bluuebunny/crossref_metadata_2025 huggingface dataset:
Source‐Related Transport of Phosphorus in Surface Runoff
Authors: Shigaki Francirose , Sharpley Andrew , Prochnow Luís Ignácio
Published: October 2006

Continual application of mineral fertilizer and manures to meet crop production goals has resulted in the buildup of soil P concentrations in many areas. A rainfall simulation study was conducted to evaluate the effect of the application of P sources differing in water‐soluble P (WSP) concentration on P transport in runoff from two grassed and one no‐till soil (2 m2 plots). Triple superphosphate (TSP)–79% WSP, low‐grade single superphosphate (LGSSP)–50% WSP, North Carolina rock phosphate (NCRP)–0.5% WSP, and swine manure (SM)–30% WSP, were broadcast (100 kg total P ha−1) and simulated rainfall (50 mm h−1 for 30 min of runoff) applied 1, 7, 21, and 42 d after P source application. In the first rainfall event one d after fertilizer application, dissolved reactive P (DRP) and total P (TP) concentrations of runoff increased (P < 0.05) for all soils with an increase of source WSP; with DRP averaging 0.27, 0.50, 14.66, 41.69, and 90.47 mg L−1; and total P averaging 0.34, 0.61, 19.05, 43.10, and 98.06 mg L−1 for the control, NCRP, SM, LGSSP, and TSP, respectively. The loss of P in runoff decreased with time for TSP and SM, such that after 42 d, losses from TSP, SM, and LGSSP did not differ. These results support that P water solubility in P sources may be considered as an indicator of P loss potential.
Impacts of Land Cover on Stream Hydrology in the West Georgia Piedmont, USA
Authors: Schoonover Jon E. , Lockaby B. Graeme , Helms Brian S.
Published: October 2006

The southeastern United States is experiencing rapid urban development. Consequently, Georgia's streams are experiencing hydrologic alterations from extensive development and from other land use activities such as livestock grazing and silviculture. A study was performed to assess stream hydrology within 18 watersheds ranging from 500 to 2500 ha. Study streams were first, second, or third order and hydrology was continuously monitored from 29 July 2003 to 23 September 2004 using InSitu pressure transducers. Rating curves between stream stage (i.e., water depth) and discharge were developed for each stream by correlating biweekly discharge measurements and stage data. Dependent variables were calculated from discharge data and placed into 4 categories: flow frequency (i.e., the number of times a predetermined discharge threshold is exceeded), flow magnitude (i.e., maximum and minimum flows), flow duration (i.e., the amount of time discharge was above or below a predetermined threshold), and flow predictability and flashiness. Fine resolution data (i.e., 15‐min interval) were also compared to daily discharge data to determine if resolution affected how streams were classified hydrologically. Urban watersheds experienced flashy discharges during storm events, whereas pastoral and forested watersheds showed less flashy hydrographs. Also, in comparison to all other flow variables, flow frequency measures were most strongly correlated to land cover. Furthermore, the stream hydrology was explained similarly with both the 15‐min and daily data resolutions.
The Legacy of Leaded Gasoline in Bottom Sediment of Small Rural Reservoirs
Authors: Juracek Kyle E. , Ziegler Andrew C.
Published: October 2006

The historical and ongoing lead (Pb) contamination caused by the 20th‐century use of leaded gasoline was investigated by an analysis of bottom sediment in eight small rural reservoirs in eastern Kansas, USA. For the reservoirs that were completed before or during the period of maximum Pb emissions from vehicles (i.e., the 1940s through the early 1980s) and that had a major highway in the basin, increased Pb concentrations reflected the pattern of historical leaded gasoline use. For at least some of these reservoirs, residual Pb is still being delivered from the basins. There was no evidence of increased Pb deposition for the reservoirs completed after the period of peak Pb emissions and (or) located in relatively remote areas with little or no highway traffic. Results indicated that several factors affected the magnitude and variability of Pb concentrations in reservoir sediment including traffic volume, reservoir age, and basin size. The increased Pb concentrations at four reservoirs exceeded the U.S. Environmental Protection Agency threshold‐effects level (30.2 mg kg−1) and frequently exceeded a consensus‐based threshold‐effects concentration (35.8 mg kg−1) for possible adverse biological effects. For two reservoirs it was estimated that it will take at least 20 to 70 yr for Pb in the newly deposited sediment to return to baseline (pre‐1920s) concentrations (30 mg kg−1) following the phase out of leaded gasoline. The buried sediment with elevated Pb concentrations may pose a future environmental concern if the reservoirs are dredged, the dams are removed, or the dams fail.
Using Simulated Rainfall to Evaluate Field and Indoor Surface Runoff Phosphorus Relationships
Authors: Guidry A. R. , Schindler F. V. , German D. R. , Gelderman R. H. , Gerwing J. R.
Published: October 2006

