bluuebunny/crossref_metadata_2025_split huggingface dataset:
Steady Flows of Water and Salt in Uniform Soil Profiles with Plant Roots
Authors: Raats P. A. C. 
Published: July 2010

AbstractSteady upward and downward flows of water in the presence of uptake of water by plant roots are analyzed. Qualitative features of possible pressure head, total head, and water content profiles for steady conditions are discussed. Specific calculations are based upon an exponential increase of the hydraulic conductivity with the pressure head and an exponential decrease of the rate of uptake with depth. For downward flows, the distribution of the matric flux potential can be expressed as a function of the rate of infiltration, the leaching fraction, and two parameters characterizing the soil and the uptake distribution, respectively. Although the water content in the root zone may be nearly uniform, the matric component of the flux may be significant. For upward flows, the distribution of the matric flux potential can be expressed as a function of the rate of infiltration, the rate of transpiration, the hydraulic conductivity of the saturated soil and the same two parameters characterizing the soil and the uptake distribution. The depth at which the flux vanishes, the minimum value of the matric flux potential for a given depth of the water table, and the maximum depth of the water table are evaluated. Finally, neglecting the effects of salt precipitation and dissolution and of diffusion and dispersion, the distribution of salts associated with the steady downward flows is evaluated.
Lysimeter and Field Measurements of Chloride and Bromide Leaching in an Uncultivated Loamy Sand
Authors: Saffigna P. G. , Keeney D. R. , Tanner C. B. 
Published: July 2010

AbstractField and lysimeter measurements were made of Cl and Br leaching in a Plainfield loamy sand at Hancock, Wisconsin. Chloride and Br were excellent companion tracers, moving in a 1:1 ratio through the 500‐cm field profile to the water table even when large differences in halide leaching occurred between adjacent sites. Half of the Cl or Br applied to the lysimeters was leached through the 125‐cm lysimeter profile in 13 or 17 cm of drainage during 22‐ and 205‐day experiments, respectively. Edge effects in the lysimeter were studied by applying Br near the edge and Cl in the center. Bromide was detected in the lysimeter drainage before Cl, but overall, edge effects were small.Lateral movement of Cl and Br in the lysimeter profile was < 20 cm. This helps explain why large localized variations in solute transport can persist to considerable depth in this sandy soil. The differences in the distribution of halide between adjacent soil profiles within the lysimeter and field exceeded the average differences between the field and the lysimeter soil profiles.
Decomposition in Soil of 14C‐labeled Coumaryl Alcohols; Free and Linked into Dehydropolymer and Plant Lignins and Model Humic Acids
Authors: Haider K. , Martin J. P. , Rietz E. 
Published: July 2010

AbstractSide chain and ring‐14C‐labeled coumaryl alcohols and coumaric acids and ring‐14C‐labeled ferulic, caffeic, protocatechuic, vanillic, and p‐hydroxybenzoic acids and coniferyl alcohol were synthesized. The coumaryl alcohols and phenolic acids were linked into model phenolase humic polymers. Labeled corn (Zea mays L.) stalk lignins were prepared by injecting the labeled coumaric acids as lignin precursors into growing corn plants. Model DHP lignins were prepared by polymerizing the labeled coumaryl alcohols with unlabeled coniferyl alcohol using peroxidase and hydrogen peroxide. Decomposition of the labeled carbons in the phenolic compounds and in the polymers was followed in a neutral sandy loam soil. After a 28‐week incubation period about 58, 44, and 47% of the CH2OH and 2‐(side chain) and ring‐14carbons, respectively, of applied coumaryl alcohols had evolved as 14CO2. Losses of ring C from other common benzenoid compounds ranged from 68 to 84%. Linkage of coumaryl alcohols into model humic acids reduced losses of ring carbons to 5 to 12%. The decomposition percentages for the CH2OH and 2‐(side chain) and ring‐14carbons of the coumaryl alcohols linked into model lignins were 33, 18, and 20%, respectively, while comparable values for the same carbons in corn stalk lignins averaged 7% higher. About 40 to 60% of the residual 14C activity from the lignins and model polymers was recovered in the humic acid fraction of the soil. The amounts of coumaryl alcohol and other phenolic compounds linking into model phenolase polymers were inversely related to the degradability of the compounds in soil.
The Production of Phytotoxins from Surface Crop Residues
Authors: Cochran V. L. , Elliott L. F. , Papendick R. I. 
Published: July 2010

