bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationships Between Enzyme Activities and Microbial Growth and Activity Indices in Soil
Authors: Frankenberger W. T. , Dick W. A. 
Published: July 2010

AbstractSoil enzyme activities are often used as indices of microbial growth and activity in soils. Quantitative information concerning which soil enzymes most accurately reflect microbial growth and activity is lacking. Relationships between the activities of 11 soil enzymes and microbial respiration, biomass, viable plate counts, and soil properties were determined in surface samples of 10 diverse soils. Correlation analyses showed that alkaline phosphatase, amidase, α‐glucosidase, and dehydrogenase activities were significantly (P < 0.01) related to microbial respiration as measured by CO2 evolution in soils which had received glucose amendments. Phosphodiesterase, arylsulfatase, invertase, α‐galactosidase, and catalase activities were correlated at the 5% level while acid phosphatase and urease activities were not significantly correlated to microbial respiration. There was no significant correlation between the 11 soil enzymes assayed and CO2 evolution in the 10 unamended soils. Only phosphodiesterase and α‐galactosidase activities were significantly (P < 0.05) related to microbial numbers obtained on some selective culture media. Alkaline phosphatase, amidase, and catalase were highly correlated (P < 0.01) with microbial biomass as determined by CO2 evolution after chloroform fumigation pretreatment. The organic C content in the 10 surface soils was correlated (P < 0.05) with acid and alkaline phosphatase, phosphodiesterase, arylsulfatase, amidase, urease, and invertase activities. Urease activity was also positively correlated with total N and cation exchange capacity and negatively correlated with the percentage of sand. These relationships suggest that urease can exist in soil as an extracellular enzyme in a three‐dimensional network of organo‐mineral complexes. Of the 11 enzymes evaluated, alkaline phosphatase, amidase, and catalase were concluded to be the most satisfactory choices in determining the relative activity and mass of the microbial population in soils. The activities of these enzymes were highly correlated with both microbial respiration and total biomass in soils.
Corn Yield‐Fragipan Depth Relations on a Zanesville Soil
Authors: Frye W. W. , Murdock L. W. , Blevins R. L. 
Published: July 2010

AbstractA fragipan is a dense, somewhat indurated, very strongly acid, and slowly or very slowly permeable soil horizon that can be a physical or a chemical barrier to plant root growth. Erosion of a fragipan soil decreases the volume of soil for root growth and water storage. The effect of depth to a fragipan horizon on yield of corn (Zea mays L.) was measured during a four‐year study on a Zanesville silt loam (Typic Fragiudalf, fine‐silty, mixed, mesic). In 3 of the 4 years, susceptibility to water stress increased with decreasing depth to the fragipan horizon. Greater depth to the fragipan was associated with an increased volume for rooting and water storage, resulting in higher grain yields.
Atterberg Limits as Indices of External Surface Areas of Soils
Authors: Hammel J. E. , Sumner M. E. , Burema J. 
Published: July 2010

AbstractSurface area measurements on soils are usually laborious and require expensive equipment. The relationship between Atterberg limits (plastic and liquid) and surface area is investigated with a view to being able to estimate the latter from the former. The results show that there is a very strong relationship (r2 > 0.9) which permits surface area to be estimated rapidly and cheaply.
Statistical and Stochastic Analyses of Hydraulic Conductivity and Particle‐Size in a Fluvial Sand
Authors: Byers Elizabeth , Stephens Daniel B. 
Published: July 2010

AbstractAn untilled medium‐grained fluvial sand near Socorro, N. Mex., was sampled in horizontal and vertical transects to study the statistical and stochastic properties of particle‐size parameters and saturated hydraulic conductivity. Hydraulic conductivity is log‐normally distributed, whereas the 10% finer, median, and geometric mean particle sizes are normally distributed. The strongest correlation between hydraulic conductivity and particle‐size distribution parameters is that of the log of hydraulic conductivity with the 10% finer particle size. Stochastic analyses using the autocorrelation function and spectrum indicate that the log of hydraulic conductivity and particle size are characterized by dissimilar spatial correlation structures in the vertical directions. In general, particle size is more structured, regular, and predictable and shows a close similarity with the stratigraphy as observed in the field. On the other hand, hydraulic conductivity in the vertical direction may best be modeled as a simple random variable. Variogram and kriging analyses indicate that both hydraulic conductivity and particle size are relatively isotropic in the horizontal plane and that marked similarities in spatial structure exist in this plane. The spatial distribution of saturated hydraulic conductivity in the horizontal plane is estimated reasonably well using the empirical relationship between particle size and conductivity along with the kriged estimates of the 10% finer particle size.
Nitrification of Fertilizer and Mineralized Ammonium in No‐Till and Plowed Soil
Authors: Rice C. W. , Smith M. S. 
Published: July 2010

