bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Total Potassium, Sodium, Calcium, and Magnesium in Plant Materials by Ion Chromatography
Authors: Basta N. T. , Tabatabai M. A.
Published: July 2010

A simple, accurate, and precise ion chromatographic (IC) method for determination of total K, Na, Ca, and Mg in plant materials was developed. It involves dry ashing approximately 0.1 g of plant material, followed by dissolution of the residue in 5 mM HCl and determination of K, Na, Ca, and Mg in the digest by using a Dionex Model 10 IC. The IC method is based on separation of the cations by a separator column containing low‐capacity, cation‐exchange resin in the H+ form and on converting the various cations to their corresponding hydroxide forms by a suppressor column in the OH‐ form. The eluent used for determination of K and Na was 5 mM HCl, and that used for determination of Ca and Mg was 2.5 mM HCl + 2.5 mM m‐phenylenediamine dihydrochloride. Electrical conductivity is used as the mode of detection. Results showed that the average total K values in 25 plant materials by IC, atomic absorption spectrophotometry (AA), and flame photometry (FP) were 3.08, 3.08, and 3.07%, respectively. The corresponding average total Na values were 0.258, 0.264, and 0.256%. The average total Ca values in the same plant samples by the IC and AA methods were 1.20 and 1.19%, respectively. The corresponding average total Mg values were 0.327 and 0.331%. The IC method developed has the same degree of precision as that of AA or FP method. The IC method has an excellent sensitivity with detection limits of 0.1, 0.05, 0.1, and 0.03 mg L−1 of K, Na, Ca, and Mg, respectively. With the IC method, K and Na can be determined simultaneously in 6 min, or Ca and Mg can be determined in 7 min. A single operator can perform about 40 analyses of K and Na or Ca and Mg in a normal working day.
Phosphate Sorption by Some Alfisols of Greece as Described by Commonly Used Isotherms
Authors: Polyzopoulos N. A. , Keramidas V. Z. , Kiosse Helen
Published: July 2010

The one‐ and two‐surface Langmuir, the Freundlich, and the Temkin isotherms were fitted to P sorption data for 14 representative alfisols of Greece. Each was found to describe P sorption by these soils with comparable success, with the Freundlich and the two‐surface Langmuir isotherms being slightly superior. The Freundlich equation is characterized by simplicity of form, based on more realistic assumptions, and now capable of rigorous derivation. It can therefore be used in preference to the others, since its parameters, as those of the Langmuir equation, allow comparisons among soils.
Electron Spin Resonance Investigation of Copper(II) Complexation by Fulvic Acid Extracted from Sewage Sludge
Authors: Senesi Nicola , Bocian David F. , Sposito Garrison
Published: July 2010

Electron spin resonance (ESR) spectra are reported for copper (II) − fulvic acid complexes prepared with fulvic acid (FA) samples extracted from two different anaerobically‐digested sewage sludges. The nominal Cu/FA molar ratios employed were in the range 0.08 to 80. In the original Cu‐FA solutions, quadridentate, nearly square planar complexes with FA donor ligands could be inferred from the ESR spectra only at the smallest Cu/FA molar ratio, whereas at the intermediate ratios mixed Cu‐FA‐H2O complexes became more evident and at the highest ratio free Cu2+ aquo‐ions prevailed. Treatment of the Cu(II)‐FA solutions at any Cu/FA molar ratio with the strongly acidic cation exchange resin Bio‐Rad AG‐MP‐50 eliminated excess Cu(II) aquo‐ions and, therefore, permitted a better differentiation of classes of FA functional groups participating, to different degrees, in the coordination of Cu(II). The ESR spectra suggested the formation of inner‐sphere, polydentate complexes, with the Cu(II) coordinated equatorially by oxygenated and nitrogenated FA ligands. ESR parameters of the resulting Cu(II)‐FA complexes showed the existence of binding sites involving both 4 O and 2 O, 2 N ligand atoms, as well as a minor, more nitrogenated site (1 O, 3 N). No saturation of the Cu(II) complexation capacity was observed, but increasing the Cu content involved less and less reactive functional groups of FA in the coordination, shifting the complexation equilibria towards the formation of weaker complexes. Further information about binding mechanisms was developed through a comparative analysis of ESR data obtained for Cu(II)‐FA complexes both in aqueous solution and in air‐dried state. A significant rearrangement of the Cu‐FA systems was suggested to take place upon air‐drying of the resin‐treated Cu/FA solutions.
Pedoturbation of a Forest Soil by Fire Ants
Authors: Lockaby B. G. , Adams J. C.
Published: July 2010

The influences of the imported fire ant (Solenopsis invicta) on the mixing of forest soils on three sites in north Louisiana were examined. Soil bulk density, pH, percent organic matter, and concentrations of P, K, Ca, and Mg were compared for samples from ant mounds vs. adjacent undisturbed soil at two depths. In surface samples bulk density was lower and organic matter, P, K, Ca, and Mg were higher on the mounds. Soil pH did not change. In subsurface comparisons only organic matter and K differed and were higher in the mound samples. Results are discussed in terms of the depth of ant activity, the quantity of soil excavated, and the organic matter, P, K, Ca, and Mg content of that soil. Questions are raised regarding the role of fire ants in the decomposition of tree stumps.
Single Column Ion Chromatography: I. Analysis of Inorganic Anions in Soils
Authors: Nieto K. Fitzpatrick , Frankenberger W. T.
Published: July 2010

