bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long‐Term Effects of Tillage and Fertilization on Soil Organic Matter Dynamics
Authors: Salinas‐Garcia J. R. , Hons F. M. , Matocha J. E. 
Published: July 2010

AbstractUnderstanding the effects of long‐term management practices on soil C and N pools and activities is essential for sustaining soil productivity. The objectives of this study were to evaluate long‐term and seasonal changes in soil organic C (SOC), soil microbial biomass C (SMBC) and N (SMBN), and mineralizable C and N in continuous corn (Zea mays L.) under conventional tillage (CT), moldboard (MB), chisel (CH), minimum tillage (MT), and no‐tillage (NT) with low (45 kg N, 10 P kg ha−1) and high (90 N kg, 10 P kg ha−1) N fertilization. An Orelia sandy clay loam (fine‐loamy, mixed, hyperthermic Typic Ochraqualf) in south Texas was sampled before corn planting in February, during pollination in May, and following corn harvest in July. No‐tillage and MT retained more corn residue C input as SOC and SMBC than the more intensive tillage systems. Soil organic C, SMBC, SMBN, and mineralizable C and N were greatest in the surface 0 to 50 mm with NT and MT. Seasonal distributions of SMBC and mineralizable C were consistently greater in reduced‐tillage systems (NT and MT), averaging 22 and 34% greater than plowed treatments at planting, 45 and 53% larger at pollination, and 36 and 34% higher at harvest, respectively, at a depth of 200 mm. The greater amount of crop residues remaining with MT and NT may have provided available substrate for maintenance of the larger SMB pool and the higher C and N mineralization in the 0‐ to 200‐mm depth during the growing season. Higher N fertilization increased seasonal mineralizable C and N, but did not consistently affect SOC and SMB. Reduced tillage systems that promote surface residue accumulation provide an opportunity for increasing sequestration of C and mineralizable nutrients within SMB.
Responses of Six Crop Species to Solution Zinc2+ Activities Buffered with HEDTA
Authors: Parker D. R. 
Published: July 2010

AbstractZinc contamination has long hampered the use of conventional nutrient solutions for attaining reproducible and severe Zn deficiencies. Chelator‐buffered solutions show promise for precisely imposing micronutrient deficiencies, but further studies are needed to fully evaluate the method and to develop methods to avoid Zn‐deficiency‐induced P toxicity. In a greenhouse study, seedlings of maize (Zea mays L. ‘Golden Cross Bantam’), wheat (Triticum aestivum L. ‘Yecora Rojo’), tall wheatgrass (Elytrigia pontica [Podp.] Holub ‘Orbit’), alfalfa (Medicago sativa L. ‘Germain's WL‐320’), soybean (Glycine max [L.] Merr. ‘Vinton 81’), and tomato (Lycopersicon esculentum L. ‘Jackpot’) were grown for 16 to 29 d in solutions containing 0.4 to 12 µM total Zn. Computed Zn2+ activities were buffered at 4 to 123 pmol L−1 by a 50‐µM excess of HEDTA, and solution P was maintained at 10 ± 3 µM. Zinc deficiencies ranged from mild to severe, dry matter yield minima ranged from 32 to 89% of controls, and critical Zn2+ activities for the onset of deficiency ranged from approximately 10 to 65 pmol L−1. The relative sensitivity of the six species to low Zn was maize > tomato > wheat > alfalfa ≈ tall wheatgrass > soybean. Shoot Zn concentrations were consistent with the widely reported critical range of 15 to 20 mg kg−1. Zinc deficiency in the three grass species led to hyperaccumulation of P to phytotoxic levels, and leaf symptoms largely reflected this toxicity. Leaf P concentrations in the three dicots tended to be lower, but may have been within the phytotoxic range. Thus, even with P concentrations that approach soil solution values, the P toxicity that often accompanies Zn deficiency in solution‐culture experiments was not eliminated. The effects of Zn deficiency on shoot concentrations of nutrients other than P were variable, although divalent cations tended to be elevated in Zn‐deficient shoots.
Properties and Classification of Cold Desert Soils from Antarctica
Authors: Bockheim J. G. 
Published: July 2010

