bluuebunny/crossref_metadata_2025 huggingface dataset:
Fulvic Acid Ultraviolet‐Visible Spectra: Influence of Solvent and pH
Authors: Baes A.U. , Bloom P. R.
Published: July 2010

The ultraviolet‐visible spectra of three fulvic acids from a Mollisol (FA1), a Histosol (FA2), and a Spodosol (FA3) were determined using four solvents: 0.05 M NaHCO3, distilled water, 95% (v/v) ethanol, and absolute ethanol. Light scattering was evaluated by varying the distance of the sample cell from the detector. This test, which gave positive results for a dilute milk sample, showed no light scattering effects for the fulvic acids. The ratios of 465 to 665 nm absorbances (E4/E6 ratios) determined in 0.05 M NaHCO3 were 16.7 for FA1, 16.8 for FA2, and 18.5 for FA3. The ultraviolet spectra in water showed only slight inflections for FA1 and FA3, but the FA2 spectrum had a pronounced shoulder centered at about 280 nm. In ethanol, the shoulder was shifted towards the red and absorbance decreased. Similar red shifts were shown to occur in 2,3‐; 2,4‐; and 2,6‐dihydroxybenzoic acids (DHB). The absorbance of bands in the range of 26 to 290 nm obeyed the Beer‐Lambert law. Estimates of molar absorptivities ranged from 2300 to 4500 L mol−1 cm−1, which is within the range of molar absorptivities of the electron transfer (ET) bands of carboxyphenols. Shifts in the position of the shoulders with pH, in both water and 95% ethanol, resembled that of carboxyphenols. Absorbance at visible wavelengths was not consistent with the behavior of simple quinones but might be due to chromophores with extended conjugation, possibly polyaromatic structures. Another possibility considered was intramolecular electron donor‐acceptor complexes.
Fluorescence Spectroscopy of Aqueous Leaf Litter Extracts and Their Complexes with Aluminum
Authors: Shotyk William , Sposito Garrison
Published: July 2010

Fluorescence spectroscopy is a sensitive method for discriminating among humic substances both in structure and in provenance. This study was conducted to determine whether the same is true for an important nonhumic organic material, the water‐soluble fraction of forest leaf litter. Aqueous extracts of leaf litter from three tree species [chestnut (Castanea sativa L. Miller), western white pine (Pinus monticola Douglas ex. D. Don), and willow (Salix spp.)] were examined by conventional excitation and synchronous‐scan excitation fluorescence spectroscopy. The spectra obtained varied with the plant source of the leaf litter extract (LLE) as well as with the LLE concentration. This sensitivity to organic‐matter origin indicates that fluorescence spectroscopy will be useful to distinguish among LLE of differing provenance. The synchronous‐scan spectra of the LLE showed some peaks that decreased in relative intensity with increasing LLE dilution, and some that increased with increasing dilution. This behavior was attributed to the presence of both Type I fluorophores, which are not quenched because they do not form charge‐transfer complexes with nonfluorescent constituents of the LLE, and Type II fluorophores, which are quenched by the formation of charge‐transfer complexes and self‐quenching processes, leading to intensity increases at high dilution. Synchronous‐scan excitation spectra also were obtained for Al/LLE mixtures at pH 4.5, with the total Al concentration varying from 0 to 60 mmol m−3. The spectra showed that Al‐complex formation may result either in increases of relative fluorescence intensity or in fluorescence quenching, depending both on the source of LLE and on its concentration. This result may reflect a concentration dependence of charge‐transfer complex formation and the possibility that excited‐state complexes of Al are less fluorescent than ground‐state Al complexes.
Residual Effects of Various Phosphorus Application Methods on Winter Wheat and Grain Sorghum
Authors: Sander D. H. , Penas E. J. , Eghball Bahman
Published: July 2010

The amount of residual P from previous applications and the performance of fertilizer P can be affected by application method. This study was conducted to determine the effects of different methods of P application on grain yield, yield components, fertilizer‐P efficiency, P‐utilization efficiency (kg grain per kg P uptake), and residual P in two cropping systems — a wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] system on Pawnee soil (fine, montmorillonitic, mesic Aquic Argiudoll) and a wheat‐fallow‐wheat system on Keith soil (fine‐silty, mixed, mesic Typic Argiustoll). Methods of P application to wheat included broadcasting and knifing in the fall and spring, and seed placement. Phosphorus applied to wheat and its residual effects were determined on sorghum following wheat and wheat following fallow. On sorghum, spring row and knife‐applied P methods were compared with residual treatments. For wheat production, P knifed in the fall and seed application were equally effective. Both were more effective than other application methods for grain yield, P uptake, and fertilizer efficiency. Fertilizer efficiency was increased from 5.5% for broadcast to 36% for knifed and 40% for seed application. Spring knifed and row applications of P were equally effective for sorghum. Knifed P, placed below tillage depth with little disturbance of the band area, resulted in greater residual value for grain sorghum following wheat than either seed or broadcast P. In the wheat‐fallow‐wheat system, the knifed spring P, which had the shortest time of soil contact, had significantly greater residual value than other methods. Wheat had much higher fertilizer‐uptake efficiencies, but was only about half as effective as sorghum in P‐utilization efficiency. This study indicated that undisturbed fertilizer P bands have more residual value than either seed‐placed or broadcast P, which can differentially influence the P‐fertilizer requirement for succeeding crops.
Phosphorus Chemistry and Mineralogy in Excessively Fertilized Soils: Solubility Equilibria
Authors: Pierzynski G. M. , Logan T. J. , Traina S. J.
Published: July 2010