A useful analytical method is described for the determination of inorganic mono‐and divalent anions in soils. Single column ion chromatography (SCIC) is a rapid, sensitive, and precise method which can simultaneously detect Cl−, NO−2, NO−3, SO2−3, and SO2−4 in soils in less than 10 min. In addition, Br−, I−, and ClO−4 can be separated within 15 min. The method can be carried out on a commercially available HPLC instrument, using a 500 µL aliquot of soil extract and an eluent stream of 4 mM phthalic acid (pH 4.5). The inorganic anions are separated on a low‐capacity anion exchange column and quantified by conductimetric detection. Results obtained by the SCIC method agree closely with those obtained by other analytical methods: Cl−, AgNO3 titrimetric method (r = 0.987***); NO−2‐N, diazonium coupling reaction (r = 0.993***); NO−3‐N, steam distillation (r = 0.998***); SO2−4‐S, autoanalyzer (r = 0.998***). Using a 500 µL loop, SCIC detection limits, expressed in mg/L of soil extract, were: Cl−, Br−, NO−3‐N, and SO2−4‐S (0.025), ClO−4 and I− (0.5); NO−2‐N and SO2−3‐S (1.0). Several extracting reagents (water, LiCl, KCl, Ca[C2H3O2l2, and CaCl2) were compared to determine the best soil extraction procedure. This method proved to be reproducible as evident by the low CV values ranging from 3.6 to 8.4%. Notable advantages of this technique include: (i) single column simplicity, (ii) application to a wide variety of inorganic anions, (iii) simultaneous determination of ions in soil extracts without interferences by soil constituents, and (iv) inherent sensitivity greater than most methods employed for the determination of inorganic soil anions.
Effect of Phosphorus on the Effectiveness of Strains of Rhizobium japonicum
Authors: Singleton P. W. , AbdelMagid H. M. , Tavares J. W.
Published: July 2010

We examined the relationship between P nutrition of soybean [Glycine max (L.) Merr. cv. ‘Davis’] and N2 fixation by five strains of Rhizobium japonicum ranging from an ineffective (SM‐5) to a highly effective (USDA 110) symbiosis with soybean. Phosphorus at 0, 50, 125, and 400 mg P kg−1 soil (P0, P50, P125, P400) as Ca(H2PO4)2 · H2O was applied to pots containing 2.7 kg of a P‐fixing humoxic tropohumult free of R. japonicum. Treatments consisting of + N and five strains of R. japonicum and the four P treatments were arranged in a complete factorial replicated three times. With 400 mg P kg−1 soil treatments ranked + N > USDA 110 > USDA 31> USDA 123> USDA 33>SM‐5 for shoot dry weight and accumulation of N in the shoot. There were no significant strain effects for shoot dry weight, shoot N or nodule activity at Po. Strain rankings were the same at the intermediate levels of P but differences were smaller. Although nodule number was somewhat enhanced by P, it bore no relationship to strain effectiveness and was not a factor limiting N2 fixation at low P. Nodule dry weight and nitrogenase activities significantly increased with P additions. The concentrations of N and P in the shoot also increased with P additions. The concentrations of shoot P and N were higher in plants provided mineral N at the low and intermediate P levels than in the inoculated plants. The results show that P nutrition is important in interpreting the N2 fixation capability of strains of Rhizobium. Synergism between P and Rhizobium inputs requires that to obtain maximal response to the application of one input necessitates employing the other at maximum levels.
Soil Profiles: Nitrogen Conversion and Salt Motility Altered by Feedlot Manure Management
Authors: Norstadt Fred A. , Duke Harold R.
Published: July 2010

Two manure management plans were successively imposed on soil profile combinations of clay loam, sand, clay loam over sand, and sand over clay loam to study salt movement and nitrogen (N) transformations in a beef cattle feedlot. These soils were placed in replicated lysimeters located in each of two areas of a feedlot stocked at the rate of one animal, weighing 270 to 450 kg, per 15.2 m2. After loading the soils with N, including nitrate nitrogen (NO−3‐N), by means of a manure‐sawdust mulch for 4 yr (first manure management plan), cores were removed for physical and chemical analyses. Then, the mulch was changed to an intact‐manure pack for 2.5 yr (second manure management plan) which was followed by a second coring and soil analyses. Each management plan and profile combination affected salt movement and N transformations differently. The intact‐manure pack decreased soil profile water and NO−3‐N contents, and increased ammonium N in that part of the soil profile near the manure‐soil interface. Clay loam over clay loam retained more salt but was slower than sand over sand in promoting desired changes and decrease of NO−3‐N. The other profile configurations had similar effects related to texture. The interaction effects of management by location or management by location by soil in either upper or lower fills were not important variables influencing shifts of soil characteristics.
Nitrogen‐15 Determination of Nonrandomly Distributed Dinitrogen in Air
Authors: Craswell E. T. , Byrnes B. H. , Holt L. S. , Austin E. R. , Fillery I. R. P. , Strong W. M.
Published: July 2010

Dinitrogen gas produced by denitrification of 15N‐enriched fertilizers does not achieve a random nitrogen (N) isotope distribution when mixed with atmospheric N2. Thus, such mixtures cannot be analyzed by the conventional mass spectrometric measurement of the 28 and 29 ion current ratio. A method is proposed which uses a high voltage arc passed between a pair of tungsten electrodes sealed in a glass vessel to fix some of the N2 as NOx species, and thereby redistribute the N isotopes of the N2 into an NOx pool. The NOx species are absorbed and oxidized by acidic permanganate, reduced to NH+4, and distilled by routine procedures. Since the are process redistributes the N isotopes randomly by ultimately converting the N to a monatomic species (NH+4), accurate isotope ratio analysis of the distilled samples by the conventional dual‐collector mass spectrometer method is possible. The method is precise, accurate, simple, inexpensive, and avoids many of the problems associated with direct 15N analysis of gas samples with nonrandom N isotopic distributions. This description of the basic methodology may enable direct measurement of denitrification losses from highly labeled fertilizer sources while its application to estimation of total denitrification losses requires additional methodologies not described in this paper.
Reacidification of Two Lime Amended Soils in Western Oregon
Authors: Doerge Thomas A. , Gardner E. Hugh
Published: July 2010