While numerous studies have evaluated the efficacy of outdoor rainfall simulations to predict P concentrations in surface runoff, few studies have linked indoor rainfall simulations to P concentrations in surface runoff from agricultural fields. The objective of this study was to evaluate the capacity of indoor rainfall simulation to predict total dissolved P concentrations [TP(<0.45)] in field runoff for four dominant agricultural soils in South Dakota. Surface runoff from 10 residue‐free field plots (2 m wide by 2 m long, 2–3% slope) and packed soil boxes (1 m long by 20 cm wide by 7.5 cm high, 2–3% slope) was compared. Surface runoff was generated via rainfall simulation at an intensity of 65 mm h−1 and was collected for 30 min. Packed boxes produced approximately 24% more runoff (range = 2.8–3.4 cm) than field plots (range = 2.3–2.7 cm) among all soils. No statistical differences in either TP(<0.45) concentration or TP(<0.45) loss was observed in runoff from packed boxes and field plots among soil series (0.17 < P < 0.83). Three of four soils showed significantly more total P lost from packed boxes than field plots. The TP(<0.45) concentration in surface runoff from field plots can be predicted from TP(<0.45) concentration in surface runoff from the packed boxes (0.68 < r2 < 0.94). A single relationship was derived to predict field TP(<0.45) concentration in surface runoff using surface runoff TP(<0.45) concentration from packed boxes. Evidence is provided that indoor runoff can adequately predict TP(<0.45) concentration in field surface runoff for select soils.
Effects of Watershed‐Scale Land Use Change on Stream Nitrate Concentrations
Authors: Schilling Keith E. , Spooner Jean
Published: October 2006

The Walnut Creek Watershed Monitoring Project was conducted from 1995 through 2005 to evaluate the response of stream nitrate concentrations to changing land use patterns in paired 5000‐ha Iowa watersheds. A large portion of the Walnut Creek watershed is being converted from row crop agriculture to native prairie and savanna by the U.S. Fish and Wildlife Service at the Neal Smith National Wildlife Refuge (NSNWR). Before restoration, land use in both Walnut Creek (treatment) and Squaw Creek (control) watersheds consisted of 70% row crops. Between 1990 and 2005, row crop area decreased 25.4% in Walnut Creek due to prairie restoration but increased 9.2% in Squaw Creek due to Conservation Reserve Program (CRP) grassland conversion back to row crop. Nitrate concentrations ranged between <0.5 to 14 mg L−1at the Walnut Creek outlet and 2.1 to 15 mg L−1at the downstream Squaw Creek outlet. Nitrate concentrations decreased 1.2 mg L−1over 10 yr in the Walnut Creek watershed but increased 1.9 mg L−1over 10 yr in Squaw Creek. Changes in nitrate were easier to detect and more pronounced in monitored subbasins, decreasing 1.2 to 3.4 mg L−1in three Walnut Creek subbasins, but increasing up to 8.0 and 11.6 mg L−1in 10 yr in two Squaw Creek subbasins. Converting row crop lands to grass reduced stream nitrate levels over time in Walnut Creek, but stream nitrate rapidly increased in Squaw Creek when CRP grasslands were converted back to row crop. Study results highlight the close association of stream nitrate to land use change and emphasize that grasslands or other perennial vegetation placed in agricultural settings should be part of a long‐term solution to water quality problems.
Chloride Effects on Nitrogen Dynamics in Forested and Suburban Stream Debris Dams
Authors: Hale Rebecca L. , Groffman Peter M.
Published: October 2006

Organic debris dams (accumulations of organic material) can function as “hotspots” of nitrogen (N) processing in streams. Suburban streams are often characterized by high flows that prevent the accumulation of organic debris and by elevated concentrations of solutes, especially nitrate (NO3−) and chloride (Cl−). In this study we (1) studied the effects of urbanization on the extent and characteristics of debris dams in large and small streams and (2) evaluated the effects of NO3−and Cl−on rates of N cycle processes in these debris dams. In some suburban streams debris dams were small and rare, but in others factors that reduce the effects of high stream flows fostered the maintenance of debris dams. Ambient denitrification enzyme activity (DEA) in these suburban and forested streams was positively correlated with stream NO3−concentrations. In laboratory microcosms, DEA in debris dam material from a forested reference stream was increased by NO3−additions. Chloride additions constrained the response of DEA to NO3−additions in material from the forested stream, but had no effect on DEA in material from streams with a history of high Cl−levels. Chloride additions changed the sign of net N mineralization from negative (consumption of inorganic N) to positive in debris dam material from the forested reference stream, but had no effect on net mineralization in material from streams with a history of exposure to Cl−Understanding the factors regulating the maintenance and N cycling activity of organic debris, and incorporating them into urban stream management plans could have important effects on N dynamics in suburban watersheds.
Sulfadimethoxine Degradation Kinetics in Manure as Affected by Initial Concentration, Moisture, and Temperature
Authors: Wang Q.‐Q. , Bradford S. A. , Zheng W. , Yates S. R.
Published: October 2006

Sulfadimethoxine is a widely used sulfonamide veterinary antibiotic and could be a source of agricultural contamination. Therefore, information is needed about its degradation kinetics in manure under aerobic conditions. Based on the analysis of first‐order kinetics and the assumption that sulfadimethoxine availability for degradation in manure could be limiting, a new kinetic model was developed and was found to fit the degradation kinetics well. The degradation rate in sterile manure was found to be much lower than in nonsterile manure, indicating that biodegradation was significant. In biologically active manure, the degradation rate constant decreased with increasing initial concentration of sulfadimethoxine, implying that the activity of the degrading microorganisms was inhibited. Increasing moisture or temperature was found to increase sulfadimethoxine degradation in manure. Mixing manure containing high levels of sulfadimethoxine with manure containing lower levels may result in more rapid degradation, thus greatly diminishing sulfadimethoxine contamination in manure and significantly reducing sulfadimethoxine inputs into the environment. During treatment, keeping the manure moist and storing in a moderately warm place under aerobic conditions may also help to diminish sulfadimethoxine contamination.
Escherichia coli Loading at or Near Base Flow in a Mixed‐Use Watershed
Authors: Gentry Randall W. , McCarthy John , Layton Alice , McKay Larry D. , Williams Dan , Koirala Shesh R. , Sayler Gary S.
Published: October 2006