Eleven samples representing six soil series were selected for this study of excessively fertilized soils. Phosphorus sources included fertilizers, sewage sludges, and manures. The samples had Bray Pl extractable P levels ranging from 29 to 640 mg P/kg and 1:1 soil/water pH values ranging from 5.4 to 7.4 The equivalent of 25 g of dry soil and 50 mL of water were incubated at 298K. Samples were sacrificed for analysis periodically during the 130‐d test period. The activities of most ions, as estimated with GEOCHEM, were relatively constant throughout the course of the experiment. The concentrations of organic and inorganic C for samples that had been amended with sewage sludges or manures varied considerably during the course of the experiment. Samples that produced high supernatant pH values (>6.8) generally were more soluble than hydroxyapatite and less soluble than octacalcium phosphate and were slow in attaining constant ion activity products relative to the Ca phosphate minerals considered. Samples that produced low supernatant pH values (<6.8) indicated an equilibrium with the amorphous analog of variscite throughout the experiment.
Fluoro‐Aluminum Complexes on Model and Soil Exchangers
Authors: Anderson M. A. , Zelazny L. W. , Bertsch P. M.
Published: July 2010

A number of investigators have suggested that complexes may exist as discrete species on the exchange phase and, thus, be important to a complete description of exchange reactions. Little evidence establishing the presence of complexes on the exchange phase has hitherto been provided, however. Adsorption experiments in which µM F solutions were equilibrated with K‐, Ca‐, and Al‐saturated cation‐exchange resins demonstrated substantial F removal to the Al‐saturated resin, with the adsorbed F quantitatively recovered with a single wash with 1.0 M NH4Cl, whereas no F removal was observed when either K or Ca occupied the exchange sites. Removal of both Al and F from Al‐F solutions equilibrated with K‐ and Ca‐saturated resins provided additional evidence for adsorption as fluoro‐Al complexes. Modeling of the competitive complexation‐exchange reactions with MINTEQA2 yielded results that under‐predicted net Al sorption in the presence of F, and thus also inaccurately predicted solution composition, by neglecting potential adsorption of fluoro‐Al complexes. Kaolinite (KGa‐2) samples also sorbed appreciable F, though both surface OH displacement and sorption to exchange‐phase Al were apparently responsible for the observed decrease in F solution concentrations. In the absence of exchange‐phase Al, however, all sorbed F was fixed against displacement by 1.0 M NH4Cl. Samples of a Fuquay soil (loamy, siliceous, thermic Arenic Plinthic Paleudult) profile from South Carolina were also extracted with water, 0.01 M CaCl2, and 1.0 M NH4Cl; no detectable F was found in the water extracts, while considerable F was solubilized in the CaCl2 and NH4Cl extracts, with NH4Cl‐extractable F being highly correlated with exchangeable Al (r2 = 0.98). These results suggest that part of the Al on the soil exchange phase may in fact exist as fluoro‐Al complexes, and also imply a role of exchange‐phase Al in regulating apparent F solubility within acid soils.
Decomposition of Wood‐Residue Amendments in Revegetated Bentonite Mine Spoils
Authors: Schuman G. E. , Belden S. E.
Published: July 2010

Restoration of decomposition processes in revegetated mine spoils is important in ensuring the long‐term success of their reclamation. This study was conducted to determine the decomposition of ponderosa pine (Pinus ponderosa Laws) wood residue amendments in a revegetated saline‐sodic bentonite mine spoil. A buried‐litter‐bag technique was used to assess the effect of wood‐residue amendment and N‐fertilizer rates on the decomposition of wood residue in revegetated bentonite spoils. Decomposition differed significantly between years and averaged 8.8, 10.4, 16.1, and 25.3% after 1, 2, 3, and 5 yr, respectfully, across all wood‐residue treatments. Decomposition increased significantly as N‐fertilizer rates increased, averaging 10.6, 14.3, 18.8, and 20.8% over 5 yr for the 0, 2.5, 5.0, and 7.5 kg N Mg−1 of wood residue treatments, respectively. Wood‐residue amendment rate did not significantly influence decomposition, even though it significantly increased spoil water content. Decomposition processes appear to be proceeding despite the unfavorable physical and chemical characteristics of the spoil and should ensure the reclamation success of these disturbed ecosystems.
Comparisons of Humic Substances Extracted from Contiguous Alfisols and Mollisols of Southwestern Ohio
Authors: Novak J. M. , Smeck N.E.
Published: July 2010

Humic and fulvic acids extracted from contiguous Alfisols and Mollisols were characterized to determine if any dissimilarities could be documented between humic substances extracted from soils formed under nearly identical environmental conditions, but belonging to different taxonomic classes. Comparisons of humic substances from two Alfisol‐Mollisol pairs, one from the Wisconsinan and one from the Illinoian till plain of southwestern Ohio, were based on wet chemical, infrared, and 13C cross‐polarization magic angle spinning nuclear magnetic resonance (CPMAS NMR) spectroscopy studies. Using 0.1 M NaOH, more humic substances were extracted from the Mollisols than the Alfisols, with the majority being humic acids. Small amounts of fulvic acids were recovered from all pedons. Data from infrared and 13C CPMAS NMR spectroscopy indicate that humic acids from both the Alfisols and Mollisols are dominated by alkyl‐substituted aromatic structures, followed by aliphatic, O‐substituted alkyl, carboxylic acid, and small amounts of carbonyl structures. Whereas 13C NMR spectroscopy data suggest Mollisol humic acids contain higher aromatic and carboxylic acid contents than those of the Alfisols, Alfisol humic acid spectra show more evidence for phenolic‐OH groups and lignin and lignin‐like products than those of the Mollisols. Fulvic acids from Alfisols and Mollisols contained mostly aliphatic, O‐substituted alkyl, and carboxylic acid, followed by aromatic groups and small amounts of carbonyl groups. The proportion of nonaromatic and aromatic structures in the fulvic acids of the Alfisols and Mollisols was similar, but slight differences were noted in elemental ratios and 13C NMR spectra. Although only minimal differences were noted among fulvic acids, differences were evident in the chemical and structural properties of humic acids from contiguous Alfisols and Mollisols in southwestern Ohio.
Tillage, Soil Depth, and Precipitation Effects on Wheat Response to Nitrogen
Authors: Rasmussen P. E. , Rohde C. R.
Published: July 2010