Leaching of basic cations by winter rainfall and irrigation water and the increasing use of NH+4‐fertilizers have resulted in wide‐spread soil acidity in western Oregon. While applications of liming materials are often made in this region, the rates at which limed soils reacidify are generally not known. The objectives of this study were to: (i) quantify long‐term acidification rates of two lime‐amended soils in western Oregon, and (ii) identify soil‐plant processes which may control acidification rates. Lime applications ranging from 0 to 14 650 kg ha−1 were made on a Nekia sicl (Xeric Haplohumults, initial pH 5.0) and from 0 to 11 200 kg ha−1 on a Woodburn sil (Aquultic Argixerolls, pH 5.3) in the Willamette Valley of western Oregon in 1971 to 72. Monitoring of soil pH and levels of extractable basic cations applied in the liming materials for 11 to 12 yr permitted estimation of the rate of acidification of soils receiving different amounts of lime. Whether estimated by declines in pH or extractable basic cations, soil acidification rates increased with increasing quantities of lime initially applied. Acidification rates of unlimed Nekia soil were 0.025 pH units yr−1 and 0.17 cmol(+) Ca2+ + Mg2+ kg−1yr−1 while the unlimed Woodburn soil showed no net acidification. Maximum rates of acidification of 0.09 pH units yr−1 and 0.62 cmol(+) extractable Ca2+ + Mg2+ kg−1yr−1 on the Nekia soil and 0.08 pH units yr−1 and 0.36 cmol(+) extractable Ca2+ kg−1yr−1 on the Woodburn soil were measured on plots receiving the highest amounts of lime. Faster reacidification of soils amended with higher lime rates is explained by the pH dependence of acidifying processes such as nitrification, CO2 release via plant and microbial respiration, mineralization of organic matter and dissociation of organic acids in soil solution. Ca2+ release from mineral weathering appeared to have an important effect on soil pH and extractable Ca2+, particularly in the absence of large inputs of acidifying materials such as NH+4‐fertilizers. Accurate prediction of soil acidfication rates will require additional information concerning the pH dependence of soil acidifying processes, the quantity and composition of seasonal through drainage, and the rates of mineral weathering in soils.
Retention and Transport of Sulfate in a Slightly Acid Forest Soil
Authors: Weaver G. T. , Khanna P. K. , Beese F.
Published: July 2010

A shallow slightly acid Terra fusca (Rendolls) soil derived from triassic limestone contains substantial amounts of sulfate. Under high sulfate input, low pH and high salt input this soil can further retain sulfate. Soil chemical data indicate that this soil contains exchangeable Al and H. This finding and the analysis of the equilibrium soil solutions from batch and percolation studies indicate that the retention of sulfate can be described by an equilibrium solid/solution phase of the type Al(OH)SO4 (aluminum hydroxy sulfate). Under similar experimental conditions of solution composition and concentration, Freundlich type adsorption/desorption isotherms and the general solute transport equation can describe the retention and transport of sulfate in this soil.
Ion Diffusion in Soils As Related to Physical and Chemical Properties
Authors: Skogley E. O. , Schaff B. E.
Published: July 2010

Ion diffusion to plant roots is known to be a major factor influencing availability of certain nutrients in the soil. Diffusion of K+, Ca2+, and Mg2+ from soil to a H‐saturated ion exchange resin sink was measured for 20 agricultural surface soils (18 from Montana and two from Iowa) to investigate the relationship between diffusion and selected chemical and physical soil properties. The soils were moistened to a tension of 0.1 mPa and packed into cylinders to a bulk density of 1.25 Mg m−3. Cylinders were placed in temperature‐controlled chambers at 5 or 30°C and ion diffusion into an ionexchange resin sink was measured after 96 h. Diffusion of K+, Ca2+, and Mg2+ was significantly different between soils and at the two temperatures, and there was a significant soil times temperature interaction. Regression of 41 independent soil physical and chemical characteristics against amount of K+, Ca2+, and Mg2+ in the resin revealed several soil chemical and physical properties that were significantly related to ion diffusion. Values for NH4OAC extractable ions were not as highly correlated to diffusion of these ions as were several other factors.
Kinetics and Mechanisms of Aluminum Adsorption on Kaolinite Using a Two‐site Nonequilibrium Transport Model
Authors: Jardine P. M. , Parker J. C. , Zelazny L. W.
Published: July 2010

