bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil Water Storage in Dryland Cropping Systems: The Significance of Cropping Intensification
Authors: Farahani H. J. , Peterson G. A. , Westfall D. G. , Sherrod L. A. , Ahuja L. R.
Published: July 2010

Soil and water conservation is essential to the sustainability of Great Plains dryland agriculture. We hypothesized that cropping intensification improves the efficient use of precipitation. We evaluated long‐term observations of soil water at three locations in eastern Colorado for a range of pan evaporations (1050–1900 mm), soils, and cropping systems. Soils at various locations were mostly of the Argiustoll subgroup except for one Ustochrept and one Haplargid, both at the higher evaporation location. Normal precipitation at the three locations ranges from 400 to 425 mm yr‐1. Systems included a 2‐yr winter wheat (Triticum aestivum L.)‐fallow (WF) and more intense 3‐yr winter wheat‐corn (Zea mays L.)‐fallow and winter wheat‐sorghum [Sorghum bicolor (L.) Moench]‐fallow and 4‐yr rotations. To quantify the effectiveness of the intensified systems at utilizing precipitation, we introduce the System‐Precipitation‐Storage Index (SPSI) and System‐Precipitation‐Use Index (SPUI). Mean SPSI values were 0.19 and 0.28 for 2‐ and 3‐yr systems, respectively, meaning that the fallow periods in the 3‐yr rotation were collectively 47% more efficient at storing precipitation than fallow in WF. Inclusion of a summer crop, such as corn or sorghum, increased the fraction of precipitation allocated to growing‐season crop production (i.e., SPUI) from 0.43 in WF to 0.56 (i.e., an increase of 30%) in 3‐yr systems. The gains in efficient use of precipitation with intensification resulted from (i) reducing the frequency of the inefficient fallow preceding wheat, and (ii) using water for transpiration that would otherwise be lost during fallow through soil evaporation, runoff, and deep percolation.
Bromide Transport under Contour Hedgerow Systems in Sloping Oxisols
Authors: Agus F. , Cassel D. K. , Garrity D. P.
Published: July 2010

Contour hedgerows promote infiltration, thereby reducing runoff and soil erosion on sloping lands. The increase in infiltration could increase the leaching of mobile chemicals. The objective of this study was to determine the effect of hedgerows on Br‐ transport in two Hapludox soils with 21 to 30% slope in the Philippines. In Exp. 1, KBr at the rate of 200 kg Br‐ ha‐1 was broadcast in June 1991 at corn (Zea mays L.) planting on (i) the alleyways of plots with pruned hedgerows of Gliricidia sepium (Jacq.) Klunth ex Walp. and paspalum (Paspalum conjugatum Bergius) (hedgerow treatment) and (ii) open field plots (control). In Exp. 2, KBr was applied at the same rate as in 1991 in strips in the hedgerow and control plots that had not received the KBr application the previous year. After Br‐ application, Br‐ was analyzed in hand‐augered soil samples at increments to 105 cm and in soil solution samples taken with suction lysimeters at the 30‐, 60‐, and 90‐cm depths. Estimated pools of Br‐ (kg ha‐1) at a given depth were usually less for the suction lysimeter than for soil samples, possibly due to percolating water bypassing Br‐ in soil aggregates above the depth of lysimeter sampling. After about 500 mm of rainfall, 50% of the Br‐ had leached below the 30‐cm depth in the hedgerow plots. Slightly greater lateral, but less vertical, Br‐ movement occurred for the control. If NO3 leaches to or below the observed Br‐ leaching depths, it would become unavailable to acidsensitive food crops displaying shallow rooting depths.
Forest Peatland Drainage and Subsidence Affect Soil Water Retention and Transport Properties in an Alberta Peatland
Authors: Silins Uldis , Rothwell Richard L.
Published: July 2010

Water table level control by drainage improves forested peatland sites for tree growth, but can also result in subsidence of the peatland surface. The purpose of this study was to investigate the effects of changes to peat bulk density associated with postdrainage subsidence on peat hydrologic properties at a peatland drained for forestry in north‐central Alberta, Canada. Peat hydrologic functions were determined by inverse techniques developed for multistep outflow experiments (MULSTP). Seven years after drainage, mean peat bulk density (0–40‐cm depth) was 63% greater and mean soil water retention (−5 to −15000 cm pressure head) was 66% greater than peat from the nearby undrained control area. Subsidence after drainage was associated with loss of pores >600‐µm diam. with concurrent increases in 3‐ to 30‐mm‐diam. pore‐size classes. Mean saturated hydraulic conductivity was 1.69 and 14.46 cm h‐1, while mean unsaturated hydraulic conductivity (−5 to −15000 cm pressure head) was 0.014 and 0.004 cm h‐1 in peat from drained and undrained areas, respectively. Changes in water transport characteristics and in the pool of “plant‐available” soil water will probably be beneficial to tree growth in the drained area.
Soil Aggregation and Organic Matter Mineralization in Forests and Grasslands: Plant Species Effects
Authors: Scott Neal A.
Published: July 2010

