bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time‐dependent Linearized Infiltration: III. Strip and Disc Sources
Authors: Warrick A. W. , Lomen D. O. 
Published: July 2010

AbstractWater flow from strip and disc surface sources is analyzed using an approach similar to previous investigations with line and point sources. A line of closely spaced trickle irrigation emitters often wets a surface strip of finite width; similarly, for a single emitter the surface wetted pattern is a disc. Lines of equal matric flux potential are wider and more shallow for these sources than wetting patterns for the line and point. The moisture regime is independent of the source shape and depends only on the total flow rate for regions beyond approximately two times the strip width or disc radius.
Scanning Electron Microscopy of a Humic Acid and of a Fulvic Acid and its Metal and Clay Complexes
Authors: Chen Y. , Schnitzer M. 
Published: July 2010

AbstractA Scanning Electron Microscope was used to explore the effect of varying the pH on the shape, size, and degree of aggregation of humic and fulvic acid particles. The structure of the complexes formed by fulvic acid when reacted with Cu2+, Al3+, Fe2+, and Fe3+ was also studied, as was the reaction product of Na‐montmorillonite and fulvic acid.At low pH (2–3), fulvic acid occurred mainly as elongated fibers and bundles of fibers, forming a relatively open structure. With increase in pH (4–7), the fibers tended to mesh into a finely‐woven network to yield a sponge‐like structure. Above pH 7, a distinct change in structural arrangement and improved orientation was observed. At pH 8, the fulvic acid formed sheets which tended to thicken at pH 9. At pH 10, fine, homogeneous grains were visible. The effect of pH on the humic acid structure was similar to that observed on fulvic acid except that because of low solubility in water, the pH range had to be narrowed to between 6 and 10 and the pH at which the major transitions occurred was higher.Micrographs of fulvic acid‐metal and fulvic acid‐clay complexes show interesting possibilities for the use of this approach in investigations on metal‐ and clay‐humic complexes.
Comments on Nitrate Reduction in Unsaturated Soil
Authors: McLaren A. Douglas 
Published: July 2010

AbstractCyclic oxidation and reduction of nitrite and nitrate in soil are analysed in terms of first‐ and zero‐order microbial kinetic reactions, respectively. A reversible reaction step involving these ions can account for a low, but constant concentration of nitrate in an unsaturated field soil for long periods or for considerable depths in a laboratory soil column.
Iron‐manganese Concretions in Hydrosequences of Soils in Loess in Bavaria
Authors: Schwertmann U. , Fanning D. S. 
Published: July 2010

AbstractTo expand knowledge about the nature and distribution of Fe‐Mn concretions in soils, and in particular about their relation to degree of hydromorphism, the amounts and composition of concretions (0.2–0.63, 0.63–2.0, and >2.0‐mm diam) in profiles of two hydrosequences on loess in Bavaria, Germany were determined. Concretions were separated by wet sieving air‐dried soil samples. Maximum concretion formation (up to 7.5 weight percent) occurred in the upper B horizons (∼50‐cm depth) approaching the surface with increasing wetness. Maximum concretion formation (up to 40 kg/m2) also occurred under medium wetness and not in the wettest profile. Mn, Fe, and P (except not P in the wettest members) were concentrated in the concretions, Fe predominantly as goethite, Mn presumably as birnessite and P (as concluded from correlations) adsorbed to Fe‐oxides, but not to Mn‐oxides. Selected concretion and microprobe studies showed that during concretion formation Mn with Some Fe is concentrated first with Mn being essentially exhausted at a later stage where nearly only Fe accumulates. Inasmuch as P from 2,000‐year‐old bones accumulated in concretions, their formation appears to have been continuing through recent time.
Prediction of Evaporation from Columns of Soil During Alternate Periods of Wetting and Drying
Authors: Staple W. J. 
Published: July 2010