Kinetics of Al adsorption on Ca‐kaolinite at selected concentrations, pH, and column lengths were studied using a miscible displacement technique. Observed breakthrough curves (BTC) for continuous injection of pH 4.3, 0.75 to 7.75 µg mL−1 Al solution were well‐described by a two‐site nonequilibrium transport model which assumes that sorption sites can be divided into two fractions: (1) instantaneous equilibrium sites and (2) sites following first‐order reversible kinetics. Independent verification of the fitted parameter β, related to the fraction of type‐1 equilibrium sites, was possible by assuming negative surface charge sites of kaolinite were in local equilibrium with the solution phase. Confirmation of the fitted parameter R, which is a measure of the total Al adsorbed, was not possible due to the nonsingular nature of the equilibrium adsorption isotherm. First‐order rate coefficients (α) for Al adsorption on kaolinite were unaffected by column length. Effects of influent Al concentration on α were small but suggested that kinetic reaction of Al with kaolinite was not strictly first‐order. Decreasing the pH of influent solution from 4.3 to 4.0, eliminated type‐2 kinetic sites. These effects indicate that kinetic reactions involve Al polymerization on kaolinite while equilibrium reactions reflect Ca‐Al exchange. This scenario is supported by Ca desorption data of the effluent and by potentiometric titrations of effluent solutions.
Transient Microsite Models of Denitrification: II. Model Results
Authors: McConnaughey P. K. , Bouldin D. R.
Published: July 2010

Solutions to four models of denitrification are presented. The models are based on four coupled reaction‐diffusion equations, each model describing a different type of reaction term. The equations were solved by standard finite‐difference methods and a boundary tracking technique when needed. For a chosen test problem, the zero‐order model predicted sequential reduction of nitrogenous species, a N2/N2O ratio of 0.17, and relatively high transient NO‐2 levels. The Michaelis‐Menten model with threshold and concentration‐dependent NO‐3 and NO‐2 inhibition of N2O reduction predicted N2/N2O ratios of 19.15 and 6.69, respectively. The competitive inhibition model predicted a N2/N2O ratio of 0.23 and N2 evolution followed N2O. A sensitivity analysis of the Michaelis‐Menten model with concentration‐dependent inhibition showed that the species of gaseous N evolved depended strongly on NO‐3 levels in the soil. N2/N2O ratios were also influenced by O2 fluxes, diffusion coefficients, and diffusion distances that affect anaerobic volume and solute transport. The predicted N2/N2O ratios were less sensitive to the Michaelis‐Menten kinetic parameters Vimax and KiM where i = nitrate, nitrite, or nitrous oxide. The qualitative behavior of gaseous N evolution as a function of nitrate levels, gaseous oxygen concentration, and depth of saturation predicted by the models agrees with data in the literature.
Field Estimation of Phosphate Retention by Andepts
Authors: Alvarado Alfredo , Buol S. W.
Published: July 2010

In an attempt to develop a field method for soil surveyors and field agronomists to rapidly evaluate whether or not a particular site would retain a large amount of applied phosphate, 59 samples of Andepts from Costa Rica and Guatemala were incubated with rates of P, then analyzed. Phosphate retention ranged from 25 to 99% and correlated quite well with ammonium oxalate extractable Al concentration (R2 = 0.56) in a linear model. In samples with <2.4% ammonium oxalate extractable Al, the amount of applied phosphate retained was related even better to this measurement, while at > 2.4% oxalate extractable Al, retention was not influenced appreciably by oxalate extractable Al concentration. Phosphate retention was also correlated with pH in NaF. By the methods used, >90% phosphate retention was predicted by an oxalate extractable Al concentration of >2.4% or a NaF pH of >10.7. A quick test was devised to assess soils with extremely high phosphate retention. The method consisted of adding a few drops of 0.1 mol NaF L−1 to approximately one gram of soil in a spot plate and, after 10 min, checking the pH with two drops of 0.04% thymolphythalein indicator. This technique was found to correctly identify 79% of the samples as having either ≷90% phosphate retention.
Sulfur Fertilization of Winter Wheat Grown on Deep Sandy Soils
Authors: Oates Kenneth M. , Kamprath E. J.
Published: July 2010

Surface horizons of sandy Coastal Plain soils of the southeastern United States are low in available SO−24, and crops are often dependent upon adsorbed SO−24 in the B horizon. The objective of this study was to determine the response of winter wheat (Triticum aestivum L.) to sulfur (S) fertilization on three soils which varied in depth to the B horizon; a Wagram soil (Arenic Paleudults) > 50 cm to the B, and two Norfolk soils (Typic Paleudults) 31 and 48 cm to the B. Sulfur rates covered the range from 0 to 90 kg S ha−1. Sources used were CaSO4 · 2H2O, elemental S plus bentonite (Sol‐U‐Sul) and (NH4)2SO4. Measurements were made of S concentration and N/S ratio of plants, root distribution with depth at spike emergence and grain yield at harvest. Yield response to S fertilization was obtained on the Wagram soil and the Norfolk soil in which root growth was restricted by a tillage pan but not on the Norfolk soil with the B horizon at 31 cm. A rate of 20 kg S ha−1 as SO2−4 applied in late February was adequate for optimum response. Sol‐U‐Sul applied in February was not effective. Ammonium sulfate was equally effective as CaSO4. Plants responded to S fertilization where nonfertilized plants had S concentrations of 0.6 g kg−1 dry weight and N/S ratios of 21. Response of wheat to S fertilization depended upon the depth to the B horizon and root distribution in the soil profile. No response to S fertilization was obtained on a Norfolk soil in which there was appreciable root growth in the 30‐ to 45‐cm depth. That depth contained an accumulation of SO2−4. Where root growth was essentially restricted to the top 30 cm of a Norfolk soil in which SO2‐4 accumulation started at the 45‐cm depth there was a large response to S fertilization.
Variance and Scale Influences on Classifying and Interpreting Soil Map Units
Authors: Edmonds W. J. , Baker J. C. , Simpson T. W.
Published: July 2010

