bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphologic Development and Clay Redistribution in Lysimeter Soils under Chaparral and Pine
Authors: Graham R. C. , Wood H. B. 
Published: July 2010

AbstractLysimeter soils under 41‐yr‐old stands of chaparral species and a pine (Pinus coulteri B. Don) were studied to determine the biotic influence on soil morphologic development. The large (5.3 by 5.3 by 2.1 m) unconfined lysimeters at the San Dimas Experimental Forest in southern California were filled in 1937 with homogenized fine sandy loam soil material derived from diorite. After a 9‐yr stabilization period, the lysimeters were planted with monocultures of species common to California chaparral ecosystems. The species represented, each on a separate lysimeter and its surrounding buffer zone, are scrub oak (Quercus dumosa Nutt.), ceanothus (Ceanothus crassifolia Torr.), chamise (Adenostoma fasciculatum Hook. & Arn.), and Coulter pine. The soils were described and sampled in triplicate in 1987. Differences in earthworm (including Aporrectodea trapezoides Dugés and Allolobophora chlorotica Savigny) activity were related to plant species and played a major role in differentiating the soils. Earthworm activity under scrub oak and ceanothus produced A horizons (7 and 2 cm thick, respectively), composed largely of worm casts, that were darker and enriched in clay compared with underlying C horizons and archived fill material. Earthworm activity was minimal under chamise, and relatively little morphologic development was apparent. The soil under pine, where earthworms were absent, had a clay‐depleted A horizon (1 cm thick) and Bt horizons with sufficient clay increase, illuviation argillans, and thickness to qualify as an argillic horizon. Mixing and sorting of soil by earthworms has acted against argillic horizon development under the other plant species.
Polyacrylamide to Improve Water Flow and Salt Removal in a High Shrink‐Swell Soil
Authors: Malik M. , Amrhein C. , Letey J. 
Published: July 2010

AbstractReclamation of salt‐affected high shrink‐swell soils using chemical amendments combined with deep loosening and tile drainage is very expensive. As an alternative, the utilization of cracks as pathways for water and salts is possible if these cracks could be stabilized by the application of a polyacrylamide (PAM) polymer and their complete closure prevented upon rewetting. A laboratory column study was conducted on two soil samples with exchangeable sodium percentages (ESP) of 8 and 25 from a heavy‐textured, swelling soil. The soil samples were packed into columns, ponded with irrigation water for 24 h, then drained and dried to create cracks. After drying, the soil samples were ponded for 24 h with irrigation water containing 0, 25, 75, and 200 mg L−1 of an anionic polyacrylamide polymer, allowed to drain, and dried. The treated soils were then ponded without drainage for 1, 6, 12, and 24 h to allow crack closure and the hydraulic conductivity (HC) and effluent salinity were measured. The experiment was repeated except that the polymer solution was added to the soil without initially creating the cracks. An additional study was carried out to test the durability of the polymer when subjected to wetting and drying cycles. Increasing the amount of polymer significantly increased the HC and salt removal in the cracked soils. When the polymer solution was applied directly onto soils without initially creating cracks, there was no increase in HC on the ESP 8 soil and a small increase on the ESP 25 soil. The polymer had a stabilizing effect on soil cracks, but the increase in HC did not persist through several wetting and drying cycles.
Macropore Characterization for Two Tillage Systems Using Resin‐Impregnation Technique
Authors: Singh Piyush , Kanwar Rameshwar S. , Thompson Michael L. 
Published: July 2010