This study analyzed the occurrence of Escherichia coli in a mixed land‐use watershed with human, cattle, and wildlife fecal inputs located in a karstic geologic region using synoptic monitoring (samples taken throughout the watershed system) during base‐flow conditions. The objective of the study was to evaluate the occurrence of E. coli during base‐flow conditions for several months at seven different main channel and nine different tributary sampling sites in the Stock Creek watershed, a 49.3‐km2 basin located in Knoxville, TN. Escherichia coli densities were measured using the Colilert (Defined Substrate Technology) method. The instantaneous loads for E. coli were determined from measured flow rates and E. coli densities, with the highest loading rates observed in the late fall. The study indicated a strong correlation between E. coli load rate (colony‐forming units [CFU]/d), 7‐d antecedent precipitation, and turbidity. Water quality data, however, also exhibited a spatial dependency; for example, the E. coli load rate was better correlated with turbidity in the slower draining basin tailwater sampling sites than in the faster draining upstream headwater sampling sites. In the headwater sites, the E. coli load rate was better correlated with 7‐d antecedent precipitation than turbidity.
Pedogenesis–Terrain Links in Zero‐Order Watersheds after Chaparral to Grass Vegetation Conversion
Authors: Williamson Tanja N. , Gessler Paul E. , Shouse Peter J. , Graham Robert C.
Published: October 2006

Four decades after conversion from chaparral to grass, zero‐order watersheds were compared to identify differences in topography and its relation to soil characteristics. Three watersheds of each vegetation type were topographically mapped and sampled at random points for depth to weathered bedrock and soil water content. Stepwise regression was used to explain spatial variability in terms of terrain variables. In chaparral watersheds, convex slopes result in widespread infiltration and significantly higher storage of water on the slopes. Topography of watersheds converted to grass is more concave, resulting in higher upslope contributing areas. This favors water convergence in the subsurface and results in significantly lower soil water content in grass watersheds. In chaparral watersheds, upslope average slope gradient best explains variability in depth to weathered bedrock. In contrast, slope gradient best explains depth to weathered bedrock in grass watersheds, suggesting that the uniform plant distribution localizes erosional processes. Soil water content is explained by depth to weathered bedrock and slope aspect in both vegetation types; however, a positive relation with profile curvature is the third indicator in chaparral watersheds, compared with an inverse relation with upslope average slope gradient in grass watersheds. The result is that grass watersheds drain water downslope, creating similar processes and forms in watersheds of various sizes. For both depth to weathered bedrock and soil water content, prediction using the regression models is only successful in grass watersheds. Thus terrain variables may be ineffective predictors of soil characteristics in shrublands where a dense canopy hides a nonuniform erosional environment.
Nutrient Accumulation and Movement from Poultry Litter
Authors: Mitchell Charles C. , Tu Shuxin
Published: October 2006

Poultry broiler litter (BL) is widely used as an alternative source of N, P, and K for crops and forages and is often applied at excessive rates of both N and P. Soil samples were periodically collected from experiments with BL at two locations in Alabama, a Coastal Plain site and a Tennessee Valley site, from 1991 though 2000. The objective was to determine the accumulation and movement of plant nutrients and metals in soil profiles when BL is compared with ammonium nitrate (AN) as a source of N for cotton (Gossypium hirsutum L.) and corn (Zea mays L.). The Tennessee Valley site was fertilized and cropped for 3 yr, and the Coastal Plain site was fertilized and cropped for 12 yr. The two N sources were applied at rates from 0 to 269 kg N ha−1 based on total N in the material. Incremental soil samples to a depth of 1 m were taken periodically from 1990 through 2000. Broiler litter maintained surface soil pH on the coarse‐textured soil at the Coastal Plain site whereas AN resulted in a decline in pH. There were no significant differences in surface soil pH due to source on the finer textured Tennessee Valley site. Application of BL resulted in increasing accumulations of total soil organic C, total N, and Mehlich‐1 extractable Ca, Mg, P, K, B, Zn, and Cu as the rates increased from 134 to 269 kg N ha−1 as BL (approximately 4.48–8.96 Mg ha−1 yr−1) over a 10‐yr period. While differences in NH4–N and NO3–N were observed to a 1‐m depth due to treatment, soil concentrations were very low compared with standards used in the presidedress soil nitrate test for corn (PSNT). No significant accumulations of heavy metals were observed during the experiments.
Soil Organic Matter Changes in a Spruce Ecosystem 25 Years after Disturbance
Authors: Spielvogel Sandra , Prietzel Jörg , Kögel-Knabner Ingrid
Published: October 2006