Plant‐soil feedbacks can alter N cycling rates in terrestrial ecosystems, but the mechanistic relationship between species characteristics, soil properties, and N dynamics is unclear. Plant species may affect patterns of soil aggregation, which can affect soil C and net N mineralization. This mechanism was examined in two common garden experiments: one containing five tree species (European larch [Larix decidua Miller], red oak [Quercus rubra L.], red pine [Pinus resinosa Ait.], white pine [Pinus strobus L.], and Norway spruce [Picea abies (L.) Karst]) and one containing six grass species (big bluestem [Andropogon gerardi Vitm.], indiangrass [Sorghastrum nutans (L.) Nash], prairie sandreed [Calamovilfa longifolia (Hook) Scrib.], switchgrass [Panicum virgatum L.], little bluestem [Schizachyrium scoparium (Michx.) Nash.], and sideoats grama [Bouteloua curtipendula (Michx.) Torr.]). The grass monocultures are burned annually. Soils were wet sieved into four size classes (>2000, 250‐2000, 53‐250, and <53 µm). Unsieved soil was incubated aerobically for 30 and 387 d to examine C and net N mineralization. For tree species, aggregate weighted mean diameter (WMD) differed between species (P = 0.01), and correlated positively with fungal biomass (r = 0.56). Large macroaggregate (>2000 µm) C concentration ranged from 15 to 26 g kg‐1, and was lowest for Norway spruce and red oak (P = 0.07). Aggregate WMD correlated weakly (and negatively) with potentially mineralizable N (r = −0.57) and in situ net N mineralization (r = −0.67), but positively (again weakly) with potentially mineralizable C (r = 0.49). Grass species had no effect on aggregate‐size distribution or organic matter concentration in spite of twofold differences in root biomass and threefold differences in N cycling rates. Species‐induced changes in soil aggregation explained little of the variation in whole‐soil C and N cycling rates, and are therefore unlikely to be an important mechanism explaining species effects on ecosystem processes.
Nitrogen Movement with Furrow Irrigation Method and Fertilizer Band Placement
Authors: Benjamin J. G. , Porter L. K. , Duke H. R. , Ahuja L. R. , Butters G.
Published: July 2010

Alternate‐furrow irrigation has been proposed as a method to increase irrigation water use efficiency, increase capture and storage of rainfall during the irrigation season, and decrease deep percolation of water. We hypothesized that less fertilizer leaching would occur if the applied fertilizer were spatially separated from the irrigation water in a furrow irrigation system. A study was conducted on a Fort Collins loam (fine‐loamy, mixed, superactive, mesic Aridic Haplustalf) in 1994 and 1995 near Fort Collins, CO. Nitrogen uptake by corn (Zea mays L.) and N leaching were determined with alternate‐furrow and every‐furrow irrigation water applications, each with fertilizer bands of 15N‐enriched (NH4)2SO4 placed either in the row or in the furrow. In 1994 fertilizer N leached to ≈1 m for the every‐furrow irrigation with fertilizer placed in the irrigated furrow, but to 0.5 m or less for the other treatments. In 1995 the fertilizer leaching was similar among the treatments because of less irrigation and more rainfall during the growing season. There were no statistically significant differences for irrigation water placement effects on plant biomass or total N uptake, indicating that alternate‐furrow irrigation is not detrimental to crop production compared with every‐furrow irrigation for similar applications of water. This study showed that placing fertilizer in the nonirrigated furrow of an alternate‐furrow irrigation system or placing fertilizer in the row with either alternate‐ or every‐furrow irrigation has the potential to decrease fertilizer leaching without reducing crop productivity.
Modeling the Crack Network of Swelling Clay Soils
Authors: Chertkov V. Y. , Ravina I.
Published: July 2010

The dynamic crack network in swelling clay soils is a major factor determining their hydraulic properties and particularly preferential flow, with important consequences for ecologically adverse processes. We developed a physically based probabilistic model for the prediction of crack network geometry that takes into account the dependence of the crack concentration on soil depth. Starting with the similarity of crack networks in rocks and soils, we used the multiple cracking and fragmentation model available for rocks. In the case of cracked soils, two fundamental parameters of the model, the average spacing between cracks and the crack connectedness, become specific functions of depth. We constructed these functions for “steady‐state” cracking after long drying times using a number of reasonable physical assumptions and introducing two additional parameters: the maximum crack depth, zm, and the thickness of the intensively cracked layer, zo. With continued drying, the ratio zm/zo ≅ 10 and the limiting values of these parameters are determined. Applications of the model include estimates of crack width, cross‐sectional area, and volume in clay soils, given a knowledge of the water content profile and the shrinkage curve of the clay soil matrix. Published data of four field and lysimeter experiments from different geographical areas were analyzed for validation of the model. A satisfactory correspondence was obtained between predicted and measured crack parameters.
Spatial Dependence of Soil Enzyme Activities along a Slope
Authors: Bergstrom D. W. , Monreal C. M. , Millette J. A. , King D. J.
Published: July 2010

