bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial Pattern of Slash Pine Roots and Its Effect on Nutrient Uptake
Authors: Escamilla J. A. , Comerford N. B. , Neary D. G. 
Published: July 2010

AbstractNutrient‐uptake models generally assume that roots are uniformly arrayed throughout a soil volume. In high‐fertility soils, departure from this regular distribution is not thought to affect nutrient‐uptake predictions if the roots are randomly arranged, but has the potential to dramatically change nutrient‐uptake predictions if roots are clumped. This study was conducted to document root spatial patterns in a forest ecosystem and to determine if spatial patterns affect how we conceptualize nutrient uptake in low‐fertility soils. Roots were mapped on horizontal faces at 2‐cm depth intervals. Spatial patterns were measured using variance/mean ratio and nearest neighbor distance (R) indices. The spatial pattern of slash pine (Pinus elliottii Engelm.) roots, using either variance/mean or R index, was random and was not affected by either the understory plant community or planting microsite. However, 63% of the pine roots in the check plots were within 0 to 0.6 cm of another pine root, while a similar percentage of pine roots was within 0 to 1.0 cm of another pine root in the weed‐controlled area. At these interroot distances, little interroot competition for K was expected. In contrast, virtually all roots had P‐uptake efficiency of <30%, regardless of understory competition. When nutrient‐uptake efficiency is a function of interroot distance for a random root population in low‐fertility soils, average interroot distance cannot be considered typical of the root population.
Aspect and Species Influences on Nitrogen and Phosphorus Availability in Arizona Chaparral Soils
Authors: Klemmedson James O. , Wienhold Brian J. 
Published: July 2010

AbstractBiota and topography are among the most important factors affecting nutrient status of wildland soils. Knowledge of these relations has a fundamental bearing on management of chaparral ecosystems. This study was conducted to determine the effect of shrub species and topographic aspect on availability of soil N and P in Arizona chaparral soils. Soil was collected under the canopy of 32 randomly selected shrubs, eight each of birchleaf mountain mahogany (Cercocarpus betuloides Nutt.) and shrub live oak (Quercus turbinella Greene) from both north and south aspects. A pot culture technique, using barley (Hordeum vulgare L. var. gustoe) and mountain mahogany (C. montanus Torr.) as test plants, was used to estimate availability of soil N. and P. Both test plants showed that shrub species and aspect influenced nutrient availability. Availability of P was very low, while that of N was quite high. Lower availability of P in soils from southerly aspects was associated with low amounts of total soil P, probably the result of long‐standing differential erosion between north and south aspects, aggravated by fire. High N availability was probably associated with inputs of N via symbiosis between actinomycetes and mountain mahogany. Higher fertility of soils from oak systems is associated with lower lignin content of litter from these shrubs.
Kinetics of Weathering in Soils from a Subalpine Watershed
Authors: Brown Aaron D. , Lund Lanny J. 
Published: July 2010

AbstractWeathering reactions were studied in samples of two subalpine soils from the Emerald Lake Watershed in Sequoia National Park, California (36°35′N, 118°40′W). Rates of weathering were measured as a function of pH and ionic strength. Reaction kinetics were characterized by rapid H+ consumption, and Si, Al3+, Ca2+, and Mg2+ release in the first week. This was followed by a period in which H+ consumption and cation release were a linear function of time for up to 4 wk. Based on reaction stoichiometry and equilibrium calculations, rapid short‐term H+ consumption in these soils was related to Al solubility. The rate laws for long‐term acid consumption were approximately first order with respect to H+ concentration in the pH range 3 to 5. The consumption of H+ was independent of NaCl concentration. These results indicate that the long‐term acid‐consumption kinetics of these soils are consistent with a surface‐reaction‐controlled mechanism. Although the distribution of products was slightly different, the fractional orders of the rate laws for Ca, Si, and Mg release in response to acid addition were similar in these two contrasting soils. Based on reaction rates and solution composition, long‐term acid consumption was attributed to weathering of plagioclase or hornblende.
High‐Elevation Forest Soils of the Southern Appalachians: II. Geomorphology, Pedogenesis, and Clay Mineralogy
Authors: Feldman S. B. , Zelazny L. W. , Baker J. C. 
Published: July 2010