AbstractExperiments were conducted to determine if crop residues, common to eastern Washington, were likely to cause phytotoxicity problems with no‐till planting of winter wheat (Triticum aestivum L.) The possible role of microorganisms was assessed also. Mats (5 to 8 cm thick) of lentil (Lens culinaris Medic.), pea (Pisum sativum L.), wheat, barley (Hordeum vulgare L.), and bluegrass (Poa pratensis L.) residues were spread over bare soil in Sept. 1975. Water extracts of the residues and soil beneath them were bioassayed weekly for wheat‐seedling phytotoxins, and the residues were plated biweekly to determine the numbers of fungi, bacteria, and pseudomonads from Sept. 1975 through May 1976. All residues produced wheat‐seedling root inhibitors, but only after conditions became favorable for microbial growth. Toxin production from these straws was irregular and was generally preceded by wet weather with air temperatures above freezing but below 15°C. Lentil‐ and pea‐straw extracts were most toxic to wheat seedlings in the fall and early winter, causing up to 90% root growth inhibition but little or no inhibition later. Wheat‐ and barley‐straw extracts were less inhibitory. However, these residues intermittently produced seedling inhibitors in the fall, late winter, and until late April when the straw dried. Bluegrass straw extracts showed toxic substances primarily in late winter and early spring. The delayed toxin production could explain why fall‐killed bluegrass sod was detrimental to no‐till seeded spring wheat, while spring‐killed no‐till seeded sod produced excellent wheat yields. The toxin(s) extracted were apparently different from those described by other researchers, since they (i) inhibited root growth only, (ii) were produced at lower temperatures, (iii) were produced cyclically over longtime periods, (iv) were stable when autoclaved, and (v) were not soluble in the organic solvents tested.
A Study of a Deep Weathering Profile on Granite in Peninsular Malaysia: II. Mineralogy of the Clay, Silt, and Sand Fractions
Authors: Eswaran H. , Bin Wong Chaw 
Published: July 2010

AbstractDifferent minerals characterize the three fractions in the different weathering zones. Halloysite in the clay fraction especially in the α and γ zones is due to a physical comminution of silt‐sized tubes. Strong peaks for halloysite (XRD) in the silt and sand fractions in these zones is shown (SEM) to be from partly altered feldspar fragments. Gibbsite is present mainly in the fine‐silt size and its presence in the sand in the α zone is due to cementation and aggregate formation. Aggregation of kaolinite also results in its being present in the silt and sand fractions.Estimates of the minerals in the three fractions are shown diagramatically as depth functions. XRD diffractograms of the three fractions and TEM micrographs of the clay fraction are also presented. It is concluded that the morphologically identified weathering zones also differ in their mineralogical properties.
Use of Goodness‐of‐fit Tests for Characterizing the Spatial Variability of Soil Properties
Authors: Rao P. V. , Rao P. S. C. , Davidson J. M. , Hammond L. C. 
Published: July 2010

AbstractApplication of the empirical distribution function (EDF) statistics to describe the spatial variability of soil properties is discussed. The Kolmogorov statistic (D) and the Cramer‐von Mises statistics (W2) were utilized to statistically evaluate the goodness‐of‐fit of a hypothesized theoretical distribution function to a sample of measurements of spatially‐varying soil properties. Because normal and log‐normal distributions have been commonly used to describe the variability of several soil properties, a Monte Carlo study was performed to determine the sample size required for selecting, with a prescribed level of confidence, between these two distributions. It was found that the required sample size increased with decreasing coefficient of variation (CV = standard deviation/mean). However, both normal and log‐normal distributions may adequately describe a set of measurements with CV ⩽ 0.4. In such cases, it was shown that accepting normal distribution as the appropriate distribution when the true distribution is, in fact, log‐normal, would involve a maximum error of about 20% when the mean is used instead of the mode.
Effects of Calcium, Manganese, and Aluminum on Growth of Rhizobia in Acid Media
Authors: Keyser H. H. , Munns D. N. 
Published: July 2010