AbstractThis analysis was undertaken to test certain approximations in using finite difference methods to compute evaporation and soil water conservation. Analysis of four evaporation experiments showed that water movement in Wood Mountain clay loam was sufficiently repeatable during wetting and drying to permit computation of evaporation losses on the basis of predetermined soil properties. The experiments involved evaporation after the following treatments: (i) infiltration penetrating partway down columns of air‐dry soil; (ii) infiltration and 7 days' redistribution; (iii) treatment (ii) plus additional infiltration; and, (iv) repeated infiltration applied at different stages of initial drying.In computing evaporation the Richards and Dalton flow equations were used with soil and atmospheric parameters. Temperature gradients in the soil were neglected. Hydraulic conductivity of the surface layers of soil were adjusted empirically to estimate combined liquid and vapor movement and to correct for disruptive effects such as dispersion, air blockage, and swelling near the surface. The independent domain theory was used to estimate the influence of hysteresis on capillary pressures during alternate wetting and drying. Agreement between measured and computed evaporation was satisfactory following infiltration except when water was added after > 7 days' evaporation.
No‐tillage Effects on Soil Properties under Different Crops in Western Nigeria
Authors: Lal R. 
Published: July 2010

AbstractFive years of no‐tillage vs. the conventional method of tractor plowing significantly affected the physical and chemical properties of an Alfisol in western Nigeria. Continuous cropping of maize for 3 consecutive years was followed by 4 seasons of cultivation with cropping sequences of maize‐maize (Zea mays L.), maize‐cowpeas (Vigna unguiculata L. walp.), pigeon peas (Cajanus cajan Millsp.)‐maize, soybeans‐soybeans (Glycine max Merr.), maize‐soybeans, and cowpeas‐cowpeas. The no‐tillage plots had higher organic matter contents in the surface soil horizons and higher concentrations of nitrate‐nitrogen, Bray‐1 available phosphorus, and ammonium acetate extractable cations such as Ca2+, Mg2+, and K+ than the plowed plots. The infiltration rates of no‐tillage plots were higher than those of the plowed plots and, thus, runoff and erosion losses were minimal. Although maximum soil temperatures were higher in the plowed plots, the no‐tillage plots had higher soil moisture contents throughout the growing seasons. Greater earthworm activity in the no‐tillage plots reduced compaction and crust formation. Yields equal to those from the plowed plots were harvested from the no‐tillage plots under suitable crop rotations.
Anomaly and Modification of pH‐Acidity Relationship in the Double Buffer Method for Lime Requirement Determination
Authors: Yuan T. L. 
Published: July 2010

AbstractA break at pH 6.2–6.3 was observed recently in the linear titration curve of the buffer used in the double buffer method (Yuan, 1974). As a result, different pH‐acidity relationships above and below this pH would have to be used in the lime requirement calculation. An attempt was made to investigate the possible cause or causes for the break. Suspected contamination of Cr2O72‐ in the K2CrO4 reagent originally used in the development of the method was investigated as was the effect of CaCl2 on buffering behavior of CrO42‐. Although a completely satisfactory explanation of the anomaly was not obtained, it appears that higher purity of currently available K2CrO4 is involved. A modification of the buffer composition was made to give a linear curve with currently available chemicals so that the soil lime requirement can be more easily calculated. A table to show the soil buffering capacity based on a linear 1:1 pH‐acidity relationship has also been added.
Soil Water Deficits Under Forested and Clearcut Areas in Northern Arkansas
Authors: Rogerson T. L. 
Published: July 2010

AbstractSoil water under forested and cut areas on northwest and southeast aspects was measured with a neutron probe system at weekly intervals to study soil water deficit patterns under these conditions. Soil water deficits were significantly different among years, seasons, and vegetative covers. Summer deficits increased at the average rate of 2.1 mm/day on the forested and 0.6 mm/day on the cut areas. Average seasonal deficits for forested and cut areas, respectively, were: spring, 23 mm and 16 mm; summer, 104 mm and 34 mm; fall, 230 mm and 45 mm; and winter, 108 mm and 24 mm. No signficiant differences were found between soil water deficits on northwest and southeast aspects.
Calcium Retention in Response to Phosphate Sorption by Soils
Authors: Ryden J. C. , Syers J. K. 
Published: July 2010