Long‐term effects of forest dieback on soil organic matter (SOM) pools in an unmanaged high‐elevation Norway spruce [Picea abies (L.) H. Karst.] forest were investigated by comparing three dieback sites with three adjacent sites with healthy spruce. The aim was to assess the long‐term biogeochemical impact of a major disturbance in unmanaged forest ecosystems due to potential modification of their soil organic carbon (OC) pool. The spruces at the dieback sites had been killed by a bark beetle (Ips typographus) infestation 25 yr ago. Total OC stocks in the topsoil of all sites were determined; different OC pools were quantified by density/particle‐size fractionation and 13C cross polarization magic angle spinning nuclear magnetic resonance (CPMAS NMR) spectroscopy. Additionally, the aboveground and belowground plant‐derived OC input was quantified and the OC species were analyzed. The forest floor at the dieback sites showed significantly lower OC stocks, storing <70% of the respective amount at the sites with healthy forest. In the forest floor and the light fraction of the Ah horizons at the dieback sites, the C/N ratio and the concentration of O‐alkyl C in the OM were significantly lower, whereas the OM of the other fractions and of the bulk SOM in Ah horizons showed no changes. The observed SOM changes were caused primarily by an accelerated SOM turnover and only secondarily caused by changed litter input. Particularly the OC pool with a low degree of humification was reduced in its amount and increased in its decomposition status while the more stable C fractions showed no significant changes.
Spatially Variable Corn Yield is a Weak Predictor of Optimal Nitrogen Rate
Authors: Scharf Peter C. , Kitchen Newell R. , Sudduth Kenneth A. , Davis J. Glenn
Published: October 2006

Historically, a mass‐balance approach (yield goal times a factor) has been the dominant method for making N fertilizer rate recommendations. Although several states have moved away from the mass‐balance approach for N rate recommendations for corn (Zea mays L.), much of the effort that has gone into variable‐rate N research has focused on combining spatial yield predictions with a mass‐balance approach. Our objectives were to evaluate, at field scale, the relationship between spatially variable yield levels and economically optimal N fertilizer rates (EONR) and to evaluate the performance of yield‐based N rate recommendations. Eight experiments were conducted in three major soil areas (Mississippi delta alluvial, deep loess, claypan) over 3 yr. Treatments were field‐length strips of discrete N rates from 0 to 280 kg N ha−1 Yield data were partitioned into 20‐m increments and a quadratic‐plateau function was used to describe yield response to N rate for each 20‐m yield cell. The EONR varied much more widely than did plateau yield. Yield level explained on average only 15% of the variability in EONR. Averaged over the eight fields, variable application of mass‐balance‐based N rates based on actual yields would have increased yield by only 31 kg ha−1, and profit by $2 ha−1, relative to uniform mass‐balance N rates based on field average yields. In comparison, variable‐rate application of EONR would have increased profit by an average of $38 ha−1 Of this, $14 ha−1 could have been obtained by uniform application of the median optimal N rate for each field. We conclude that although we observed considerable spatial variability in optimal N rates, this was due mainly to variations in soil N supply and N uptake efficiency, rather than to variations in crop demand for N. Yield variability appears to be at best a small part of the information that must be used to make successful variable‐rate N recommendations for corn.
Protecting Life's Foundation
Authors: Drohan P. J. , Farnham T. J.
Published: October 2006

Worldwide pressure on soil resources and the recognition by many international organizations, scientists, and universities of the importance of soils to humans and the natural world has recently led to further exploration of soils and their rarity. Using the example of species protection from wildlife conservation, we define a rare soil as one of limited areal extent and a threatened soil as one of greater areal extent undergoing a transformation that alters the soil's characteristics and function and makes it less able to carry out that characteristic or function (e.g., growing food or supporting a native plant community). We propose a process to recognize natural rare and/or threatened soils based on five categories that could be used to describe the values associated with these soils: (1) economic; (2) ecosystem; (3) scientific; (4) historic/cultural; and (5) rarity. We propose not a legally binding designation, but a program modeled on several successful wildlife‐oriented conservation awareness and education programs. We aim to create a non‐politically mired system that draws attention to rare and threatened soils and their role in supporting people and ecosystems while lending support to the soils' study and management. Land‐use planners might find this system valuable in helping to identify ecologically important areas. Conservation organizations might find the scientifically based assessments of soil value useful in defining their designations of important conservation areas. The publicity generated by designating rare and threatened soils might help U.S. citizens and politicians appreciate the importance of soils in so many aspects of our lives.
A Soil Probe Pulling Device Facilitates Soil Sampling
Authors: Wendt John W.
Published: October 2006

Soil probes are hammered into the soil to sample uniform, undisturbed soil cores, and can also be used to dig uniform holes for permanent installation of devices to monitor soil moisture and soil solution composition. Extracting soil probes becomes increasingly difficult at increasing depths, particularly when the soil is dry, frozen, or has a cohesive consistency. The construction and operation of a device for extracting soil probes is described. The device can be constructed from inexpensive and universally available galvanized pipe and pipe joints, and a 25 mm width × 2 m length nylon strap. The device can be used to extract other soil sampling equipment that requires upward vertical force. A single person can generate over 1000 kg of upward force on the probe without excessive effort. Use of the probe does not strain the back, which is an important consideration as back injuries are a serious concern with manual soil probe extraction.
Stabilization of Organic Matter at Micropores (<2 nm) in Acid Forest Subsoils
Authors: Mikutta Robert , Mikutta Christian
Published: October 2006

