bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical Transformations of Urea‐Nitrogen and Movement of Nitrogen in a Shortgrass Prairie Soil
Authors: Stillwell M. A. , Woodmansee R. G. 
Published: July 2010

AbstractThis study, conducted on the Central Plains Experimental Range during the summer of 1979, was to (i) quantify the temporal dynamics of the transformations of nitrogen (N) in a simulated urine spot, (ii) determine the effect of urea hydrolysis on pH, and (iii) determine the depth of movement of nitrate by leaching. Miniplots of blue grama were established, and open‐ended aluminum cylinders 10 cm in diameter and 40 cm in length were embedded in each plot. Simulated urine was applied to two‐thirds of the plots at a rate of up to 45 g N m−2. The remaining plots were controls.After the simulated urine application, only 6% of the added N remained as urea at 2 days; no urea‐N remained at 4 days. Maximum accumulation of ammonium‐N (39.9 g N m−2) was simultaneous with the disappearance of urea. Elevated levels of nitrate were first detected at day 12 when 6.7 g N m−2 had accumulated. No measurable nitrite accumulated during the experiment.Through the first 4 days, 83% of the (urea + ammonium)‐N in the profile was in the top 15cm of the soil. With the rains near the end of the study, nitrification proceeded, and nitrate was leached through the profile to below the depth of the cores.Simulated urine significantly affected soil pH to 15 cm. From an initial pH near 6.0, urea hydrolysis increased soil pH from 0.6 to 1.3 units. As nitrification prodeeded after day 40, the pH decreased to below control levels.
Classification and Genesis of Spodosols in the Central Appalachians
Authors: Stanley Scott R. , Ciolkosz Edward J. 
Published: July 2010

AbstractSeventeen well‐drained pedons were sampled in Pennsylvania and northern West Virginia. Sixteen of the pedons had well‐expressed Spodosol morphology while one had very marginal Spodosol morphology. These pedons were classified according to Soil Taxonomy and the Canadian soil classification system. The degree of spodic horizon development in relation to soil temperature was examined. Only three of the 17 pedons studied met the chemical criteria of Soil Taxonomy for Spodosol identification, while 13 met the chemical criteria of the Canadian system. Three pedons were examined for cracked coatings on sand grains and dark pellets of coarse‐silt size; all three pedons qualified as Spodosols on the basis of these criteria. These data indicate that more emphasis should be placed on the field criteria described in Soil Taxonomy and less on the chemical criteria or that the chemical criteria should be amended.The spodic horizon (Bh and Bir) in each of the 17 pedons contained the largest amount of illuvial Al, Fe, and C of the various horizons of the soil. As the mean annual soil temperature (MAST) of these soils increased, the Fe (pyrophosphate extracted) and C (total organic) content of the spodic horizon decreased (correlation coefficients of −0.70 and −0.46, respectively). The thickness of the spodic horizon was also related to soil temperature. There was a weak correlation (r = −0.31) of decreased thickness with increased MAST. In addition, Al (pyrophosphate extracted) content in the spodic horizon and the depth to the top of the spodic horizon showed a very weak correlation to MAST (correlation coefficients of −0.27 and 0.23, respectively). Although weak, these correlations show that Al, Fe, and C accumulate in spodic horizons of well‐drained soils in colder areas of the Appalachians to a greater extent than in warmer areas, and result in a more strongly expressed Spodosol in the cooler areas. The lack of stronger relationships may be a reflection of the effect of varying vegetation types (e.g., hemlock vs. maple) in the mixed hardwood‐conifer forest that was the natural vegetation of these soil pedons, or of varying vegetation during the development of these soils.
Effect of Differential Adsorption of Potassium and Magnesium in Soils on Magnesium Uptake by Corn
Authors: Stout W. L. , Baker D. E. 
Published: July 2010

AbstractIndices of the differential adsorption of potassium (K) and magnesium (Mg) were used to explain the differences in magnesium uptake by corn seedlings (Zea mays L.) grown on two widely different soils of the Rayne (a fine‐loamy, mixed, mesic Typic Hapludult) and the Hublersburg (a clayey, kaolinic, mesic Typic Hapludult) series. The differential adsorption of potassium was found to be the controlling factor in the uptake of magnesium by corn seedlings in these two soils. The differential adsorption concept may be useful in predicting which soils may or may not respond readily to magnesium fertilization.
Interrelationship Between the One‐Step and Increment Methods of Determining Diffusivity
Authors: Prunty Lyle 
Published: July 2010