AbstractEight pedons representing three climatic zones and parent materials ranging from Holocene to Pliocene were characterized from the Dry Valleys region of Antarctica. All of the soils contain abundant water‐soluble salts, including NaCl in coastal regions, NaNO3 along the polar plateau, and Na2SO4 in intermediate areas. The salts originate primarily from atmospheric deposition and accumulate linearly with time. Based on a comparison of salt input by precipitation and the salt content of the profiles, minimal leaching of salts has occurred during the past 3 million yr in soils along the polar plateau. Chemical weathering generally is restricted to oxidation of Fe‐bearing minerals and some clay authigenesis. Some of the soils contain ice‐cemented permafrost; however, many of the older soils with <5% moisture content have dry permafrost. Although the soils bear many features of Aridisols, they fail to meet the requirements of an aridic soil moisture regime because of the very cold temperatures. They could be classified as Cryids if the Aridisols suborder were expanded to include soils with temperatures that never exceed 5 or 8°C. In the proposed Gelisols order for permafrost‐affected soils, the soils are classified as Natric, Glacic, and Typic Anhyturbels (evidence of cryoturbation) and Salic and Petrosalic Anhyhaplels (no cryoturbation).
Release and Fixation of Ammonium and Potassium under Long‐Term Fertility Management
Authors: Liu Y. J. , Laird D. A. , Barak P. 
Published: July 2010

AbstractImproved nutrient use efficiency in production agriculture is a research priority for both agronomic and environmental reasons. To achieve this goal, a thorough understanding is needed of both short‐term and long‐term nutrient dynamics in soils. The specific object of this study was to investigate the effect of long‐term fertility management on the dynamics of fixed and exchangeable NH4 and K in a typical Upper Midwestern agricultural soil. Soil samples (0–20 cm) were collected from long‐term (30‐yr) fertility plots near Arlington, WI. Fixed and exchangeable NH4 and K were determined for plots receiving 0 and 252 kg ha−1 K (from 1962–1982) and 0, 68, 112, 168 kg ha−1 N (from 1962–1993) as urea or NH4NO3. Levels of exchangeable NH4, fixed NH4, and fixed K were similar for all treatments. Exchangeable K was significantly higher in plots receiving 252 kg ha−1 K than in those receiving no K. Levels of exchangeable K were also higher in plots receiving no N than in plots receiving N fertilizer. Fixation capacities for both NH4 and K were significantly reduced by sustained high rates of K fertilization, but not by N fertilization. These results suggest that levels of fixed NH4 can be neither built up nor depleted through long‐term fertility management. On the other hand, levels of exchangeable K and both NH4 and K fixation capacities are influenced by long‐term fertility management.
Silicon Concentrations of Biological Standards
Authors: Bell Paul F. , Simmons Tracey F. 
Published: July 2010

AbstractNo NIST (National Institutes Standards Technology) standards for the Si concentration of biological materials are available, although Si has been determined for one NIST material by non‐NIST personnel. We determined the Si concentrations of NIST materials and a proposed rice‐straw (Oryza sativa L.) standard using an autoclave‐induced digestion, colorimetric method. We measured 1410 mg Si kg−1 for NIST material no. 1575, which was not significantly different from five of seven analyses reported in the literature (P < 0.05). Silicon concentrations of NIST and other materials were 2160 mg kg−1 (no. 1547), 1500 mg kg−1 (no. 1515), 1920 mg kg−1 (no. 8412), and 69 300 mg kg−1 (rice straw).
Sorption‐Desorption of Atrazine and Simazine by Model Soil Colloidal Components
Authors: Celis R. , Cornejo J. , Hermosín M. C. , Koskinen W. C. 
Published: July 2010

AbstractSorption‐desorption of atrazine and simazine on montmorillonite, ferrihydrite, and humic acid was determined using the batch equilibration procedure. Sorption of atrazine and simazine was higher on humic acid than on montmorillonite. Ferrihydrite does not sorb triazine herbicides. Enhanced sorption of atrazine and simazine on montmorillonite was measured after increasing the surface acidity of the clay. Results indicate sorption of s‐triazine herbicides on montmorillonite as protonated species must be preceded by sorption as molecular species on hydrophobic microsites of the clay unless the pH of the bulk solution is close to the pKa of the herbicide. In this latter case, cation exchange would be also operative. Sorption‐desorption of atrazine and simazine was more hysteretic for humic acid than for montmorillonite, indicating that these herbicides desorb more difficultly from organic matter than from montmorillonite because of the contribution of hydrophobic interactions with humic acid. It is suggested that, besides organic matter, smectites of low charge density and high surface acidity should increase the retention of s‐triazine herbicides in soils.
Comparison of Methods for Predicting Ternary Exchange from Binary Isotherms
Authors: Bond W. J. , Verburg K. 
Published: July 2010

