bluuebunny/crossref_metadata_2025_split huggingface dataset:
Forms of Phosphorus in Soil Profiles from Dairies of South Florida
Authors: Nair V. D. , Graetz D. A. , Portier K. M. 
Published: July 2010

AbstractSoil P fractions of current and abandoned dairy systems in South Florida's Lake Okeechobee watershed were evaluated to develop an understanding of the stability of P in this basin. Land use within the dairies was classified as intensive (high cattle impacted) and pasture, forage, or native (low cattle impacted) areas. All soils (Spodosols) were characterized for labile P (1 M NH4Cl), Fe‐Al‐associated P (0.1 M NaOH), Ca‐Mg‐associated P (0.5 M HCl), residual P, and organic P in the NaOH fraction. The A horizons of the intensive areas had ≈9% of total P as labile P, though most of the Ca‐Mg‐associated P (≈70% of total P) in these particular systems could also be removed by sequential NH4Cl extractions. Therefore, almost 80% of the P in the surface horizons of the high cattle impacted areas had the potential to move eventually with drainage water into the lake. The P in the E horizons of the intensive areas consisted primarily of labile P and Ca‐Mg‐associated P forms as well, though the total P in these horizons was <5% of that for the A horizons. About 80% of the total P in the spodic (Bh) horizons was extractable by NaOH, of which only 4 to 18% was associated with organic matter. The total P contents for all horizons of the soil profiles from the low cattle impacted areas were considerably less than those from the high cattle impacted areas. There were apparently no major shifts of P to more stable P forms, with time, for soils of high cattle impacted areas. Therefore, the possibility of P release from high cattle impacted soils, even after dairies were abandoned for more than 12 yr, cannot be ruled out.
New Method for Assessment of Long‐Term Phosphate Desorption from Soils
Authors: Freese D. , Lookman R. , Merckx R. , van Riemsdijk W. H. 
Published: July 2010

AbstractA new method was developed to study P desorption kinetics. This new technique uses dialysis membrane tubes, filled with hydrous ferric oxide (ferrihydrite) acting as an “infinite” P sink. This system is mechanically stable for very long reaction periods, provided that a microbial inhibitor, e.g., chloroform, is added to the soil suspension to prevent hydrolysis of the membrane. The pH of the soil solution during desorption remains almost constant. After the desired time of contact between soil suspension and P sink, the sink can be easily separated from the soil suspension with practically no loss of soil material. As such, the new technique has important advantages to the Fe oxide impregnated filter paper P extraction method. The system is capable of maintaining a constant low P activity in solution, necessary to study long‐term P desorption kinetics of soils. This method was tested on six sandy soil samples and a comparison made with the amount of P desorbed by a single Fe oxide impregnated filter paper extraction (Pi). An important finding from this experiment was that P desorption continues for long periods. No desorption maximum was reached within 500 h, as is often suggested by desorption results based on repeated extractions with Fe‐impregnated filter paper. Furthermore, relatively large differences were observed between different soils with respect to the quantity of oxalate‐extractable phosphate released by the soils after a specified time of desorption.
Time of Nitrogen Application: Effects on Winter Wheat and Residual Soil Nitrate
Authors: Boman R. K. , Westerman R. L. , Raun W. R. , Jojola M. E. 
Published: July 2010

AbstractRate and time of N fertilizer application can affect winter wheat (Triticum aestivum L.) forage and grain yield and quality, and may influence residual NO3‐N concentration and distribution in the soil profile. Objectives of this experiment were to determine the effects of N fertilizer rate and time of application on forage and grain yield, N uptake, and distribution of residual soil NO3‐N. Field experiments were conducted for four consecutive years on a Teller sandy loam (fine‐loamy, mixed, thermic Udic Argiustoll) cropped to winter wheat under conventional tillage. Urea‐ammonium nitrate (UAN) was broadcast and incorporated before planting (PPI) or topdressed in December (Feekes 3), January (late Feekes 3), February (Feekes 4), or March (Feekes 5–6) at rates of 34, 67, 101, and 134 kg N ha−1. Soil samples were taken from each plot after each grain harvest to 1.2 m and analyzed for NH4‐N and NO3‐N. Forage yield response (measured in late March to mid‐April) to January and December N application was comparable to PPI when adequate precipitation was received after N was applied. Applying N in February and March resulted in plant tissue damage and lower forage yields due to less early‐season growth than with other applications. Apparent fertilizer N recovery in forage was highest when N was applied at or before mid‐January. Date of N application had minimal influence on grain yields. Quadratic response surface models suggest the optimum time of N application for maximum forage and grain yields to be mid‐November and early January, respectively. Timing of N application had no effect on residual NH4‐N and little influence on residual NO3‐N concentration and distribution in the soil profile at the end of each cropping cycle.
Landscape Evolution and Shallow Groundwater Hydrology of a Till Landscape in Central Iowa
Authors: Steinwand A. L. , Fenton T. E. 
Published: July 2010

