bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dissolution of Phosphate Rocks in a Flooded Acid Soil
Authors: Chien S. H. 
Published: July 2010

AbstractSeven phosphate rocks from widely separated locations were used to investigate the dissolution of phosphate rocks in an acid, P‐deficient soil (Mountview silt loam, pH 4.8) under waterlogged conditions. The phosphate rock was added at a rate of 400 ppm P in the soil. The objective of the study was to investigate the way in which the P concentration in the soil solution equilibrated with the various phosphate rocks was related to the apatite composition and the citrate solubility of the phosphate rocks used.The concentration of P in the soil solution equilibrated with various phosphate rocks during incubation varied considerably among sources of the rock, ranging from 0.03 to 0.35 ppm in 1 week and 0.04 to 0.11 ppm in 10 weeks after the soil was flooded. The solubility differences of various phosphate rocks decreased as incubation time increased.The P concentrations in the soil equilibrated with phosphate rocks reached a maximum 1‐3 weeks after the soil was flooded. There was a linear relationship (r = 0.93) between the logarithm of the maximum P concentrations in the soil solution equilibrated with phosphate rocks and the degree of carbonate substitution for phosphate in the apatite structure of the phosphate rocks used. A highly significant linear correlation (r = 0.95) was found between the maximum P concentration in the soil solution and the citrate solubility of the phosphate rocks used. The correlation, however, decreased to 0.82 in 10 weeks after the flooding. Apparently, factors other than apatite composition were also affecting the dissolution of phosphate rocks in the soil solution after prolonged incubation.
Phosphorus Fractions in Selected Nigerian Soils
Authors: Udo E. J. , Ogunwale J. A. 
Published: July 2010

AbstractThe distribution of total, organic, and various inorganic phosphorus forms was determined for six Nigerian soil profiles selected to cover different ecological zones and geological formations. Total P was generally low in most of the profiles ranging from 144 to 791 ppm. The basaltic Dogon Gaba soil contained the highest amounts while the soil formed on sedimentary deposits had the lowest values. The relative abundance of the extractable inorganic fractions was generally in the order of occluded P > Fe − P > Al − P > Ca − P except in Dogon Gaba and Agbaru (Etinan) where Al − P was more abundant than Fe − P and in Egbeda with Ca − P more important than Al − P (the latter being negligible in this soil). A large fraction of the inorganic P remained in the nonextractable or residual form especially in soils from the savanna region. Organic P was low in the soils from the savanna zone, but high in those soils from the forest region. The high percentage of occluded and residual P and the low level of active P indicated a high degree of weathering and a low available P status of the soils.
Correction for Dissolved Nitrous Oxide in Nitrogen Studies
Authors: Moraghan J. T. , Buresh R. 
Published: July 2010

AbstractRapid methods for the accurate determination of N2O in atmospheres of closed incubation flasks are now available. However, serious errors in measuring total N2O within a closed system may arise if dissolved N2O is not considered. Temperature and the ratio of solution volume to atmosphere volume are important factors determining the magnitude of errors resulting from this cause. A simple formula for calculating dissolved N2O based on solution and atmosphere volumes, the mass of N2O in the gaseous phase, and published solubility data for N2O in water is presented. If the chemical composition of the solution phase is likely to influence solubility coefficients, these values can be experimentally determined using a described technique.
Solute Transport Through Soil With Nonuniform Water Content
Authors: De Smedt F. , Wierenga P. J. 
Published: July 2010

AbstractAn approximate analytical solution is presented for steady flow of salt through soil with a nonuniform distribution of the water content. The solution is in good agreement with a numerical computer solution, provided by the CSMP simulation language. Both solutions also agree with the analytical solution for soils with a uniform distribution of the water content. It is shown that effluent curves from soil profiles, with the same average water content and leached at the same steady rate, are basically the same and thus independent of the variation of the water content in such profiles.
Cumulative Effects of Nitrogen, Phosphorus, and Potassium Fertilizer Additions on Soil Respiration, pH, and Organic Matter Content
Authors: Van Cleve Keith , Moore Terry A. 
Published: July 2010