AbstractThis study used resin impregnation and image analysis to characterize macroporosity of a Nicollet loam soil (fine‐loamy, mixed, mesic Aquic Hapludoll) under no‐tillage and conventional tillage. Soil samples (7.5 by 5 by 5 cm) were taken at each 5‐cm depth interval to determine macroporosity after conducting solute‐leaching experiments on undisturbed soil columns. These soil samples were impregnated with either polyester or epoxy resin. Impregnated soil blocks were sectioned in the middle and ground to a smooth finish. Photographic slides were made of the horizontal faces and an automatic image analyzer was used to calculate the percentage of area occupied by macropores, and total perimeter, number, and size‐frequency distribution of macropores. Percentage of area, perimeter, and number of macropores were not statistically different for the two treatments. Macroporosity data obtained from the samples did not support the observations made in the solute‐leaching studies on saturated soil columns (i.e., a greater degree of preferential flow in no‐tillage columns) because the air‐dried samples and the saturated columns had different porosity characteristics and because small, two‐dimensional images were unable to sample any less frequently occurring larger pores. Another source of discrepancy between the results of the two studies may be macropore continuity. Two‐dimensional analysis of porosity images does not provide a measure of pore continuity, which can be a decisive factor in solute transport through soil columns under different tillage systems. Results from the resin‐impregnation study were not consistent with the results of a related field study. Inconsistency between the macroporosity data of these two studies were attributed to: the difference in minimum cut‐off diameter of macropores in the two studies, the difference in sample size, and the difference in moisture status of the field and lab samples.
Factors Controlling Denitrification in a Chihuahuan Desert Ecosystem
Authors: Peterjohn William T. , Schlesinger William H. 
Published: July 2010

AbstractDenitrification may be an important pathway for N loss from desert ecosystems. Few studies, however, have investigated the factors limiting this process in a desert environment. A factorial experiment was conducted to determine the factors controlling denitrification in the northern Chihuahuan Desert. Specifically, we measured the response of denitrification to additions of water, C, N, and C + N. Soil cores were collected from four vegetation zones along an alluvial piedmont. Dry cores were subjected to five treatments: (i) water; (ii) water + NO3; (iii) water + C; (iv) water + NO3 + C; and (v) a control (no additions). When denitrification rates were averaged across vegetation zones and patch types (between or under vegetation), the following treatment effects were significantly different: water + NO3 + C > > > water + NO3 = water » water + C > control. These results indicate that denitrification at this site is limited by the availability of water. In wet soil cores, C additions immobilized available NO3 and suppressed denitrification. When water + NO3 + C was added (C/N = 22), however, denitrification was significantly greater than when water + NO3 were added. This result indicates that C and N interact to control denitrification in wet desert soils. No evidence for an overall NO3 limitation in moist cores was found. Surprisingly, denitrification rates in wet cores of nutrient‐poor desert soils (≈32.9 ng N cm−2 h−1) were similar to those measured in the nutrient‐rich soils of temperate and tropical forests. When extrapolated to an annual rate, denitrification for this site is 7.22 kg N ha−1 yr−1. Extreme drying‐wetting cycles common in desert ecosystems may account for the high rates observed.
Variation in Forest Soil Properties along a Great Lakes Air Pollution Gradient
Authors: MacDonald Neil W. , Burton Andrew J. , Jurgensen Martin F. , McLaughlin James W. , Mroz Glenn D. 
Published: July 2010

AbstractA pronounced air‐pollution gradient exists across the Great Lakes region, with deposition of SO4, NO3, and H increasing from northern Minnesota to southern lower Michigan. Soils at six northern hardwood sites along this gradient were examined to characterize soil physical and chemical properties relevant to retention of pollutants, and to investigate the impact of differences in pollutant loading on soil chemical properties. Three randomly located pedons at each site were described and sampled. Soils at all sites were classified in closely related subgroups within the Spodosol order (Entic Haplorthods, Typic Haplorthods, Alfic Haplorthods, and Alfic Fragiorthods). Cation‐exchange capacity and SO4‐adsorption potential tended to decrease from north to south along the gradient, largely related to trends in inherent soil properties. In upper B horizons, additional significant positive deposition effects on water‐soluble and adsorbed SO4, and negative deposition effects on SO4‐adsorbing potentials were consistent with hypothesized pollutant impacts on soil SO4 pools and soil capacities to retain additional atmospheric SO4. Exchangeable nutrient‐cation contents (Ca, Mg, K) in upper B horizons tended to decrease as pollutant deposition increased. Regression analyses suggested that observed trends in nutrient‐cation contents were primarily related to inherent soil properties such as clay, organic matter, and cation‐exchange capacity. Differential effects of pollutant deposition and natural acidification processes on nutrient‐cation reserves could not be separated at this time.
Soil Water and Ammonia Volatilization Relationships with Surface‐Applied Nitrogen Fertilizer Solutions
Authors: Al‐Kanani T. , MacKenzie A. F. , Barthakur N. N. 
Published: July 2010