Wheat (Triticum aestivum L.) response to N in semiarid climates is highly influenced by precipitation and tillage, leading to inefficient use of fertilizer and greater potential for groundwater contamination. To improve fertilizer recommendations, we measured white winter wheat response to 45, 90, 135, and 180 kg N ha−1 for 10 crops grown in a wheat‐fallow rotation with three tillage treatments, one conventional (moldboard plow) and two stubble‐mulch (offset disk, subsurface sweep). The soil was a Walla Walla silt loam (coarse‐silty, mixed, mesic Typic Haploxeroll) with three depths to bedrock (208, 132, and 111 cm). Grain yield averaged 5.51, 4.07, and 3.55 Mg ha−1 with above‐ (147), near‐ (88), and below‐normal (61 mm) growing‐season precipitation (GSP). Nitrogen increased yield 3.0, 1.9, and 0.4 Mg ha−1 in these precipitation regimes. Grain yield was not affected by soil depth when GSP was above normal, but 10 to 20% less on the shallower soils when GSP was below normal. There was a trend towards higher yield with conventional tillage when GSP was above normal. The amount of applied N required for optimum yield was >135 kg N ha−1 with above‐normal GSP and <45 kg N ha−1 with below‐normal GSP. Excess N decreased grain yield when GSP was near normal, but not when above or below. Applied N increased straw yield curvilinearly, with little influence of tillage or soil depth. Straw/grain ratio averaged 1.53 and 1.70 on the 208‐ and 111‐cm soils, respectively. Nitrogen uptake tended to be greater in conventional than in stubble‐mulch tillage, and was not affected by soil depth. Grain protein exceeded the desirable level for white wheat only when applied‐N was above that needed for optimum yield. Precise selection of the amount of N to apply each year was difficult because of the strong influence of GSP on yield and the need to apply N before GSP is known.
Land Clearing and Use in the Humid Nigerian Tropics: I. Soil Physical Properties
Authors: Ghuman B. S. , Lal R. , Shearer W.
Published: July 2010

Soil physical properties are affected by land clearing use. Long‐range planning in the humid tropics requires monitoring of these effects for an extended period of time. The effects of two land‐clearing methods and six land‐use systems on soil physical properties of an Ultisol were studied for 4 yr in the humid coastal belt of Nigeria. The land‐clearing methods were bulldozer clearing with a shear blade and manual clearing. The six land‐use systems were comprised of cassava (Manihot esculenta Crantz)‐based cropping, oil palm (Elaeis guineensis Jacq.)‐based cropping, alley cropping, plantain (Musa spp.), pasture, and improved forestry, all under no‐tillage. Soil physical properties were measured 90 d after clearing prior to planting, and at 2 and 4 yr after cropping. The soil texture of the 0–10 cm layer was not affected by clearing methods. Soil compaction increased to 30 cm with shear blade and 20 cm with manual clearing. With respect to the forested control, shear blade and manual clearing increased the bulk density in the 0‐ to 10‐cm layer by 22 and 14%, respectively. The bulk density in the surface layer after 2 yr of cropping was significantly more for the pasture than the other systems. Three months after clearing, the steady infiltration rates were 89, 20 and 32 cm h−1 in the forested control, and shear‐blade and manually cleared plots, respectively. Infiltration rate increased to 47 and 51 cm h−1 in the shear‐blade cleared and increased to 290 and then decreased to 156 cm h−1 in the manually cleared plots after 2 and 4 yr of cropping, respectively.
Land Clearing and Use in the Humid Nigerian Tropics: II. Soil Chemical Properties
Authors: Ghuman B. S. , Lal R.
Published: July 2010

A 4‐yr study was conducted to investigate the effects of land clearing and subsequent land use on chemical properties of an Ultisol at Okomu, southern Nigeria. After 1 yr of cropping, soil pH, available P, and exchangeable Ca, Mg and K in the topsoil (0–10 cm) were significantly higher in the windrow zones of the shear‐blade‐cleared plots than in the nonwindrow zones, manually cleared plots, or forested control. In manual clearing, the organic‐C and total‐N contents declined below that of the forested control with 3 yr of cropping. Soil pH after 4 yrs and exchangeable K after 2 and 4 yr of cropping were significantly higher in the pasture system than in the other systems. In a given system, pH, organic C, and available P decreased with cropping time. Total N decreased with cropping time in all systems but pasture where there was a little increase. The levels of exchangeable Ca+2 and Mg+2 also decreased with cropping duration in all systems except the alley cropping in which their concentrations increased. The K+ content decreased with time in all systems but the pasture in which its level remained unchanged owing to returning of the hay to the field after cutting.
Uptake of Point‐Injected Nitrogen by Winter Wheat as Influenced by Time of Application
Authors: Janzen H. H. , Roberts T. L. , Lindwall C. W.
Published: July 2010

