bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aluminum Transformations and Solution Equilibria Induced by Banded Phosphorus Fertilizer in Acid Soil
Authors: Sloan J. J. , Basta N. T. , Westerman R. L. 
Published: July 2010

AbstractBanded P fertilizer may alleviate Al toxicity in strongly acid surface soils (pH < 5) and is a useful remediation management practice when liming is not possible. The objective of this study was to determine the effect of banded P fertilizer on Al transformations and soil solution composition in acid soils. Pond Creek silt loam (fine‐silty, mixed, thermic Pachic Argiustoll; pH = 4.0) was amended with five P fertilizer rates and incubated at 24°C for 70 d. Dissolved Al, Mn, Ca, Mg, K, PO4, SO4, Cl, and NO3, pH, electrical conductivity, and exchangeable cations were measured after 1, 5, 10, 15, 30, and 70 d of incubation. Soil solution Al, Ca, Mg, and Mn decreased but SO4 increased with P fertilizer rate. The concentration of dissolved metals increased and soil solution pH decreased with time. Soil solution Al3+ decreased and Al‐orthophosphate complexes increased with P fertilizer rate. Saturation indices derived using MINTEQA2 suggest possible precipitation of Al as gibbsite at low P rates (<175 mg P kg−1) and incubation times ≤15 d, K‐taranakite at high P rates (>262 mg P kg−1) and incubation times ≤30 d, and amorphous variscite analogs at all P rates. Soil solution was undersaturated with respect to Ca and Mg phosphates. Formation of MnPO4·1.5H2O was consistent with the well‐aerated conditions of this study. Significant (P < 0.05) reductions in exchangeable Al, Ca, and Mg were correlated with P fertilizer rate. Phosphorus additions did not affect exchangeable Fe or Mn. Banded P fertilizer is a viable alternative method to reduce toxic forms of Al in strongly acidic soils.
Design and Construction of a Personal‐Computer‐Based Automatic Titrator
Authors: Kinniburgh D. G. , Milne C. J. , Venema P. 
Published: July 2010

AbstractWe designed and constructed an automatic titrator that uses a personal computer (PC) and commercially available components. The titrator can be used for a wide variety of tasks including pH logging, titrations (including “salt titrations”), and two‐way pH stats. The titrator is programmed using a simple command language that enables it to carry out a timed sequence of commands. Examples are given that illustrate the titrator's use for: conventional acid‐base titration using dynamic dose sizing; the base‐acid‐base titration of an acid soil; and the automatic determination of Cd binding by humic acid at a fixed pH.
Kinetics of Potassium Fixation in Vermiculitic Soils under Different Moisture Regimes
Authors: Olk D. C. , Cassman K. G. , Carlson R. M. 
Published: July 2010

AbstractFixation of K in vermiculitic soil and the residual benefit from fertilizer‐K addition are influenced by soil moisture. The purpose of this study was to determine K fixation rates under simulated field moisture regimes. Fixation rates were measured during three consecutive wetting‐drying cycles and in long‐term aerobic incubations with soil moisture held constant at different matric pressures. In all studies, 12 mmol KCl kg−1 soil was applied before monitoring K fixation. All rates conformed to first‐order kinetics. Each wetting‐drying cycle had a rapid fixation phase lasting 2 d with slower fixation thereafter, and rate constants of fixation decreased in each successive cycle for both phases. Depending on the soil, rate constants of the rapid phase in the first cycle ranged from 0.064 to 0.143 d−1 and were 0.026 to 0.061 d−1 in the second cycle. Slow‐phase rate constants ranged from 0.030 to 0.058 d−1 in the first cycle and 0.005 to 0.021 d−1 in the second cycle. In samples maintained as saturated pastes, the rapid phase was extended to 5 d but the rate constant was smaller in magnitude than when soil was drying. The rapid phase represented an abiotic process that was controlled by K+ diffusion. When soil moisture was held constant in a long‐term aerobic incubation, K fixation rate constants increased at lower soil moisture levels. Rate constants of fixation were 0.00055 d−1 at −0.03 MPa and 0.00114 d−1 at −0.48 MPa, an increase of 107%. The measured fixation rates were sufficient to explain long‐term fixation measured in a related field study.
Tolerance of Clover Rhizobia to Heat and Desiccation Stresses in Soil
Authors: Trotman A. P. , Weaver R. W. 
Published: July 2010