AbstractGrowth studies were done in defined liquid media to assess effects of Mn toxicity and Ca deficiency associated with soil acidity. The study included 23 strains of cowpea rhizobia previously found capable of growth at 4.5 and 10 strains of Rhizobium japonicum tolerant of pH 4.8. The low level of Ca (50 µM) represented the extreme low range in soil solutions, and the high level of Mn (200 µM) has been found toxic to legume hosts of the strains tested.In a detailed growth study of three cowpea strains at pH 4.6, low P (10 µM) limited maximum population density in all three strains. Low Ca limited it in one strain.A rapid screening method based on attainment of turbidity from a small inoculum was applied to the cowpea rhizobia at pH 4.5 and soybean rhizobia at 4.8. High Mn and low Ca slowed growth of some strains, but Mn stopped growth of none and low Ca stopped growth of only three strains. Neither was as severe a stress as 25–50 µM Al, simultaneously observed and previously reported. All strains tolerant of Al were tolerant of Mn and low Ca.Possible amelioration of Al toxicity by Ca was tested in three cowpea strains, by a factorial experiment with three Ca levels (50–1,000 µM) and four Al levels (0–100 µM), at pH 4.5 in liquid media. Calcium had a statistically significant protective effect against Al in two strains, but the effects were small and probably of no biological or practical significance.In acid soils, Al toxicity and acidity itself are probably more important limiters of rhizobial growth than Mn toxicity and Ca deficiency.
Denitrification Intensity and Capacity of Three Irrigated Alberta Soils
Authors: Cho C. M. , Sakdinan L. , Chang C. 
Published: July 2010

AbstractSamples from three Alberta soil profiles were used to investigate the denitrification intensity of the soils as related to depth. At 20°C, the intensity was high at the surface and decreased exponentially with depth. The temperature dependency of the intensity on several samples was also studied. By combining the depth and temperature dependencies, the denitrification intensity was predicted for an arbitary temperature and depth. A simple mathematical formulation relating soil temperature with seasonal time and depth was substituted, thus enabling the calculation of denitrification intensity at any time of the year. The calculation indicated that denitrification activity was restricted in the deep hrozions in December and January and in the surface horizons in early May. There was no activity throughout the soil profile in February and March. Loading capacity of a soil for nitrate N expressed as input rate (flux) was equal to the denitrification capacity which was obtained by integrating the intensity throughout the soil profile. The values were approximately 70 kg N ha−1 day−1 in August and 5 kg N ha−1 day−1 in December. The maximum allowable nitrate concentration is directly proportional to the denitrification capacity and inversely related to the percolating water speed.
The Effect of Amprolium and Aureomycin on the Nitrification of Poultry Manure‐Amended Soil
Authors: Warman P. R. 
Published: July 2010

AbstractPoultry manure from animals fed recommended levels of amprolium and aureomycin was added to a Guelph loam soil. A soil perfusion experiment indicated that the feed additives in the manure had no effect on the nitrification rate of the soil. The rates of nitrification were 8.8 µg NO3‐‐N·g soil−1·day−1 for the 11.2 metric tons/ha addition, 28.8 µg NO3‐‐N·g soil−1·day−1 for the 33.6 metric tons/ha manure addition, and 32.4 µg NO3‐‐N·g soil−1·day1‐ for the addition of 0.0028M (NH4)2SO4 solution.
Flow of Kaolinite and Sewage Suspensions in Sand and Sand‐Silt: I. Accumulation of Suspension Particles
Authors: Uebler R. L. , Swartzendruber D. 
Published: July 2010