AbstractRetention of Ca increased in response to P sorption by soils, but was independent of the amounts of added Ca. Rather constant values were obtained for the molar ratio of Ca/P retained (0.19 to 0.34). Retained Ca was essentially recovered in 1M KCl washings in contrast to the fractional recovery of sorbed P. The retention of Ca in response to P sorption by soils is interpreted as arising from a sorption rather than a precipitation reaction, and results from the increase in negative charge induced by P sorption.
Soil Labile Pools of Manganese, Iron, and Zinc as Measured by Plant Uptake and DTPA Equilibrium
Authors: Rule J. H. , Graham E. R. 
Published: July 2010

AbstractLabile pools of Mn, Fe, and Zn were measured on soil samples having varying pH levels at both air‐dry and field‐moist conditions using DTPA. Labile pools of Mn and Fe varied with respect to both pH and soil moisture. The effects of soil moisture and pH on Zn labile pools were slight.Air‐dry soil samples at three pH levels were labelled with carrierfree 54Mn, 59Fe, and 65Zn, and ladino clover (Trifolium repens) and tall fescue (Festuca elatior, var. Ky 31) were grown on each in a growth chamber. Uptake of the stable isotopes and radioisotopes was determined and the data were used to calculate soil labile pools of each element.Soil labile pools of Mn measured by ladino clover uptake were very similar to the values obtained from DTPA equilibration. Values for Fe labile pools were higher and generally in disagreement with DTPA‐measured pools. Plant measured values for Zn varied depending on soil pH with respect to DTPA‐measured pools.Tall fescue‐measured soil labile pools of Mn, Fe, and Zn were calculated from uptake data of various combinations of cuttings. At a given pH, Mn labile pools calculated from any of the combinations were remarkably similar, but were lower than DTPA measured pools. Iron and zince labile pools were erratic with respect to both soil pH and cutting used. Uptake data suggested that a single harvest of tall fescue at ground level after a 5‐week growing period could be adequate to measure the soil labile pools of Mn, Fe, and Zn, especially if these elements were studied simultaneously.
Viscosity Measurements on Soil Humic Substances
Authors: Chen Y. , Schnitzer M. 
Published: July 2010

AbstractViscosity measurements were done on a humic acid and a fulvic acid to obtain information on particle shapes and dimensions, particle weights and polyelectroytic behavior in aqueous solutions. The pH of the humic acid solutions ranged from 7.0 to 10.5, that of the fulvic acid solutions from 1.0 to 10.0.Humic acid at pH 7.0 and fulvic acid at pH 1.0 and 1.5 behaved like uncharged polymers. At higher pH levels, both humic and fulvic acids exhibited strong polyelectrolytic characteristics. The viscosity data fitted an equation developed by Fuoss and Strauss for linear, flexible polyelectrolytes.In the case of fulvic acid, it was possible to assess the effect of a wide range of pH values. At very low pH, fulvic acid had the highest particle weight and particle volume. With increase in pH, the two parameters decreased to a minimum at pH 3, and then began to increase moderately. An analysis of the data for particle shapes and dimensions showed that the most likely particle configuration was rods. Viscometry offers an almost unique opportunity to study important structural characteristics of humic substances in aqueous solutions. Molecular modifications associated with drying, heating, and exposure to high vacuum can so be avoided.
A Semiautomated Procedure for Total Nitrogen in Plant and Soil Samples
Authors: Gallaher R. N. , Weldon C. O. , Boswell F. C. 
Published: July 2010

AbstractThis study evaluated inexpensive alternatives for the determination of total N in plant and soil samples. Plant and soil samples which varied widely in N concentration were digested in a 126‐sample‐capacity Al block digester followed by determination of total N with the ammonium electrode in a semiautomated reaction vessel assembly. The proposed Ammonium electrode semiautomated (AES) procedure was compared to standard micro‐Kjeldahl and aluminum block digested‐steam distilled‐titrated (ABDDT) procedures. Thirty to 50 more samples could be analyzed per 8‐hour day with the proposed semiautomated procedure as compared to standard micro‐Kjeldahl methods. The precision of the methods were comparable but significantly more N was found by using the ABDDT procedure.
Geography of Soil Test Results
Authors: Westin Frederick C. 
Published: July 2010