AbstractMethods for predicting ternary and higher order cation exchange from binary isotherms are required because it is impossible to measure isotherms for all possible combinations when there are three or more competing ions. One important use for ternary and higher order exchange predictions is for modeling cation transport in multicomponent systems. We review several existing methods for predicting ternary exchange from binary isotherm data and introduce a new method based on the Rothmund‐Kornfeld approach. Existing methods include the Valocchi and Gapon equations as well as the Wilson and subregular models used in conjunction with the Vanselow‐Argersinger exchange formulation. The methods were used with three data sets: Na‐K‐Ca exchange at 50 and 200 molc m−3 in Brucedale soil, and NH4‐Ba‐La exchange at 100 molc m−3 in montmorillonite. The resulting predictions were compared with measured ternary exchange data. It was found that all methods that account for the variation of the exchange coefficient and/or the exchanger phase cation activity coefficients performed similarly well. Their performance was much better than methods that assume that conditional exchange coefficients are constant, such as the Valocchi and Gapon methods. For the data examined, the Gaines‐Thomas formulation of the Rothmund‐Kornfeld equation consistently gave the best predictions for the least computational effort.
Kinetics of Nonexchangeable Ammonium Release from Soils
Authors: Steffens D. , Sparks D. L. 
Published: July 2010

AbstractThe rate of nonexchangeable NH4+ release from soils can have a significant effect on N dynamics and environmental quality. Nonexchangeable NH4+ is that N fraction which is fixed in the interlayers of clay minerals. The objective of this study was to determine the kinetics of nonexchangeable NH4+ release from two topsoils from Germany [Giessen Ap (Aqualf) and Hungen Ap (Alfisol)] and from two subsoils, one from Germany [Hungen C (Alfisol)] and one from Kentucky [Shrouts Bt (Hapludalf)]. Calcium‐saturated, freeze‐dried soils were extracted with H‐resin for 0.25 to 384 h. Sodiumethylmercurythio‐salisylate (Thimerosal) was added to the soil/H‐resin suspension to inhibit microbiological ammonification. The kinetics of nonexchangeable NH4+ release from the soils were biphasic and were best described by Elovich and heterogeneous diffusion models. The release of nonexchangeable NH4+ as a percentage of total nonexchangeable NH4+ in the soils ranged from 4 to 25% and was lower in subsoils than in topsoils. This was ascribed to the higher levels of indigenous nonexchangeable NH4+ in the subsoils, which is more tightly held than recently fixed nonexchangeable NH4+.
Quantifying Rhizosphere Respiration in a Corn Crop under Field Conditions
Authors: Rochette Philippe , Flanagan Lawrence B. 
Published: July 2010

AbstractIn order to quantify rhizosphere respiration (Rrh) during the growing season, we monitored the isotope ratio (δ13C) of soil CO2 in a corn (Zea mays L.) crop that was grown on a soil developed from C3 plant material. The Rrh was defined as the sum of CO2 respired by plant roots and CO2 respired by microbes that feed on organic material produced by the roots. The δ13C of soil CO2 in the corn plot changed from an early season low of approximately −20‰, to mid‐season values of approximately −14‰, before declining again at the end of the growing season. In the control plot (no C4 plants present) δ13C values of soil CO2 were significantly lower than values in the corn plot, averaging approximately −22‰ throughout most of the season. We observed no significant change in the δ13C value of soil CO2 in either the corn or control plots during a diurnal sampling period. The value of Rrh was 1.71 g CO2 m−2 d−1 27 d after planting (DAP), reached 10 g CO2 m−2 d−1 at 44 DAP, remained at about that value until 76 DAP, and gradually decreased to 2.6 g CO2 m−2 d−1 at 141 DAP. The CO2 respired by the rhizosphere was equivalent to 18 to 25% of crop net photosynthesis and 24 to 35% of crop net CO2 assimilation during most of the growing season.
Pedogenic Influence on Base Saturation and Calcium/Magnesium Ratios in Soils of Southeastern Ohio
Authors: Saif H. T. , Smeck N. E. , Bigham J. M. 
Published: July 2010