AbstractThe “one‐step” and “increment” methods for determining soil‐water diffusivity (D) are shown to be fundamentally the same. Only a slight modification of the development of the outflow equation for the increment method is needed in order to obtain identical formulas for calculating D by either method.
Portable System for Furrow Irrigation of Small Plots
Authors: Heatherly Larry G. , Ginn L. H. 
Published: July 2010

AbstractA portable apparatus designed for furrow irrigation of small plots was constructed with a 3,800‐liter water wagon and a piece of gated aluminum irrigation pipe mounted laterally on the wagon. The pipe is long enough to water the middles of a four‐row plot. It is clamped by two brackets to a frame which is hinged at two points on the underside of the wagon. The hydraulic system of a standard row‐crop tractor is used to operate two double‐action hydraulic cylinders which are pivoted on the underside of the wagon and to each arm of the support frame for the gated pipe. A pump mounted on the rear of the wagon is attached to the water tank by noncollapsing suction hose and to the gated pipe by flexible fire hose. A graduated sight gauge on the pump end of the water tank allows for accurate measurement of applied water. The maximum output of the system is 380 liters/min.; a fully‐loaded trailer can provide 10 cm of water to a plot with four 100‐cm‐wide rows 9.1 m long without refilling.
An Adaptive Finite Difference Scheme for The One‐Dimensional Water Flow Equation
Authors: Dane J. H. , Mathis F. H. 
Published: July 2010

AbstractThe pressure bead form of the general flow equation for water in a porous medium was numerically solved using a scheme that allowed both the time step (Δt) and the space increment (Δz) to be changed during the flow process. The mass balance equation was used as a check for the accuracy of the simulation. A fixed number of grid points in the space direction was continuously redistributed to allow for small Δz values in regions of large changes in pressure head gradients while allowing large Δz values in regions of small changes. The method, which is unconditionally stable, is demonstrated for an infiltration and an evaporation process.
Thermodynamics of Sodium‐Copper Exchange on Wyoming Bentonite at 298°K
Authors: Sposito Garrison , Holtzclaw Kenneth M. , Johnston Cliff T. , LeVesque‐Madore C. S. 
Published: July 2010

AbstractThe exchange of copper (Cu2+) for sodium (Na+) at 298°K on Wyoming bentonite was investigated in a perchlorate background medium maintained at pH 5.0 to 6.0 and at a total normality of 0.01N. It was found that the exchange process could be well characterized by a Vanselow selectivity coefficient that was equal to 1.32, independent of the exchanger composition, and by a similarly constant apparent adsorbed metal charge equal to 0.92 ± 0.05 eq kg−1. These results are in conflict with previous data obtained at 295°K for Na+‐Cu2+ exchange on montmorillonite in a 0.01N chloride background medium. It was concluded that a principal cause for the differences between the two sets of data could be the presence of CuCl+ complexes in the chloride medium.
Amidase Activity in Soils: IV. Effects of Trace Elements and Pesticides
Authors: Frankenberger W. T. , Tabatabai M. A. 
Published: July 2010

AbstractAmidase was recently detected in soils, and this study was carried out to assess the effects of 21 trace elements, 12 herbicides, 2 fungicides, and 2 insecticides on the activity of this enzyme. Results showed that most of the trace elements and pesticides studied inhibited amidase activity in soils. The degree of inhibition varied among the soils used. When the trace elements were compared by using 5 µmol/g of soil, the average inhibition of amidase in three soils showed that Ag(I), Hg(II), As(III), and Se(IV) were the most effective Inhibitors, but only Ag(I) and As(III) showed average inhibition > 50%. The least effective inhibitors (average inhibition < 3%) included Cu(I), Ba(II), Cu(II), Fe(II), Ni(II), Al(III), Fe(III), Ti(IV), V(IV), As(V), Mo(VI), and W(VI). Other elements that inhibited amidase activity in soils were Cd(II), Co(II), Mn(II), Pb(II), Sn(II), Zn(II), B(III), and Cr(III). Enzyme kinetic studies showed that As(III) was a competitive Inhibitor of amidase, whereas Ag(I), Hg(II), and Se(IV) were noncompetitive inhibitors.When the pesticldes studied were compared by using 10µg of active ingredlent per gram of soil, the average inhibition of amidase in three soils ranged from 2% with dinitroamine, EPTC plus R‐25788, and captan to 10% with butylate. Other pesticides that inhibited amidase activity in soils were atrazine, naptalam, cbloramben, dicamba, cyanazine, 2,4‐D, alachlor, paraquat, trifluralin, maneb, diazinon, and malathion. The inhibition of amidase by diazinon, alachlor, and butylate followed noncompetitive kinetics.
A Comparison of Calcium Carbonate Precipitation and pH Depression on Calcium‐Reduced Ammonia Loss from Surface‐Applied Urea
Authors: Fenn L. B. , Matocha J. E. , Wu E. 
Published: July 2010