Binding of soil organic matter (OM) at micropore entrances within small mesopores (2–10 nm) has been suggested as a potential mechanism for the stabilization of OM against biodegradation. We hypothesized that the mineral‐associated fraction of stable OM [OM resisting treatment with 6% sodium hypochlorite (NaOCl) and subsequently extracted by 10% hydrofluoric acid] is associated with pores <10 nm in 12 acid subsoil horizons. To study the coverage of micropores by stable OM sorbed in mesopores, we assumed that most micropores have entrances of mesopore size. We compared the accessibility of CO2 at 273 K to micropores after NaOCl treatment with that of N2 at 77 K. In contrast to N2, diffusion of CO2 into micropores is little affected by OM and the difference in both micropore volumes (MIV) is taken as a measure of micropore clogging and thus of the association of stable OM with mesopores. The MIV measured by CO2 adsorption was corrected for CO2 sorption in OM (MIV‐CO2corr). In 7 out of 12 samples, the MIV‐CO2corr equaled the MIV‐N2, suggesting that micropore entrances are not blocked by stable OM. For four samples the results were ambiguous, whereas in an Eutric Hapludand Bw horizon, a threefold larger MIV‐CO2corr compared with the MIV‐N2 indicates that stable OM was associated with pores < 10 nm. Based on the findings that (i) mineral MIVs derived from CO2 and N2 adsorption were similar for most samples after exposure to NaOCl, (ii) the change of MIV‐N2 on NaOCl treatment was small in all samples, and (iii) no relationship existed of the MIV‐CO2corr and small mesopore volume with the content of mineral‐associated stable organic C (OC), we conclude that the association of OM with micropore entrances in small mesopores does not primarily control the stabilization of OM in these acid subsoils.
Kinetics of Arsenate Sorption–Desorption from Metal Oxides
Authors: Pigna M. , Krishnamurti G. S. R. , Violante A.
Published: October 2006

Sorption and desorption processes control the mobility, toxicity, and availability of As in natural environments. Surface coverage and residence time may affect the kinetics of As sorption–desorption from soil components and the transformation of As from desorbable into resistant or undesorbable forms. We performed kinetic studies on the sorption of As(V) onto crystalline or poorly crystalline metal oxides (noncrystalline Al(OH)x, gibbsite, ferrihydrite, and goethite) and its desorption by PO4 at pH 6.0 as affected by the residence time and the surface coverage (50 or 100%) of As(V). Significant amounts of As(V) were sorbed during the initial period of 0.167 h, ranging from 37.9 to 71.8% when the surface coverage was about 100%. The kinetic data, explained best by the Elovich kinetic model, indicated the following order in As(V) sorption: gibbsite < Al(OH)x < goethite < ferrihydrite. By adding PO4 immediately after complete sorption of As(V) onto the oxides (50% surface coverage; PO4 added/As(V) sorbed molar ratio of 4), a much higher proportion of As(V) was desorbed after 24 h of reaction from Al oxides (48–56%) than from Fe oxides (18–23%). The amount of As(V) desorbed decreased with increasing residence time. The kinetics of As(V) desorption by PO4 as a function of residence time was explained best by the Elovich kinetic model. The kinetics described the rate of rearrangement of As(V) from desorbable into resistant or undesorbable forms, which occurred more rapidly in Al than Fe oxides. After a residence time of 360 h, the percentage of As(V) desorbed from the oxides was reduced significantly (<13%).
2,4‐D Residues in Aggregates of Tropical Soils as a Function of Water Content
Authors: Rocha Wadson S. D. , Regitano Jussara B. , Alleoni Luís R. F.
Published: October 2006

The effects of soil moisture on reactions between pesticides and soil aggregates are little understood, particularly in soils from the humid tropics. Thus, the influence of soil water content on retention and mineralization of the herbicide 2,4‐D [(2,4‐dichlorophenoxy)acetic acid], as well as its distribution on the aggregate fractions (diameter >150, 53 to 150, 20 to 53, 2 to 20, and <2 μm) were evaluated. Soil samples from a Xanthic Dystrudox, a Xanthic Acrudox, and two Rhodic Acrudoxes were collected and moisture was adjusted to 25, 50, and 75% maximum water holding capacity.14C 2,4‐D was then applied and the flasks incubated in a semi‐dark, climatized room at 22 ± 2°C, for 42 d. 2,4‐D mineralization was determined weekly. After three extractions with a 0.01 mol L−1CaCl2solution, soil aggregates were sonicated using water as a dispersing agent. 2,4‐D retention increased with soil moisture. Higher soil moisture favored 2,4‐D retention in aggregates < 20 μm, ratifying the hypothesis of 2,4‐D diffusion to less accessible soil sites. 2,4‐D mineralization was also enhanced with soil moisture. For the Acrudoxes, in which the clay fraction was less dispersed in water, 2,4‐D retention was higher in larger aggregates (>53 μm), having higher total organic C (OC) content and higher degree of humification of its organic matter (OM).
Incorporating Electromagnetic Induction Methods into Regional Soil Salinity Survey of Irrigation Districts
Authors: Nogués J. , Robinson D. A. , Herrero J.
Published: October 2006