Residual variance including the variance contributed by sampling and laboratory procedures, by soil profiles within circular 7‐m diam sites, by sites within delineated soil bodies, and by delineated soil bodies within each of three second‐order soil survey map units were evaluated using a nested sampling design. Residual variances were small for base saturation, clay, and free iron and large for pH, quartz in the sand fraction, kaolinite, and gibbsite in the clay fraction, and the oxidic ratio. Naming and interpreting map units using classes based on the dissection of variable with large residual variances will be confounded by the sampling and laboratory procedures. Distributions of variance for the soil properties studied revealed that mutually‐exclusive classes were not delineated by these map units. Shortrange variability in field observable soil properties was not mapped because of the constraint of scale. Therefore, users of soil survey information would be better served by procedures for naming and interpreting map units that describe the content and pattern of occurrence of soils rather than relying on classificational units or soil series defined by limits of taxa in Soil Taxonomy to convey map unit content and interpretations.
Thixotropic Changes in the Stability of Molded Soil Aggregates
Authors: Molope M. B. , Grieve I. C. , Page E. R.
Published: July 2010

Thixotropic age hardening of clays has long been familiar to civil engineers but its contribution to the stabilization of aggregates produced by cultivation has been little studied. We report changes in stability after simulated cultivation of soil samples from arable and pasture fields. The contribution of biological processes to stabilization was eliminated by sterilization and the effects of the “polysaccharide” fraction of the soil organic matter were removed by periodate oxidation. Thixotropic changes were shown to make a contribution to the age hardening process in both molded and remolded soil aggregates similar in magnitude to the contribution made by biological processes. These changes were reversible and accompanied by soil matric water potential changes. Destruction of the polysaccharide fraction of soil organic matter reduced aggregate stability and removed most of the differences between arable and pasture soils of the same series, but polysaccharides do not appear to contribute to the thixotropic aging process.
Soil Erosion Class and Landscape Position in the North Carolina Piedmont
Authors: Daniels R. B. , Gilliam J. W. , Cassel D. K. , Nelson L. A.
Published: July 2010

Soil map units in the North Carolina Piedmont are a complex of interfluves, valley slopes and foot slopes. Specific landscape positions are commonly too small to delineate on 1:15 480 or larger scale maps and most contain areas with varying degress of erosion that cannot be separated at common map scales. Munsell color hues are a good indicator of clay content of the Ap horizon and can be used as a guide to erosion class. Within Cecil map units the clay content of the Ap horizons increases from about 10 to 30% as the Munsell hue shifts from 10YR to 5YR. Within Georgeville map units the clay content of the Ap horizons increase from about 30 to > 40% as the Munsell hues change from 7.5YR to 2.5YR. The distribution of erosion classes within a soil map unit delineation varies with landscape position. Within the Cecil map units there are about equal areas of slight and severe erosion on interfluves. Shoulders and linear valley slopes are moderately to severely eroded whereas head and foot slopes (depositional areas) are usually slightly to moderately eroded. The interrelationships between landscape position and erosion class, and among landscape positions, growing season moisture and crop yield, create difficulty for quantifying the effects of erosion on soil productivity. The close relationship between landscape position and erosion class also suggests that a large variation in the original thickness of the A plus E horizons may have contributed to present distribution of erosion classes. The variability in surface properties within a map unit is not necessarily random but is related to the range of intensities of the processes that have been operating within a local landscape.
Corn Fertility Treatments and the Surface Structure of a Poorly Drained Soil
Authors: Stone J. A. , Allen N. H. E. , Grant C. D.
Published: July 2010

Fertility treatment effects on annual measurements of bulk density, total porosity, and air‐filled porosity taken from the 0.05‐ to 0.15‐m depth of a Brookston clay loam soil (clayey, mixed, mexic Typic Haplaquolls), inclusive from 1957 to 1982, were evaluated. Additional bulk density, porosity, stability, and penetration resistance measurements were made on samples taken from the 0.05‐ to 0.15‐m and 0.15‐ to 0.25‐m depths in 1983. The treatments were (i) continuous corn (Zea mays L.) with no fertilizer; (ii) continuous corn with 298 kg/ha NH4NO3 annually; (iii) continuous corn as in (ii) plus 672 kg/ha of 5–8.8–16.6 (5–20–20) annually; and (iv) a corn, oats (Avena sativa L.), and alfalfa (Medicago sativa L.) rotation receiving 168 kg/ha of 5–8.8–16.6 (5–20–20) for oats. In general, bulk density increased as total and air‐filled porosities decreased with time for all treatments. However, the rotation treatment had lower bulk densities and higher total porosities than the continuous corn treatments. There were no significant differences in bulk density or porosity among the continuous corn treatments. The 1983 stability and penetration data did not show any meaningful treatment effects. However, the stability data illustrate the weak structure of this soil. Monoculture corn appears to play a minor role in the structural deterioration of this poorly drained, weakly structured soil.
Electron Paramagnetic Resonance of Manganese (II) in Newly Humified Clover Leaves
Authors: Sonbol H. A. , Baverez M.
Published: July 2010

Clover leaves (Trifolium alexandrium L.) were humified by incubation at 30°C for 60 d. Electron paramagnetic resonance (EPR) and infrared (IR) spectra were recorded during that time. The EPR spectra of the leaves exhibited a hyperfine structure characteristic of Mn(II). The theory of the EPR experiment was discussed and the parameters of the spin Hamiltonian were determined. The A and D values of −265 and 150 Mc s−1 respectively, indicated that Mn(II) was coordinated by six oxygen‐containing functional group ligands in an appreciably distorted octahedron environment.
Characterization of Potassium Uptake and Translocation in Soybeans
Authors: Sallam A. , Scott H. D. , Brewer D. W. , Sojka R. E.
Published: July 2010