AbstractThe role of calcium (Ca) in reducing ammonia (NH3) loss from soil by way of calcium carbonate (CaCO3) precipitation and soil pH depression was investigated by applying increasing rates of urea with fixed ratios of Ca/N in the laboratory and greenhouse. Soil pH, Ca precipitation, and the rate of hydrolysis of added urea were related to reduction of NH3 loss.Calcium/nitrogen ratios of 0.25 were equally effective in reducing NH3 loss independent of N application rates. Higher ratios of Ca/N at at 55 and 110 kg N/ha application rates did not further depress NH3 loss. At application rates of 550 and 1,100 kg N/ha, Ca levels above a Ca/N ratio of 0.25 resulted in additional large depressions of NH3 loss. This additional effect was due to a depression in soil pH from increased Ca activity and a dramatically reduced rate of urea hydrolysis. The chemical reaction of Ca with urea was complete at a Ca/N ratio of 0.25. Additional Ca, if added with a high enough rate of urea (550 and 1,100 kg N/ha) remained soluble and reduced the soil pH and was responsible for one half of the total reduction in NH3 loss.Greenhouse data showed that the addition of Ca with urea increased plant recovery of fertilizer N more than predicted from laboratory data. Nitrogen rates as low as 55 kg/ha, applied in a surface band or as large granules, resulted in improved plant recovery of added N. Broadcast applications at 165 kg N/ha also resulted in good fertilizer N recovery at Ca/N ratios of 0.25 and 0.50.
Walkley‐Black Digestion Efficiency and Relationship to Loss on Ignition for Selected Sierra Leone Soils
Authors: Rhodes E. R. , Kamara P. Y. , Sutton P. M. 
Published: July 2010

AbstractTen top soils sampled from six physiographic positions in the Njala Survey Area of Sierra Leone, West Africa, varied in organic carbon content from 1.02 to 7.82% and in clay content from 22 to 65%. Walkley‐Black oxidation efficlency ranged from 93 to 100% and averaged 97%, using Wet Combustion as standard. Organic matter in these tropical soils is apparently in forms easily oxidized by the sulphuric acid‐dichromate digestion.Simple correlation between organic carbon (C) and loss on ignition (L.O.I.) was very strong, r = 0.997; partial correlations showed that when organic C was held constant, 31% of the variation in L.O.I. was associated with clay content variation, and when clay content was held constant, 98% of the variation in L.O.I. was associated with organic C.Ignition loss of organic C was closely predicted by the linear relationship y = 0.505 x − 0.094, where x = % organic C. Prediction error (about 0.5%) was proportionately greater at lower levels of ignition loss.
The Effect of Land Forming on Subsidence in the Florida Everglades' Organic Soil
Authors: Shih S. F. , Vandergrift D. E. , Myhre D. L. , Rahi G. S. , Harrison D. S. 
Published: July 2010