Many land use decisions are made without the aid of soil maps in countries without National soil surveys. The purpose of this research was to create a soil survey delineating salinity phases at a regional scale that could serve as the basis for improved decision making, or highlight areas for further investigation. Soil salinity survey at a regional scale remains a challenge. We demonstrate a survey methodology suited to small fields, often found in Europe and developing countries, and present a streamlined survey methodology making this typically labor‐intensive process more efficient. A regional soil survey was conducted at a scale of 1:25 000, mapping consociations and complexes of soil series. The soil survey information was then used to guide an electromagnetic induction (EMI) survey of the soils with observed salinity, to delineate phases. A calibration method for estimating the electrical conductivity of the extract of the saturated paste (ECe) from the EMI measurements was devised. After testing several statistical methods, a single calibration of the EMI data was found to be suitable using a nonparametric regression. The use of the EMI method reduced operation costs, where time, personnel, analysis time, and budget are limitations.
Potassium Movement and Transformation in an Acid Soil as Affected by Phosphorus
Authors: Du Zhenyu , Zhou Jianmin , Wang Huoyan , Du Changwen , Chen Xiaoqin
Published: October 2006

When P and K fertilizer are applied to soil at the same time, the movement and transformation of K may be affected by P. This study was conducted to quantify the effects of monocalcium phosphate (MCP) co‐applied with KCl on the distance of K movement, the concentration of K in different forms and soil pH change at different distances from the fertilizer application site in an incubation experiment with an acid red soil from Yingtan, Jianxi province in southern China. Fertilizers of 0.5 g KCl alone or in combination with 0.98 g MCP were added to the surface of soil cylinders with a height of 150 mm and packed in wax blocks. The fertilizers and soil were incubated at field capacity moisture content for 7 and 28 d. Extraction and analysis of each layer (first 25 layers of 2 mm thickness and then 20 layers of 5 mm) from the interface of soil and fertilizer showed that the movement distance of K was not affected by the addition of MCP. However, the concentration of water‐extractable K decreased and the concentrations of exchangeable and nonexchangeable K increased significantly near the fertilizer site in the presence of P. The application of MCP also slowed down the decrease of KCl‐induced soil pH close to fertilizer site. The results suggested that the transformation of K in soil close to the fertilizer placement site was significantly affected by the addition of MCP, probably due to the reactions of MCP with Al and Fe in soil. The amounts of K in different forms in soil columns implied that the addition of MCP could reduce the bioavailability of K at the beginning of fertilizer application.
Dissolved Organic Matter Characterization Using Multiway Spectral Decomposition of Fluorescence Landscapes
Authors: Ohno Tsutomu , Bro Rasmus
Published: October 2006

Dissolved organic matter (DOM) plays an important role in many soil ecosystem functions. Multidimensional fluorescence spectroscopy of DOM with parallel factor analysis (PARAFAC) of the resulting spectral landscape has been successful in characterizing DOM from a variety of aquatic sources. This study was conducted to assess the multiway PARAFAC approach for quantitatively characterizing the fluorescent landscapes of DOM from aqueous extracts of soils and soil amendments. The DOM was extracted from plant biomass representative of crop, wetlands, and tree species; animal manures; and soils from controlled studies of cropping systems with known histories of organic amendments. The fluorescence landscape spectra were collected in the excitation range from 240 to 400 nm and emission range from 300 to 500 nm in 3‐nm increments. The excitation and emission spectra modeled from the PARAFAC analysis showed that the plant biomass, animal manure, and soil DOM contained five fluorescing components: tryptophan‐like (peak location at excitation 270 nm, emission 354 nm), tyrosine‐like (273/309 nm), and three humic‐substance‐like components (>240/465 nm, 306/405 nm, and 315/447 nm). Principal component analysis of the concentration loading showed that the soil‐derived DOM was very similar despite the different types and quantities of organic amendments incorporated in the different cropping systems. This study shows that PARAFAC analysis of multidimensional fluorescence spectra can model the chemical profile of terrestrial DOM in a chemically meaningful way. This represents a significant advance over current approaches to interpreting the complex DOM fluorescence spectra.
Tillage Effects on Hydraulic Properties and Macroporosity in Silty and Sandy Soils
Authors: Buczko U. , Bens O. , Hüttl R. F.
Published: October 2006

In agricultural soils, macroporosity and hydraulic properties are influenced by tillage practices. The objective of this study was to characterize macroporosity and surface soil hydraulic properties in two soils of different texture (Lietzen: sandy loam–Humic Dystrudept; Adenstedt: silt loam; Typic Hapludoll) under conventional (CT) and conservational (RT) tillage systems. Soil hydraulic conductivity was assessed in situ by ponded infiltration with single rings (n = 70) and tension infiltration by means of a “closed‐top” hood infiltrometer (HIF; n = 48). Macroporosity (pore diameters >1 mm) was estimated from differences in infiltration at saturation and at −3 cm H2O soil matric potential. Mean saturated hydraulic conductivity (Ks) for Lietzen was 3.1 × 10−5 m s−1 and for Adenstedt was 4.3 × 10−5 m s−1 These values are by one order of magnitude higher than values estimated from soil texture. This implies that soil structure has a dominant influence on hydraulic conductivity. Mean values of macroporosity were 0.005% for Lietzen and 0.018% for Adenstedt (using the method of Watson and Luxmoore). The respective values were 0.0008 and 0.0013% when the method of Bodhinayake et al. was used. For Adenstedt, RT showed higher macroporosity than CT (not significant at P < 0.05 for n = 12). Such treatment‐induced differences were less developed for Lietzen. The Ks values measured with the ponded ring infiltrometer (RIF) at the sandy Lietzen site were higher than the corresponding values measured with the tension infiltrometer. These differences may be caused by subcritical soil water repellency (i.e., contact angles of the soil‐water‐air interface below 90°), although further factors could also be important (e.g., air entrapment, differences in water saturation, geometry of infiltration devices).
Speciation and Distribution of Phosphorus in a Fertilized Soil
Authors: Lombi E. , Scheckel K. G. , Armstrong R. D. , Forrester S. , Cutler J. N. , Paterson D.
Published: October 2006