This study measured the spatial dependence of soil enzyme activities and other properties of the Ap horizon in a Gray Brown Luvisol (Hapludalf). Soil samples were collected at 74 positions along a slope following harvest of soybean [Glycine max (L.) Merr.] and fall tillage. Parameters measured were activity of dehydrogenase, urease, glutaminase, phosphatase, arylsulfatase, and β‐glucosidase; water, organic carbon (OC), mineral N, and inorganic P contents; the light fraction of soil organic matter; and depth of the Ap horizon. Rank correlation indicated significant relationships between water and dehydrogenase, urease, glutaminase, phosphatase, and arylsulfatase activities, and between water and OC content. Depth of the Ap horizon, water content, and arylsulfatase activity were strongly spatially dependent; OC and inorganic P contents and phosphatase activity were moderately spatially dependent. Other properties showed little or no spatial dependence. The ranges of spatial dependence were similar for depth of the Ap horizon, inorganic P content, and phosphatase activity (≈20 m). The range for arylsulfatase activity was 16 m, while that of OC content was 32 m. The relatively long range estimate for water content (98 m) was influenced by a trend along the slope. Maps of water and OC contents and phosphatase and arylsulfatase activities indicated similar spatial patterns along the slope. The magnitude of these soil properties was minimal in the middle or upper portion of the slope, and maximal at the footslope. Similarity in spatial patterns along the slope was interpreted as evidence for influence of water or OC content on amounts of phosphatase and arylsulfatase at that scale.
Manuring and Soil Type Influence on Spatial Variation of Soil Organic Matter Properties
Authors: Bragato G. , Primavera F.
Published: July 2010

The spatial variability of microbial biomass C and three humification indexes (the degree of humification, DH; the index of humification, HI; and the humification rate, HR) were investigated in order to evaluate their usefulness as indicators of the response of soil organic matter to altered soil environments. The investigation was carried out by examining the topsoil layer of an experimental field characterized by the presence of four phases of one soil series and, except for the addition of cattle manure in part of the field, by fairly uniform agricultural practices. A rectangular area of 350 by 800 m was sampled on a square grid scheme coupled with nesting. The experimental objective was to determine if the investigated properties were influenced by changes in soil type and by the addition of cattle manure. All properties measured showed spatial dependence at the sampling distances adopted. Two groups of properties were identified based on their degree of spatial variability: microbial biomass C, DH, and HI exhibited short‐range variability, whereas HR varied across longer distances. Microbial biomass C and HR showed a spatial pattern related to soil amendment and soil types, respectively. Therefore, these variables provided complementary information about the condition of soil organic matter in the study area.
A Simple Multisampler for Hydraulic Soil Probes
Authors: Zerkoune M. A. , Shapiro C. A. , Post L.
Published: July 2010

Nutrient distribution near fertilizer bands is studied by sampling soil perpendicular to band orientation. These studies require intensive hand sampling, which is time consuming and difficult. More research can be conducted if sampling techniques are improved and made cost effective. We designed and constructed a multisampler system that fits a hydraulic probe and doubled sampling efficiency. The system consists of a sampler, sampling tubes, a template, and a tray to hold soil boxes. These components can be used to construct a sampler and a template that correspond to a specific sampling scheme, and can be adapted to a wide range of configurations. The system can be constructed with tools readily available at most farm shops and the materials are easily obtainable.
Noninvasive Water Content and Electrical Conductivity Laboratory Measurements using Time Domain Reflectometry
Authors: Persson Magnus , Berndtsson Ronny
Published: July 2010

A noninvasive approach for measurements of near‐surface water content (θ) and bulk electrical conductivity (σa) using time domain reflectometry (TDR) is presented. In this approach, an ordinary three‐rod TDR probe is used together with a polyvinyl chloride (PVC) surface block that surrounds half the measurement volume. Theoretical and experimental results show that an analytical solution of the apparent dielectric constant Ka and the σa of the soil is possible. Thus, the suggested technique does not require a separate calibration of the relationship between the measured effective Ka and Ka of the soil. The variability of the measurements was shown to be slightly higher than using the traditional approach. The spatial sensitivity of the suggested technique was also investigated. It was shown that using a three‐rod TDR probe with a rod spacing of 0.05 m allows the θ and σa to be measured in the uppermost 2 cm of the soil.
Short‐term Changes in Soil Carbon and Nitrogen Pools during Tillage Management Transition
Authors: McCarty G. W. , Lyssenko N. N. , Starr J. L.
Published: July 2010

It is well established that distribution of organic C and N within a soil profile is substantially influenced by long‐term conversion of soil from plow‐tillage to no‐tillage management, but little is known about the short‐term changes in the character of soil organic matter during transition between these two soil management systems. To characterize the changes in composition of organic C and N pools in soil during tillage transition, we measured total N, organic C, active N, biomass N, and biomass C at depth intervals of 0 to 2.5, 2.5 to 5, 5 to 12.5, and 12.5 to 20 cm within the profile of soil during the first 3 yr in the transition from plow tillage to no tillage. The results obtained showed that transformation of a soil profile from that typical of plow tillage management to one characteristic of no tillage occurred rapidly within a 3‐yr period of transition. In this time period, stratification of organic matter in the profile progressed significantly toward that which occurs after 20 yr of no‐tillage treatment. For example, substantial increases in total N (30%), organic C (38%), biomass N (87%), and biomass C (33%) were detected in the top layer of notillage soil along with corresponding decreases of 6%, 7%, 35%, and 15% of those respective components in the bottom layer. With transition, the biomass C, biomass N, and active N pools increased more rapidly in the upper soil profile than did the total pools of C and N. Although the characteristic profile of no‐tillage soil developed quickly during tillage transition, evidence was equivocal for any significant increase in organic matter content within the first 3 yr after conversion to no‐tillage management.
Corn Yield and Nitrogen Uptake in Monoculture and in Rotation with Soybean
Authors: Omay A. B. , Rice C. W. , Maddux L. D. , Gordon W. B.
Published: July 2010