AbstractCumulative effects of annual additions of NH4NO3 (111 kg/ha N), treble superphosphate (55 kg/ha P), and KCl (111 kg/ha K) on aspen (Populus tremuloides Michx.) soil respiration, pH, and soil organic matter content were examined. Total fertilizer additions from fall 1969 through spring 1975 were 777 kg/ha N and K and 385 kg/ha P.The main effect of N and P additions was to increase soil biological activity by up to 42% and 33%, respectively, with the greatest increases occurring at the 15‐ to 30‐cm soil depth. For K, a 21% reduction in soil biological activity occurred at 0‐ to 15‐cm, while a 20% increase was found at 15‐ to 30‐cm. Fertilization with N and P increased but K showed no effect on surface soil organic matter content. Subsurface soil (15‐ to 30‐cm) organic matter content was not affected by any treatment. Higher soil organic matter content probably resulted largely from greater aspen growth response to N. Increased soil biological activity was attributed to a combination of increased soil organic matter content and improved levels of soil N and P.Treatment with N, K, or N + K reduced soil pH, possibly because of microbial nitrification of NH4+ associated with uptake by aspen of NH4+ and K+ with replacement of H+ in the soil.
Comparative Foliar Analysis of Young Balsam Fir Fertilized With Nitrogen, Phosphorus, Potassium, and Lime
Authors: Timmer V. R. , Stone E. L. 
Published: July 2010

AbstractFoliar analyses of individually fertilized balsam fir trees [Abies balsamea (L.) Mill.] were examined to explain significant growth responses and nutrient status changes. Treatments consisted of factorial combinations of N, P, and K, and one separate treatment of dolomitic lime. Simultaneous comparisons of first year changes in foliar nutrient concentration, content, and dry weight simplified assessment of deficiency, dilution, and luxury consumption. N fertilization increased both needle dry weight and N composition, but lowered foliar P, K, Ca, and Mg concentrations by dilution. Additions of P and/or K did not change needle weight and led to luxury consumption of P and K. Lime alone had no measurable effect in the first year. Overall correlations between foliar concentration and content of individual nutrients accounted for 68–78% of the total variability for foliar P, K, Ca, and Mg, but 99% for foliar N which was unaffected by dilution. A concentration of 2.1–2.3% N in current foliage is the approximate upper limit for growth response for these balsam fir trees.
Leguminous Plants Increase Sycamore Growth in Northern Alabama
Authors: Haines Sharon G. , Haines L. Wayne , White Gordon 
Published: July 2010

AbstractTree growth in a 2‐year‐old sycamore (Platanus occidentalis L.) plantation in northern Alabama significantly increased over the following 4 years after three clovers and two vetches were grown with the trees. Leguminous plants were chosen to: (i) provide weed control through good ground coverage, (ii) maintain a low profile, (iii) grow during the cool season so as not to compete with the sycamore, (iv) provide cover for several years after establishment through their ability to reseed, and (v) make additional nitrogen (N) available through the fixation process. Following establishment of the leguminous plants, sycamore height and volume growth were increased as were N concentrations in sycamore foliage. Of the plants tested, Mississippi subterranean (Trifolium subteraneum L.) and crimson clovers (T. incarnatum L.) gave good ground coverage, maintained a low profile, reseeded themselves well, and increased the N content of sycamore foliage in addition to improving height and volume growth.
An Improved Moistening Technique for Aggregate Stability Measurement
Authors: Mubarak A. , Klages M. G. , Olsen R. A. 
Published: July 2010

AbstractAn ultrasonic nebulization technique has been used for uniform wetting of soil by introduction of an aerosol. Values obtained for aggregate stability of air‐dried soils were greater when this technique was used than with conventional wetting techniques, apparently because of reduced slaking effect.
Nutrient Effectiveness in Relation to Rates Applied for Pot Experiments: I. Nitrogen and Potassium
Authors: Terman G. L. , Mortvedt J. J. 
Published: July 2010