Phosphorus availability is often a limiting factor for crop production around the world. The efficiency of P fertilizers in calcareous soils is limited by reactions that decrease P availability; however, fluid fertilizers have recently been shown, in highly calcareous soils of southern Australia, to be more efficient for crop (wheat [Triticum aestivum L.]) P nutrition than granular products. To elucidate the mechanisms responsible for this differential response, an isotopic dilution technique (E value) coupled with a synchrotron‐based spectroscopic investigation were used to assess the reaction products of a granular (monoammonium phosphate, MAP) and a fluid P (technical‐grade monoammonium phosphate, TG‐MAP) fertilizer in a highly calcareous soil. The isotopic exchangeability of P from the fluid fertilizer, measured with the E‐value technique, was higher than that of the granular product. The spatially resolved spectroscopic investigation, performed using nano x‐ray fluorescence and nano x‐ray absorption near‐edge structure (n‐XANES), showed that P is heterogeneously distributed in soil and that, at least in this highly calcareous soil, it is invariably associated with Ca rather than Fe at the nanoscale. “Bulk” XANES spectroscopy revealed that, in the soil surrounding fertilizer granules, P precipitation in the form of octacalcium phosphate and apatite‐like compounds is the dominant mechanism responsible for decreases in P exchangeability. This process was less prominent when the fluid P fertilizer was applied to the soil.
Carbon Turnover Kinetics with Depth in a French Loamy Soil
Authors: Rasse Daniel P. , Mulder Jan , Moni Christophe , Chenu Claire
Published: October 2006

Soil C dynamics below the plow layer have been little studied, in spite of proven large C stocks and suspected large C stabilization potential. The objective of the present study was to determine C‐turnover kinetics throughout the 1‐m profile of a cultivated loam soil of the Paris basin, France. The soil 13C signature was determined to depths of 1.05 m in 32 replicated plots having received from 0 to 10 yr of maize after wheat. Above‐ and below‐ground maize‐residue biomass inputs were estimated throughout the 10‐yr period. After 10 yr, maize‐derived soil organic carbon (SOC) constituted about 10, 5, and 2% of the total SOC at 15‐, 50‐, and 100‐cm depths, respectively. About one‐third of recently deposited maize‐derived SOM present in the 1‐m soil profile was retrieved below the Ap horizon. The ratios of maize‐derived soil C to the cumulative maize above‐ and below‐ground inputs over the 10‐yr period averaged 17% across the soil profile. This ratio was lower in the Ap horizon (i.e., 13%) than in deeper soil horizons. Circumstantial evidences suggest that the distribution profile of recently deposited maize‐derived C was influenced by fine root activities, bioturbation, and dissolved organic carbon (DOC) transport, the latter being substantiated by a high correlation (r2 = 0.86) between SOC contents and amorphous Fe + Al contents. In conclusion, our study stresses the need to take into account the full 1‐m soil profile in C sequestration studies.
New Method to Simulate Soil Freezing and Thawing Cycles for Studying Nitrous Oxide Flux
Authors: Hu Q. C. , van Bochove E. , Warland Jon , Kay Bev , Wagner-Riddle C.
Published: October 2006

Field experiments are essential for elucidating the processes involved in N2O production during soil freezing/thawing (FT) cycles, but laboratory simulations can provide the advantage of controlled conditions. Past studies have used disturbed or undisturbed soil cores placed in a controlled temperature environment, so that FT occurred from the external surface to the inside of the core (omni‐directional method, OD). A new method of soil FT for simulating field conditions more closely in the laboratory was developed and its effect on N2O fluxes evaluated. Three methods were examined: OD, uni‐directional (UD) with the soil column surrounded by filled‐in soil, and a variant of UD with water accessible to the base of the core (UDW). The rate of soil cooling with time was significantly faster and similar at all depths (−0.29°C h−1) for OD, than for UD or UDW methods (−0.16°C h−1 at 1 cm, −0.10°C h−1 at 20 cm). This differential cooling resulted in a significant change in soil temperature with depth for UD and UDW methods 0.125°C cm−1 during freezing and −0.35°C cm−1 during thawing, but of only 0.04 and −0.02°C cm−1 for the OD method. Comparison with field temperature data indicated that the UD and UDW method more closely resembled the gradual top‐to‐bottom freezing of soil layers that occurs in field conditions (changes of −0.20°C h−1 at 1 cm; −0.05°C h−1 at 20 cm). Gravimetric water content in the frozen layer 0 to 20 mm in the UDW (60.6 g kg−1) was significantly higher than in UD (44.4 g kg−1) and OD (37.6 g kg−1) soil columns. Fluxes of N2O during thawing were significantly affected by the incubation method used, probably due to the intensity and duration of freezing, and the water content prevalent under each method with OD (13 ng N2O‐N m−2 s−1) > UDW (4.8 ng N2O‐N m−2 s−1) > UD (2.1 ng N2O‐N m−2 s−1). We conclude that the UD (and UDW) method allows for manipulation of FT in soil columns gradually layer‐by‐layer providing the conditions needed to link the site of N2O production in the soil profile with surface N2O fluxes in laboratory studies.
Sorption of a Hydrophilic Pesticide
Authors: Ochsner T. E. , Stephens B. M. , Koskinen W. C. , Kookana R. S.
Published: October 2006