AbstractDeciphering the effects of land use on environmental quality requires detailed knowledge of the processes governing soil and landscape genesis. The objective of this study was to describe the landscape evolution and shallow groundwater hydrology of a glaciated landscape in Iowa and to relate the soil color pattern to water table fluctuations. Stratigraphic and geomorphic maps and cross sections were prepared using characterization data from 128 soil cores collected from a 32‐ha site. One transect crossing several hillslopes was instrumented with 47 piezometers to determine groundwater flow direction. Three strata of surficial sediments overlying till were identified. The upper two strata were slope alluvium deposited after 4300 YBP, which limits the age of the soils to the late Holocene or younger. The lower sediment resembled alluvium and may be supraglacial sediment draped on the till and later eroded from adjacent hillslopes. The hydrology was characterized by recharge under topographic highs, lateral groundwater flow on sideslopes and discharge in swales. During dry periods, however, portions of higher swales acted as recharge areas and groundwater flow was directed between swales. Morphologic indicators of wetness are better expressed and shallower in soils at footslope and toeslope positions, but some of these features are relict because of the lowering of the water table by artificial drainage.
Residual Deep Plowing Effects on Irrigation Intake for Pullman Clay Loam
Authors: Allen R. R. , Musick J. T. , Schneider A. D. 
Published: July 2010

AbstractPullman clay loam (fine, mixed, thermic Torrertic Paleustoll) and related soils predominate in the southern High Plains of the USA. They are slowly permeable but respond to deep tillage with increased irrigation water intake. A one‐time deep moldboard plowing to 0.4‐, 0.6‐, or 0.8‐m depths was performed in 1966 to evaluate the inversion and mixing of the slowly permeable Bt1 horizon with the Ap horizon. We hypothesized that these deep tillage effects would still be present after 25 yr. We report irrigation intake effects with 5 yr (four growing seasons) of cropping to winter wheat (Triticum aestivum L.) beginning in 1988. After moldboard plowing to 0.2 m to restore surface tillage layer permeability, residual effects from the 1966 deep plowing caused an average increase in intake of 26% (129–163 mm) for the 0.4‐m plow depth, compared with the 0.2‐m check, for the first irrigation after tillage from 1988 to 1992. Irrigation intake increased 40% (52 mm) with 0.6‐m deep plowing; however, there was no additional increase for 0.8‐m plowing. Grain yields increased from 4.2 to 5.0 Mg ha−1 (19%) for the 0.4‐m or deeper plowing. The 1966 deep tillage also increased deep soil water storage between the 1‐ and 2.3‐m depths during 1988 to 1992. Water use efficiencies were ≈8% greater for the deep plowing treatments.
Tillage Effects on Corn Production and Soil Physical Conditions
Authors: Cassel D. K. , Raczkowski C. W. , Denton H. P. 
Published: July 2010

AbstractRow crop production on highly erodible soils of the Piedmont in the southeastern USA is often limited by surface sealing, excessive surface water runoff, soil erosion, and low crop yields. The effects of four tillage practices on corn (Zea mays L.) growth and soil properties on two crust‐prone soils were evaluated. Tillage treatments at two Piedmont locations, Oxford and Reidsville, NC, were no‐till (NT), in‐row subsoiling (IRS) (1987 only), chisel plow (CP), and moldboard plow‐disk (MP). Residue cover was 1% for MP and ranged from 75 to 87% for NT and 38 to 27% for CP. The interaction between tillage, soil properties, and plant performance was complex. Mean bulk density of the Ap horizon at Reidsville for the 2‐yr period was 1.56 Mg m−3 for NT, compared with 1.48 Mg m−3 for CP and 1.46 Mg m−3 for MP. Cone index was not affected by tillage but was greatest in the trafficked interrow, 3.50 MPa, compared with 1.91 and 1.09 MPa in the row and nontrafficked interrow, respectively. Mean corn grain yield for the four year‐locations was least, 1.23 Mg ha−1, for MP, compared with 2.97 Mg ha−1 for NT and 2.44 Mg ha−1 for CP; mean yield for IRS in 1987 was 3.69 Mg ha−1. Tillage practices leaving crop residues on the soil surface, such as NT, CP, and IRS, can reduce or eliminate surface crusting, increase infiltration, and reduce surface runoff and soil loss while increasing crop yield.
Evaluating Shrub‐Associated Spatial Patterns of Soil Properties in a Shrub‐Steppe Ecosystem Using Multiple‐Variable Geostatistics
Authors: Halvorson Jonathan J. , Bolton Harvey , Rossi Richard E. , Smith Jeffrey L. 
Published: July 2010

