bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Grazing on Infiltration Rates in Waste Water Spray Fields
Authors: Pearson George A. , Jung Gerald A. , Fowler Richard E. , Mitchell Donald M. 
Published: July 2010

AbstractMany food‐processors use grass‐covered sprayfields for treating waste water. These fields are generally mowed one or more times each year. To eliminate mowing costs, such fields could be fenced and used as irrigated pastures. However, since the primary purpose of such fields is waste water treatment, adverse effects on infiltration must be avoided, particularly in areas with shallow soils that cannot be manipulated for overland‐flow.A portion of a food‐processor's wastewater treatment field was fenced and grazed for approximately 5 months during the summer and fall of 2 successive years. The soil series was Sassafras sandy loam and the grass species were ‘Kentucky 31’ tall fescue [Festuca elatior var. arundinacea (Schreb.) Wimm.] and orchardgrass (Dactylis glomerata, L.).The infiltration rate at saturation was measured frequently throughout the period of grazing. It was found that trampling reduced the infiltration rate from an initial value of 2–2.5 cm/hr to a final value of 0.3 cm/hr.If these fields are to be grazed, it will be necessary to use low wastewater application rates to avoid surface runoff and ponding in low spots.
Predicting Anion Movement in Disturbed and Undisturbed Soils
Authors: Cassel D. K. , Van Genuchten M. Th. , Wierenga P. J. 
Published: July 2010

AbstractPrediction of anion displacement in soils has proven difficult owing to anion exclusion and the occurrence of anion sources or sinks within the soil system. In addition, variations in bulk density and texture with depth cause mean pore water velocity and soil water content to be functions of depth. In this paper a numerical solution of a modified convective diffusion equation, which accounts for apparent anion exclusion and variations in soil water content and mean pore water velocity as functions of depth, is discussed. Moreover, a zero‐order rate term is incorporated to account for nitrification occurring in the upper portion of the soil profile.The model was tested using previously published NO3 and 36Cl displacement data for disturbed and undisturbed cores of Aberdeen loam. The model predicted 36Cl displacement well. Incorporation of the source term improved prediction of the nitrate breakthrough curve, but agreement of the predicted curve with observed data was only fair. When average values for water content and bulk density were used throughout the entire column, instead of depth dependent values, the description of anion movement was not as good. It is suggested, however, that the improvement in accuracy of prediction of anion displacement may be less than the variation in solute movement observed among replicate soil cores.
Potassium‐Calcium Exchange Equilibria in Volcanic‐Ash Soils
Authors: Schalscha E. B. , Pratt P. F. , de Andrade L. 
Published: July 2010

AbstractPotassium‐Ca exchange equilibria were determined at potassium adsorption ratios (PAR) of 0.2, 2.0, and 20 for pH values of 4.8, 6.0, and 7.5 for four volcanic‐ash soils of southern Chile. Increases in pH produced large increases in CEC which were largely balanced by increases in the amount of Ca adsorbed. The increases in exchangeable K with increase in CEC were relatively small. The relative affinities for K versus Ca at a PAR of 0.2 indicated that for each soil a small, but nearly constant, amount of negative charge had a high specificity for K. Beyond this small amount of CEC with a high affinity for K, the affinities for K were relatively low.
Infiltration of Organic Phosphate Compounds in Soil
Authors: Rolston D. E. , Rauschkolb R. S. , Hoffman D. L. 
Published: July 2010