Transport of pesticide to groundwater is governed in part by sorption of the pesticide to soil particles. Sorption may be dependent on soil moisture conditions, but limited data are available from which to elucidate the effect. Our objective was to determine the effect of soil water content on the sorption coefficient of a hydrophilic pesticide. Sorption of dicamba (3,6‐dichloro‐2‐methoxybenzoic acid) was measured in three soils, each at two initial water contents. At low water contents (∼0.05 kg kg−1), sorption coefficients were similar for all three soils, ranging from 0.01 L kg−1 for the loamy sand to 0.07 L kg−1 for the silty clay loam. At higher water contents (0.19–0.24 kg kg−1), the sorption coefficient for the loamy sand was unchanged, for the silt loam it was doubled, and for the silty clay loam it was increased almost sixfold. Multiple regression analysis revealed a strong linear relationship between the sorption coefficient and the product of soil water content and organic C content (r2 = 0.86). The number of dicamba sorption sites probably increases with soil organic C content, while the accessibility of these sites appears to increase with soil water content. This may be caused by the decreasing hydrophobicity of soil organic matter with increasing water content. The effects of water content on pesticide sorption require further research and may ultimately have implications for the methods used to determine sorption and for managing pesticide application.
Did You Say ‘Intellectual Property’? It's a Seductive Mirage
Authors: Stallman Richard M.
Published: October 2006

The term ‘intellectual property’ tends to warp thinking wherever it is used. It carries a bias in favor of dealing with a variety of issues as kinds of ‘property’; even worse, applying the term to various disparate issues focuses attention erroneously on the little that they have in common. The term should never be used, and we should not let others lead us into using it.
The Properties of Locke's Common-Wealth of Learning
Authors: Willinksy John
Published: October 2006

This article reads the educational implications of ‘intellectual property’ that are found in the double meaning of property, as the word refers to an economic right and a quality of being. It briefly visits the seventeenth-century origins of this double concept of intellectual property (IP), with particular attention paid to John Locke (who provides the basis of IP as a personal possession as well as furthering the idea of a ‘common-wealth of learning’) and the emergence of ‘open science’. The argument proceeds on two levels, educational and public, as it draws parallels between the way that students are taught to regard learning and the way in which a knowledge-based global economy treats learning. On the first level, that of the personal, the article puts forward a critique of the common educational tendency to treat learning as a private good, in terms of personal asset management, which ultimately undermines the common-wealth of learning and the idea of knowledge as a public good. On the second level, that of the public sphere, the article turns to the increasing privatization and capitalization of knowledge that is making inroads into the common-wealth of learning, particularly around publicly funded research and scholarship. The article considers the prospects, finally, of ‘open’ responses (e.g. open access, open source, etc.) to reassert the vital role of the common-wealth, through new technologies of knowledge sharing, and it considers the educational policy implications of preparing a new generation of students who, as they are prepared to participate in knowledge-based economies, should also understand the implications of sustaining the common-wealth of learning.
The Rise of Open Access in the Creative, Educational and Science Commons
Authors: Kiel-Chisholm Scott , Fitzgerald Brian
Published: October 2006

Management of intellectual property and, in particular, copyright is one of the most challenging issues in an increasingly digital world. The rise of the open access (OA) movement provides a new model for managing intellectual property in educational and research environments. OA aims to promote greater and more efficient access to educational and research materials and has an international profile. This article overviews the basic charter of OA and explain how it proposes to transform academic communication and publishing in an online world. Importantly, this article also overviews the legal issues that surround the move towards OA and the concept of open content licensing (including the Creative Commons Project).
Aboriginal Knowledges in the Australian Market Place: Different Issue, Same Story
Authors: Chalmers Gordon
Published: October 2006

With Indigenous knowledges being increasingly available via different media, there is the risk of these knowledges becoming disengaged from the peoples who imparted them. A consequence of this disengagement is that it creates the conditions for the creation and perpetuation of misunderstanding and misuse of Indigenous peoples’ lifeworlds. This article explores issues surrounding tensions between Indigenous and non-Indigenous ways of disseminating knowledge and it points to areas of possible change whereby the latter may seek to find its processes normalised within the former. In particular, it suggests that an approach to Indigenous knowledges that incorporates many of their original regulatory mechanisms would go a long way towards avoiding both the misunderstanding and misuse of these knowledges. The article draws upon examples from particular Aboriginal groups in the Northern Territory of Australia who, it can be said, have for a long time engaged in this process of ‘Indigenising’ dominant modes of information dissemination and use. In some cases, this process has proven successful but in others it has proven unsuccessful. The reasons for these different outcomes will be explored in regard to the extent to which ‘outsiders’ have personally engaged with the peoples from whom the knowledge was originally imparted and the extent to which the outsiders have themselves Indigenised their own normative Western modes of information use.
Intellectual Property Rights: Governing Cultural and Educational Futures
Authors: Kapitzke Cushla
Published: October 2006

This article uses Nikolas Rose's theory of governmentality to examine ways in which intellectual property is imbricated in a broad spectrum of globalised and globalising discourses. Using the 2004 Australia–United States Free Trade Agreement as a case in point, it shows how discourses of culture, trade, foreign policy, and security intersect and potentially restrict access to cultural knowledge and textual resources for young people and educators.