AbstractGeostatistics are often calculated for a single variable at a time, even though many natural phenomena are functions of several variables. The objective of this work was to demonstrate a nonparametric approach for assessing the spatial characteristics of multiple‐variable phenomena. Specifically, we analyzed the spatial characteristics of resource islands in the soil under big sagebrush (Artemisia tridentata Nutt.), a dominant shrub in the intermountain western USA. For our example, we defined resource islands as a function of six soil variables representing concentrations of soil resources, populations of microorganisms, and soil microbial physiological variables. By collectively evaluating the indicator transformations of these individual variables, we created a new data set, termed a multiple‐variable indicator transform or MVIT. Alternate MVITs were obtained by varying the selection criteria. Each MVIT was analyzed with variography to characterize spatial continuity, and with indicator kriging to predict the combined probability of their occurrence at unsampled locations in the landscape. Simple graphical analysis and variography demonstrated spatial dependence for all individual soil variables. Analysis also showed that ensembles of variables were not randomly distributed, but rather were correlated systematically within the landscape. Maps derived from ordinary kriging of MVITs suggested that the combined probabilities for encountering zones of above‐median resources were greatest near big sagebrush. As the selection criteria for defining a resource island became more stringent, the area of the resource island decreased. Cross‐variography revealed that big sagebrush was more positively correlated with MVIT resource islands than were grass species, the other major plant type.
Authigenic Dolomite in a Saline Soil in Alberta, Canada
Authors: Kohut Connie , Dudas M. J. , Muehlenbachs K. 
Published: July 2010

AbstractThe formation of dolomite is poorly understood and highly controversial, since well‐ordered dolomite has never been synthesized under earth surface conditions and natural occurrences of modern dolomite have been reported only rarely from restricted sedimentary environments. It is generally accepted that dolomite does not form in soils. This study investigates the characteristics and origin of dolomite in a sulfatic saline soil in east‐central Alberta, Canada, in which dolomite makes up more than half of the <2‐µm fraction. X‐ray diffraction analysis shows that the dolomite is stoichiometric and ordered, with only slight deviations in unit cell parameters relative to ideal dolomite. The clay‐sized dolomite is enriched in 18O and depleted in 13C relative to detrital dolomite and dolomite present in larger size fractions, and has a radiocarbon age ranging from 1270 to 5270 yr before present, clearly indicating an authigenic origin. The very small dolomite particle size and differences in isotope content from coexisting calcite suggests that the dolomite formed by direct precipitation in the soil rather than by dolomitization of a preexisting calcite.
Predicting Phosphate Adsorption‐Desorption in a Soilscape
Authors: Scheinost A. C. , Schwertmann U. 
Published: July 2010

AbstractModeling the P availability in a soilscape requires knowledge about the three‐dimensional variability of the phosphate adsorption‐desorption (AD) curves. The high variabilities of soil parent material and of agricultural P input in a 1.5‐km2 study area were taken into account by taking 2555 samples at the intersections of a 50‐m grid. To reduce the necessary laboratory work, pedotransfer functions (PTFs) were developed that could predict the AD curves from more easily obtainable soil characteristics. Therefore, AD curves were measured for only 40 representative samples. The AD curves were fitted with an extended and rearranged Freundlich equation with a constant adsorption energy parameter k = 0.29. The adsorption capacity parameter A of this equation was predicted from clay, dithionite‐extractable Fe (Fed), and pH using a nonlinear regression method. With increasing pH, A decreased for 4 < pH < 6.5 but increased for 6.5 < pH < 7.5. The Fed could be replaced by the soil color yellowness component b*, which was easily determined with a chroma meter. The equilibrium P concentration of the soil solution, ceq, was closely related to a one‐point measurement of the AD curves, c1.2 (the final concentration after adding 1.2 mg L−1 P). Thus, only the four soil properties clay, Fed (or b*), pH, and c1.2 were necessary to predict complete AD curves using the developed equations. The equations proved to be reliable when tested by an independently selected subset of the 2555 samples and by a functional validation. The developed equations can therefore be used as PTFs.
Tillage and Crop Effects on Seasonal Soil Carbon and Nitrogen Dynamics
Authors: Franzluebbers A. J. , Hons F. M. , Zuberer D. A. 
Published: July 2010