Nutrients taken up by plant roots are translocated and distributed to plant parts in order for the plant to carry on its normal functions. To understand these functions better, we developed a five compartment mathematical model which describes K translocation within soybean [Glycine max (L.) Merrill] plant parts during vegetative and reproductive growth. The instantaneous rate of change of K contents in the five‐compartment soil‐soybean system was described using mass balance equations. The seasonal dry matter accumulation, nutrient concentrations, and nutrient contents of the stems, branches, leaves, and pods were used as inputs into the model to determine the effect of growth stage on uptake and translocation parameters. Among the various plant parts, the maximum K fluxes were in the pods (0.257 g m−2 d−1) followed by the branches (0.191 g m−2 d−1), the stems (0.118 g m−2 d−1), and the leaves (0.108 g m−2 d−1). The maximum fluxes of K for the stems, branches, and leaves were reached at the same time during vegetative growth. In general, K uptake was higher during vegetative than during reproductive growth. The magnitudes of the transport coefficients were variable during the growing season. During vegetative growth the highest K transport coefficient (15.18 g m−2 d−1) was from the stem to the branches indicating that the main transport pathway of K was from the stem to the branch. During reproductive growth the highest transport coefficient (23.26 g m−2 d−1) was from the stem to the pods which means that the major movement of K between plant parts during this time was from the stem to the pod. Transport coefficients of K between the branches and pods were low. These results show that the net fluxes of K in soybeans varies with transport pathway within the plant and with plant age.
Ground Cover Estimates for Seedling Cereal Crops
Authors: Rickman R. W. , Rasmussen Paul E.
Published: July 2010

Fields sown to winter cereals are often damaged by water erosion. Erosion can be reduced if sufficient green plant or crop residue cover is present over winter. The selection of a planting date that will provide adequate overwinter cover is critical to successful management. This manuscript explains how plant cover can be predicted for any date after planting of a winter cereal from historic air temperature records. Degree‐days accumulated from planting are linearly related to cereal leaf development at 80 to 120 degree‐days per leaf. The lengths of successive leaves provide the radii of successively larger circles which are used as the basic unit for computing field cover. A plant is assumed to uniformly shade the circular area surrounding it. The area of overlap of adjacent circles is assumed to be shaded by the sum of the shading from each circle. Formulas are provided to illustrate the effect of row spacing, seeding rate, leaf size, and plant development rate on the rate and pattern of formation of cover. Comparison of calculated and observed field cover from four different growing seasons demonstrated the need for correcting the calculations for mutual shading of leaves. When mutual shading by leaves of 1% per layer of overlap is used, calculated and observed percent field cover are not different. Historic air temperature records can be used with leaf length values characteristic of a cultivar and specific field management choices to provide the latest seeding date that will provide a desired amount of field cover.
Orthophosphate Solubility Transformations and Availability from Dual Applied Nitrogen and Phosphorus
Authors: Hanson R. L. , Westfall D. G.
Published: July 2010

Knife applications of NH+4‐N and P fertilizers into common injection zones (dual N and P) have produced higher crop yields and P absorption than other N and P application methods. Enhanced solubility of the P fertilizer reaction products due to the presence of NH+4 could account, in part, for these crop responses. Greenhouse studies were conducted to characterize P reaction product solubility transformations and P availability in dual N and P injection zones. Treatments were ammonium polyphosphate (APP) + NH4OH (used to simulate anhydrous ammonia), NH4OH or KNO3 + nitrapyrin solutions injected simultaneously (dual N and P application) into four different soils (Aridic Argiustolls, Udic Argiustolls, Mollic Albaqualfs, and Typic Argiborolls). Monocalcium phosphate potentials and NaHCO3 or Bray extractable P were used to characterize P solubility and availability relationships in the injection zones. Dual application of NH4OH plus APP with and without nitrapyrin resulted in increased NaHCO3 or Bray‐extractable P in three of the four soils. The mechanisms that resulted in higher extractable P are concluded to be associated with the high injection zone pH caused by NH4OH applications. The postulated mechanisms are: (i) the initial high (alkaline) pH immediately after dual application allows formation of highly available Ca‐P reaction products as opposed to less available Al‐ and Fe‐P reaction products that exist in slightly acid soils, (ii) then the production of H+ during nitrification increases P solubility as phosphate potentials move up the dicalcium phosphate dihydrate and dicalcium phosphate isotherms, and (iii) this rapidly decreasing pH allows the soluble reaction products to persist which results in higher P availability and solubility for a longer period of time. Inclusion of nitrapyrin (a nitrification inhibitor) prolonged the time of Ca‐P reaction product persistence in the injection zone. Dual KNO3 + APP applications resulted in suppressed P availability, as compared to NH4OH + APP, apparently due to formation of less soluble reaction products. This suppressed P availability could account for the relative ineffectiveness of NO‐3 ‐N in dual application.
A Method for Preparing Small Soil Samples with Specified Bulk Densities and Water Contents
Authors: Stypa M. L. , Mayfield C. I. , Dumbroff E. B.
Published: July 2010

A centrifugation procedure is described for producing different degrees of compaction in both wet and dry soils. To ensure uniform distribution of water in the test samples, appropriate quantities of crushed ice are mixed with the oven‐dry soils 24 h prior to the centrifugation step.
Effect of Soil Thickness on Nitrogen Distribution and Use by Crested Wheatgrass
Authors: Power J. F. , Merrill S. D. , Smith S. J.
Published: July 2010