AbstractThe influence of tillage on nitrification was examined using a variety of assays of no‐till and conventional tillage (plowed) soils. Ratios of NO‐3 to NH+4 were higher in plowed soils except immediately after fertilization. However, concentrations of total inorganic soil N were about equal in the two tillage systems. Nitrification rates, following NH+4 additions to mixed sieved soils and to intact soil cores in the laboratory, were measured under various moisture regimes. Tillage did not consistently affect nitrification when soils of both tillage treatments were maintained at the same water content. Yet, nitrification was sensitive to soil moisture and since water evaporated more rapidly from plowed soils, nitrification was sometimes more rapid in no‐till soils. One week after addition of 15NH+4 to field plots, more NH+4 had been converted to NO‐3 in the no‐till soil. It is suggested that nitrification of NH+4 fertilizer often will be more rapid in no‐till soils because of more favorable moisture conditions. Without NH+4 additions, however, nitrifier substrate (NH+4) limitations may be more severe in no‐till soils, causing slower or less complete NH+4 oxidation.
Annual Cycles of Carbon Dioxide Level in Soil Air
Authors: Buyanovsky G. A. , Wagner G. H. 
Published: July 2010

AbstractThe CO2 concentration of the gaseous phase of a silt loam soil (Udollic Ochraqualf) was studied under cultivation of wheat (Triticum aestivum), corn (Zea mays L.), and soybeans (Glycine max L. Merr.) over a 2‐year period. Disposable chromatographic tubes for direct field measurements of CO2 in soil air were used. Dynamics of CO2 in the soil air were observed to be conditioned by both biological and abiotic factors. Under wheat, periods of highest CO2 concentration (6–8%) corresponded to times of intensive decomposition of plant residue within the soil profile. Under corn and soybeans, highest CO2 concentrations were related to the periods of intensive plant growth. Soil moisture and soil temperature combined, were found to be responsible for just > 50% of CO2 fluctuations. The influence of water tension on CO2 in the soil atmosphere was more significant (r2 = 0.83) if data were restricted to that where temperature was 20 ± 2°C, and in transformations of the two parameters were used. The ln‐to‐ln dependence was linear within the limits from field capacity to wilting point. Under conditions of optimum soil water content, ln of CO2 concentration increased linearly with ln of soil temperature within the limits of 10 to 20°C.
Measurement of Gas Diffusion Coefficient under Relatively Low Air‐filled Porosity
Authors: Sallam A. , Jury W. A. , Letey J. 
Published: July 2010

AbstractKnowledge of the diffusion coefficient is necessary for modeling gas movement through soil. Various equations have been proposed relating apparent gas diffusion to soil parameters. A laboratory study was conducted to measure gas diffusion through soil at low air‐filled porosity (0.05, 0.10, and 0.15) using an inert gas (Freon: CCl2F2). The Penman model DS/DA = 0.66a, where DA and DS are gas diffusion coefficients in air and soil, respectively, and a is the volumetric soil air content, greatly overestimated the measured DS at all porosities. The Millington‐Quirk model DS/DA = a3.33/φ2, where φ is the soil porosity, had the same curve shape but slightly underestimated the measured DS. Much better agreement between calculated and measured DS was obtained by reducing the exponent 3.33 in the Millington‐Quirk model to 3.10.
Moisture Regimes and Morphological Characteristics in a Hydrosequence in Central Massachusetts
Authors: Pickering E. W. , Veneman P. L. M. 
Published: July 2010