AbstractSince the factors that control soil formation and soil geography must also affect levels of soil K, P, organic matter, and pH, this study was undertaken to determine the correlations that might exist between soil geography and soil test results. Soil test results for over 80,000 farmer samples were correlated with soils classified at the series, family, subgroup, great group, suborder, and order categories of the comprehensive soil classification system. Then the regional effects of climate and native vegetation on soil test results were isolated, followed by a determination of the local effects on the soil test results of soil parent material, slope and age. Chi square statistical procedures were used to determine significance. Increasing precipitation resulted in decreased K and P and lower pH but higher organic matter. Increasing temperature lowered K and organic matter and increased P but had no effect on pH. Within a climatic zone, as sandiness increased, levels of K, P and organic matter decreased, while pH rose. When carbonate content increased, K and P decreased and pH increased, while organic matter remained constant. As slopes became steeper, levels of K, P, and organic matter decreased, while pH rose. And as soils became older, K and pH decreased, while P and organic matter remained essentially constant. Except for the influence of soil texture on organic matter, all other data were highly significant. Although precise amounts of K, P, organic matter and pH require individual field sampling, a consideration of the geography of the soils as expressed in soil taxonomic terms gives a rational starting point in plant nutrient assessment and a tool for extension of fertility‐related data.
The Evolution of Soil Properties as it Relates to the Genesis of Volcanic Ash Soils in Costa Rica
Authors: Martini J. A. 
Published: July 2010

AbstractFive soil profiles developed on andesitic volcanic ash, under welldrained conditions and at various elevations associated with different climatic conditions, were studied.These soils varied in profile development and degree of weathering from Incipient Ando soil (Umbric Vitrandept), Mature Ando soil (Typic Dystrandept), and Senile Ando soil (Hydric Dystrandept) to Incipient Latosol (Typic Humitropept) and Mature Latosol (Typic Palehumult).Profile development associated with time of ash deposition and climate and recognized by virtue of morphological properties was closely related to progressive weathering and a consistent evolution of physical, chemical, and mineralogical properties, as well as to an increasing degradation of the native soil fertility.This investigation served as a basis for developing a working hypothesis on the genesis of volcanic ash soils from Regosols and Ando soils to Latosols.
Effects of Various Camping Intensities on Soil Properties in Illinois Campgrounds
Authors: Young R. A. , Gilmore A. R. 
Published: July 2010

AbstractSelected chemical and physical soil properties were measured at nine Illinois campgrounds, representing three major soil association groups. At each campground the following four levels of camping use were compared: unused‐control; used < 33 days per season; 34 to 66 days; and over 66 days of use per 100 day season. Differences between the interior (0 – 2.5 m radius) and exteriors (2.5 – 5.0 m) of the campsites were also investigated. There were no significant differences in any of the properties between the interiors and exteriors of the campsites. Campsites on the deep loessial soils had less compaction, more organic matter and nutrients (Mg, Ca, K, P, Na, N), and were less acid than those on fragipan or claypan soils. Most soil properties considered in the study increased with increased camping use when compared with the unused sites. The percentage of organic matter ranged from 2.57, 3.12, 3.52, and 3.18 from the unused to the most heavily used sites. Compaction for the four levels of use starting with the control sites was 3.46, 8.45, 9.14, and 9.79 kg/cm2. Soil pH was 5.1, 5.7, 6.1 and 6.3 for the same four levels of use. Ca, K, Na, P and N were also found at higher levels on heavily used sites than on the unused or lightly used sites. There was no difference in Mg levels on any of the four levels of use.
Soil Air Pressure Effects on Route and Rate of Infiltration
Authors: Linden D. R. , Dixon R. M. 
Published: July 2010

AbstractOne centimeter of 0.1% methylene blue solution was infiltrated into soil with various constant soil air pressures beneath the wetting surface to measure flow into and through soil macropores. Flow was increasingly impeded as soil air pressure increased from 0 to 5 mbars. Infiltration rates during the first 3 min of wetting were decreased by an order of magnitude with 5 mbars of air‐back pressure.
Nutrient Concentration in Black Spruce Foliage Immediately Following Fertilization
Authors: Salonius P. O. 
Published: July 2010