AbstractOrganic phosphate compounds may be moved greater distances into soil than is possible with inorganic phosphates inasmuch as organic phosphates must be enzymatically hydrolyzed to orthophosphate before soil reactions inhibit movement. The hydrolysis in solution and movement in soil of six organic phosphates were investigated in order to evaluate possible advantages of the compounds as fertilizers. The compounds studied were glycerophosphate, methyl ester phosphate, glycol phosphate, ethyl ester phosphate, glucose 1‐phosphate, and glucose 6‐phosphate. The infiltration of organic P compounds into Panoche clay loam soil and glycerophosphate into five soils differing in texture, clay type, organic matter, and pH and into one soil at three water contents was investigated by infiltrating organic P solution into columns of dry or moist soil at a rate of 66 kg of P/ha. Inorganic P concentration in bicarbonate extracts was measured as a function of soil depth at the termination of infiltration. The movement of P from organic compounds was compared with the movement of potassium phosphate. All the organic phosphates hydrolyzed at similar rates. The P from all the organic compounds moved to approximately the 12‐cm depth in the calcareous Panoche clay loam soil with only slight differences in P concentration above that depth, whereas inorganic phosphate moved no more than 2–3 cm. The enzymatic hydrolysis rate of glycerophosphate and the resulting P distribution after infiltration was influenced by soil type. The greatest P movement (12 cm) occurred in Panoche clay loam, and the least amount of movement occurred with Aiken clay loam. Soil‐water content had only a slight effect on glycerophosphate movement for the one soil studied.
Translocation of Iron In Acid Sulfate Soils: I. Soil Morphology, and the Chemistry and Mineralogy of Iron in a Chronosequence of Acid Sulfate Soils
Authors: van Breemen N. , Harmsen K. 
Published: July 2010

AbstractIn periodically flooded acid sulfate soils from Thailand various iron compounds are confined to distinct soil horizons. The unmottled substratum, which starts at several decimeters below the surface in the (youngest) mangrove and stage and at 2 m in well‐developed soils, invariably contains between 2 and 5% pyrite. Drainage of the mangrove mud is followed by pyrite oxidation which results in acidification of the soil and accumulation of iron as ferric oxide or jarosite at some distance above the pyritic substratum. Very little iron is precipitated just above the unmottled C horizon. As the soils become older and better drained, the upper boundary of the pyritic substratum and the B horizon with ferric oxide and jarosite, occur at progressively greater depths. Hydrolysis of pale yellow jarosite to ferric oxide at relatively shallow depth accounts for a separation of the B horizon in a brown mottled upper part and a predominantly yellow mottled lower part. The X‐ray amorphous ferric oxide is transformed to goethite, or, in the better drained soils, to hematite. In the older soils especially, periodic reduction of immobile ferric iron to mobile ferrous iron in the surface soil and at the top of the pyritic substratum, combined with perennially oxidized conditions in the B horizon, may contribute to the strong iron accumulation in the B horizon. Differences, in organic matter content and stability of ferric oxide, and the presence or absence of pyrite, probably account for the dissimilar behavior of the various horizons upon flooding. Besides conventional soil analyses, results of water analyses, EH‐pH determinations, and various laboratory experiments involving field samples are helpful in explaining details of the soil‐forming process involved.
Water Retention by Core and Sieved Soil Samples
Authors: Unger Paul W. 
Published: July 2010

AbstractMechanical analyses and water retention by core and sieved soil at ‐⅓ and −15 bar matric potentials were determined for samples from 26 sites ranging in texture from sand to clay.Objectives were to obtain a basis for identifying which soils may be influenced by deep tillage and profile modification with respect to water storage capacity and to determine the magnitude of errors possible when using sieved soils to establish field soil water contents.At ‐⅓ bar potential, cores retained more water than sieved soil when the water content was below 11%. The opposite occurred at higher water contents. At −15 bars potential, cores contained about 1 percentage point more water than sieved soils throughout the water content range encountered. These results show that treatments which thoroughly disrupt the natural soil structure may decrease and increase the storage capacity of coarse‐ and fine‐textured soils, respectively.When expressed as a percent of the core water content, differences between core and sieved soil contents at ‐⅓ bar potential ranged from −40 to +25% at 5 and 40% core water contents, respectively. At −15 bars potential, the range was from −52 to −4% at 5 and 25% core water contents, respectively. These differences indicate caution should be used when using sieved soils to infer water retention by field soils, regardless of texture.This study suggests deep tillage and profile modification may decrease and increase water storage in coarse‐ and fine‐textured soils, respectively. However, because of structural development, organic matter content, and possibly clay size and type, results for individual soils may differ from those indicated by the relationships established. To more accurately evaluate the possible effects of deep tillage and profile modification on water retention, the soil in question must be analyzed.
Soil Moisture Flux and Evapotranspiration Determined from Soil Hydraulic Properties in a Chaparral Stand
Authors: Scholl David G. 
Published: July 2010