Soil thickness can affect nitrogen (N) cycling and use in several ways, particularly if the solum contains materials restrictive to root growth. Microplots of 0.093 m2 were established on a reconstructed mine soil composed of 0.2 m A horizon (Haploborolls) over 0.05, 0.30, 0.55, or 0.80 m of B and C horizon material spread over sodic (SAR 29.5) minespoil, giving soil thicknesses of 0.25, 0.50, 0.75, and 1.00 m, respectively. The area had previously been seeded to crested wheatgrass (Agropyron desertorum var. Mandan) and fertilized annually with 55 kg N ha−1. In spring 1978, the grass on eight microplots received enriched (27.5%) K15NO3 at 48.6 kg N ha−1. Grass on 16 other microplots harvested in 1979 and 1980 also received enriched 15N fertilizer in late November 1978 and commercial ammonium nitrate (NH4NO3) (50 kg N ha−1) in November 1979. After harvest in each of the 3 yr, soil in the eight microplots was excavated, and 15N enrichment in forage, roots, and soil organic N was determined. Increased soil thickness greatly increased forage and root growth, but had much less effect on N concentration in plant material. Uptake of labeled N in neither forage nor roots was greatly influenced by soil thickness, either in the year of application or the following year. Uptake of labeled N in forage the 2nd yr was only 5 to 10% of that found the 1st yr. However, uptake of soil N in both forage and roots generally increased two‐ to threefold as soil thickness increased from 0.25 to 1.00 m. Soil inorganic N and forage N concentrations suggested that available N supply was not limiting. Thus, the increase in soil N uptake probably resulted from deeper and more effective root functioning with increased soil thickness. Approximately 35% of the labeled N applied was removed in harvested forage and 12% remained in roots, regardless of soil thickness. However, the quantity of labeled N immobilized as soil organic N varied from over 40% of that applied with 0.25‐m soil thickness to about 30% for 1.00‐m thickness. Because there was no runoff or leaching, this difference was probably due to gaseous losses, possibly by ammonia volatilization from plant material.
Spatial Variability of Hydraulic Properties in the Emporia Series
Authors: Albrecht K. A. , Logsdon S. D. , Parker J. C. , Baker J. C.
Published: July 2010

Variability of soil hydraulic properties of one soil series is evaluated, observation scale effects are analyzed, and sampling requirements for series characterization are determined. One site was selected in each of four counties. Every site had four subsites about 30‐m apart. Undisturbed cores were taken in triplicate about 0.3‐m apart at each subsite and disturbed samples taken in single replicate within sampling pits at each subsite. Three depths were examined—the A, E, and Bt horizons. Coefficients of variation (CV) for moisture retention data were low ranging from 1.0 to 15.4%, while CVs of saturated hydraulic conductivities (Ks) ranged from 112 to 297%. Nested analyses of variance revealed that variance generally increased with increasing sample separation distance. The majority of the variance occurred at the site level. Numbers of samples needed to estimate means to selected confidence levels for series characterization were determined for each parameter by depth. Assuming costs to be equal between sites, subsites, and replicates, it was found that 10 to 26 sites with one subsite per site and one replicate per subsite should be sampled to adequately describe moisture retention to within 0.05 m3 m−3 and 7 to 15 sites would be necessary for Ks evaluation to within one order magnitude. Results emphasize the need to sample many sites for hydraulic properties which have most of their variance at this level.
Computer Simulation of Water Drop Impact in a 9.6‐mm Deep Pool
Authors: Ferreira Alfredo G. , Larock Bruce E. , Singer Michael J.
Published: July 2010

The interaction between impact of a 3.2‐mm drop and a water layer over the soil surface was studied by simulating drop impact through the solution of the Navier‐Stokes and continuity equations for a viscous and incompressible fluid on an Eulerian grid, using a finite difference method. The simulation was validated by experiments. The velocity field produced by the simulation showed a reversal of the velocity vectors at the time of maximum crater development, followed by crater collapse and formation of the Rayleigh jet. A comparison of measured and simulated crater and crown development showed good agreement. The energy balance from the computer simulation showed that the shear energy development along the bottom of the pool reached a maximum value during the crater collapse when the velocity vectors in the corresponding velocity field were pointing inwards and upwards.
Soil Nutrient Changes Following Whole Tree Harvesting on Three Northern Hardwood Sites
Authors: Mroz G. D. , Jurgensen M. F. , Frederick D. J.
Published: July 2010

Three northern hardwood stands were clearcut to evaluate the effect of whole tree harvesting on sites of varying quality. Stands were growing on sandy, outwash soils and had red maple (Acer rubrum L.) site indices of 15, 19, and 20 and biomass values of 114, 165, and 181 Mg ha−1. Harvesting did not alter extractable soil P levels significantly on any site. Forest floor weights decreased to similar values on all sites 1.5 yr after harvest. Nitrogen losses of over 1.3 Mg ha−1 occurred in the top meter of soil on all sites. This was attributed to the mixing of the forest floor with the surface mineral soil by the full tree skidding and the subsequent leaching of mineralized N. Soil exchangeable K decreased more than 1 Mg ha−1 on all sites. Changes in Ca and Mg were much smaller on the low and medium than on the high site. These losses from surface soil horizons are higher than reported previously for clearcutting northern hardwoods on till soils. The greatest impact of whole tree harvest on soil nutrients occurred on the better sites in this study rather than on the poor quality site.
Sodicity Levels of Soils Equilibrated with Wastewaters
Authors: Levy Rachel , Fine P. , Feigin A.
Published: July 2010