AbstractAn N source experiment was conducted on infertile Mountview sil (Typic Paleudult) to evaluate four N sources at multiple rates of applied N and P. Granular ammonium nitrate (AN), sulfur‐coated urea (SCU), oxamide (Ox), and isobutylidene diurea (IBDU) were evaluated for corn (Zea mays L.) at N rates of 0, 400, 800, and 1,200 mg/pot (5 kg of soil), each at P rates of 0, 60, 120, 480, and 960 mg/pot. Yield response to applied N was in the order AN >> SCU > Ox > IBDU at the higher rates of applied P. At 60 and 120 mg of applied P/pot, however, P was too deficient for satisfactory evaluation of the N sources. In an experiment with flooded rice (Oryza sativa L.), P limited yields less than did N. In other N‐P and P‐K factorial experiments, rates of other nutrients and length of growth period also greatly affected crop response to applied N and K. These results show that satisfactory evaluations of N or K sources are possible only at adequate rates of nontest nutrients. Nutrient rates adequate for small greenhouse pots are much higher than rates equivalent to normal rates recommended for crops grown under field conditions. Length of growth period and other growth‐limiting factors are equally important.
Hydraulic Conductivity of Soils: Unified Approach to the Statistical Models
Authors: Mualem Y. , Dagan G. 
Published: July 2010

AbstractConceptual theory of the hydraulic conductivity of unsaturated porous media is presented. This analysis permits us to derive systematically the models of R. C. Childs and N. Collis George (1950), M. R. J. Wyllie and G. H. F. Gardner (1958) and Y. Mualem (1976) as well as other existing and new versions, from some common statistical principles.The resulting formulas of unsaturated hydraulic conductivity can be classified into three categories: (i) universal formulas independent of the soil type which result from extremely simplifying assumptions; (ii) formulas with one degree of freedom, and (iii) formulas with two degrees of freedom. The latter two types of equations result from accounting for the correlation between pores and the tortuosity of flow path. These formulas can be adjusted to soil type to represent better the variability of soil properties and increase the accuracy of the predicted hydraulic conductivity. However, in this stage it is a potential advantage only. Empirical study should be followed in order to derive the optimal methods of estimating the unknown parameters.
Water Redistribution in Partially Frozen, Saturated Silt Under Several Temperature Gradients and Overburden Loads
Authors: Loch J. P. G. , Kay B. D. 
Published: July 2010

AbstractThe flux of water and the resultant formation of discrete ice lenses were studied in samples of New Hampshire silt which were saturated and then frozen under different temperature gradients and overburden pressures. A dual energy gamma scanning system was employed to locate the position of the growing ice lens relative to the freezing front. Parameters controlling water flow and the location of the ice lenses were employed to evaluate theories that have been proposed to describe the mechanisms of ice lens formation. The capillary theory was employed to locate the freezing front. However, the ice lenses were found to be located 0.2–0.4 cm behind the freezing front, which is inconsistent with the location of the ice lenses predicted by the capillary theory. Neither the hydrodynamic theory, nor the secondary frost heaving theory account for the redistribution of overburden pressure between soil particles, ice, and water. These theories cannot be employed to predict the location of the ice lens relative to the freezing front until overburden pressure effects are incorporated into the theory.
Influence of FeEDDHA on Growth and Manganese Accumulation in Flax
Authors: Moraghan J. T. , Freeman T. J. 
Published: July 2010

AbstractA lower leaf‐scorch abnormality, resembling Mn toxicity, was observed in flax (Linum usitatissium L.) plants growing on certain calcareous soils. The cause of this problem was studied in greenhouse experiments using a naturally occurring, slightly calcareous (pH 8.1) soil. Above‐ground parts, but not roots, of afflicted plants contained relatively high levels of Mn. Addition of 2 ppm FeEDDHA‐Fe eliminated the appearance of brownish spots on the distal portions of older leaves and subsequent leaf necrosis, decreased Mn accumulation in above‐ground plant parts, and increased yields. Ammonium molybdate (0.05 and 0.5 ppm Mo) had no effect on the severity of the abnormality or on Mn accumulation. Cytological examination of brown spots showed distortion of chloroplast membranes, absence of starch, decrease in grana membranes, absence of plastid ribosomes, and increase in plastoglobuli. It is hypothesized that the lower leaf scorch was caused by Mn toxicity. Flax, in the absence of FeEDDHA, was a Mn‐accumulator plant even though the soil in question was calcareous. Available soil Fe level appeared to be a dominant factor influencing Mn accumulation by flax.
Influence of Vegetation on Water Repellency in Selected Western Wisconsin Soils
Authors: Richardson J. L. , Hole F. D. 
Published: July 2010