AbstractMoisture regimes and associated soil mottling patterns were investigated over a 2‐y period in a Paxton‐Rainbow‐Ridgebury‐Scarboro hydrosequence in central Massachusetts. Changes in physical conditions in these coarse‐loamy fragipan soils were monitored with well points, tensiometers, soil temperature probes, and redox potential electrodes. Well‐drained soils appeared uniformly brown, reflective of a generally strongly oxidized environment. They also showed the greatest seasonal fluctuations in soil temperature ranging from 0 to 23°C. Matrix colors of highest chromas (6 or higher) occurred in the moderately well‐drained (MWD) soils where reducing and oxidizing environments coexist within the profile at some time during the growing season. Prominent ferrans and albans in the 2Cx horizons of MWD soils were related to sustained groundwater levels, although higher water tables often occurred for periods too short or too cold for development of strongly reducing conditions. The characteristics grey streaking patterns of fragipans were best expressed in the 2Cx horizons of MWD soils and can be attributed to reducing environments during periods with soil temperature above biologic zero when conditions are wet but unsaturated. Significant translocation and leaching of iron occurred in the somewhat poorly drained soils, as evidenced by olive‐grey matrix colors. Channel neoferrans and some neoalbans indicated that a reducing environment may persist within the B2 horizon long after it has become unsaturated. Lowest chroma colors in this hydrosequence was found in the very poorly drained soils where perennial conditions of saturation or near saturation exists up to the soil surface resulting in the strongest reducing environment and least fluctuations in seasonal temperatures.
Soil Mixing by Scarab Beetles and Pocket Gophers in North‐Central Florida
Authors: Kalisz P. J. , Stone E. L. 
Published: July 2010

AbstractSoil mixing by scarab beetles (Peltotrupes youngi) and pocket gophers (Geomys pinetus) was studied on deep sands in north‐central Florida. Mound construction was monitored for 2 y on longleaf pine (Pinus palustris) (LLP) sites with dense and sparse wiregrass (Aristida stricta), and on sand pine (P. clausa) (SP) sites with dense and sparse scrub (Quercus spp.) understories. Adult beetles were active from November to April and constructed vertical tunnels at least as deep as 360 cm. Soil deposited in beetle mounds averaged 20 and 580 kg ha−1 yr−1 in SP stands with dense and sparse understories, respectively, and 1510 and 3700 kg ha−1 yr−1 in LLP stands with dense and sparse grass. Pocket gophers were absent from SP, but mounding averaged 8160 and 290 kg ha−1 yr−1 on LLP sites with dense and sparse grass. Mounding by beetles was as high as 7800 kg ha−1 yr−1, and pocket gopher mounds covered 4% of the surface area and weighed 37 500 kg ha−1 on some LLP sites. On areas with chemically contrasting soil layers, beetle mounds contained significantly greater amounts of extractable P, Ca, and Mg than the surrounding 0‐ to 10‐cm soil. Burrowing and upward soil transport also alter surface textures and produce tunnels that may function as root pathways through the generally dense subsoil. The occurrence and thickness of A horizons under LLP and E horizons under SP are also related to differences in extent of faunal mixing between the two vegetations.
Impact of Harvesting and Site Preparation on Physical Properties of Piedmont Forest Soils
Authors: Gent J. A. , Ballard R. , Hassan A. E. , Cassel D. K. 
Published: July 2010

AbstractThe impact of intensive forest management practices on soil bulk density, aeration porosity, and saturated hydraulic conductivity was examined to a depth of 0.3 m before harvest, after harvest, and after site preparation. Harvesting caused significant changes in soil physical properties to an average depth of 0.17 m in whole tree harvest plots and 0.22 m in skid trail plots. Disking was effective in restoring soil physical properties to preharvest levels in the upper 0.07 to 0.12 m of soil. Soil compaction in chop/burn plots may result in reduced root growth because of mechanical impedance, reduced aeration, or both.
Mineral Transformations in Soils Formed in Glacialmarine Drift, Northwestern Washington
Authors: Pevear D. R. , Goldin A. , Sprague J. W. 
Published: July 2010