AbstractMeasurements of rainfall, overland flow, soil moisture, and hydraulic properties were obtained from a sloping plot in a chaparral stand. The moisture characteristic and dynamic conductivity were determined from core samples of several soil layers to a depth of 420 cm. A water balance model requiring the above parameters and a Darcian moisture flux analysis was used to predict drainage below the root zone and loss by evapotranspiration. Daily results of the water balance were summarized during 2 water years. Predicted values agreed well with values measured on a nearby watershed during both years—the first an unusually dry year, the second unusually wet.
Infrared and X‐ray Study of Parathion‐Montmorillonite Sorption Complexes
Authors: Saltzman Sarina , Yariv S. 
Published: July 2010

AbstractInfrared spectra indicate that parathion sorbed by montmorillonite coordinates through water molecules to the metallic cations in the interlayer space of the clay. By dehydrating the clay‐parathion complexes, parathion becomes directly coordinated with the monovalent cations. The main interaction is through the oxygen atoms of the nitrogroup, although interactions through the P=S group were also observed, especially for complexes saturated with polyvalent cations.
Octan‐I‐ol Extraction of Molybdophosphoric Acid in the Colorimetric Determination of Orthophosphate
Authors: Helyar K. R. , Brown A. L. 
Published: July 2010

AbstractA method for the analysis of orthophosphate in aqueous solutions is described. The detection limit of the method is <0.1 µg orthophosphate P, and the molybdophosphoric acid can be concentrated at least 300 times by extraction into octan‐I‐ol. The complex is reduced to the colored form after extraction into octan‐I‐ol and Beer's Law is obeyed at least to an absorbance value of 1.5. A study of the effects of temperature, shaking time and rate, and the organic to aqueous ratio on the extraction of molybdophosphoric acid was carried out. The extinction coefficient for the method was 22,000 liters mole‐1 cm‐1. Possible interference by various cations and anions in the determination was investigated and the technique was used successfully to analyze for phosphate in calcium chloride extracts from soil.
Nitrite Decomposition in Flooded Soil Under Different pH and Redox Potential Conditions
Authors: Van Cleemput O. , Patrick W. H. , McIlhenny R. C. 
Published: July 2010

AbstractNitrite decomposition products were studied in a flooded soil suspension maintained under different pH and redox potential conditions. The effect of a sterilant, HgCl2, on nitrite breakdown was also investigated. Soil suspensions were incubated for several days with the pH maintained at 4.5, 6, and 8 and the redox potential maintained at 0 and + 200 mV. Nitrite was then added to the suspensions and the decomposition products were determined by mass spectrometry.Under acid conditions significant amounts of N2 and nitrogen oxide gases (N2O, NO) were formed in both the moderately reduced (+200 mV) and reduced (0 mV) suspensions. At higher pH's the nitrite reduction rate was slightly less and the amounts of nitrogen oxide gases formed were considerably less with N2 being the major product. The chemical sterilant decreased the conversion of nitrite to N2 and markedly increased the formation of NO. The significant production of NO under acid conditions both with and without the sterilant, suggests the likelihood of self‐decomposition of nitrous acid as a major mechanism of nitrite loss.
Nitrogen Accretion in Developing Ceanothus Velutinus Stands
Authors: Youngberg C. T. , Wollum A. G. 
Published: July 2010

AbstractNodulation, N accretion, and above‐ground biomass production were investigated in Ceanothus velutinus (snowbrush) stands developing following wildfire and salvage logging in second growth ponderosa pine (Pinus ponderosa Laws) and logging and slash burning in old growth Douglas‐fir stands [Pseudotsuga menziesii (Mirb.) Franco]. In the pine site 82% of the Ceanothus plants were nodulated the first year, whereas in the fir site only 42% were nodulated. Above‐ground snow‐brush biomass production at the end of 10 years was 48,000 and 54,000 kg/ha, respectively, for the pine and fir sites. Nitrogen accretion in biomass, litter, and soil for the 10‐year period was 715 and 1,080 kg/ha, respectively, for the pine and fir sites. The higher accretion in the fir site despite slower nodulation is due to more favorable temperature and moisture conditions at the fir site than at the pine site.
Sulfur‐coated Fertilizers for Sugarcane: I. Plant Response to Sulfur‐coated Urea
Authors: Gascho G. J. , Snyder G. H. 
Published: July 2010