AbstractWater repellency in several western Wisconsin soils was characterized by three tests: wetting angle (θ), wetting drop penetration‐time (WDPT), and 90°‐surface tension (γη). It appears that the high contents of organic matter in the A horizon of Mollisols and Alfisols are associated with slight repellency as measured by θ and WDPT. Frequent burning of a prairie on a Mollisol increased persistence (WDPT) and γη, as compared with soil at a nearby control site, but had no influence on θ, indicating that repellency is present at initial water contact but is unstable and disappears with prolonged water contact.Mor litter layers having observable fungal mycelia had repellent surfaces as measured by all three of the above tests. These repellent materials were observed in Spodosols under red pine (Pinus resinosa), hemlock (Tsuga canadensis), and under a mixed hard and soft wood stand with dense ericaceous shrub understory. The repellency of mor horizons of Spodosols may relate in some significant way to process of genesis of Spodic horizon.
Nitrogen Mineralization and Uptake from Douglas‐Fir Forest Floors
Authors: Youngberg C. T. 
Published: July 2010

AbstractMany different plant species grow in the understory in association with Douglas‐fir [Pseudotsuga menziesii (Mirb.) Franco]. The nature of the forest floor that accumulates in a Douglas‐fir forest is influenced by these associated species. Nitrogen uptake from forest floor materials developed under nine commonly occurring stand understory conditions was evaluated in a greenhouse experiment with Douglas‐fir seedlings. The net mobilization of N as measured by the uptake of N by two successive crops of Douglas‐fir seedlings ranged for 0.34 to 9.89% of the amount added as organic matter. Net N mobilization was related only partially to total N content of the material.
Proposed Changes in Sandy Textural Class Definitions
Authors: Franzmeier D. P. , Norton L. D. 
Published: July 2010

AbstractAccording to present definitions of USDA textural classes, some sandy particle‐size distributions can not be placed in any class. We propose changes in the definitions of fine sandy loam, sandy loam, loamy sand, and sand so that all distributions can be classified, facilitating computer computation of texture classes.
Solute Transport During Absorption of Water by Soil: Laboratory Studies and Their Practical Implications
Authors: Smiles D. E. , Philip J. R. 
Published: July 2010

AbstractAn experimental study of solute transport during absorption into uniform horizontal soil columns is reported.Three pairs of experiments were performed. Each pair had a common initial moisture content (0.04, 0.1, or 0.15), with one experiment involving displacement of concentrated soil solution by dilute solution and the other, vice versa.In all experiments, both the soil solution content and the salt concentration preserved similarity in terms of distance divided by square root of time. This confirmed earlier observations that the longitudinal dispersion coefficient for the conditions of these experiments is effectively independent of volume flux density. These results were found to be consistent with the studies of Saffman (1959) and Pfannkuch (1963) on transport during steady flow.The inferred dispersion coefficient is essentially independent also of the volumetric moisture content (at least in the range 0.18–0.28). It is approximately equal to the product of the volumetric moisture content and the molecular diffusivity of KCl in water.The practical implications of the work for field problems are explored, use being made of scaling theory for flow processes involving capillarity and viscous flow. It is concluded that, for the majority of field soils, solute transport during unsaturated flow of any practical duration may be described by a velocity‐independent dispersion coefficient. This represents a very great simplification of the formulation, analysis, and prediction of solute transport in such systems.The observed pistonlike displacement of the initial water in the columns by the absorbed water suggests that there is no basis for subdividing the water in the system into mobile and immobile fractions.Further theoretical and experimental work is under way on solute transport during infiltration, and during absorption into very coarsetextured soils (for which the dispersion coefficient is not velocity independent).
Transient Changes in the Soil‐water System from Irrigation with Saline Water: I. Theory
Authors: Jury W. A. , Frenkel H. , Stolzy L. H. 
Published: July 2010