AbstractWe investigated soil mineral weathering sequences in three geologically distinct high‐elevation areas of southern Appalachian spruce‐fir (Picea rubens Sarg.‐Abies fraseri [Pursh.] Poir) forests in order to elucidate the pedogenic factors that distinguish these unique soils from their low‐elevation counterparts. Four pedons representing a developmental sequence ranging from soils having distinct spodic field morphology (E plus Bhs horizons) to those having either minimal (weak E horizons) or no spodic character (umbric epipedons/cambic horizons) were selected for further study from a total of 35 excavated pits. Whereas the mineralogy of sand and silt fractions reflected inheritance from parent materials, clay mineral suites of all soils were very similar, indicating biotic and climatic controls on weathering. Surface‐horizon clay fractions were dominated by regularly interstratified mica/vermiculite and high‐charge smectite, which decreased with depth in all profiles. Subsoil clay fractions were principally composed of gibbsite and hydroxy‐interlayered vermiculite. Genesis of secondary 2:1 layer silicates in these soils occurs initially by the pseudomorphic transformation of biotite to both hydrobiotite and vermiculite. However, direct conversion of biotite to kaolinite is of little importance in these soils. The demonstrated mobility of Al‐organic complexes out of surface horizons and the inability of hydroxy‐Al interlayers to form in vermiculite in the presence of organic acids suggest that these soils are undergoing early stages of podzolization and that they are more similar to northern Appalachian Spodosols than they are to adjacent low‐elevation soils of the southern mountains.
Potassium Accumulation and Corn Yield Related to Potassium Fertilizer Rate and Placement
Authors: Heckman J. R. , Kamprath E. J. 
Published: July 2010

AbstractSandy Coastal Plain soils have relatively low reserves of K and may not be able to supply adequate K for intensive corn (Zea mays L.) production. Field experiments were conducted on Dothan loamy sand (fine‐loamy, siliceous, thermic Plinthic Paleudult) for 3 y to determine K fertilizer rate and placement effects on corn growth and seasonal K accumulation. Treatments were 0, 56, 112, 168, and 224 kg K ha‐1 broadcast and 56 kg K ha‐1 banded plus 0, 56, 112, and 168 kg K ha‐1 broadcast. Total K accumulation was increased by K fertilization rate each year. Method of application had a significant effect in a relatively dry year when the broadcast‐plus‐banded treatments resulted in greater K accumulation. Stover dry matter was increased in two of three years with 56 kg K ha‐1, but grain yield was increased in only one year. Yield increased linearly with K rates up to 112 kg K ha‐1 when the initial exchangeable‐K level was 0.21 cmol L‐1. Critical exchangeable‐K level was 0.35 cmol L‐1 and the critical soil solution K concentration was 0.48 mmol L‐1 for dry‐matter yield. When corn is grown with intensive production practices, there is little benefit in applying banded K with broadcast K on sandy soils testing high in K.
Nitrogen Fertilizer and Dairy Manure Effects on Corn Yield and Soil Nitrate
Authors: Jokela William E. 
Published: July 2010

AbstractManure from livestock is an important source of N for crop production in many areas, but efficient management of manure is critical to improve the economics of manure use and to minimize the impact on water quality. A field study was conducted on an Enosburg fine sandy loam (sandy over loamy, mixed, nonacid, mesic Mollic Haplaquent) in northwestern Vermont to evaluate the effect of dairy‐manure and N‐fertilizer application on corn (Zea mays L.) yields and soil profile NO3 in a silage production system. Treatments consisted of a factorial arrangement of manure (0 and 9 Mg ha‐1, dry‐matter basis), N rate (56 and 112 kg ha‐1 as NH4NO3), and time of N application (planting or six‐leaf stage), as well as 0 and 168 kg N ha‐1 rate at planting (with and without manure). Yields and N uptake were increased by N fertilizer and by manure. Without manure, grain and silage yields were increased by fertilizer N to the 112 kg ha‐1 rate in all years; with manure, N fertilizer did not increase yields significantly. Time of application had little or no effect on yield. Plant uptake of N followed a similar pattern but with somewhat more pronounced effects. A presidedress NO3 soil test reflected N availability, as indicated by relative yields. Manure application rates were equivalent, in terms of yield response, to 73 to 122 kg fertilizer N ha‐1 in individual years, which represented 27 to 44% of the total manure N in the year of application. Sampling of the 1.5‐m soil profile before planting and after harvest showed increases in soil NO3 that were related to the amounts of manure and fertilizer N applied. Some decreases in NO3 were measured from fall to spring sampling times, but net losses were minimal where <60 kg ha‐1 NO3‐N was present in the fall. Application of manure resulted in similar or slightly lower soil profile NO3 than agronomincally equivalent rates of fertilizer N.
Organic Carbon Effects on Available Water Capacity of Three Soil Textural Groups
Authors: Bauer Armand , Black A. L. 
Published: July 2010