AbstractContiguous Alfisols and Ultisols occur across the unglaciated, upland landscape of southeastern Ohio. Difficulties are encountered in distinguishing and mapping these soils due to morphological similarities and base saturation differences. The soils have formed in a loess mantle of varying thickness overlying colluvium and residuum derived from sedimentary bedrocks. Four pedons were studied to evaluate the influence of the loess mantle and bedrock chemistry on base saturation and extractable Ca/Mg ratios in order to facilitate soil mapping in southeastern Ohio. Loess thickness and Cr horizon chemistry could adequately account for base saturation and extractable Ca/Mg ratios in three of the four pedons, but a pedogenic effect is essential to explain extractable Ca/Mg ratios in the other pedon. In the latter pedon, extractable Ca exceeded Mg in both the loess mantle (upper solum) and deep Cr horizons, but extractable Mg exceeded Ca in the lower solum and uppermost Cr horizons. We conclude that bases leached from the loess mantle accumulate in the underlying residuum and that Mg is preferentially retained during base recharge. We speculate that a transient Mg‐Al double hydroxide is formed in the residuum during base recharge and is responsible for preferential Mg retention.
Evaluating Soil Movement Using Cesium‐137 and the Revised Universal Soil Loss Equation
Authors: Montgomery J. A. , Busacca A. J. , Frazier B. E. , McCool D. K. 
Published: July 2010

AbstractMore complete information is needed on the rates and patterns of soil movement in Palouse watersheds to better guide conservation planning. Water erosion has historically been predicted from rates using the Universal Soil Loss Equation (USLE) or the Revised USLE (RUSLE). These equations, however, do not account for deposition or tillage erosion. This study was conducted to assess patterns of soil movement in an open Palouse watershed during a 27‐yr period using the 137Cs tracer technique and to statistically compare transect‐ and point‐based RUSLE soil loss rates with 137Cs‐based soil loss rates measured at 74 137Cs sampling points located on 89 landscape profiles. One hundred fifty‐eight soil samples were collected from a modified grid pattern and analyzed for 137Cs activity. Soil movement rates were interpolated at 8025 points in the sample grid using ordinary point kriging. Hillslopes were classified into geometric and geomorphic components. The kriged mean net soil movement rate for the 27‐yr period was −3.3 kg m−2 yr−1. Doubly convex landscape positions have experienced the most severe erosion, apparently due to tillage erosion. The measured 137Cs and transect‐based RUSLE median soil loss rates were both significantly higher than the point‐based RUSLE median; however, no significant difference existed between the transect‐based RUSLE and measured 137Cs median soil loss rates (α = 0.05). Meaningful comparisons between 137Cs and RUSLE soil loss rates can only be made if a tillage movement rate, history of crop management, and the accuracy of RUSLE relationships and operating files are known.
Hydroxy‐Interlayered Minerals in Japanese Soils Influenced by Eolian Deposition
Authors: Bautista‐Tulin A. T. , Inoue K. 
Published: July 2010

AbstractThe influence of eolian dust deposition on the development of Red‐Yellow soils and nonallophanic Andisols in Japan has been well documented. In these studies, it was reported that the clay fractions of these soils are dominated by fine‐grained quartz, 2:1 layer silicates and their intergrades, and kaolinite. However, the nature and composition of hydroxy‐interlayered minerals on these soils influenced by eolian dust addition from China is largely unknown. To address this problem, we collected and characterized 28 soil samples from seven pedons in Japan classified as Hapludalfs, Hapludults, or Melanudands, and two soil samples from a pedon in China classified as a Vermiboroll. These samples were extracted with 0.15 M acid oxalate and 0.3 M sodium citrate solutions and the amounts of Al, Fe, and Si present in the extracts were determined. This information was used in combination with x‐ray diffraction patterns of the samples obtained before and after extraction to determine the mineralogy and estimate the composition of the interlayer material. Except for the Vermiboroll samples, which contained kaolinite and highly charged smectite, the dominant minerals in these soil samples were hydroxy‐interlayered vermiculites (HIV). The citrate extracts yielded low Si/Al atomic ratios (i.e., 0.12–0.86 after 4 h and 0.39–0.90 after 24 h) suggesting that the interlayer materials of the HIV minerals were hydroxyaluminosilicate, hydroxy‐Al, and/or hydroxy‐Fe ions. Our results provide chemical and mineralogical evidence for the occurrence of hydroxy‐interlayer materials in loess‐derived Japanese soils developed under temperate, humid climates.
Error Analysis of an Evaporation Method for Determining Hydrodynamic Properties in Unsaturated Soil
Authors: Mohrath D. , Bruckler L. , Bertuzzi P. , Gaudu J. C. , Bourlet M. 
Published: July 2010