Conventional methods of N application to winter wheat often lead to low fertilizer‐use efficiency. Point injection may improve fertilizer efficiency but the optimum time of application has not been established. A field experiment was conducted during two growing seasons at Lethbridge, AB, Canada, on a Typic Haploborall sandy clay loam to determine 15N‐fertilizer uptake as a function of application time and method. The experiment included a factorial of three methods (point‐injected urea‐NH4NO3, broadcast urea, and broadcast NH4NO3,) and four application times (at seeding, late fall, early spring, and late spring) along with two banding treatments (urea and NH4NO3) applied at seeding and a control. For all methods of application, efficiency of fertilizer tended to be highest when applied in early spring. In the point‐injection treatments, average recovery of applied N by wheat was 32% for the seeding, 43% for late fall, 56% for early spring, and 29% for late spring applications. At the optimum time of application, point injection exhibited significantly higher fertilizer recovery than broadcast applications, probably because of direct placement of N into the rooting zone. Fertilizer recovery from banding treatments applied at seeding was lower than from early‐spring point injection, presumably because of overwinter N losses. The results suggest that point injection can significantly enhance fertilizer‐use efficiency and that optimum time of injection is in the early spring just prior to the period of maximum N assimilation by the crop.
Dinitrogen and Nitrous Oxide Flux from Urea Basally Applied to Puddled Rice Soils
Authors: Buresh R. J. , De Datta S. K. , Samson M. I. , Phongpan Sakorn , Snitwongse Patoom , Fagi A. M. , Tejasarwana R.
Published: July 2010

Nitrification‐denitrification is often regarded as an important N loss process in puddled rice soils, but few direct field measurements of denitrification loss have been reported. Field studies were conducted on a Typic Tropaquept in Thailand, an Aeric Tropaqualf in Indonesia, and an Andaqueptic Haplaquoll in the Philippines to measure (N2 + N2O)‐15N flux, (N2 + N2O)‐15N trapped in soil, and total gaseous 15N loss following basal application of 15N‐labeled urea (87 kg N ha−1) to irrigated rice (Oryza sativa L.) grown on puddled soils. Urea treatments included broadcast applications with and without incorporation to 0.07‐m soil depth. Directly measured (N2 + N2O)‐15N flux during the 10 d following urea application by each method was less than 0.1% of the applied N at the Thailand and Indonesia sites. The (N2 + N2O)‐15N collected from the soil after 10 d did not exceed 0.02% of the applied N. Total gaseous N loss determined from a 15N balance at 10 d after N application without incorporation was 34% of the applied N in Thailand and 31% in Indonesia. Incorporation reduced total N loss to 22% in Thailand and 10% in Indonesia. In the Philippines, the measured (N2 + N2O)‐15N flux during the 15 d immediately following urea application with incorporation was 2.2% of the applied N with chambers placed between rice plants and 3.0% with chambers over the plants. Total N loss at the Philippine site was 40% of the applied N. Ammonia volatilization appeared to be much more important than nitrification‐denitrification as a mechanism of urea‐N loss at the three irrigated lowland study sites.
Chromate Reduction by Subsurface Soils under Acidic Conditions
Authors: Eary L. E. , Rai Dhanpat
Published: July 2010

Experimental studies of Cr(VI) reduction by five subsoils (Holston‐Cloudland, Kenoma, Cecil‐Paculet, Watson‐Alvira, and Ocala) were conducted to determine whether the Fe(II) contained in soil minerals could cause Cr(VI) to be reduced to Cr(III) and precipitated as hydroxide solids. All of the subsoils contained small amounts of Fe(II) and organic matter, but only the acidic subsoils (1:2 soil pH = 4.2‐4.3) caused Cr(VI) reduction at their natural pH values. Rates of Cr(VI) reduction by four of the subsoils increased with a decrease in pH below 4.0. Consideration of available kinetic information, coincidental timing of Cr(VI) disappearance and Fe(II) appearance in solution, and observed reaction stoichiometries indicate that Cr(VI) reduction by Fe(II) species is of equivalent importance as reduction by organic material under acidic conditions. Chromium(VI) reduction in the acidic subsoils resulted in the precipitation of (Fe,Cr)(OH)3(am), depending on the solution pH. The amount of NH2OH·HCl‐extractable Fe in the acidic subsoils was found to be useful for determining the mole fraction of Fe(III) in the (Fe,Cr)(OH)3(am) solid solution, allowing prediction of Cr(III) concentrations in acidic solutions to within a logarithmic unit of those observed in experimental soil‐water suspensions.
Sodium‐Calcium Exchange with Anion Exclusion and Weathering Corrections
Authors: Amrhein C. , Suarez D. L.
Published: July 2010