AbstractSoil water content is an important factor influencing NH3 volatilization from N fertilizers. Information on the relationship between water evaporation and NH3 volatilization from urea (U) or urea‐ammonium nitrate (UAN) solutions, and on the kinetics of both processes is lacking. We examined NH3 volatilization from surface‐applied solutions of U and UAN in samples of St. Bernard (loamy, mixed, nonacid, frigid Typic Hapludoll) and Ste. Sophie (sandy, mixed, nonacid, frigid Typic Haplorthod) soils exposed to water potentials ranging from < −1.5 to −0.01 MPa. An air‐train system was used. Ammonia volatilization increased as soil water content increased. Volatilization differences between moist (> −0.038 MPa) and air‐dry (< −1.5 MPa) samples were reduced as the clay content of the soil increased. However, the effect of clay content on NH3 volatilization became more pronounced as soil approached air dryness. Water evaporation was consistent with first‐order kinetics, whereas NH3 volatilzation followed two first‐order kinetics. The initial rate constants (k1) for NH3 volatilization (0.338–0.348 d−1) from U solution were consistently higher than those for water evaporation (0.099–0.104 d−1) at −0.01 MPa water potential and 70% relative humidity. Differences could be attributed to different energy requirements. Ammonia volatilization vs. water evaporation followed a logarithmic relationship.
Simulation of Surface Energy Balance and Soil Temperature under Strip Tillage: I. Model Description
Authors: Hares Mohammad A. , Novak Michael D. 
Published: July 2010

AbstractConservation‐tillage practices that reduce soil erosion and conserve moisture are becoming more widespread. In northern latitudes, germination and early crop development may be hindered due to slower soil warming under mulched surfaces. Strip tillage, in which mulch or stubble strips alternate with bare planting strips, represents a compromise between conservation of soil and water by mulch or stubble and more rapid spring warming of bare soil. The object of our research was to identify the processes that determine surface energy‐balance components and soil temperatures under strip tillage and simulate them using a physically based numerical model, which consists of soil‐temperature and surface‐energy‐balance submodels. Dynamic inputs to the model are solar irradiances, air temperatures, water‐vapor densities, and wind speeds measured above the surface. The energy‐balance model determines radiation, heat, and water‐vapor transfers within the mulch and between the mulch surface and atmosphere, as well as the surface energy balance in the bare strip, including shading, shortwave and longwave reflection, and emission effects of the mulch sides. An explicit finite‐difference numerical technique is used to predict soil temperatures and heat fluxes. The soil‐temperature model was in excellent agreement with analytical solutions to periodic heat‐transfer problems in one‐dimensional nonbomogeneous and two‐dimensional homogeneous semi‐infinite soils with surface boundary conditions of the third kind (linear combination of soil heat flux and temperature specified at the surface).
Potential Sampling Error: Trace Metal Adsorption on Vacuum Porous Cup Samplers
Authors: McGuire P. E. , Lowery B. , Helmke P. A. 
Published: July 2010

AbstractThe adsorption of trace metals on ceramic, polytetrafluoroethylene (PTFE or Teflon), fritted glass, and stainless steel vacuum pore‐water samplers and silica packing material used to seat samplers was evaluated with respect to potential sampling errors. A solution containing radio‐labeled Cd+2, Co+2, Cr+3, and Zn+2 and a mix of ions typically found in soil solutions was used to assess specific absorption of inorganics to porous cups of samplers and to silica. Four sets of samplers were cleaned with acid or water and then treated with a solution containing trace metals at concentrations near primary or secondary drinking‐water standards or one order of magnitude lower for 2 or 7 d. After treatment, the samplers were rinsed with 10 or 30 pore volumes (PV) of simulated soil solution and radioassayed. Duplicate silica samples were treated with the high‐trace‐metal solution adjusted to a pH of 4, 6, or 8 for a 5‐d period, rinsed with simulated soil solution, and radioassayed. Adsorption was greatest on samplers treated with high trace‐meal concentrations and samplers cleaned with water. Desorption of both Co and Zn occurred with the 30‐PV soil solution rinse for all sampler types except stainless steel. The general pattern of metal adsorption on samplers was ceramic > stainless steel >> fritted glass = PTFE. The general order that trace metal adsorbed to samplers and silica was Zn >> Co > Cr > Cd. At pH values of 6 to 8, trace‐metal adsorption on silica (mass of adsorbent/mass of adsorbate) was similar to or greater than that observed for ceramic samplers. This study shows that adsorption‐desorption processes can cause sampling error when analysis of trace metals at microgram‐per‐liter concentration levels is necessary.
Characterization of Humic Acids, Composts, and Peat by Diffuse Reflectance Fourier‐Transform Infrared Spectroscopy
Authors: Niemeyer J. , Chen Y. , Bollag J.‐M. 
Published: July 2010