AbstractThe Whatcom (Aquic Xerochrept) and Labounty (Typic Humaquept) series are soils formed in volcanic ash‐influenced, 10000‐year‐old glacialmarine drift. Surface horizons contain 5 to 10% volcanic ash; pyroxenes show pronounced cockscomb morphology, but associated hornblende is less weathered. Clay‐size minerals in unweathered drift are chlorite, smectite, mica, and in minor amounts, kaolinite and amphibole. The constant abundance of kaolinite throughout the profile and in the fresh parent drift suggests that it is not pedogenic. In the C horizon, chlorite has weathered to mixed‐layer chlorite/vermiculite (or chlorite/smectite) with 40 to 50% chlorite layers. The B horizon is dominated by chlorite, vermiculite, and chlorite/vermiculite. Smectite decreases upward and is absent from the uppermost part of the profile, where it has dissolved or possibly been converted to mixed‐layer kaolinite/smectite and chlorite/smectite.
Root Water Uptake and Soil Water Distribution: Test of an Availability Concept
Authors: Lascano R.J. , van Bavel C.H.M. 
Published: July 2010

AbstractAn experimental test was made of the hypothesis that the fractional water uptake by the root system from a soil layer is proportional to the root density and to the difference between the water potential in that layer and the mean leaf water potential. This theory adequately explained the water uptake by a cotton root system that was divided over a wet and a dry soil compartment. It was also established that the absolute rate of water uptake from each compartment could be accurately calculated from the measured potential difference between soil and plant leaf, and from a separately measured plant hydraulic resistance, which was shown to have a value of 0.67 × 109 s, independent of transpiration rate.
Enrichment of Transported Sediments with Organic Carbon, Nutrients, and Clay
Authors: Avnimelech Yoram , McHenry J. R. 
Published: July 2010

AbstractMuch of the nutrient inflow into impoundments is the result of erosion of soil particles on the watershed, together with adsorbed nutrients and their movement from the upland watershed soils. As the detached particles move downstream, they undergo selective size segregation and the nutrients are subject to selective desorption and adsorption between the particles and the water. During transport an enrichment of clay sized particles within the system occurs as well as that of P, N, and organic C. The ratio of the concentration of any given component in the eroded material system to that in the contributing soils is defined as the enrichment ratio. The selectivity of the erosional and sediment delivery processes involved in the transfer of eroded materials from watersheds to lakes or reservoirs is assumed to be proportional to the time, or distance, of travel. This study compares the composition of the eroded material at the onset and at the termination of the erosion, or sedimentation, cycle. From this information insight into the mechanisms affecting the compositional changes along the erosional route may be obtained. Organic carbon, total nitrogen, and total phosphorus concentrations and clay contents in sediments from 41 impoundments or lakes were compared with the equivalent parameters in the soils of the contributing watersheds. The enrichment ratio of a given component (S/So, the concentration of the component in the eroded material divided by its concentration in the soil) was theoretically predicted to be: S/So = 1/So × L, where L is a limiting value representing a stable level of this component in the erosion sequence. The measured enrichment ratios for organic C and total N were in good agreement with the theoretical model, the stable levels being 24 and 1.7 g kg−1 for organic C and total N. No such agreement was found for P and clay enrichment ratios, possibly due to the effect of the variable flow conditions on the selective erosion of these components.
Boron Toxicity to Sycamore of Minesoil Mixed with Sewage Sludge Containing Glass Fibers
Authors: Vimmerstedt John P. , Glover Thomas N. 
Published: July 2010

AbstractAcid, infertile, erosive, barren “orphan” coal minesoils are a regional problem in the eastern coal fields. Learning how to establish permanent forest ecosystems on these minesoils is a goal of reclamation research in Ohio. This greenhouse research tested Newark, Ohio sewage sludge at 70, 160, 250, and 340 Mg ha−1 as treatments to promote growth of American sycamore (Platanus occidentalis L.) seedlings in toxic minesoils. Sycamore seed did germinate and grow in sludge‐amended minesoil, whereas growth was nil in the absence of sewage sludge. Soil pH, available P, exchangeable K and Ca, available Zn and extractable B all increased with sludge addition, but exchangeable Mg, available Mn and CEC declined. Regressions of N, P, K, Ca, Fe, and Cu content of seedlings on rate of sludge addition were significant and positive; a similar regression for manganese was significant and negative. Stress symptoms appearing on lower leaves of sycamore seedlings grown in sludge‐minesoil mixtures matched boron toxicity symptoms of sycamore produced in solution cultures containing 2 or 4 mg kg−1 of B and in mixtures of glass fiber insulation, a component of the sludge, with peat and vermiculite.
Characterization of Iron Oxide Minerals by Second‐Derivative Visible Spectroscopy
Authors: Kosmas C. S. , Curi N. , Bryant R. B. , Franzmeier D. P. 
Published: July 2010