In order to accurately model soil reclamation with concentrated electrolytes such as CaCl2 or sea water, it must be determined if there is an effect of salinity on the Na‐Ca exchange selectivity. A new procedure for determining Na‐Ca selectivity in calcareous and gypsiferous soils was used to study the effects of ionic strength and mineralogy on Na‐Ca exchange. Four specimen clay minerals and three whole soils were equilibrated with solutions ranging in concentration from 10 to 1000 mmolc L−1 and at Na adsorption ratios from 1 to 50 (mmol L−1)1/2. Exchangeable‐cation values were corrected for calcite and gypsum dissolution as well as anion exclusion. The selectivity data were compared with other reported values for Na‐Ca exchange in order to determine if there were any trends in selectivity with mineralogy or surface charge density. Generally, Na‐Ca selectivity was independent of ionic strength. Vermiculite exhibited near‐ideal exchange when compared with the nonpreference isotherm. There was no effect of mineralogy on the Na‐Ca selectivity, even though the soils and minerals had various surface charge densities. The Gapon selectivity coefficients (KG) for the calcareous Many Farms soil (a mesic Torrifluvent) and the gypsiferous Shiprock soil (a mesic Torriorthent) averaged 0.011 and 0.013 (mmol L−1)−1/2, respectively. Failure to correct for anion exclusion and mineral weathering lowered these average KG values to 0.0085 and 0.0064, respectively. The data were compared with the Vanselow (Kv = 4.3), nonpreference (Kv = 1.0), Gapon (KG = 0.015), and the diffuse double‐layer (DDL) models. After the review of the problems associated with the various methods of determining exchangeable cations, we recommend that the alcohol rinse method to remove soluble salts not be used.
Microbial Biomass and Soil Structure Associated with Corn, Grasses, and Legumes
Authors: Drury C. F. , Stone J. A. , Findlay W. I.
Published: July 2010

Maintaining long‐term soil productivity requires development of cropping systems that provide maintenance or improvement in soil structure and an understanding of associated rhizosphere microbial populations. The objectives of this study were to determine the effects of several crops on soil biomass C and biomass N contents, their within‐season variability, and the relationships between changes in soil biomass C, biomass N, and soil structure on a Brookston clay loam soil (fine‐loamy, mixed, mesic Typic Argiaquoll). Soil microbial biomass C, biomass N, and soil‐structure parameters (wet aggregate stability [WAS], organic carbon [OC], dry aggregate mean weight diameter [MWD], bulk density, and total and air‐filled porosity) were measured during the third year of corn (Zea mays L.), soybean (Glycine max [L.], Merr.) alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), reed canarygrass (Phalaris arundinacea L.), orchardgrass (Dactylis glomerata L.), and no‐crop (bare, covered, and shaded) plots at monthly intervals (June, July, August, and September). Reed canarygrass resulted in greater biomass‐C contents than both the corn and soybean at all four sampling dates. Soil biomass C under alfalfa was significantly greater than under corn and soybean for both the first and last sampling dates. Forage species did not affect the soil biomass‐N content. No consistent effects of the no‐crop treatment on biomass C or biomass N were observed between sampling dates. Biomass C was significantly correlated with WAS, OC, and MWD for the cropping treatments. Wet aggregate stability was negatively correlated with soil water content for both the no‐crop and cropping treatments, indicating that improvements in structure were not solely the result of the cropping treatments and associated rhizosphere populations. Reed canarygrass resulted in greater soil biomass C/N than the alfalfa, corn, and orchard grass plots, suggesting that fungal activity, and therefore soil structure, may be preferentially enhanced in the presence of reed canarygrass. This study demonstrated the influence of forage species and seasonal variability on concurrent changes in microbial biomass and soil structural properties.
Loblolly Pine Seedling Response to Fertilizer and Lime Treatments on a Spodosol
Authors: Coultas C. L. , Hsieh Y. P. , McKee W. H.
Published: July 2010

Loblolly pine trees (Pinus taeda L.) grow poorly on the Spodosols of the mid‐Atlantic Coastal Plain. This greenhouse study was undertaken to determine the effects of N, P, S, micronutrients, and lime on the growth of Loblolly pine seedlings in the Al horizon of a Lynn Haven fine sand (sandy, siliceous, thermic Typic Haplaquod). Nitrogen, and N‐P in combination resulted in increased growth of the pine seedlings. A small application of CaCO3 (2337 kg/ha) resulted in reduced growth and increased foliage necrosis. This negative effect was overcome by N applications. Micronutrients alone had little effect on growth and the foliage concentrations were adequate with all treatments. Sulfur treatment had a slight effect on plant growth but, with S, foliage N was increased from 17.5 to 19.0 g/kg. Aluminum concentrations were determined to be at nontoxic levels in this soil horizon. We postulate that the negative effect of CaCO3 on plant growth was due to reduction of available N. The mechanism for this result has yet to be elucidated.
Soil Permeability in an Ammonium and Phosphorus Application Zone
Authors: Myers R. , Thien S. J.
Published: July 2010

Soil organic matter plays a primary role in the development and maintenance of aggregate stability necessary for good soil permeability. Studies showing that some N and P fertilizers dissolve soil organic matter raise questions about effects these fertilizers have on permeability. In this work, filtration rates (FR) in Kennebec silt loam (fine‐silty, mixed, mesic Cumulic Hapludoll) were monitored after addition of NH4OH and NH4 phosphates to determine whether organic‐matter dissolution occurring after fertilizer application affected soil permeability. Twenty combinations of NH4OH and either monoammonium phosphate (MAP) or triammonium pyrophosphate (TPP) were applied to soil columns 70 mm in diameter. The columns were incubated for 0.5, 1, 2, 4, 8, 16, or 32 d at 35 °C. Soil from the application zone was removed from the column and analyzed. Increasing NH4OH levels usually decreased FR. Compared with FR when no NH4OH was applied, NH4OH levels of 1500, 3000, and 6000 mg kg−1 reduced FR 20, 30, and 33%, respectively. Treatments including P had variable effects on permeability. With the following P sources and levels (mg P kg−1): 0 P, 300 MAP‐P, 300 TPP‐P, 600 MAP‐P, and 600 TPP‐P, average FR (1 + log mL min−1) were 2.13, 1.99, 1.88, 2.25, and 1.72, respectively. The NH4OH and P treatments dissolved between 0.1 and 4.8% of the total organic matter in the analyzed samples. Increases in dissolved organic matter were highly correlated with decreases in FR (R2 = 0.78‐0.98). Increased dissolution of organic matter increased soil dispersion and lowered permeability in the application zone.
Corn Uptake and Soil Accumulation of Nitrogen: Management and Hybrid Effects
Authors: Ferguson R. B. , Schepers J. S. , Hergert G. W. , Lohry R. D.
Published: July 2010