AbstractWater suspensions of kaolinite clay and sewage solids were applied to vertical columns of initially air‐dry fine quartz sand and sand‐silt (95% fine quartz sand and 5% quartz silt), and sand‐silt initially satiated (nearly saturated) with water. Water content and suspension‐particle content (bulk density) were measured at various vertical positions in the column by dual‐energy gamma‐ray attenuation, beginning with the application of suspension and continuing until the overall hydraulic conductivity of the column had decreased to 1 mm/hour. The attenuation technique was successful for measuring the kaolinite bulk density but was of limited value for determining the sewage‐solid bulk density. By postulating a mechanism of suspension‐particle entrapment within the porous medium, an exponential equation was derived to describe the accumulation of suspension particles with time at a fixed position. The constants in this equation were determined from the experimental data by nonlinear least‐squares regression and appeared to offer promise for characterizing the kaolinite accumulation in the sand and sand‐silt. In general, the maximum accumulation of kaolinite occurred in the several millimeters nearest the suspension‐application surface. The initial water content (air‐dry or satiated) had little effect on kaolinite accumulation in the sand‐silt, and the detectable depth of penetration was 3 to 4 cm in both cases. In contrast, kaolinite penetration to about 16 cm was detected in the initially air‐dry sand, whereas the maximum (near‐surface) accumulations were larger than in the sand‐silt but required much more time to attain.
Accumulation of Nitrogen in Minesoils Seeded to Black Locust
Authors: Jencks E. M. , Tyron E. H. , Contri M. 
Published: July 2010

AbstractNitrogen accumulation in minesoils developing in replaced coal surface‐mine overburden seeded with black locust (Robinia pseudoacacia L.) was surveyed. Nitrogen increased significantly with age from 5 to 18 years at depths of 0 to 5, 5 to 10, and 10 to 15 cm, until it equaled or exceeded that in adjacent, native soils; however, the rate of increase was slower in the lower depths. Averages of the N content in all three depths showed that the oldest age group of minesoils (16 to 18 years) accumulated 2,974 kg/ha under black locust, which was slightly higher than the 2,808 kg/ha of N found in an adjacent native soil under mixed hardwood.
Temperature Dependence of Soil Hydraulic Properties
Authors: Hopmans J. W. , Dane J. H. 
Published: July 2010

AbstractThe study of soil water movement under nonisothermal conditions requires knowledge of the hydraulic properties as a function of temperature. A dual‐energy gamma system was used to investigate temperature effects on the water retention curve and the hydraulic conductivity function of a Norfolk sandy loam soil (Typic Paleudults). These hydraulic properties were determined from simultaneous measurements of soil water pressure head, volumetric water content, and soil temperature at 13 measurement points along a lucite flow cell during transient drainage conditions while maintaining a temperature gradient. It was concluded that temperature influences water retention more than can be explained by surface tension changes of pure water only. Entrapped air was not considered to be the primary cause of the larger temperature effect. The influence of temperature on measured hydraulic conductivities was close to predictions from viscosity changes for most of the measurement points. Deviations from predicted hydraulic conductivity values were attributed to thermal vapor flow. Temperature had little or no effect when the hydraulic conductivity was plotted vs. soil water pressure head.
Soil Strength Properties Under Four Tillage Systems at Three Long‐Term Study Sites in Indiana
Authors: Larney Francis J. , Kladivko Eileen J. 
Published: July 2010

AbstractThere is increasing concern that long‐term continuous conservation tillage may cause increased surface soil strength and compaction detrimental to root growth and crop yield. The objective of this study was to characterize distribution of cone index (CI) and vane shear strength (VS) values at three row positions: in row (R), non‐wheeltrack interrow (NW), and wheeltrack interrow (WT), under four tillage systems: conventional moldboard plow (PL), chisel plow (CH), ridge‐till‐plant (RT), and no‐till (NT), on three long‐term tillage studies on silty soils in Indiana. The Mollisol and Alfisols studied had been under the continuous tillage treatments for 13, 8, and 4 yr, respectively. Maximum cone index (CImax) averaged over three row positions was in the order RT > CH, NT > PL. As less tillage was performed, the zone of maximum strength was closer to the soil surface. Depth of CImax was in the order PL > CH > NT, RT. On the two Alfisols, soil strength in the non‐trafficked positions (NW and R) tended to be lower in no‐till than in the other tillage treatments, especially in the lower portion (below 15 cm) of the formerly tilled zone. High‐strength layers were recorded at 23 to 40 cm and 15 to 22 cm on the PL and CH treatments, respectively. Wheeltrack compaction was more severe under RT and NT than on PL and CH. Vane shear data generally verified the tillage and row position effects found with the cone penetrometer.
Quantitative Determination of Vermiculite by a Rubidium Fixation Method
Authors: Ross G. J. , Schuppli P. A. , Wang C. 
Published: July 2010