Increasing crop N use efficiency and minimizing environmental risk require an accurate assessment of N taken up by the crop from different sources. We conducted this study to: (i) compare the grain yields of corn (Zea mays L.) in monoculture and in rotation with soybean [Glycine max (L.) Merr.]; (ii) determine the contributions of N from fertilizer, soil, and legume residue to corn in the rotation; and (iii) compare N fertilizer recovery in monoculture and in rotation. Two existing (>10 yr) irrigated corn‐soybean rotation areas in Kansas were used. The soils were Crete silt loam (fine, smectitic, mesic Pachic Argiustolls) and Eudora loam (coarse‐silty, mixed, superactive, mesic Fluventic Hapludolls). To trace the N through the rotation, 15N microplots (2.4 m2) were established int he corn. Microplots also were established in soybean to separately follow 15N from roots + soil and shoots to corn. Crop rotation and fertilizer addition increased corn yield at both sites for two growing seasons. Averaged for 2 yr, the amount of N needed in the continuous corn to achieve yield equal to that in rotation with no N added was equivalent to 144 kg N ha‐1 in the Crete silt loam and 155 kg N ha‐1 in the Eudora loam. Response to N was greater on the Eudora loam, probably because of textural and organic matter differences. In the Eudora soil, significantly higher amounts of soil N were taken up at harvest by corn in rotation, whereas, in the Crete soil, corn in monoculture took up significantly higher amounts of soil N. Corn plants recovered 3 kg N ha‐1 (3%) from soybean residue in the Eudora soil and 5 kg N ha‐1 (14%) in the Crete soil. The main value of legume residue appears to be long‐term maintenance of soil N to ensure adequate delivery to future crops.
Aggregation of Soil Cropped to Dryland Wheat and Grain Sorghum
Authors: Unger P. W. , Jones O. R. , McClenagan J. D. , Stewart B. A.
Published: July 2010

Successful and sustainable semiarid dryland cropping depends on effective soil water storage and erosion control, which are influenced by surface soil aggregate size and stability. We hypothesized long‐term tillage and cropping system treatments affect water‐stable aggregate size distribution, aggregate water stability, and dry soil aggregation. A study on a Torrertic Paleustoll from 1982 to 1994 at Bushland, TX, involved tillage methods (no‐tillage, NT; stubble mulch tillage, SMT) and cropping systems for dryland winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] production. In 1994, mean percentages of >4‐mm water‐stable aggregates at 0 to 2 cm were 3.5 with NT and 1.0 with SMT in wheat, sorghum, fallow, rotation phase, or crop comparison plots. Mean percentages of <0.25‐mm aggregates were 49.0 with NT and 37.8 with SMT. More small aggregates with NT help explain why infiltration was 90% greater with SMT than with NT during fallow after sorghum and 26% greater with SMT during fallow after wheat in a similar study on the same soil when surface coverage by residues was limited (25% with SMT, 57% with NT for sorghum; 73% with SMT, 86% with NT for wheat). Aggregate sizes differed due to cropping system, rotation phase, and crop, but aggregate water stability and dry aggregation differences generally were nonsignificant. Both NT and SMT are deemed suitable for dryland crops under conditions as in this study because neither resulted in unfavorable soil conditions or major yield differences.
Effects of Agricultural Runoff Dispersion on Nitrate Reduction in Forested Filter Zone Soils
Authors: Verchot Louis V. , Franklin E. Carlyle , Gilliam J. Wendell
Published: July 2010

Forested filter zones (FFZ) are being used more frequently for remediation of agricultural non‐point source pollution. The objective of this study was to determine the effects of short‐term dispersal (1–2 yr) of agricultural runoff on the denitrification potential of the soil microbial population and denitrification rates, to a depth of 1 m, in forest soils in two small watersheds (W1 and W2) in the Piedmont of North Carolina. Each watershed consisted of a field and a FFZ. Denitrification potential was measured in a series of soil slurry incubations of soils from inside the FFZ that received agricultural runoff and from soils immediately adjacent to the FFZ that received no runoff (control). Soils were amended with both glucose and nitrate (G + NO3) to ensure adequate supply of substrate and energy source. Denitrification rates were measured at ambient C conditions in a similar incubation with only NO3‐N amendment (NO3). We measured NO3‐N disappearance in both incubations and reported loss as a percentage of initial concentrations. For the FFZ soils, >80% of the added NO3‐N was lost in the G + NO3 incubation from soils from the upper 50 cm in W1 and from the upper 30 cm in W2. In control soils, high levels of NO3‐N loss were observed in only the upper 20 cm of the profile in W1, and in W2 surface soils had significantly lower denitrification potential than FFZ soils at all depths. Denitrification potential was greatly enhanced (P = 0.05) throughout the entire first 100 cm in the first FFZ and in the surface 40 cm in the second FFZ. Denitrification rates under ambient C conditions were higher (>40%) in the surface 20 cm of the profile of the FFZ in W1, compared with the unexposed control (∼20%), but no enhancement was observed on W2. Exposure of soil to agricultural runoff had a significant impact on the soil microbial community. Denitrification potential in subsoil was limited by the absence of denitrifiers in unexposed soils, but subsoils exposed to agricultural runoff had a significant denitrifier population. The fact that higher denitrification potential did not translate to higher denitrification rates in these incubations indicates that C availability limited the denitrification process at all depths in these Piedmont forest soils.
Discriminating Dyes in Soil with Color Image Analysis
Authors: Ewing R. P. , Horton R.
Published: July 2010