AbstractLand forming in the Everglades Agricultural Area (EAA) can become an important practice for reducing the organic soil subsidence. Before the land forming practice can be successfully implemented in the EAA, ground elevation variation with time, concepts of ground elevation distribution, and managing different types of water table depth need to be clearly defined. A new concept of general low spot elevation was introduced. It was estimated from general deviation of ground elevation, composited from 68% of 1 standard deviation (SD) of ground elevation, 27% of 2 SD, and 5% of 3 SD. Three types of water table depths involved in this study, which were used to evaluate the impact of land forming on reducing subsidence, were conventional water table (CWT), recommended water table (RWT), and unifrom water table (UWT). The results showed that the SD of ground elevation in virgin land decreased from 6.2 cm in 1958 to 2.6 cm in 1978. the St. Augustine grass (Stenotaphrum secundatum) field had a similar trend of decrease in SD from 3.6 cm in 1958 to 2.6 cm in 1978. As the time progresses, the range of ground elevations decreases. The ground elevation in EAA is approximately a normal distribution because the probability distribution in ground elevation is similar to normal condition. The land forming has the potential of extending the life of organic soil by about 10 years in EAA with either RWT or UWT management conditions.
Effect of Particle Surface Roughness on Mechanical Impedance of Coarse‐Textured Soil Materials
Authors: Cruse R. M. , Cassel D. K. , Stitt R. E. , Averette F. G. 
Published: July 2010

AbstractPacking energy required to increase bulk density in coarse‐textured soils is influenced by particle surface roughness, i.e., by interparticle friction. It was, therefore, hypothesized that particle surface roughness would influence soil resistance to movement of a cone penetrometer, because soil bulk density is increased in the zone surrounding the penetrometer tip during its advance. The cone index (C.I.) was calculated for all penetrometer measurements, and C.I. was compared in both disturbed and undisturbed coarse‐textured soil material, with each soil having a unique particle surface roughness as determined by the dense soil angle of repose measurement. For soil materials with similar particle size distributions and bulk densities, C.I. increased as particle surface roughness increased.The role of particle surface roughness in tillage pan formation and in root growth restriction is discussed. It is suggested that, due to poorer aeration during rainy periods and higher mechanical resistance during drier conditions, tillage pans formed in soil materials having smoother‐surfaced particles will be more restrictive to root growth compared to those pans formed in soil materials having rougher‐surfaced particles. Consequently, among soils having root‐restricting tillage pans, the greater enhancement of rooting depth due to subsoiling would likely occur on soils with smooth particles compared to soils with rough soil particles.
Effects of Time and Leaching on Phosphate‐Induced Increase in Cation Exchange Capacity in Volcanic Ash Soils
Authors: Schalscha E. B. , Ahumada I. , Pratt P. F. 
Published: July 2010

AbstractIncubation of phosphorus (P)‐treated soils for up to 240 days had no effect on the P‐induced cation exchange capacity (CEC) of subsoil samples of three volcanic ash‐derived soils of southern Chile. Washing one soil with large volumes of distilled water desorbed small quantities of P but had no effect on CEC.
Clays and the Survival of Rhizobium in Soil During Desiccation
Authors: Osa‐Afiana L. O. , Alexander M. 
Published: July 2010

AbstractA study was conducted to assess the effect of drying on populations of two strains of Rhizobium japonicum and two cowpea rhizobia. The numbers of these bacteria fell markedly in soils undergoing drying. The extent of the decline varied with the strain and the soil. The decline in the population of a cowpea rhizobium occurred during the time of rapid water loss from four soils. The fall in numbers of three of the strains during desiccation was greater if the organisms were on glass beads than in soil. Illite did not increase survival on the beads, and kaolinite reduced the number of survivors of three strains dried on fine sand. Montmorillonite at the same concentrations protected against viability loss of two rhizobia undergoing desiccation on fine sand, but had no such effect on the more desiccation‐sensitive strain. The percent survival of three strains in a soil and in sand‐montmorillonite mixtures was directly related to the amount of water remaining after drying and was also affected by relative humidity. A possible relation between tolerance to desiccation and cell water content is suggested.
Effect of Cultural Practices on the Soil Population of Aspergillus flavus and Aspergillus parasiticus
Authors: Angle J. S. , Dunn K. A. , Wagner G. H. 
Published: July 2010