AbstractSolving soil unsaturated flow problems requires knowledge of the water retention θ(h) and unsaturated hydraulic conductivity K(θ) relationships. The purpose of this study was to investigate more thoroughly the properties and accuracy of an evaporation method described by Wind (1969) for determining θ(h) and K(θ) from laboratory cores. Evaporation from a vertical column of soil was first simulated using numerical solution of Richards equation for a given set of soil hydraulic properties. The simulated data were then used to evaluate the ability of Wind's method to provide estimations of the retention and unsaturated conductivity curves when measurement errors were taken into account. The main sources of error were (i) errors due to the position of the tensiometers in the sample, (ii) errors due to the calibration of the transducers used for the pressure head measurements, and (iii) errors due to layering in the soil column. The estimated water retention curves were sensitive only to soil layering. On the other hand, small uncertainties in the position of the tensiometers (1 or 2 mm) and in the calibration curve of the transducers for the pressure head measurements (1–5%) had a great influence on the estimated hydraulic conductivity curves. A correction procedure was proposed and was satisfactory when errors of position in the tensiometers were taken into account. Results also showed that temperature corrections related to viscosity of liquid water were large. Finally, this method gives poor estimates of hydraulic conductivities when raw tensiometric data are corrupted with small errors in their position or calibration.
Inorganic Phosphorus Transformation and Transport in Soils: Mathematical Modeling in ecosys
Authors: Grant R. F. , Heaney D. J. 
Published: July 2010

AbstractThe movement and uptake of P in soils occur primarily in the soluble phase, so that the reliable simulation of P movement and uptake requires that the concentrations of soluble P forms be explicitly represented in mathematical models. To represent soluble P concentrations under dynamic boundary conditions, a convective‐dispersive model of P transport has been coupled to a model of P transformation in which adsorption‐desorption, precipitation‐dissolution, and ion pairing are explicitly represented as concurrent equilibrium reactions. This model is used to explain the temporal and spatial distribution of P among soluble and resin‐, NaHCO3‐, NaOH‐, and HCl‐extractable fractions in soils following amendment with KH2PO4. Simulated reductions in soil pH following different P amendments caused solid‐phase P in the model to be recovered more from resin‐ and NaOH‐extractable forms and less from HCl‐extractable forms as solution P concentration increased. These changes were consistent with those observed experimentally using a P fractionation procedure on a Malmo silt loam (Typic Cryoborall) following its equilibration with 0 to 512 mg L‐1 of KH2PO4 and following its irrigation for 205 d with 50 mg L‐1 of KH2PO4. Simulated displacement of cation coprecipitates from exchange sites allowed the model to reproduce the temporal and spatial patterns of water‐ and HCl‐extractable P in resin columns of different cation‐exchange capacities following a KH2PO4 surface amendment. The results of model testing suggest that changes in soluble P concentrations following P amendments may be represented from concurrent equilibrium reactions for adsorption‐desorption, precipitation‐dissolution, and ion pairing. However, the rate at which these reactions proceed remains uncertain.
Apparent Salt Sorption Reactions in an Unfertilized Acid Subsoil
Authors: Pearce R. C. , Sumner M. E. 
Published: July 2010

AbstractThe equivalent retention of Ca2+ and SO2‐4 from gypsum solutions in acid subsoils has recently been reported. The term salt sorption has been coined to describe this process, yet little is known about the nature of the reactions involved. This study was conducted to determine if other cation‐anion combinations would exhibit similar behavior and to examine the extractability of the sorbed ions. An unfertilized acid Cecil (clayey, kaolinitic, thermic Typic Kanhapludult) subsoil was equilibrated using a saturated paste technique, with solutions of six different salts at a loading rate of ≈14.0 mmolc kg‐1. The salt solutions used were CaSO4, MgSO4, Na2SO4, CaCl2, MgCl2, and a deionized water control. This soil exhibited salt sorption with all six electrolyte solutions. The SO4 salts were almost completely sorbed with both cation and anion uptake on the order 13.8 mmolc kg‐1. Calcium and magnesium chloride were sorbed at ≈11.7 mmolc kg‐1, and NaCl was sorbed at 8.2 mmolc kg‐1. The treated soils were air dried and extracted with successive portions of deionized water or 0.5 M NH4NO3. A relatively large proportion of both cations and anions were removed by repeated extraction with water, suggesting that ionic strength played an important role in the salt sorption process. Nearly all of the sorbed cations and Cl‐ were recovered by neutral salt extraction, but <100% of the SO2‐4 could be accounted for by neutral salt extraction. Neutral salt extractable Al was significantly reduced by salt treatment. It appeared that salt sorption in this soil may have resulted from several mechanisms including precipitation, specific adsorption, ionic strength induced charging, and ion pair adsorption operating concurrently.