AbstractTransmission infrared (IR) spectroscopy, either dispersive or Fourier transformed (FTIR), has been used extensively in studies on humic substances. A variety of bands characteristic of molecular structures and functional groups have been identified for these substances. The development of an attachment mounted onto FTIR spectrophotometers has allowed the determination of diffuse reflectance Fourier‐transformed infrared (DRIFT) spectra. The purpose of this work was to study the applicability of DRIFT to soil organic‐matter research and to compare the use of this instrumentation to dispersive and Fourier‐transformed transmission IR spectroscopy. The DRIFT spectra were determined for humic acids, peat samples, and composts. In addition, the possibility of using DRIFT spectra to quantitatively measure sample concentration and measuring the relative concentration of functional groups was assessed. Sample preparation for DRIFT is much simpler than for transmission IR spectroscopy, interferences due to water adsorption are reduced, and resolution is improved. The spectra obtained using DRIFT had a higher degree of resolution as compared with dispersive and Fourier‐transform transmission IR spectroscopy. Bands indicative of aliphatic C‐H, carboxyl and corboxylate functional groups, aromatic C=C, and C‐O stretch of polysaccharides were prominent and very well resolved. The DRIFT spectra obtained can also he used to fingerprint organic matter acquired from various sources. Spectra obtained at various concentrations of humic acid indicated that DRIFT cannot be used to estimate concentrations of organic matter in a given mixture. Relative concentrations of functional groups, however, were found to be fairly constant regardless of sample concentration. Therefore, changes in the relative concentration of functional groups can he measured during the humification process. It is expected that the application of DRIFT to organic‐matter research will prove especially useful for characterizing bulky heterogeneous samples such as peat and composts.
Changes in a Sandy Sahelian Soil Following Crop Residue and Fertilizer Additions
Authors: Geiger S. C. , Manu A. , Bationo A. 
Published: July 2010

AbstractThe use of crop residues as surface mulches has been shown to have a beneficial effect on the growth of pearl millet [Pennisetum glaucum (L.) R.Br.] in the Sahelian zone of West Africa. This study was conducted to discern the mechanism(s) responsible for yield increases resulting from crop‐residue additions in a field trial located on a sandy soil at the ICRISAT Sahelian Center near Niamey, Niger. Soil chemical and physical properties were examined to a depth of 120 cm after 5 yr of application of millet residue as a surface muich, P and N fertilizer, or a combination of fertilizer and residue. Annual residue application resulted in a higher exchangeable‐base content, lower Al saturation, and slightly higher available‐P values than the control. The use of fertilizer resulted in an increase in available P and exchangeable Ca. The combination of residue plus fertilizer resulted in greater enhancement of soil fertility parameters than the use of tbese inputs alone. Differences in soil chemistry were operative in only the top 20 cm of the soil profile, bowever, the surfaces of the plots receiving residues were 15 to 20 cm higher than the surfaces of the control and fertilizer‐only plots. The surfaces of the residue plots also had lower clay contents than the surface soils in the nonresidue plots. The increase in soil fertility following the application of millet residue as a surface mulch was due to two mechanisms: (i) the recycling of nutrient elements to the soil following termite and microbial decomposition of the residue, and (ii) the entrapment of eolian materials, which generally have better fertility characteristics than the subsoil, or protection of the more fertile surface soil from the erosive effects of the strong winds that are common in the Sahel.
Cesium‐137 Distribution in a California Pelloxerert: Evidence of Pedoturbation
Authors: Southard R. J. , Graham R. C. 
Published: July 2010