Inefficient use of fertilizer N by corn (Zea mays L.) can result in the accumulation of excessive amounts of NO‐3 subject to leaching losses in the crop root zone. The fate of fertilizer N as influenced by N rate, nitrapyrin [2‐chloro‐6‐(trichloromethyl)pyridine], and corn hybrid was evaluated in a 3‐yr study with sprinkler‐irrigated corn. Variables were fertilizer‐N rate (75, 150, and 300 kg N/ha); nitrapyrin (0 and 0.5 kg/ha); and corn hybrid (Pioneer hybrids 3377, 3475, and 3551). Nitrogen was applied as late‐sidedressed (V6‐V9) NH3. The fate of fertilizer N was evaluated by measurement of apparent fertilizer‐N uptake (AFU), form of N in the fertilizer band prior to and following anthesis, and accumulation and distribution of N in the soil profile. There were no significant effects of hybrid on AFU across years, and no significant hybrid × nitrapyrin interactions on AFU. Nitrapyrin significantly reduced AFU across N rates and hybrids in 2 of 3 yr. Nitrate‐N concentrations in the fertilizer band, in the presence of nitrapyrin, were reduced prior to anthesis in 1986. Higher NH+4‐N concentrations in the fertilizer band in 1986, as well as trends towards higher total inorganic‐N concentrations all 3 yr following anthesis, suggest mineralization of temporarily immobilized fertilizer NH+4. Reduced AFU in the presence of nitrapyrin in 1986 and 1987 indicates reduced availability of fertilizer N consistent with a temporary immobilization process. Nitrate accumulation in the soil to a depth of 1.8 m after three growing seasons indicates a trend toward less NO‐3 accumulation where nitrapyrin was applied at N rates of 75 and 150 kg/ha. Nitrate concentrations in the soil at a depth of 1.8 m were significantly greater at the 150 and 300 kg N/ha rates, compared with the 75 kg N/ha rate or unfertilized soil, indicating probable movement of fertilizer N below the 1.8‐m depth at the higher rates. These results indicate that nitrapyrin should not be applied with NH3 at late‐sidedress time for this soil.
Variability of an Unsaturated Sand Unit Underlying a Radioactive‐Waste Trench
Authors: Healy Richard W. , Mills Patrick C.
Published: July 2010

Properties of soils vary considerably within any field. This study was conducted to investigate the variability in properties of an unsaturated sand unit that lies at a depth of 13 m below land surface. Four‐hundred‐forty soil core samples, obtained from a 1.75 by 18‐m horizontal plane within a sand unit underlying a waste trench, were used to describe the variability of moisture content, tritium concentration, and several physical properties. A simple model based on unit‐gradient theory was used to calculate fluxes of water and tritium through the study plane. The effects of including spatial variability of properties in model calculations were examined. The sand was uniform in terms of median particle size, bulk density, and proposity, but several variables, including saturated hydraulic conductivity (Ks) and tritium concentration, showed considerable variability. In general, correlation coefficients calculated between variables were low. Spatial correlation structures were identified for moisture content, tritium concentration, and a few particle‐size variables, but were absent for Ks and most other variables. Variances of Ks and field‐measured volumetric moisture content (θ) were lower than published values for soils. Model‐calculated fluxes of water and tritium that accounted for spatial variability of properties were considerably higher than those that did not account for the variability. Model results were more sensitive to changes in θ and residual moisture content (each parameters of the relative hydraulic conductivity function) than to changes in Ks.
Hydraulic Conductivity of Saprolite as Determined by Channels and Porous Groundmass
Authors: Vepraskas M. J. , Hoover M. T. , Jongmans A. G. , Bouma J.
Published: July 2010

Saprolite (weathered bedrock) is being evaluated in some regions for use in on‐site disposal of household wastewater. As part of this evaluation, contributions of channels and planes to the saturated and unsaturated hydraulic conductivities were estimated for a mica‐schist saprolite. Undisturbed cores (76 mm in diam. by 76 mm in height) were collected from a 5‐ha forested site. Cores were oriented both vertically and parallel to saprolite foliation, and some contained continuous shear planes. Saturated hydraulic conductivity (Ksat) was measured on all cores, and then a dye tracer was passed through the cores. Unsaturated hydraulic conductivities were estimated for nine additional core samples. Volume percentages of dyed (water‐conducting) and undyed components, channels, groundmass, and other characteristics were determined from thin sections made from all dyed core samples. The Ksat values ranged from 0.01 to 1.71 cm h−1 and had a geometric mean of 0.27 cm h−1. Channels (primarily 0.1–0.5 mm in diam.) comprised 1.9% of the sample volume and accounted for 93% of the Ksat. At a soil water potential of −10 cm, 50% of the K value was due to flow through channels. The channels conducted no water when the soil water potential was ≤‐30 cm and the hydraulic conductivity was ≤0.02 cm h−1. Foliation planes and shear planes were plugged with Fe‐Mn oxides or clay, and their effect on hydraulic conductivity was negligible.
Effect of Chloride Ions on Sodium‐Calcium and Sodium‐Magnesium Exchange on Montmorillonite
Authors: Sposito Garrison
Published: July 2010