Dyes are useful tools for revealing flow patterns, but because analysis of dyes is time‐consuming and often only qualitative, soil scientists have not used them to their full advantage. We developed a method for discriminating dyed from undyed soil in the field and for determining the dye concentration from point to point. The method requires a 35‐mm camera, a specially constructed camera stand for uniform illumination during field work, and a color scanner. Working with Brilliant Blue FCF dye on a gray (chroma of one) soil, we determined dye concentrations <2.0 g L‐1 with an r2 of 0.85 and a median absolute error of 0.17 g L‐1. At concentrations >2.0 g L‐1, analysis was more problematic due to dye precipitating out of solution onto the soil surface, but we obtained an r2 of 0.70. Use of this method allows convenient and rapid quantitative analysis of dye concentration and other color contrast patterns.
Soil Warming and Carbon Loss from a Lake States Spodosol
Authors: MacDonald Neil W. , Randlett Diana L. , Zak Donald R.
Published: July 2010

Elevated soil temperatures may increase C loss from soils by accelerating microbial respiration and dissolved organic C leaching. We evaluated the effect of elevated soil temperatures on C losses from a forest Spodosol by incubating soil cores from surface (Oa + A + E) and subsurface (Bhs) horizons at two seasonal temperature regimes. One regime simulated the normal course of soil temperatures in northern lower Michigan, and the other simulated soil temperatures representing an amount of warming that might occur under some global warming theory calculations. We measured the amounts of CO2‐C respired and dissolved organic C leached from the soil cores during a 33‐wk period. Microbial respiration rates, after adjustment for variation in initial rates, were significantly increased by soil warming and were greater in surface than in subsurface horizons. Warming significantly increased cumulative C respired, with greater losses from surface soils (≥50 mg C g‐1 C) as compared with subsurface soils (≤25 mg C g‐1 C). Mean quantities of dissolved organic C leached, ranging from 2.3 to 3.2 mg C g‐1 C, did not differ significantly by soil horizon or temperature regime. Increased microbial respiration in surface soil horizons was the process most responsive to soil warming in the Spodosol samples we examined. Whether this is a short‐term effect that would disappear once pools of labile C are exhausted, or represents a long‐term response to soil warming, remains uncertain.
In Situ Measurement of Solute Transport Coefficients: Assumptions and Errors
Authors: Snow V. O.
Published: July 2010

Single‐tracer and sequential‐tracer techniques for directly measuring the immobile water content, θim, and a sequential‐tracer technique for measuring the solute transfer rate coefficient, α, have been proposed. These techniques have not been subjected to a comprehensive analysis of their assumptions, nor of the errors resulting if those assumptions are violated. Here, an analytical solution to the mobile‐immobile convection‐dispersion equation was used to assess the range of soil and sampling conditions that can lead to accurate estimates of θim and α. Both techniques were shown to result in considerable error in soils possessing high dispersivity (λ) and high α when conductivity (q) was low, or if sampling was done when the cumulative infiltration (I) was too small. For a wide range of conditions, the single‐tracer technique resulted in estimates of θim within 15% of the true value if sampling took place when q > 10 mm h‐1, I > λ, and sampling time <1.25 h. The value of θm/θ had only a small effect on appropriate sampling conditions. Sampling conditions were more restrictive for the sequential‐tracer technique than for the single‐tracer technique. When θm/θ ≈ 0.6, if λ ≈ 5 mm and q > 10 mm h‐1, and I > 30 mm, acceptable values of θim and α were calculated. Sampling conditions became more restrictive as λ increased. If λ > 20 mm, there seemed little possibility for obtaining reasonable estimates of either θim or α. Sampling conditions varied strongly with θm/θ, becoming more lenient as θm/θ decreased.
Alteration of Soil Properties through a Weathering Sequence as Evaluated by Spectral Reflectance
Authors: Demattê José Alexandre M. , Garcia Gilberto J.
Published: July 2010

In the study of physical, chemical, and mineralogical data related to the weathering of soils and the quantification of their properties, remote sensing constitutes an important technique that, in addition to conventional analyses, can contribute to soil survey. The objectives of this research were to characterize and differentiate soils developed from basaltic rocks that occur in the Paraná state, Brazil and to quantify soil properties based on their spectral reflectance. These observations were used to verify the relationship between the soils and reflectance with regard to weathering, organic matter (OM), and forms of Fe. From the least to the most weathered soil, we used a Typic Argiudoll (Reddish Brunizem), Rhodudalf (Terra Roxa Estruturada), and Rhodic Hapludox (Very Dark Red Latosol). The spectral reflectances between 400 and 2500 nm were obtained in the laboratory from soil samples collected at two depth increments, 0‐ to 20‐ and 40‐ to 60‐cm, using an Infra Red Intelligent Spectroradiometer (IRIS). Correlation, regression, and discriminant estimates were used in analyzing the soil and spectral data. Results of this study indicated that soils could be separated at the soil‐type level based on reflectance intensity in various absorption bands. Soil collected in the 40‐ to 60‐cm depth appeared to have higher reflectance intensities than those from the 0‐ to 20‐cm depth. Removal of OM from soil samples promoted higher reflectance intensity in the entire spectrum. Amorphous and crystalline Fe influenced reflectance differently. Weathering of basaltic soils was correlated with alterations in the reflectance intensities and absorption features of the spectral curves. Multivariate analysis demonstrated that this technique was efficient in the estimation of clay, silt, kaolinite, crystalline Fe, amorphous Fe, and Mg through the use of reflected energy of the soils.
Relating Suspended Sediment to its Original Soil Depth Using Fallout Radionuclides
Authors: Wallbrink P. J. , Olley J. M. , Murray A. S.
Published: July 2010