AbstractCrop growth and yield on sand soils is often limited by low N availability due to leaching losses from the soil. This study was initiated to determine if sulfur‐coated urea (SCU) could supply adequate N nutrition and eliminate the need for repeated N applications for sugarcane (Saccharum spp.) grown on previously uncropped Immokalee fine sand in southern Florida. Single applications of two SCU's were compared with split applications of (NH4)2SO4 (AS), each at three N rates, 56, 112, and 168 kg/ha. Application of SCU at planting in November resulted in excellent growth and high leaf N concentrations in the spring but did not provide optimum N throughout the growing season. Leaf N concentrations in late summer and tonnages of sugarcane and sugar for SCU plots approached, but did not equal, those attained with four applications of AS. Higher tonnages were recorded for the slower releasing SCU than for the faster releasing source but both SCU sources released large amounts of N before the warm summer months when N is required in the highest quantities. The data indicate that SCU's which release N more slowly and/or a later application date should provide better N nutrition and eliminate the need for several split applications of soluble sources.
Analytical Properties of the Soluble, Metal‐Complexing Fractions in Sludge‐Soil Mixtures: I. Extraction and Purification of Fulvic Acid
Authors: Holtzclaw Kenneth M. , Sposito Garrison , Bradford Gordon R. 
Published: July 2010

AbstractA laboratory method is described for extracting and purifying the fulvic acid fraction of sludge‐soil mixtures. The method, which does not include dialysis or the use of destructive chemical reagents, consists of: (i) extraction with 0.5N NaOH and acidification to pH 1.0 with HCl, (ii) repeated high‐speed centrifugation to remove Al‐Fe‐hydroxy phosphates, and (iii) use of both chelating and H‐form cation exchange resins to remove complexed metal impurities. The existing procedures for preparing fulvic acid, based upon research on natural soil organic matter, were concluded to be not fully adequate for studies on sludge‐soil mixtures. Primarily, this inadequacy is the result of the loss, through dialysis, of important reactive fractions during purification and the lack of specific steps that treat the greater variety of trace elements to be found in sludge materials. In addition, the presence of significant amounts of P in these mixtures complicates the removal of colloidal and complexed metal impurities. The application of the present method to representative sludge‐soil mixtures showed that ash contents are reduced to I‐2%. The procedure should be generally applicable in soil or sediment organic matter studies as well as to studies on the chemistry of sludge‐amended soil.
Relative Importance of Soil Resistance and Plant Resistance in Root Water Absorption
Authors: Reicosky D. C. , Ritchie J. T. 
Published: July 2010

AbstractSoil water potentials, leaf water potentials, and transpiration rates of sweet corn (Zea mays L.), growing in a greenhouse, and grain sorghum (Sorghum bicolor L.), growing in a field, were determined to evaluate the magnitude of the combined soil and plant resistances to water flow in the plant system. Using a theoretical analysis of water absorption by roots, soil resistance was estimated. Plant resistance was inferred by the difference between the measured combined resistances and the estimated soil resistance. A wide range of soil hydraulic conductivity values for the plant rooting media which included nutrient solutions, peat‐vermiculite‐sand mixture, and a sand and clay soil maintained at various water potentials provided variations in calculated soil resistances. Our results showed that when root density was not unusually low, plant resistance to water transport was much larger than soil resistance, until the threshold soil hydraulic conductivity reached about 10‐6 to 10‐7 cm/day. This conductivity usually occurred at about −1 and −8 bars for the sandy and clay soils, respectively. These findings emphasize the need to consider plant resistance in water‐uptake calculations when using equations that evaluate water potential gradients along the water flow path.
Rhodanese Activity of Soils
Authors: Tabatabai M. A. , Singh B. B. 
Published: July 2010