Recent theoretical and experimental studies of the effect of Cl− ions on Na‐Ca and Na‐Mg exchange reactions with montmorillonite have produced conflicting data and conceptual models. A discussion is given of three of the key issues involved in this controversy with the objective of posing them more precisely as a guide to future research. The importance of clay mineral suspension characteristics (mineral purification, particle‐size fraction, suspension density) is emphasized, and a charge balance condition on the surface excesses of Na+ and CaCl+ or MgCl+ species is pointed out. The role of anion exclusion in generating differences of adsorbed metal charge between Na‐ and either Ca‐ or Mg‐montmorillonite also is clarified as it relates to exchange reactions in Cl− vs. ClO−4 ionic media.
Nitrogen Mineralization: Root and Microbial Interactions in Pitch Pine Microcosms
Authors: Tate Robert L. , O'Reilly Laurie , Parmelee Robert W. , Ehrenfeld Joan G.
Published: July 2010

In forest ecosystems, mineralization of native organic N provides the primary plant N nutrient source. The rate of this N mineralization is affected directly and indirectly by interactions with plant root biomass and is also probably impacted by interactions with the soil microbial community. Thus, the objectives of this study were to evaluate the relationship of N‐mineralization rates in an acid forest soil (Lakehurst sand, a mesic, coated Haplaquodic Quartzipsamment) with microbial metabolic and enzymological activities and to determine the impact of proximity to the growing roots of pitch pine (Pinus rigida Miller) on these interactions. Potential proteolytic activity, amino acid metabolism, N mineralization, microbial growth rate, glucose metabolism, and microbial biomass N were measured in microcosms planted with varying densities of pitch pine seedlings. Nitrogen mineralization, amino acid metabolism, and proteolytic activity in the organic‐matter‐poor A horizon soil were 0.01 to 0.5 of the levels in the organic‐matter‐rich O horizon of the soil. After 21 to 22 wk of growth of pine seedlings in the soil, amino acid metabolic rates in the O horizon soil were not affected by root mass. Amino acid metabolism rates declined between 10 and 25% in soils from the A horizon with increasing root density. Proteolytic activity was reduced between 10 and 50% in both soils due to root growth. In the O horizon soil, amino acid metabolic rates correlated with microbial growth rate, glucose metabolism, and microbial biomass C and N, but not with protease activity in both rhizosphere and near‐rhizosphere soils. Proteolytic activity varied independently of microbial growth rate, glucose metabolism, and biomass C and N. Except for a highly significant relationship to microbial growth rate, net N‐mineralization rates were not correlated with the measured microbial and enzymological activities. Glucose metabolism and microbial biomass N correlated with protease activity in rhizosphere soils, but not in near‐rhizosphere soils; otherwise, proximity to the pine tree roots had little effect on the relationship of N‐metabolism parameters in the acid soils used in this study.
Topsoil Depth, Fertility, Water Management, and Weather Influences on Yield
Authors: Thompson A. L. , Gantzer C. J. , Anderson S. H.
Published: July 2010

The productive capacity of a soil is generally related to topsoil depth. This study was conducted to determine the influence of topsoil depth, soil fertility, and water management on grain yield for corn (Zea mays L.) and soybean (Glycine max [L.] Merr.). A field experiment at Columbia, MO, was initiated in 1983 and maintained through 1987 on a Mexico silt loam (fine, montmorillonitic, mesic Udolic Ochraqualf). The study was conducted using a split‐plot experiment for each crop. Main effects included topsoil (depth to claypan), soil fertility, and water management. Desurfaced plots were constructed having topsoil depths of 0, 125, 250, and 375 mm. Plots were either fertilized according to soil‐test recommendations or unfertilized. Water management was either rain fed or with supplemental irrigation. Overall, corn yield was 5.7 times more sensitive than soybean to topsoil depth when averaged over both fertility and water management. The topsoil × soil fertility interaction was characterized by a 34% reduction in corn yield with topsoil depths < 125 mm in the fertilized treatments when averaged across water management. Similar yield reductions for unfertilized plots were observed but were linearly related to topsoil depth. The fertility × irrigation interaction described a multiplicative increase in corn yield when corn was both fertilized and irrigated. Only topsoil depth and water management significantly influenced overall soybean yield.
Urea Transformations in Flooded Soil Columns: II. Derivation of Model and Implications to Ammonia Volatilization
Authors: Bouldin D. R. , Hongprayoon C. , Patrick W. H. , Lindau C. W.
Published: July 2010

Ammonia volatilization from rice (Oryza sativa L.) paddies following urea application reduces the effectiveness of the urea‐N. The objectives of this study were to: (i) derive, for flooded soils, a model describing hydrolysis and diffusion of urea and diffusion of ammoniacal N; (ii) derive the necessary parameters from experimental data, and (iii) use the model to study implications of hydrolysis/transport parameters and management variables to NH3 volatilization. The parameters are diffusion coefficients of urea and NH4 in soil, hydrolysis coefficients of urea in the soil and overlying floodwater, and the sorption coefficient for NH4 on the soil. The effects on potential for NH3 volatilization of variation in these parameters and the management factors of depth of flood water and depth of fertilizer incorporation were calculated. The results illustrate that urea‐hydrolysis rates in the floodwater and soil are the most important factors influencing the potential for NH3 volatilization. If urea‐hydrolysis rates are very high, incorporation and shallow floodwater are the indicated management while, with low hydrolysis rates, deep floodwater and no incorporation are the indicated management.
Predicting Cation Mobility in Kaolinitic Media Based on Exchange Selectivities of Kaolinite
Authors: Gaston L. A. , Selim H. M.
Published: July 2010

