammer Seismic Timing as a Tool for Artificial Recharge Site Selection
Authors: Bianchi W. C. , Nightingale H. I.
Published: July 2010

Hand‐carried hammer impact seismic timing equipment utilizes the physics of seismic wave refraction to explore stratigraphic changes deeper then those found on soils maps. In alluvial areas, artificial recharge and liquid waste disposal sites are selected from sandy, single‐grained soil series noted for their high water‐transmitting properties through the surface 2 m. The surface horizon seismic velocity exhibited by these soils in the San Joaquin Valley has a very narrow range (V1 = 315–440 m/sec) which gives good definition to the refraction off the second horizon (V2 = 610–2,100 m/sec). Accurate information on depth and horizontal continuity of this second horizon can be obtained in areal surveys. A third horizon may often be described, but its areal continuity is usually masked by intermediate discontinuous layers above it of equal or lesser refractivity. All these horizons are of hydraulic significance for ground‐water recharge by water spreading.
Reflectance Differences Between Crop Residues and Bare Soils
Authors: Gausman H. W. , Gerbermann A. H. , Wiegand C. L. , Leamer R. W. , Rodriguez R. R. , Noriega J. R.
Published: July 2010

To find the best spectral waveband for identifying crop residues by remote sensing, reflectance spectra of standing and littered crop residues were compared, and the utility of ERTS‐1 Multispectral Scanner (MSS) data for distinguishing soils with crop residues from bare soils was tested.

Field spectroradiometric investigations were conducted using the 0.5‐ to 1.8‐µm waveband. Crop residue littered on the soil had higher reflectance than bare soil, but standing crop residue had lower reflectance than bare soil.

The ERTS‐1 MSS digital counts (signal strengths) were statistically different between soils with and without crop residues more times (8 out of 12) for band 4 (0.5 to 0.6 µm) than for bands 5 (0.6 to 0.7 µm), 6 (0.7 to 0.8 µm), and 7 (0.8 to 1.1 µ), or for band ratios 4/7, 5/7, 4/6, and 5/6. Statistically, for band 4, soils with crop residues had lower reflectance than bare soils five out of eight times.

Present reflectance techniques are unable to distinguish quantities of crop residue on the soil, and better parameters are needed to describe crop residues.

Additional study of ERTS‐1 MSS data relating crop residues to wind and water erosion susceptibility of the soil is merited.
An Aluminum Block Digester for Plant and Soil Analysis
Authors: Gallaher R. N. , Weldon C. O. , Futral J. G.
Published: July 2010

Almost every institution, whether it be a university, a government agency, or a medical or industrial facility, that conducts research on and is concerned with the elemental analysis of biological material has a need for equipment to ash or acid‐digest samples. Often funds are not available with which to purchase commercial equipment and the researcher is required to be innovative and to design and engineer his own. Because of the lack of research funds and a need for soil and plant analysis equipment, this study was made to design and construct a large capacity, electrically‐heated and thermostatically‐controlled aluminum block digester for plant and soil samples. A drawing was prepared giving dimensions needed for shop‐work to be performed. A block of aluminum 10.2 cm (4 inches) thick was used. The block has a capacity of 126, 2.54‐cm (1 inch) diameter test tubes. The overall block dimensions are 10.2 cm (4 inches) thick, 35.6 cm (14 inches) wide, and 55.1 cm (21 11/16 inches) long. Electric heater strips are bolted to the block inside 1.9‐cm (¾ inch) milled slots. The temperature control sensor is a thermocouple inserted into the block and wired to the thermostat controller. The block heats almost linearly from room temperature to 240C at a rate of almost 4C/minute. The heating rate from room temperature to 375C is over 2C/minute and requires 2.5 hours heating time.
The Mechanism of Phosphate Fixation by Iron Oxides
Authors: Parfitt Roger L. , Atkinson Roger J. , Smart Roger St.C.
Published: July 2010

Infrared spectroscopic techniques have been used to obtain a structural model for the surface reaction between iron oxides and phosphate ions. Two surface hydroxyl ions (or water molecules) are replaced by one phosphate ion. Two of the oxygen atoms of the phosphate ion are coordinated, each to a different Fe3+ ion, resulting in a binuclear surface complex of the type Fe‐O‐P(O2)‐O‐Fe. Evidence is given for phosphate adsorption producing this coordination structure on the surfaces of goethite, hematite, lepidocrocite, β‐ferric hydroxide, and amorphous ferric hydroxide gel.
Relationships Between the Hydraulic Conductance of Surface Crusts and Soil Management in a Typic Hapludalf
Authors: Falayi O. , Bouma J.
Published: July 2010

The effect of different soil management, in terms of soil till‐age and crop rotation, on soil crusting was investigated by applying continuous artificial rain (8.5 cm/hr) to experimental plots until steady‐state conditions were reached. Comparisons were made with bare plots subjected to natural rainfall for a period of 4 months. Significant differences in soil roughness between the plow only and the plow, disk, and harrow treatments resulted in higher infiltration and longer times to incipient runoff for the plow treatment. However, differences in surface roughness and infiltration and runoff rates were insignificant among treatments when steady‐state conditions were reached after only 2 hours. Crust conductances, measured in situ, were significantly lower in the plow, disk, and harrow treatments for the sod as compared with the continuous corn rotation. Crusts had a significantly higher conductance when formed on top of clods as compared with crusts formed between clods in the plow treatment. Conductances of crusts formed under short‐term high‐energy experimental rainfall were not significantly different from those formed under natural conditions, the latter characterized by intermittent low‐energy rainfall during a 4‐month period. However, their morphology was significantly different.
Dissolution of Illite—A Possible Mechanism of Potassium Release
Authors: Feigenbaum Sala , Shainberg I.
Published: July 2010

The rate of potassium aluminum, iron and magnesium release from Fithian illite in dilute salt solutions and at pH ⩾ 3, was studied. It was found that cumulative cation release was proportional to the square root of the duration of the treatment. The rate of Al release was similar to the rate of K release, whereas the rate of Fe and Mg release was about three × that of K and Al release. Since the only known mechanism for the release of the lattice cations is the dissolution of the clay, it is proposed that dissolution of the clay lattice is also the dominant mechanism by which potassium is released from the clay. Two consecutive reactions, a rapid exchange reaction and a slow first‐order reaction, explain the experimental observations.