AbstractA major cause of soil productivity loss through erosion is attributed to changes in soil water‐holding properties or a reduction in thickness of the plant rooting zone. The objective of this study was to measure the effect of management‐induced changes in soil organic carbon (OC) concentration on soil characteristics affecting the available water capacity. Four sites each of moderately coarse (sandy), medium, and moderately fine or fine (fine) soils were sampled in four increments to 0.457 m within each of two cropland management systems (conventionally cultivated and stubble mulched) and each of two virgin grassland management systems (grazed virgin and relict virgin). Measurements of the water concentration by weight (Pw) at field capacity (FC) and permanent wilting point (PWP) were made on disturbed soil samples. Bulk density decreased with increasing OC concentration. The magnitude of change was greatest in sandy and least in the medium‐textured soils. For all soils combined, a change in sand fraction accounted for about 75% of the change in Pw at both the FC and the PWP. The change in Pw was greater at FC than the PWP. A unit change in OC concentration in the sandy soils caused a greater change in Pw at FC than at the PWP, but in the medium and fine soils the change in Pw at FC essentially paralleled the change at the PWP. An increase in OC concentration did not change the available water capacity in the sandy group and decreased it in the medium and fine textural groups. Loss of soil productivity induced by erosion in the northern Great Plains is probably more closely associated with a decline in nutrients and biological activity than from a change in available water capacity.
Estimating Crop Residue Decomposition from Air Temperature, Initial Nitrogen Content, and Residue Placement
Authors: Douglas C. L. , Rickman R. W. 
Published: July 2010

AbstractManaging cereal residues to control soil erosion by wind and water requires knowledge of residue decomposition. Four equations were developed to estimate decomposition of cereal residues based on cumulative degree days (CDD) calculated from daily maximum and minimum air temperature. Each is based on the general equation Rr = Ir exp(fN fW k CDD), where Rr = residue remaining, Ir = initial residue, fN is an N coefficient based on initial residue N content, fW is a water coefficient based on a combination of residue and field management, and k is a general decomposition coefficient. Projected decomposition was tested against data for different varieties of soft white and hard red spring and winter wheat (Triticum aestivum L.), durum wheat (T. durum Desf.), spring and winter barley (Hordeum vulgare L.), triticale (× triticosecale Wittm.) corn (Zea mays L.), and soybean [Glycine max (L.) Merr.] from Alaska, Idaho, Indiana, Missouri, Oregon, Texas, and Washington. The mean slope of the line relating observed to projected decomposition for all locations was 1.10 ± 0.543 with r2 values ranging from 0.76 to 0.99, with most > 0.95.
Overlaying Soil and Timber Inventories to Assess Aspen Productivity in Northern Minnesota
Authors: Bates P. C. , Robert P. C. , Blinn C. R. 
Published: July 2010

AbstractForest soil productivity is a difficult quantity to measure, yet it is an integral component of forest management decisions and an important interpretation of soil inventories conducted in forested areas. Soil‐site studies are time consuming and expensive, and often cannot identify productivity differences between soil units. Merging timber‐inventory data with soil‐survey data may provide an efficient means for evaluating forest productivity. In this study, timber‐inventory data were overlaid with soil‐survey data for Beltrami County, Minnesota. Soil map units were grouped into 10 soil classes based on drainage and parent material. Productivity of aspen (Populus tremuloides Michx. and P. grandidentata Michx.) was compared between soil classes using the estimates of volume, site index, and basal area collected during the timber inventory. Analysis of the volume data indicated that the soils formed in outwash deposits were significantly less productive (mean volume of stands between 40 and 55 yr = 126 m3 ha‐1) than soils formed in calcareous glacial till or calcareous deposits of stratified fine sands and silts (mean volume of stands between 40 and 55 yr = 155 m3 ha‐1). Very poorly drained soils were also in the higher productivity group, though aspen was a relatively minor cover type on these soils. The site‐index data was of minimal value in separating soils into productivity groups. Basal area was highly correlated with volume estimates and may be a useful stand attribute for assessing forest productivity during land‐resource inventories.
A pH‐Stat Procedure for Evaluating Reactivity of Agricultural Limestone
Authors: Hartwig R. C. , Loeppert R. H. 
Published: July 2010