Predictive modeling of cation transport in soils requires knowledge of the distribution of exchangeable species between solution and adsorbed phases. Such distribution of exchangeable species may be described with an exchange selectivity coefficient. Typically, the selectivity coefficient for any cation‐exchange pair varies among soils. If the exchange complex of a soil is dominated by one type of exchanger, however, then the selectivity coefficient for that soil may be similar in magnitude to that for the principal mineral (or organic) constituent. Therefore, reasonably accurate predictions of cation transport in that soil might be obtained using exchange data for the dominant exchange material. This study was undertaken to determine whether exchange data for kaolinite could be successfully used in predicting Ca, Mg, and Na retention during movement in a Mahan series soil (clayey, kaolinitic, thermic Typic Hapludult). Binary‐exchange isotherms for Ca‐Mg, Ca‐Na, and Mg‐Na were generated for Ga‐1 kaolinite (well crystallized). Selectivity coefficients derived from these data were used to describe cation exchange during miscible displacement through columns of (i) kaolinite admixed with acid‐washed sand and (ii) Mahan soil. Use of the selectivity coefficients for kaolinite provided good predictions of cation transport in the kaolinite/sand mixture. Predictions for the kaolinitic Mahan soil were not as good. The presence of small amounts of 2:1 minerals may have influenced the overall exchange behavior of the Mahan soil. When the uncertainty in values for selectivity coefficients and other exchange or transport parameters was considered, however, the exchange selectivity data for kaolinite could adequately describe cation transport in the Mahan soil.
Spectroscopic and Chemical Evidence of Variability across a Pine Litter Layer
Authors: Tam Shuk‐Ching , Sposito Garrison , Senesi Nicola
Published: July 2010

Chemical‐composition data and spectroscopic analyses are reported for three layers in a ponderosa pine (Pinus ponderosa Dougl. ex P. Lawson & Lawson) litter sample (O horizon) and for fresh needles sampled from a plantation site. The data were taken to obtain evidence for variability in chemical properties accompanying well‐known changes in the visual characteristics of a litter layer that result from the gradual humification of its organic matter. Composition data for Mg, Al, Si, P, S, Ca, Mn, Fe, Cu, and Pb showed that all but Mg, P, S, and Pb increased in content in the litter relative to the needles, and that the content of Al, S, Mn, and Fe increased, while that of Mg decreased, in passing from the Oi to the Oa layer. The increases for Al and Fe were especially large. Fourier‐transform infrared and electron spin resonance spectra of the litter samples indicated, respectively, the presence of a variety of aromatic and aliphatic structures with carboxyl and hydroxyl functionalities and an increase in organic free‐radical content with depth in the litter layer. The electron spin resonance spectra further indicated that Fe(III) was bound in inner‐sphere complexes uniformly down the litter layer, whereas Mn(II) was bound in outer‐sphere complexes. Aqueous extracts of the litter samples showed increases in pH and decreases in the concentration of organic C, carboxyl groups, and free organic acids with depth, some of the changes being as large as an order of magnitude. Composition data for aqueous extracts of the needle and litter samples showed that the water extractability of Mg, Al, P, Ca, and Mn was greater in the needles than in the litter, and that extractability decreased with increasing depth for all of the elements examined except Si and Pb. The largest relative decrease in water extractability (20‐fold) was for Al. These trends, which require confirmation for other Pinus species litter samples, were interpreted as an effect of the variability in organic structures in the litter that develop from differing degrees of humification, bioassimilation, and leaching/retention processes.
Phytoavailability Soil Test: Development and Verification of Theory
Authors: Yang J. E. , Skogley E. O. , Georgitis S. J. , Schaff B. E. , Ferguson A. H.
Published: July 2010

A new approach to soil testing, designed to improve accuracy and usefulness, is being developed. A spherical, mixed‐bed ion‐exchange resin capsule is embedded in saturated‐paste soil samples and allowed to accumulate all nutrients the soil can deliver, as a function of diffusive ion movement. This simulates the action of nutrient movement to plant roots. The approach is called the Phytoavailability Soil Test (PST). Objectives were to determine if nutrient accumulation by the resin capsule was described by diffusion models, and to investigate rate‐limiting diffusion processes. Nutrient‐uptake curves were obtained on Ap horizon samples from 20 Montana agricultural soils by measuring time dependence of K, P, and S accumulation in resin capsules during 15 d. Also, a planar system was used in which both sides of a cylinder of resins accumulated P, K, and S from saturated pastes during 96 h. Fluxes to the resin were compared with nutrient gradients, measured by two other extraction methods, on soil slices from successive distances beyond the resin‐soil interface. The mass of nutrients adsorbed by the resin as a function of time was consistent with a diffusion process, as was the concentration of nutrients in the soil vs. distance from the resin‐soil interface. The process appeared to be that termed film diffusion. Results demonstrated independence of specific nutrient diffusion and resin adsorption. The PST may provide an improved approach to soil testing because it is sensitive to nutrient diffusion, a governing factor in plant availability of most nutrients.