AbstractThe distribution of 137Cs activity in soils provides a means of assessing physical transport of soil particles. We measured the activity of 137Cs along cracks and within peds of a Chromic Pelloxerert on the flood plain of an ephemeral stream in the Central Valley of California to assess the role of pedoturbation in the formation of a Vertisol. The 137Cs activity is highest in the upper 10 cm of the soil and generally decreases with increasing depth, although 137Cs activity is also high locally along cracks and at the bottom of some cracks near the average depth of cracking (base of Bss horizon, 72‐cm depth). Laterally (along cracks vs. ped interiors), the 137Cs activity varies greatly and shows no consistent pattern. Micromorphological evidence of stress‐oriented clay in soil fabric and locally high 137Cs activity below 72 cm indicate incorporation of surface materials into deeper cracks during drier‐than‐average years. Organic carbon (OC) content decreases regularly with depth, whereas CaCO3 content is uniform throughout the upper 72 cm. The nonhomogeneous 137Cs distribution demonstrates that pedoturbation has occurred. The rate of homogenization of soil material in the upper 72 cm exceeds 25 yr and is slower than the rate of OC accumulation and humification, but faster than the rate of carbonate redistribution. We attribute relatively high 137Cs activity throughout the upper 20 to 30 cm of the soil to incorporation of surface material into minor cracks that open during the dry season. The incorporation of sloughed materials at the base of larger cracks, where evidence of shearing (slickensides) is most strongly developed, is only locally significant and is probably not the dominant mechanism of pedoturbation.
Partitioning Variability of Soil Properties Affecting Solute Movement with Soil Taxonomy
Authors: Seyfried M. S. , Hornsby A. G. , Rao P. V. 
Published: July 2010

AbstractSoil taxonomy provides a classification framework for large amounts of data collected in conjunction with soil survey work. This framework may be very useful in parameterizing models of solute movement. An important criteria for usefulness is that the classification groupings reduce sample variability. We used nested analysis of variance to assess the effectiveness of the USDA soil taxonomy in describing sample variability. Soil characterization data from a total of 689 pedons sampled by horizon in Florida were analyzed. Eleven different soil physical and chemical properties important to the modeling of solute movement in soils were selected. Depth effects were incorporated by using surface horizon and depth‐weighted average values to depths of 50, 100, and 150 cm. We found that the USDA soil taxonomy very effectively partitioned variance, as evidenced by average R2 values of 0.80 for surface samples and 0.90 for depth‐weighted averages. Effectiveness improved with depth of consideration, reflecting the importance of subsoil characteristics in the USDA soil taxonomy. In general, the most effective taxonomic levels were the order, great group, and subgroup. This indicates that it is reasonable to lump or extrapolate data within the family or subgroup levels to obtain better estimates of soil property values in Florida. We believe that these results are probahly qualitatively applicable to other soil properties and locations, hut that quantitative extrapolation should not be done without further study.
Methods for Analyzing Constant‐Head Well Permeameter Data
Authors: Elrick D. E. , Reynolds W. D. 
Published: July 2010

AbstractThe constant‐head well permeameter has proven to be a useful and versatile instrument for determining the in situ hydraulic properties of soils in the unsaturated (vadose) zone. The flow measurements are obtained under conditions of saturated‐unsaturated, three‐dimensional flow in the unsaturated zone. As a consequence, the steady‐state flow rate out of the permeameter is determined by both the field‐saturated hydraulic conductivity (Kfs) and the matric flux potential (φm) of the unsaturated soil. Because both Kfs and φm contribute to the flow, calculation of these parameters from well permeameter data requires either the solution of two (or more) simultaneous equations, or reduction of the problem to one equation in one unknown if additional information is known or estimated. Use of the simultaneous‐equations approach in heterogeneous soils can result in a high percentage of invalid (i.e., negative) Kfs and φm values. Negative results can be avoided and good estimates obtained, however, by using an independent measurement or site estimate of the ratio α* = Kfs/φm.