We present and test a new method for determining the original soil depth of suspended sediment through analysis of fallout radionuclide properties. We propose that combining the different depth distributions of fallout 7Be, 210Pb, and 137Cs in soils with one another provides reference curves that can be used as a framework for interpreting the tracer concentrations of sediments derived from them. If it is assumed that the soil depth sources of the sediment are from the surface and the subsurface, the tracer concentrations from these two sources can be used to calculate the actual soil depth(s) from which the sediment originated. The proportion of sediment from each depth can also be calculated. We tested this method by generating sediment from a hillslope with treatments simulating: (T1) surface erosion, (T2) shallow rills to 10 mm, (T3) deep rills to 100 mm, and (T4) small gullies to 250 mm. The tracer‐based calculations of sediment source matched the known incision depths of these features. Material was predicted to be from 1 ± 2 mm and 4 ± 4 mm soil depth for T1 and T2 respectively. In T3, the material was predicted to be from 1.25 ± 0.5 mm at the surface and >78 ± 6 mm depth from the deep rills. In T4, the sediment was predicted to be from <2.5 ± 1.5 mm at the soil surface and > 86 ± 6 mm from the small gullies. The subsoil contribution to sediments increased from ≈50% (T3) to 75% (T4) as rill and gully depths and widths increased.
Dynamics of Physical Organic Matter Fractions During De‐inking Sludge Decomposition
Authors: Fierro Alejandro , Angers Denis A. , Beauchamp Chantal J.
Published: July 2010

Replenishment of soil C and N is essential for sustainable revegetation of minesoils. Our study investigated paper de‐inking sludge as the organic amendment for revegetating an abandoned sandpit in Québec, Canada. Sludge was incorporated at 0 (check) and 105 Mg dry matter ha−1 before seeding tall wheatgrass (Agropyron elongatum (Host) Beauv.). Nitrogen (at 315, 630 and 945 kg N ha−1) and P (at 52.5 and 105 kg P ha−1) were also applied to all plots. Distribution of C and N was determined periodically in two sizes (<53 μm and >53 μm) and two densities (<1.8 g cm−3 and >1.8 g cm−3) of soil fractions during 823 d. After 823 d, C concentrations were 43 and 69% of those of Day 5, for the low and high N rates, respectively. With time, the proportion of C in the heavy (>1.8 g cm−3) fraction increased from 20 to 55%, but remained near 20% in the fine (<53 μm) fraction. Increasing N rates increased C conservation mainly in the coarse (>53 μm) fraction. The amount of N recovered in all fractions decreased after Day 86, in accordance with a previous litter bag study. Although inorganic N was positively correlated with total N in all fractions, the fine fraction was the best indicator of the size of the mineral N pool. Addition of sludge to the sandpit favored the restoration of C and N pools, and high levels of mineral N increased this effect. Residues became denser but remained relatively coarse during their decomposition.
Soft X‐ray Radiography of Drainage Patterns of Structured Soils
Authors: Mori Y. , Maruyama T. , Mitsuno T.
Published: July 2010

Characterization of unsaturated hydraulic and geometrical properties of undisturbed soils is essential for understanding water flow and solute transport in soils. We visualized the drainage pattern by soft x‐ray radiography using a contrast medium. Outflow experiments were conducted simultaneously and unsaturated hydraulic conductivity was calculated by parameter estimation. Time sequential drainage patterns were obtained by the subtraction technique, which was done by subtracting a reference image from the image of interest. Drainage patterns of paddy and upland field soils showed that drainage occurs through macropores first, followed by interaggregate macropores, and then finally through the soil matrix. The drainage pattern resembles two‐domain flow of macropore and matrix. On the other hand, drainage occurred through the entire sample in forest soils. Unsaturated hydraulic conductivity data showed a discontinuity near saturation, providing evidence of two‐domain flow. This was explained by differences in bulk density. Tightly packed soils allowed macropore flow. The differences increased in the order: forest, upland field, and paddy field soils. An exception was observed in paddy field soils, where roughly packed deeper soils showed significant macropore flow. The thin section photograph of paddy field soils from deeper layers revealed that the macropore wall was coated with alluvial materials that prevented smooth water flow across the macropore wall. In this regard, we should also consider the resistance caused by these materials. Soft x‐ray radiography of the drainage pattern was helpful in characterizing the unsaturated hydraulic properties of structured soils.
Quantifying the Influence of Intra‐Aggregate Concentration Gradients on Solute Transport
Authors: Cote C. M. , Bristow K. L. , Ross P. J.
Published: July 2010