AbstractTransient soil solution concentrations and salt precipitation rates in the root zone are shown to be influenced by the ion composition and concentration of the applied water and soil exchange complex as well as by the water uptake distribution and infiltration rate. Calculations are performed on three kinds of infiltration water to estimate the ionic composition of the soil solution, the rate of gypsum and CaCO3 precipitation, and the time to reach steady state for a given irrigation management. Solution concentrations adjusted for exchange interactions were shown to precipitate twice the quantity of salt in a given time, resulting in lowered solution concentration and altered composition of Ca2+, Mg2+, Na2+, and SO42‐ ion concentrations in the solution phase, with up to 1,600 days required to reach steady state through the top 150 cm for a leaching fraction of 0.05. The extent of precipitation is also found to depend strongly on the concentration of sulfate and degree of saturation with gypsum in the irrigation water. Diffusion and dispersion are also shown to influence the duration of the transient phase.
Water Harvesting for Afforestation: I. Efficiency and Life Span of Asphalt Cover
Authors: Mehdizadeh P. , Kowsar A. , Vaziri E. , Boersma L. 
Published: July 2010

AbstractThe water required to irrigate greenbelts being established around cities in Iran is a major cause of concern in a country with insufficient supplies. Methods of afforestation which do not require irrigation must be found. One such method is to concentrate water, received by a watershed without vegetation, for distribution over a smaller area where plants are growing by making portions of the watershed area impervious to water through application of asphalt. This principle was tested on runoff plots 2 m wide and 10 m long. Runoff from each plot was measured to study its variations as a function of age of asphalt cover and rainfall amount and intensity. The concept was further tested by constructing 2‐m wide terraces along contour lines at 5‐m intervals on a hillside with a slope of about 30%. Tree species, ecologically adapted to the area, were planted on the terraces. Calibrated gypsum blocks were placed at depths of 15, 30, 45, and 60 cm in the terraces and at depths of 10 and 30 cm in the watershed area between the terraces to measure soil water potentials.As the asphalt membrane aged, its efficiency in inducing runoff decreased. The runoff efficiency was nearly 75% initially, but decreased to 25% after 4 years. A regression equation was obtained correlating the runoff efficiency with age of the asphalt membrane. Freezing and thawing of the soil, growth of plants, and shrinking and swelling of clays resulted in the deterioration of the membrane. It remained effective for about 5 years.The runoff from the asphalt‐sprayed microwatersheds resulted in high soil water contents of the terraces, with average potentials of −0.4, −7.7, and −2.5 bars during 1972, 1973, and 1974 where runoff was received, corresponding to −7.7, −23.8, and −21.8 bars on control plots.The technique is being developed as an alternative to the irrigation practices now in use for the establishment of greenbelts. It will result in savings of water, which in some localities could amount to 5,000 m3/ha/year, an amount sufficient to satisfy the needs of 50 people per year.
Relationship of Extractable Soil Manganese to Soil Properties
Authors: Shuman L. M. , Anderson O. E. 
Published: July 2010

AbstractIn a greenhouse experiment eight Southeastern soils were amended to give pH levels of 4.8, 5.8, and 6.8 and were treated with 0, 25, and 50 ppm Mn. After growing wheat (Triticum aestivium L.) for 40 days, the soils were extracted for Mn using six extractants: H2O, neutral 1N NH4OAc (with and without 0.2% hydroquinone), “double acid”, diethylenetriaminepentaacetic acid (DTPA) and ethylenediaminedi‐o‐hydroxyphenylacetic acid (EDDHA). Except for the low‐Mn soils, greater differences in extractable Mn were observed among soil types and soil pH levels than among Mn rates. Extractable Mn was correlated with soil clay content and total soil Mn. Organic matter content with a narrow range from 1.0 to 2.9%, silt content and cation exchange capacity (CEC) were not correlated with extractable Mn. The extractable Mn decreased as soil pH increased for the H2O, NH4OAc alone, and DTPA extractants making them preferable for predicting soil Mn availability since higher pH causes Mn to be less available to the plant.