AbstractAmmonium sulfate, triple superphosphate, or K sulfate were applied to plots in a 60‐year‐old black spruce (Picea mariana (Mill.) B.S.P.) stand, and seasonal changes in foliar nutrient levels on the treated plots were compared with those on the control before and after fertilization. Nitrogen was absorbed initially very quickly but there appeared to be some delay in the initial uptake of P. Both N and P were absorbed steadily throughout the remainder of the growth season. Possible methods of capitalizing on this fact and thus increasing fertilizer efficiency and decreasing losses of applied nutrients are discussed.
Soil Microbiology—It's a Small World
Authors: Clark Francis E. 
Published: July 2010

AbstractSoil Microbiology—It's a Small World.The accomplishments and personalities of some notable early American soil microbiologists are discussed. The tangled skeins of influences and interactions among them are used to justify the small world concept used in the title. In discussing the subject matter of soil microbiology, it is noted that as society becomes more concerned with population growth and world food supply, energy sources and requirements, and econology and the environment, soil microbiology is shifting its emphasis from soil and the growing plant to man and the biosphere. The soil microbiologist is becoming increasingly involved in exposing such unesthetic substrates as sewage, animal manures, and food and fiber processing and sanitary landfill organic wastes to microbial attacks. His objectives are to make such substrates less objectionable environmentally and to exploit their residual food and energy potentials. Together with these endeavors he is expanding his efforts to define the dominant roles of microorganisms in the functions of terrestrial ecosystems. Therein, microorganisms metabolize a far larger amount of the net primary productivity than do all of the higher forms of life, inclusive of man, taken collectively.
Mass Transfer Studies in Sorbing Porous Media: III. Experimental Evaluation with 2,4,5‐T
Authors: van Genuchten M. Th. , Wierenga P. J. , O'Connor G. A. 
Published: July 2010

AbstractComparisons are made between observed and calculated effluent concentration distributions for the movement of 2,4,5‐T (2,4,5‐trichlorophenoxyacetic acid) through 30‐cm long unsaturated soil columns. The comparisons are made using both analytical and numerical solutions of a previously published model, which included the effects of intra‐aggregate diffusion and adsorption. The results in this study indicate that intra‐aggregate diffusion and adsorption/desorption are the main mechanisms responsible for effluent tailing. An estimated 60% of the adsorption. Was found to occur in the stagnant region of the soil. When intra‐aggregate diffusion was included in the model, the observed adsorption/desorption hysteresis phenomenon found to be significant in several earlier studies, was shown to be much less important in describing the observed concentration distributions.
Effects of Trace Elements on Phosphatase Activity in Soils
Authors: Juma N. G. , Tabatabai M. A. 
Published: July 2010

AbstractStudies to evaluate the effects on the activity of acid and alkaline phosphatases of 20 trace elements showed that all trace elements inhibit the activity of phosphatases in soils. Results showed that the relative effectiveness of the trace elements in inhibition of phosphatase activity depends on the soil. When the trace elements were compared by using 25 µmole/g soil, the average inhibition of acid phosphatase in three soils showed that Hg(II), As (V), W(VI), and Mo(VI) were the most effective (average inhibition >50%) and that Ba(II), Co(II), and As(III) were the least effective (average inhibition <10%) inhibitors. Other elements that inhibited acid phosphatase activity in soils were: Cu(I), Ag(I), Cd(II), Cu(II), Zn(II), Mn(II), Sn(II), Ni(II), Pb(II), Fe(II), Cr(III), Fe(III), B(III), Al(III), V(IV), and Se(IV); their degrees of effectiveness varied in the three soils used.The most effective inhibitors of alkaline phosphatase activity in soils were Ag(I), Cd(II), V(IV), and As(V). All the trace elements that inhibited acid phosphatase activity also inhibited alkaline phosphatase activity. The order of effectiveness of the trace elements in inhibition of acid phosphatase activity was different from that of inhibition of alkaline phosphatase activity. Generally, the inhibitory effect of trace elements was less in the presence of 2.5 µmole/g soil than in the presence of 25 µmole/g soil. In addition to the effect of trace elements, phosphate ion inhibited acid and alkaline phosphatase activities in soils. Related anions such as NO2‐, NO3‐, Cl‐, and SO42‐ were not inhibitory in the presence and absence of buffer.