AbstractA rubidium‐fixation method for the quantitative determination of vermiculite is described. The results obtained by this procedure were similar to, but more precise than, the results obtained by the conventional cation exchange procedures. The exchangeable Rb of a Rb‐saturated and heated sample is replaced by NH4 and the remaining fixed Rb is determined directly by dissolving the sample. The vermiculite content is calculated from the fixed Rb content. The Rb‐fixation method is well suited for determining small changes of vermiculite content in soils.
Blue Grama Herbage Yield in Relation to Available Soil and Herbage Zinc Contents
Authors: White E. M. , Gartner F. R. 
Published: July 2010

AbstractBlue grama (Bouteloua gracilis [HBK] Lag. ex Steud.) growth on weathered claypan soils can be increased by Zn fertilization. Relationships between herbage yield and Zn content and soil dimethylenetriaminepentaacetic acid (DTPA)‐extracted Zn need to be established so that areas needing Zn can be identified more accurately. The objectives are to determine the soil DTPA‐Zn and herbage‐Zn contents needed by blue grama. Zinc‐deficient claypan soils and glacial‐till‐derived soils with adequate Zn were used to grow blue grama that was unfertilized or fertilized with N, NPK, or NPK plus minor elements (ME). The DTPA‐extracted soil Zn, Cu, Mn, and Fe were determined to establish the soil Zn levels needed and the possible interaction of other cationic ME on Zn. For the same reason, the ash, Zn, Mg, Co, Mn, Fe, and P contents were determined for blue grama herbage grown in the greenhouse on a Zn‐deficient claypan soil treated with eight Hoagland‐type solutions. Solution 1 contained NPK; 2, NPK + B; 3, NPK + B + Zn, and additively in succession Mn, Fe, Cu, Mo, and Co. Possible changes in Zn content with increasing herbage age were studied with two groups of plants harvested after different‐length, but overlapping, growth periods. The herbage harvested was analyzed for Zn, P, and N. The DTPA‐extracted soil Zn must be about 2 mg kg−1 for growth, although NPK fertilization may increase growth and decrease extractable Zn to a lower amount, at least temporarily. For vigorous plants, young herbage has at least 11 to 13 mg Zn kg−1. Older herbage has less Zn, particularly if Zn is limiting growth after NPK has been added. The DTPA‐extractable soil Zn contents were not related to the extracted Fe, Cu, or Mn contents. Plant Zn and Mg contents were correlated, but not to Co, Mn, Fe, or P contents.
Single‐Tree Influence on Earthworms in Forest Soils in Eastern Kentucky
Authors: Boettcher S. E. , Kalisz P. J. 
Published: July 2010

AbstractVegetation may affect earthworm populations directly through inputs of litter and leachates, and indirectly through alteration of soil properties. This study examined the characteristics of earthworm populations on an area where small‐scale spatial patterns in soil properties were previously shown to be due to the influence of individual trees and understory species. Earthworm densities in the O horizon and in the upper 20 cm of mineral soil ranged from 0 to 20 and from 0 to 80 individuals/m2, respectively. Density was significantly lower in mineral soils under both yellow poplar (Liriodendron tulipifera L.) and eastern hemlock (Tsuga canadensis [L.] Carr.) when rhododendron (Rhododendron maximum L.) was present in the understory, compared with under the same two tree species when rhododendron was absent. Bimastos parvus Eisen, a species characteristic of inhospitable sites, was dominant on rhododendron plots, but was replaced by Komarekiona eatoni Gates and Eisenoides carolinensis Michaelsen in the absence of rhododendron, especially on plots under yellow poplar. In mixed‐species forests, abundance and species composition of earthworm assemblages are spatially variable in correspondence with patterns of soil properties and of the occurrence of tree and understory plant species.