The physical nonequilibrium of solute concentration resulting from preferential flow of soil water has often led to models where the soil is partitioned into two regions: preferential flow paths, where solute transport occurs mainly by advection, and the remaining region, where significant solute transport occurs through diffusive exchange with the flow paths. These two‐region models commonly ignore concentration gradients within the regions. Our objective was to develop a simple model to assess the influence of concentration gradients on solute transport and to compare model results with experiments conducted on structured materials. The model calculates the distribution of solutes in a single spherical aggregate surrounded by preferential flow paths and subjected to alternating boundary conditions representing either an exchange of solutes between the two regions (a wet period) or no exchange but redistribution of solutes within the aggregate (a dry period). The key parameter in the model is the aggregate radius, which defines the diffusive time scales. We conducted intermittent leaching experiments on a column of packed porous spheres and on a large (300 mm long by 216 mm diameter) undisturbed field soil core to test the validity of the model and its application to field soils. Alternating wet and dry periods enhanced leaching by up to 20% for this soil, which was consistent with the model's prediction, given a fitted equivalent aggregate radius of 1.8 cm. If similar results are obtained for other soils, use of alternating wet and dry periods could improve management of solutes, for example in salinity control and in soil remediation.
Comparing Field Methods that Estimate Mobile–Immobile Model Parameters
Authors: Casey F. X. M. , Jaynes D. B. , Horton R. , Logsdon S. D.
Published: July 2010

Recent studies have used field techniques that estimate soil hydraulic and solute transport parameters. These methods utilize a tension infiltrometer to infiltrate either a single tracer or a series of tracers in order to estimate immobile water content (θim) and mass exchange coefficient (α) of the mobile–immobile solute transport model. The objective of this study was to compare two single tracer methods (basic and variance) with one multiple tracer method for estimating θim and α from data obtained on the same field soil location. Hydraulic conductivity (K(h0)) was also estimated using these methods. Research was done at five interrow sites in a ridge‐tilled corn (Zea mays L.) field, and the soil was mapped as a Nicollet series (fine‐loamy, mixed, superactive, mesic, Aquic Hapludoll). The values of θim and α estimated by the multiple tracer method compared well with previously measured values using the same technique on the same field. The θim values for the multiple tracer technique were larger than values derived from the basic single tracer technique. The basic single tracer technique did not take into consideration a mass exchange between θim and the mobile water domain (θm). The α values were less variable for the multiple tracer method than for the single tracer‐variance method. Values of immobile water fraction (θim/θ) for the multiple and basic single tracer techniques ranged from 0.30 to 0.52 and from 0.24 to 0.35, respectively. The values of α for the multiple and single tracer‐variance techniques ranged from 0.06 to 0.9 d−1 and from 0.03 to 60 d−1, respectively. The volumetric water content (θ) changed considerably over the course of the experiment for the estimation of α using the single tracer‐variance method; thus, the assumptions of this technique were compromised. The measured values of K(h0) at the five sites ranged from 0.47 to 1.66 μm s−1 There was evidence that the basic single tracer method underestimated θim and overestimated θm, because this method considers α = 0 during the tracer application.
Neutral and Acidic Sugars in Particle‐Size Fractions as Influenced by Climate
Authors: Amelung W. , Flach K.W. , Zech W.
Published: July 2010

Changes in the composition and amount of saccharides have been shown to reflect soil organic matter (SOM) dynamics. The effect of climate on soil monosaccharide pools was investigated in this study. Particle‐size fractions were obtained from composite samples taken from the top 10 cm of soil at 18 native grassland sites along mean annual temperature (MAT) and precipitation (MAP) transects from Saskatoon, Canada to southern Texas, USA. Neutral and acidic sugars were determined in the bulk soil, <2‐μm (clay), 2‐ to 20‐μm (silt), 20‐ to 250‐μm (fine sand), and 250‐ to 2000‐μm (coarse sand) size separates. As particle size decreased, the concentration of monosaccharides decreased significantly from 297 g kg−1 soil organic C (SOC) in coarse sand to 174 g kg−1 SOC in the silt fractions, but increased to 239 g kg−1 SOC in clay. Ratios of hexoses to pentoses increased with decreasing particle size, indicating that SOM of the finer fractions contained more microbe‐derived saccharides, this effect being more pronounced at lower MAT. The concentrations of neutral saccharides decreased in silt and fine‐sand fractions as MAT decreased, but increased in all fractions <250 μm as MAP increased. The concentration of acidic sugars in clay and silt was related only to MAP. The results suggest that the moisture regime primarily affected the saccharide concentrations of the finer particle‐size fractions, whereas the temperature regime affected primarily the saccharide concentrations of the coarser fractions. Particle‐size fractionation was thus a useful tool in decoding the differing effects of MAT and MAP on saccharide dynamics.
Role of Free Silicon, Aluminum, and Iron in Fragipan Formation
Authors: Duncan M. M. , Franzmeier D. P.
Published: July 2010

Fragipans form by various physical and chemical processes. The objective of this study was to elucidate the role of free Si, Al, and Fe in weak cementation of fragipan soils. We studied a toposequence of soils in which natural drainage ranged from poor to good on a dissected pre‐Wisconsinan plain covered with loess in southern Indiana. Soils were sampled in 10 to 15 cm layers. In the laboratory, strength was determined by a rupture test on disturbed samples, and Si, Al, and Fe were determined on citrate–bicarbonate–dithionite (CBD) extracts (with d subscripts). Strength reached a profile maximum in the fragipan. With molar Sid/(Sid + Ald) ratio of ≤0.5 there was no correlation between this ratio and strength, but in horizons in which the ratio was >0.5, mainly in fragipans, the correlation was strong. Strength was also correlated with exchangeable Mg. In fragipans the molar Ald/(Ald + Fed) ratio was ≈0.20, and above the fragipan the ratio was greater. We propose that in the fragipan most of the Ald is derived from Al substituted for Fe in Fe oxides, but in horizons above the fragipan there is more Al than the Fe oxides can accommodate. The extra Ald combines with free Si in these horizons to form aluminosilicates. In the fragipan, however, most free Al is tied up in the Fe oxides and cannot react with Si, so the free Si that is translocated from upper horizons bonds to clay minerals, and especially to Fe oxides, to cause cementation.
Morphological Analysis of Soil Aggregates Using Euler's Polyeder Formula
Authors: Hartge Karl Heinrich , Bachmann Joerg , Pesci Nestor
Published: July 2010