AbstractDerivative spectroscopy is a technique of calculating and plotting the first, second, or higher order derivative of the spectral curve relating absorption and wavelength. The second derivative greatly enhances minor convexities and concavities of the original (zero order) spectrum and gives a much narrower band width which provides improved resolution of subtle or overlapping bands. The visible spectrum and its second derivative were determined for natural and synthetic goethite and synthetic hematite. The two minerals have distinctive second‐derivative patterns. The minimum at 423 nm and the maximum at 447 nm in the second‐derivative patterns were used to estimate the amount of goethite in a mixture with kaolinite. Whole soil samples can be analyzed without pretreatment by this method, assuring that the result of the analysis is a property of the soil itself and not an artifact of a pretreatment.
Salinity and Uniformity of Water Infiltration as Factors in Yield and Economically Optimal Water Application
Authors: Feinerman E. , Knapp K. C. , Letey J. 
Published: July 2010

AbstractThe effects of irrigation water salinity and uniformity of infiltered water on average crop yields, economically optimal water applications, and profits are analyzed for steady‐state and transient salinity conditions. Input data specific for corn (Zea mays L.) are used in the analysis to illustrate results. Except at very low water application levels, decreasing uniformity of infiltered water results in decreasing yield at a given water application rate and at all levels of water salinity under both steady‐state and transient conditions. Profitmaximizing water applications increase under conditions of increased irrigation water salinity, decreased uniformity of infiltered water, and decreased water price; whereas profits decrease with increased salt concentrations and decreased infiltered water uniformity. Economically optimal water applications and profit can vary by factors of three or more depending on water prices, salt concentrations, and uniformity of infiltered water. Therefore accurate determination of these variables is important for decision making at the farm level.
Trace Metal Chemistry in Arid‐Zone Field Soils Amended with Sewage Sludge: IV. Correlations Between Zinc Uptake and Extracted Soil Zinc Fractions
Authors: LeClaire Joseph P. , Chang A. C. , Levesque C. S. , Sposito Garrison 
Published: July 2010

AbstractThe surface horizons of two field soils that had been amended with composted or liquid sewage sludge for 3 to 6 y were extracted with a series of reagents [KNO3, H2O, NaOH, EDTA (ethylenedinitrilotetraacetic acid), HNO3, in sequence] and with DTPA (1,4,7‐triazaheptane‐1,1,7,7‐pentaacetic acid) to characterize the zinc (Zn) pool in the soils with respect to lability and bioavailability. Statistical correlation analysis, comparing the extracted Zn fractions with the concentration of Zn in the leaves of barley (Hordeum vulgare L.) grown on the two soils, led to the following conclusions: (i) Zinc extracted by KNO3 and H2O in sequence is associated with the highly labile, soluble pool, dominated by Zn2+, which determines immediate bioavailability. (ii) Zinc extracted by KNO3, H2O, and NaOH in sequence has a strong, positive, 1:1 correlation with DTPA‐extractable Zn and, therefore, is associated with the labile, plant‐available Zn pool. (iii) EDTA‐extractable Zn represents a reservoir of potentially bioavailable Zn, and (iv) HNO3‐extractable Zn is associated with a nonlabile pool that is not bioavailable. These general relationships between extracted Zn fractions and bioavailability were applicable to both soils investigated and did not depend on the type of sludge applied or the length of time of sludge application.
Phosphate Sorption by Soils: III. The P Diffusion‐Precipitation Model Tested for Three Acid Sandy Soils
Authors: van Riemsdijk W. H. , van der Linden A. M. A. , Boumans L. J. M. 
Published: July 2010

AbstractA recently developed diffusion‐precipitation model was tested for three acid sandy soils: two topsoils and one subsoil. It is shown that experimental data fit the model when constant P concentrations are used. As the model predicts no particular curve, third degree polynomials were used to describe the data. For further testing, increasing and decreasing P concentrations were used. Comparison of experimental and computer simulation data show that the model is also valid for varying concentrations. The concentration at the metal‐oxide/metal‐phosphate interface (indicated as C4) is relatively high: 0.1 to 0.25 mmol/L. The diffusion‐precipitation model is useful in modeling P behavior in soils.