AbstractLimestone dissolution occurs as a surface reaction; therefore, the particle‐size distribution of the material influences its reactivity. Particle‐size distribution alone, however, may not provide a good comparative index of reactivity because of differences in mineralogy, surface composition, and morphology. A pH‐stat titration procedure was previously developed to determine the “effective” reactivity of soil carbonate. The objective of this study was to evaluate the pH‐stat procedure as a method for comparing the reactivities of liming materials. Eighteen liming materials, representing a wide range of physical and chemical properties, were analyzed. The relative reactivities of the materials are expressed as Iceland‐spar reactivity equivalent (ISRE), and reported as particle‐size distribution (ISRE‐PSD) or surface area (ISRE‐SA) of a standard Iceland‐spar calcite that has the equivalent quantity and reactivity as the sample. The ISRE‐PSD of the calcitic materials gave higher proportions of fine‐clay‐size particles than were obtained by sieving and sedimentation, indicating that the calcitic liming materials had greater surface reactivities than the Iceland‐spar calcite standard. The dolomitic materials, being less reactive than the calcitic materials, exhibited large proportions of ISRE fine‐sand‐size particles and small proportions of ISRE clay‐size particles. Calculations of surface area using ISRE‐PSD data provide a more explicit index of reactivity than the ISRE‐PSD. The ISRE‐SA values of the calcitic and dolomitic materials were not highly correlated with surface areas determined by the Brunauer‐Emmett‐Teller (BET) or sedimentation procedures, indicating the pH‐stat procedure provides a method for comparing the reactivities of liming materials not possible by BET, sieving, or sedimentation methods.
Oxalate Determination in Soils Using Ion Chromatography
Authors: Lilieholm B. C. , Dudley L. M. , Jurinak J. J. 
Published: July 2010

AbstractA method was developed for determining oxalate in soils with variable levels of CaCO3. The soils were extracted with 1.0 M HCl for varying periods of time at 80 °C and room temperature, as well as being extracted as saturation pastes. Oxalate in the extracts was determined on and ion chromatograph, with special care taken in the cleaning of the column and suppressor. The eluant was 0.85 mM NaHCO3 and 0.90 mM Na2CO3. Recovery of oxalate from CaC2O4 spiked samples extracted with HCl ranged from 16 to 104%. Each soil required a different extraction time to obtain maximum release of oxalate. Soil with the greatest CaCO3 content yielded the lowest oxalate recovery. Oxalate content of unspiked samples was also determined. Recovery of oxalate as CaC2O4 from the saturation pastes ranged from 0.1 to 25.0%. Detection limits were 15 µg L‐1 in the HCl extracts and 22 µg L‐1 in the saturation‐paste extracts.
Apparent Solubility Products of Phosphorus Impurity Compounds in Commercial Monoammonium Phosphate Fertilizers
Authors: Sikora F. J. , Copeland J. P. , Mullins G. L. 
Published: July 2010