To determine the effect of NH+4, K, and Na exchange reactions concurrent with carbonate precipitation on the sodicity levels of soil effluents, samples of sandy, loessial, and clay soils were treated with two wastewaters, a secondary sewage and a liquid sludge. More calcium carbonate (CaCO3) precipitated following the liquid sludge treatment than after the secondary sewage treatment. However, the sodicity levels of the liquid sludge leachates of the three soils were almost unchanged, as compared with that of the wastewater, while those of the secondary sewage increased slightly. It was assumed that this difference was due to the higher concentrations of NH+4 and K found in the liquid sludge as compared with those in the secondary sewage. To verify this assumption, the preference for NH+4, K, and Na of the three soils was evaluated from cation exchange batch experiments; the preference for NH+4 and K was an order of magnitude higher than that for Na. At a given total salt concentration, the sodicity levels decreased as more NH+4 and K substituted for Na. The ionic activity product of CaCO3 which precipitated during the treatments with both waste‐waters had the same value and was higher than that of soil CaCO3. This difference was attributed to the inhibiting effect of the organic residues. The sodicity levels of soils equilibrated with wastewaters were affected both by NH+4 and K exchange and by the higher solubility of the precipitated CaCO3.
Effects of Phosphorus, Sulfur, Calcium Hydroxide, and pH on Growth of Annual Bluegrass
Authors: Varco J. J. , Sartain J. B.
Published: July 2010

The degree of annual bluegrass (Poa annua L.) infestation of turfgrass areas has been observed to be dependent on applied elemental sulfur (S) and phosphorus (P). The purpose of these experiments was to elucidate the effects of P, S, Ca(OH)2, and imbibitional solution pH and acid source on germination, establishment, and clipping yield of annual bluegrass in monoculture. Annual bluegrass was grown in 15‐ by 15‐cm pots filled with Myakka fine sand (sandy siliceous, hyperthermic Typic Haplaquods) in two glasshouse experiments. Treatments for Experiment I were factorial combinations of the following: 0, 250, and 500 kg S ha−1; 0, 40, and 120 kg P ha−1; and 1.5 and 2.0 cmol(+) Ca(OH)2 kg−1. Establishment and average clipping yield responded positively to applied P and Ca(OH)2, while the response to applied S was negative. The magnitude of the response to added P was dependent on S and Ca(OH)2 rates. Conversely, the magnitude of the negative response to S was dependent on P and Ca(OH)2 levels. An optimum tissue P concentration was predicted at 0.52 dag P kg−1 indicating a high requirement for P. In Experiment II, annual bluegrass emergence, establishment, and clipping yield responded in a negative linear fashion to S mixed with the 0‐ to 2.5‐cm soil depth at 0, 50, 100, and 150 kg ha−1. At this soil depth a pH range of 5.6 to 4.3 resulted from these S treatments. These results suggest that annual bluegrass stands can be reduced by acidifying the zone of seed germination using S. Under growth chamber conditions annual bluegrass seed was subjected to acid imbibitional solutions derived from either HCl, H2SO4, or H3PO4 at various pH levels. The first phase was performed at pH levels of 3.0, 4.0, 5.0, and 7.0. Nongermination of annual bluegrass seed was greatest at pH 3.0, but declined rapidly with increasing pH. Abnormal germination or emergence of the plumule only was greatest at pH 4.0 and still evident at pH 5.0. The second phase involved germination of annual bluegrass seed at pH levels of 4.3, 4.8, 5.3, and 7.0. Non‐germination of seed was minimized for this pH range so the decrease in normal germination with increasing acidity was reflected in abnormal germination levels. The decrease in radicle development under high H+ ion concentrations may be due to a loss of membrane integrity and thus, inhibition of cell division in the root tip. Annual bluegrass infestation of turfgrasses may be reduced by limiting P applications and maintaining the soil pH near 5.0, but the infested turfgrass must be tolerant of these conditions.
Soils at Prehistoric Agricultural Terracing Sites in New Mexico: II. Organic Matter and Bulk Density Changes
Authors: Sandor J. A. , Gersper P. L. , Hawley J. W.
Published: July 2010

Soil changes initiated by prehistoric cultivation in a semiarid region of southwest New Mexico are still evident about 900 yr after cultivation ceased. Bulk density increases and reductions in organic C and total N were inferred by comparing cultivated soils with nearby, similarly developed uncultivated soils. Comparisons were also made between A horizons and sediment deposits accumulated upslope of recently fallen trees. These deposits are considered analogous to fresh agricultural terrace deposits just prior to cultivation. Depth of cultivation‐induced changes varies but is generally limited to the upper solum. Mean bulk density of cultivated A horizons is 9 and 15% higher than that of uncultivated A horizons and recent sediment deposits, respectively. Cultivated soils are lower in organic C than uncultivated soils by 45, 38, and 32% in the A, BAt, and Bt horizons, respectively. The trend continues through the Bt horizon but is not statistically significant at p < 0.05. Recent sediment deposits tend to be higher in organic C than uncultivated soils and are 54% higher than cultivated A horizons. Total N data give results similar to that of organic C. The significant negative correlation between organic C and bulk density in uncultivated A horizons is not present in cultivated A horizons as values tend to group around a narrower range of lower organic C and higher bulk density values. The long‐term degradation of these cultivated Mollisols is attributed to their sensitivity to disturbance.