AbstractSeasonal changes in the active fractions of soil C and N are important in understanding mineralization‐immobilization processes that influence soil N availability. Our objective was to determine the effect of tillage (conventional tillage [CT] and no tillage [NT]) in monoculture sorghum [Sorghum bicolor (L.) Moench], wheat (Triticum aestivum L.), and soybean [Glycine max (L.) Merr.] on the seasonal dynamics of in situ inorganic soil N, potential C and N mineralization, and soil microbial biomass C (SMBC). A Weswood silty clay loam (fine‐silty, mixed, thermic Fluventic Ustochrept) located in south‐central Texas was sampled to a depth of 200 mm 57 times during a 2‐yr period. In situ soil NO3− accumulated at a rate of ≈0.03 g N m−2 d−1 following harvest when temperature and moisture were adequate. Potential soil C mineralization was 35, 39, and 53% greater under NT than under CT when averaged across months in wheat, sorghum, and soybean, respectively. However, following harvest of each crop, potential soil C mineralization increased at a faster rate under CT than under NT and differences between tillage regimes were reduced for several months, which caused temporary N immobilization in CT. Periods of net N immobilization at the end of the growing season and beginning of the fallow period were often associated with an increasing SMBC pool. Large seasonal changes in active soil C and N pools could be related to rhizodeposition, crop residue addition, and the long fallow period. The type, placement, and timing of residue input significantly altered the seasonal dynamics of the active soil C and N pools and their effect on soil N availability.
Phosphorus Soil Test Correlation to Sugarcane Grown on Histosols in the Everglades
Authors: Korndörfer G. H. , Anderson D. L. , Portier K. M. , Hanlon E. A. 
Published: July 2010

AbstractSugarcane (Saccharum spp.) in Florida is principally grown on Histosols in the Everglades Agricultural Area. Soil‐test‐based P fertilization recommendations have not been addressed since the 1970s. The objectives of this research were to evaluate the most acceptable soil test P extractant that best correlates to crop yield, and to define soil test P groupings associated with crop response to applied P. Results will be used in the future to recalibrate soil test data to yield and rate of P application. Phosphorus trials were conducted at four sites on organic soils between 1968 and 1972 and additionally at eight sites on organic soils between 1982 and 1990. Phosphorus applications ranging from 0 to 98 kg P ha−1 were broadcast or row‐applied in combination with different cultivars, and/or K, Si, or S rates at 12 sites (multiple experiments used per site per crop). The effectiveness of water, acetic acid, and Mehlich‐1 extractable soil P as yield response predictors was determined. Acetic acid extractable P was more highly correlated to sugar and cane yields (r = 0.72* and 0.63**, respectively) than water‐extractable P (r = 0.27** and 0.39**, respectively). Mehlich‐1 extractable P was poorly correlated to sugar (r = 0.25*) and cane (r = 0.05ns) yields. Acetic acid extractable P was selected as the best‐suited extractant related to crop yield response to P fertilization. Soil test calibration curves (i.e., relative yield as a function of acetic acid extractable P) were determined from the choice of seven types of regression models, in which the reciprocal function was chosen with the highest coefficient of determination (R2) and minimized residuals. Soil acetic acid extractable P criteria were developed to define soil test level groups associated with yield response conditions: low soil test levels ranged from 0 to 9 mg L−1, medium from 9 to 39 mg L−1, and high exceeded 39 mg P L−1.
Nitrogen Use Efficiency of Winter Wheat among Landscape Positions
Authors: Fiez T. E. , Pan W. L. , Miller B. C. 
Published: July 2010