AbstractMonoammonium phosphate (MAP) fertilizers contain P impurity compounds that have low solubility and bioavailability. Solubility products of fertilizer impurity compounds not currently documented would be useful data to predict the solubility and subsequent P bioavailability of the compounds in soil. Water‐insoluble MAP fractions from seven commercial MAP fertilizers were equilibrated with water and the filtrate was analyzed for total concentration of chemical components. Activities of individual elements were calculated using a chemical speciation program, MINEQL, and were used to determine apparent solubility products (Kosp) of P impurity compounds. The apparent log Kosp values were −16.33, −9.33, and −14.59 for Al‐NH4HPO4F2, FeNH4(HPO4)2, and MgAl(NH4)2H(PO4)2F2, respectively. The values were only considered estimates because they were determined from a heterogeneous mixture of compounds in the water‐in‐soluble MAP fractions rather than pure solid phases. The approximate log Kosp values were instructive for comparing solubilities of the impurity compounds with solubilities of variscite, strengite, monetite, brushite, struvite, and FePO4(c) in water and soil. At pH 6 in water, the general order of decreasing P solubility was struvite > brushite > monetite > MgAl(NH4)2(PO4)2F2 = AlNH4HPO4F2 > FeNH4(HPO4)2 > > FePO4(c) > variscite ≈ strengite. In soil, the P impurity compounds have a greater solubility than variscite, strengite, monetite, and brushite between pH 5.5 and 7. Therefore, the impurity compounds are not expected to remain intact in soil for long periods of time. Of the three impurity compounds, MgAl(NH4)2H(PO4)2F2 appears to be the least desirable because of lower calculated solubility in soil.
Desorption and Extraction of Selected Heavy Metals from Soils
Authors: Sheppard Marsha I. , Thibault Denis H. 
Published: July 2010

AbstractThe need for proper disposal of industrial wastes and for remediation methods for soils contaminated with heavy metals necessitates a better understanding of the processes involved in mobilizing, transporting, and retaining elements in surface soils. The objective of this study was to investigate the desorption in water and efficacy of several traditional extraction agents in removing Tc, Np, Mo, U, Cr, Pb, Cs, and Th. Selected slices were taken with depth in acidic sand (Dystrochrept) soil cores that were spiked for 4 yr. Similarly, Tc, Np, and U were desorbed and extracted from the clay subsoil of reed/sedge peat cores following a one‐season migration study. Technetium and Mo behaved as anions, and the small amount of Tc retained was attributed to insoluble organic complexes and oxides in the sandy soil and carbonates in the clay subsoil. The retention of Mo was attributed to colloidal Fe(III) oxides and organic colloids or complexes. Neptunium sorption appears to be dependent on the variable charge of the soil, making organic matter and pH important factors. Uranium and Pb were associated with the oxides. Cesium and Cr took part in inorganic reactions that fixed them rigorously to the soil solids or formed precipitates; Th formed organic complexes. Results suggest that remediation techniques for soils contaminated with Tc, Mo, and Np could be quite successful using intense leaching with acidified water. Soils containing U, Pb, and Th may be partially reclaimed by manipulation of the organic matter or leaching with organic acids; however, soils contaminated with Cs and Cr would require extensive chemical treatment.
Phosphorus Distribution in Calcareous Soil Profiles of the Central Plains
Authors: Bowman R. A. , Savory D. J. 
Published: July 2010

AbstractDeep‐rooted crops benefit from high subsurface P content. While some documentation exists for high levels of available inorganic P well below the soil solum, very little information exists on organic‐P contents deep in the soil profile. This research was conducted to document the presence of large pools of available organic and inorganic P on top of a carbonate layer 2.2 m below the soil surface. Additionally, soil organic C, N, texture, and selected mineral concentrations were determined to assess their correlations with total P. Soil samples (Aridic Argiustolls) from two fields that have been out of cultivation for at least 10 yr were taken in 0.15‐m increments to a depth of =2.5 m. The surface soils (0.0–0.3 m) were high in nutrients (11.0 g C and 1.1 g N/kg soil) and negligible in carbonates; the middle soil layers (0.30–0.25 m) were low in nutrients (4.0 g C and 0.3 g N/kg) and intermediate in carbonates (90 g/kg); and the deep soil layers (2.25–2.55 m) were high in available inorganic and total organic P, and very high in carbonates (> 300 g/kg). The total P concentration in the profile was inversely correlated with the percentages of sand and Ca, and directly correlated with the total content of Fe and Al. Total organic C and N and, to a greater extent, total organic P accumulated near or on top of a carbonate layer. Most of the organic C and P below 0.45 m were soluble in 2 M HCl. For the surface soil (0.0–0.45 m), the bulk of the organic P was extracted only after 2 M HCl pretreatment. Alfalfa and similar deep‐rooted crops may benefit from this large reserve of available P near the water table.