AbstractThe detection of rhodanese (enzyme catalyzes the formation of SCN‐ from S2O32‐ and CN‐) in soils is reported, and a simple method of assaying rhodanese activity in soils is described. This method involves colorimetric determination of the SCN‐ produced by rhodanese activity when soil is incubated with buffered (0.05M THAM, pH 6.0) S2O32‐ and CN‐ solutions and toluene at 37°C for 1 hour. The method developed is rapid, sensitive, and precise. The procedure used to extract SCN‐ stops rhodanese activity in soils and gives quantitative recovery of the SCN‐ formed. Results showed that steam sterilization and formaldehyde inhibit, sulfate and chloride activate, and toluene has no effect on rhodanese activity in soils. The initial rates of SCN‐ formation obeyed zero‐order kinetics; in one soil, the rate slowed with time of incubation. The temperature dependence of the rate constant conformed to the Arrhenius equation up to the point of enzyme inactivation (65°C). The activation energy of rhodanese activity of the eight soils studied ranged from 5,160 to 8,110 (avg. 6,690) calories/mole. Studies of other properties of rhodanese activity in soils are reported.
Line Source Sprinkler for Continuous Variable Irrigation‐crop Production Studies
Authors: Hanks R. J. , Keller J. , Rasmussen V. P. , Wilson G. D. 
Published: July 2010

AbstractThe design details and a sample set of field test results for a line source sprinkler plot irrigation system are presented. The system produces a water application pattern which is uniform along the length of the plot and continuously, but uniformly variable across the plot.By applying a fertility variable along a plot (at right angles to the water variable) planted in some test crop, the system offers a convenient means for developing crop production function data. The system test area and water supply are both small. However, the application of the system may be limited by wind and all water application levels within a plot must be supplied at the same irrigation frequency.
Estimation of Components of Soil Cation Exchange Capacity from Measurements of Specific Surface and Organic Matter
Authors: Curtin D. , Smillie G. W. 
Published: July 2010

AbstractCation exchange capacities of Irish soils developed from a wide range of parent materials were found to be highly correlated with organic matter content and specific surface but not with clay content. Multiple regression analysis showed that organic matter in combination with specific surface accounted for 97% of the variation in CEC whereas organic matter and clay content only accounted for 58% of the variation. The better correlation between CEC and specific surface than between CEC and clay content, is attributed to the ability of surface area measurements to reflect the presence of phyllosilicates in silt and sand fractions of soils and to the fact that these minerals have less variable surface charge densities than cation exchange capacities. It is proposed that specific surface provides a better estimate than clay content, of the mineral component of CEC for soils of varying mineralogy.
Estimate of Organic Carbon in World Soils
Authors: Bohn Hinrich L. 
Published: July 2010

AbstractThe current estimate of organic carbon in world soils, 7.1 × 1014 kg, is based on such meager data that it must be viewed skeptically. The FAO‐UNESCO soil map and other recent soil data indicate that the amount of organic soil carbon is about 30 × 1014 kg. This new estimate should allow more accurate portrayal of the role of soil carbon in the carbon cycle.
Heat and Water Movement Under Surface Rocks in a Field Soil: II. Moisture Effects
Authors: Jury W. A. , Bellantuoni B. 
Published: July 2010

AbstractResults are presented from a field experiment conducted to determine the effect of surface rocks on soil water content changes under bare soil. First, stones were placed at intervals over an initially‐dry field (gravimetric water content = 0.021 g/g) and left for 6 weeks. Subsequent sampling showed a small but detectable excess of water stored under the rock compared to adjacent bare soil. Following an irrigation, buried thermal conductivity probes were used to monitor water content changes under and adjacent to surface rocks. After 24 days, the soil under the rock contained significantly more water than did the soil region adjacent to the rock, a finding confirmed by gravimetric sampling. Following this, the stones and probes were relocated for a further 24 days of observation, with similar results obtained.In a separate laboratory experiment using a large sealed soil column with a rock covering part of the surface it was demonstrated that a significant amount of water moved to the cylinder of soil under the rock from the soil region under the bare surface due to horizontal temperature gradients induced by the rock covering part of the surface.A two‐dimensional computer program calculating water vapor movement under thermal gradients was used with measured field temperature boundary conditions to estimate the amount of water vapor movement expected to occur due to a rock cover on the soil surface. Results qualitatively confirmed the observations of the sealed laboratory column experiment.