AbstractAflatoxin is a highly toxic compound and potent carcinogen produced by the fungi Aspergillus flavus and Aspergillus parasiticus. Corn infected by these organisms is frequently contaminated with aflatoxin. The infection of corn by A. flavus and A. parasiticus often occurs while the crop is still in the field. Because A. flavus and A. parasiticus are indigenous soil inhabitants, the soil is an important source of inoculum.This study was undertaken to quantify the population of A. flavus and A. parasiticus in soil and the ability of these organisms to produce aflatoxin. Soils under 11 different cultural systems were examined to determine the effects of the different practices on A. flavus and A. parasiticus.The maximum number of A. flavus and A. parasiticus propagules was found in soil cropped to a rotation of wheat, red clover, and corn using conventional tillage practices. In this soil, which had also been amended with manure, the count of A. flavus was 68 and that of A. parasiticus was 211 propagules per gram of dry soil. No A. flavus or A. parasiticus isolates were observed in a virgin prairie soil. Of all isolates observed from all cropping systems, 43% were A. flavus while 57% were A. parasiticus. The ability of the different isolates to produce aflatoxin varied significantly. In general, however, A. parasiticus isolates exhibited a greater ability to produce aflatoxin than did A. flavus.
Characterization of Sulfur in Fulvic Acids Extracted from Anaerobically Digested Sewage Sludge
Authors: Schaumberg Gene D. , Holtzclaw Kenneth M. , LeVesque C. S. , Sposito Garrison 
Published: July 2010

AbstractA variety of analytical methods were employed to characterize 80 to 90% of the sulfur (S) in two representative fulvic acids extracted from anaerobically digested sewage sludge. As in fulvic acids extracted from soils and peats, the majority of the sulfur (69%) was present as organic ester sulfate, with smaller contributions from LAS‐type detergents, amino acids, and inorganic sulfates. Of the ester sulfate, between 20 and 30% was identified as sulfate esters of fatty alcohols, presumably of detergent origin, and about 5% was accounted for by sulfated acidic polysaccharides. It was concluded that, because of the ubiquitous distribution of sulfate esters, the disposal of anaerobically digested sewage sludge should not alter drastically the character of sulfur in natural soil and water systems. Perhaps of greater concern would be the contribution of carbon‐bonded sulfur from LAS‐type detergents, which have no common natural analogs.
Interaction of Phosphorus Rates and Soil pH on Soybean Yield and Soil Solution Composition of Two Phosphorus‐Sufficient Ultisols
Authors: Adams J. F. , Adams Fred , Odom J. W. 
Published: July 2010

AbstractBecause growers continue to use phosphorus (P) fertilizer on soils that test high in available P, two field experiments were conducted to determine what nutritional problem, if any, would develop in soybeans (Glycine max L.) when high levels of P were established on Ultisols. Soil pH levels, ranging from 5.0 to > 7.0, were established by differential limiting; five P rates as concentrated superphosphate were superimposed on the pH levels. Zinc (Zn) deficiency was induced by high P rates and high pH, and the magnitude of yield reduction corresponded with the intensity of deficiency symptoms on foliage. Leaf Zn, acid‐extractable soil Zn, and soil solution Zn were poor indicators of Zn deficiency. The ratio of P/Zn in leaves was a fair indicator in one soil and a poor one in the other, possibly because of differences in availability of subsoil Zn. Soil solution Zn, which ranged between 0.1 and 5.1 µM, was affected by pH but not P level. Soil solution P, which ranged between 5 and 230 µM, was affected primarily by P rates. Both SO4 and Si concentrations in soil solutions were increased by increasing P rates. Calculated ion activity products for Ca5OH(PO4)3 showed numerous soil solutions to be supersaturated with respect to hydroxyapatite.
Response of Corn and Inoculated Legumes to Urea, Lime, Phosphorus, and Sulfur on Guadalupe Clay
Authors: Jones U. S. , Samonte H. P. , Jariel D. M. 
Published: July 2010

AbstractResponses of soybean (Glycine max L.), mung bean (Vigna radiata L.), and corn (Zea mays L.) to CO(NH2)2, CaCO3, Ca(H2PO4)2·H2O, and CaSO4, and of legumes to single strain Rhizobium inoculants on a Vertisol was determined during the dry season at Los Banōs, Philippines. Irrigation well water and precipitation were used to maintain soil moisture slightly below saturation in 6‐kg crocks. Relevant chemical analyses were made on soils, water, and plants. Inoculation increased N concentration of soybean tops. Soybean yield was greater with seed inoculation before planting than without, but mung bean did not respond to seed inoculation before planting. Neither legume responded to 30 kg N/ha as urea. Nodules on legume roots were greatly increased by 40 kg P/ha. All yields were more than doubled by addition of 40 kg P/ha. Increased yield of corn and soybeans resulted from the addition of 20 kg S/ha. The addition of sulfur as CaSO4 resulted in an increased soil S concentration as measured by dilute NH4C2H3O2, CH3COOH extraction.