AbstractSpatially variable N fertilizer application may reduce environmental impacts and increase the economic return of N fertilization. To achieve these benefits, N recommendations must account for within‐field differences in the amount of N required to produce a unit of yield (unit N requirement, UNR). Component analysis was used to determine the sources of variation in the UNRs of winter wheat (Triticum aestivum L.) among landscape positions. The UNRs were divided into two components, N uptake efficiency (plant N/N supply) and N utilization efficiency (grain yield/plant N) observed in N rate trials (0–140 kg N ha−1 fall applications) established on footslope, south backslope, shoulder, and north backslope positions of two farms for 2 yr. Variation in the UNR among the 16 landscape positions studied was most associated with differences in N uptake efficiency (r = −0.80), although N utilization efficiency (r = −0.62) also contributed to the variation. Nitrogen uptake efficiency among landscape positions declined as more fertilizer was required to reach optimum yield (r = −0.56) due to low N fertilizer uptake efficiencies (Δplant N/ΔN fertilizer). Nitrogen fertilizer uptake efficiency was related to the degree of apparent N loss (r = −0.87), indicating that N availability limited N uptake efficiency among landscapes. Overall, low N fertilizer uptake efficiencies (<50%) and high N loss percentages (>50%) indicate the need to reduce N losses and lower UNRs, particularly on north‐facing backslopes susceptible to N leaching.
Phosphorus Forms in Particle‐Size Fractions of a Toposequence from Northeast Brazil
Authors: Agbenin J. O. , Tiessen H. 
Published: July 2010

AbstractA previous study of this toposequence from semiarid northeastern Brazil concluded that processes of P transformation in semiarid tropical landscapes with steep slopes are difficult to describe with concepts developed in temperate regions. In these soils, derived from syenitic rocks, particle‐size fractions reflect increasing effects of weathering processes from sands to clays. We therefore document the association of P and different sequentially extracted P fractions with particle‐size fractions along the toposequence to further investigate P transformations during pedogenesis in the tropics. Total P was exceptionally high in these soils and in all particle‐size fractions. Total P increased with decreasing particle size and decreased downslope. Total P in sand and silt correlated with total Ca in these fractions. The Ca‐bound phosphate, largely of primary origin, was most abundant in sands and decreased downslope in all particle‐size fractions. At the lower slope, all particle‐size fractions were dominated by resistant inorganic P forms that correlated with total Fe. Comparison of the proportion of Ca‐associated and resistant P between different profile depths and with the underlying saprolite at the mid and lower slopes indicated increased transformations and P losses in deeper horizons and substantial weathering and leaching extending through the solum into the saprolite underlying the soil. The interpretation of P transformations with soil development and landscape position is complicated by intense weathering, highly variable leaching, and colluvial mixing that results from the complex interactions of lithology, weathering, and colluvial action in this semiarid tropical environment of steep slopes, annual moisture deficits, and intense rainfalls.
Aggregate Stability under Oak and Pine after Four Decades of Soil Development
Authors: Graham R. C. , Ervin J. O. , Wood H. B. 
Published: July 2010

AbstractThe development of water‐stable aggregates is an important soil genesis process because it strongly influences important soil characteristics, including infiltration, aeration, and erodibility. We studied a 41‐yr‐old biosequence of lysimeter soils at the San Dimas Experimental Forest in southern California to assess water‐stable aggregates as a function of the imposed scrub oak (Quercus dumosa Nutt.) and Coulter pine (Pinus coulteri B. Don) communities. Significantly different aggregate stabilities developed in these initially identical and homogeneous soils. Earthworms under the oak produced a 7‐cm‐thick A horizon composed almost entirely of worm casts. Casts were also deposited within the litter of the Oi horizon. The A horizon and the Oi horizon worm casts had aggregate stabilities near 90%, ≈35 g kg−1 organic C, and abundant fungal hyphae, as observed by scanning electron microscopy. The 1‐cm‐thick A horizon under pine contained no worm casts and had 78% water‐stable aggregates, 12.9 g kg−1 organic C, and abundant very fine roots and fungal hyphae. Subsoils under both oak and pine had 43 to 51% water‐stable aggregates, attributable to inorganic binding mechanisms since organic C contents were ≤4 g kg−1, roots were relatively few, and no fungal hyphae were observed. After 41 yr of soil formation, aggregate stability was ≈15% greater and the volume of stable aggregates was seven times larger under scrub oak than under Coulter pine.