In present morphologic analysis of soil aggregates, a subdivision between polyhedra and prisms is commonly performed using the relation between their axis lengths. Further description is limited to qualitative alternatives like “rounded/not rounded.” The objective of this study was to obtain a more detailed subdivision of polyhedra using a quantitative approach, thus satisfying a prerequisite for statistical analysis. A series of experiments were carried out to determine the shape of aggregates using the parameters of Euler's polyhedron formula, which states that the number of corners plus the number of faces is equal to the number of edges plus 2. Results were evaluated from sets of 10 aggregates from each of six sites and from several depths as well as from artificial new loess aggregates made from the material of one of the samples. The results indicate that the number of faces was the least variable term. Most aggregates were found to have five faces, so are called pentahedra. The number of edges is generally smaller on field aggregates than on perfect polyhedra. For artificial fresh loess aggregates, however, the number of edges corresponds more closely to that of perfect polyhedra. The number of corners is similar to those in perfect polyhedra in all cases. Thus the number of edges is the element that is most promising for a more detailed subdivision of soil aggregates. Even though there is a general correlation between number of faces and number of edges, the edge/face ratio can provide independent information on the degree of rounding. Difficulties in discerning faces, edges, and corners, and the individual influence of personal assessment by the observer have shown to be of minor importance.
Characterization of Placic Horizons in Two Subalpine Forest Inceptisols
Authors: Hseu Zeng-Yei , Chen Zueng-Sang , Wu Zeng-Dong
Published: July 2010

Two Inceptisols (Typic Placaquept and Typic Epiaquept) with placic horizons were selected from the subalpine forest soils in northern Taiwan to evaluate the characteristics and genesis of the placic horizons commonly found in these soils. The placic horizon in the Placaquept had sharp upper and diffuse lower boundaries and was only 10 mm thick. The placic horizon in the Epiaquept was thought to have formed originally as a Spodosol. It had sharp upper and lower boundaries and a thickness of up to 40 mm. The upper hard iron pan and the lower dense plasma constituted the placic horizon in the Placaquept, while the multilayered band with darker color and the interwoven dense plasma with lighter color characterized the placic horizon in the Epiaquepts. The microfabric of the placic horizon was isotropic due to precipitated Fe–organic matter complexes, a pedogenic material indicated by the high ratio of oxalate/dithionite‐citrate‐bicarbonate extractable Fe (Feo/Fed). The maximum contents of Fe occurred in the placic horizons of these two Inceptisols. The formation of the placic horizon in the Placaquept was largely the result of redox processes that were enhanced by perched water. Under the saturated condition, Fe was reduced then translocated vertically down through the E horizon where it was subsequently reoxidized and precipitated to form the placic horizon. The characteristics of the placic horizon in the original soil of the Epiaquept met the criteria of a spodic horizon. The genesis model is related to cycles of landscape evolution. The original soil of this Epiaquept may have had a surface horizon prior to truncation and emplacement of a younger, more deeply deposited, new soil materials. The original soil of Epiaquept might have formed a cemented spodic horizon below the E horizon.
Field Calibration of a Capacitance Water Content Probe in Fine Sand Soils
Authors: Morgan K. T. , Parsons L. R. , Wheaton T. A. , Pitts D. J. , Obreza T. A.
Published: July 2010

Fine sand soils important to Florida agriculture have volumetric soil water content values (θv) of <0.10 cm3 cm−3 after drainage due to gravity has ceased. Small changes in θv in the range of 0.02 to 0.08 cm3 cm−3 can greatly affect plant available water and, therefore, good calibration of soil water content sensors is necessary. The EnviroSCAN (Sentek Pty. Ltd., South Australia) is a multiple sensor capacitance probe capable of continuous measurement of soil water content by volume (θv). Many fine sand soils in Florida have plant available θv values of ≤0.08 cm3 cm−3 The manufacturer's calibration curve has very few data points <0.10 cm3 cm−3 θv and no data in the 0.02 to 0.04 cm3 cm−3 θv range. Because of the lack of data in this range, a calibration curve from 0.02 to 0.08 cm3 cm−3 θv was developed for Candler fine sand (hyperthermic, uncoated Typic Quartzipsamments), Apopka fine sand (loamy, siliceous, hyperthermic Grossarenic Paleudults), and Immokalee fine sand (sandy, siliceous, hyperthermic Arenic Alaquods) in two locations in Florida. Since calibration curves for the three soils did not differ significantly, data from the three soils were combined. An exponential calibration curve was developed This equation provides substantially different estimates of water content in the 0.02 to 0.08 range than values obtained from the manufacturer's calibration. This improved calibration extends the useful range of the EnviroSCAN to include an important group of soils with very low water holding capacity.