AbstractThe ability to withstand desiccation and heat is an important attribute of Rhizobium leguminosarum bv. trifolii for inoculation of clover (Trifolium spp.). Desiccation and heat tolerances of 10 commercial strains of rhizobia and 150 isolates from 15 clover fields in Texas were determined by studying survival of rhizobia in soil incubated at 37°C and −30 J kg−1 water potential for heat stress and 28°C and −1.5 kJ kg−1 water potential for desiccation stress. Fewer commercial strains were tolerant to these environmental stresses than field isolates. Of 150 field isolates, 31 and 19 were able to maintain at least 1% of their initial populations for 1 wk under desiccation and temperature stresses, respectively. Six of the field isolates were tolerant to both stresses, and three of these were effective in N2 fixation. Only one of 10 commercial strains were tolerant to either stress, and none was tolerant to both stresses. Rhizobia in inoculants are usually selected on their ability to fix N2, but it appears that there is good genetic material in field populations for developing strains that have greater tolerance to environmental stresses.
Carbon and Nitrogen Mineralized from Leaves and Stems of Four Cover Crops
Authors: Quemada M. , Cabrera M. L. 
Published: July 2010

AbstractIncreased understanding of surface residue decomposition may improve cover crop management in no‐till systems. Most decomposition studies of cover crop residues have been conducted with samples composed of a mixture of leaves and stems. Because leaves and stems have different composition, however, they would be expected to show different mineralization kinetics. The objective of this work was to study C and N mineralization from isolated stems, isolated leaves, and a mix of leaves and stems of wheat (Triticum aestivum L.), rye (Secale cereale L.) oat (Avena sativa L.), and crimson clover (Trifolium incarnatum L.). Cecil loamy sand soil (clayey, kaolinitic, thermic Typic Kanhapludult) was packed into acrylic plastic cylinders, adjusted to 55% water‐filled porosity, treated with either leaves, stems, or a mix of both (1‐cm pieces) on the surface, and incubated at 35°C for 160 d. Air samples for CO2 and N2O determinations were taken periodically and NH3 evolved was trapped during the first 16 d. Soil columns were leached periodically and leachates were analyzed for N (total and inorganic) and total C. The dynamics of C and N mineralization of a mix of leaves and stems was different from the patterns predicted from isolated leaves and isolated stems. These results indicate a strong interaction between stems and leaves during early stages of decomposition, which may be relevant for predicting N mineralization from cover crop residues. The best predictors for N mineralization were residue C/N ratio and the reciprocal of residue N concentration.
Loess Toposequences in the Lower Mississippi River Valley: I. Fragipan Morphology and Identification
Authors: Lindbo D. L. , Rhoton F. E. , Bigham J. M. , Jones F. S. , Smeck N. E. , Hudnall W. H. , Tyler D. D. 
Published: July 2010

AbstractDespite large acreages of agronomically important fragipan soils in the Lower Mississippi River Valley, relatively little information is available regarding their morphology, particularly in regard to fragipan definition and formation. This study was designed to evaluate morphological differences between nonfragipan (memphis [fine‐silty, mixed, thermic Typic Hapludalf]) and fragipan (Loring [fine‐silty, mixed, thermic Typic Fragiudalf] and Grenada [fine silty, mixed, thermic Glossic Fragiudalf]) soils occurring on the same landscape. A secondary objective was to determine if morphological characteristics of the Loring and Grenada pedons are consistent with taxonomic criteria. Five representative sites were selected based on published soil survey maps and landscape relations. Morphological characteristics associated with fragipans are present in all the Loring and Grenada pedons. The most obvious and consistent indicators of a fragipan are vertical gray seams and associated redoximorphic features. Because brittleness is subjective and a function of moisture content, it is not always a reliable indicator of fragipan occurrence. Likewise, root distribution is not particularly useful since deep‐rooted vegetation did not occur on these soils. Several Memphis pedons exhibit protofragipan development, but based primarily on the organization of gray seams, these should not be considered fragipan soils. Overall, the published criteria are adequate, with the notable exception of slaking, and the characteristics of the Loring and Grenada pedons are consistent with them. Greater relative root penetration and less brittleness also assist in differentiating between the nonfragipan horizons within the Memphis pedons and fragipan horizons of the other members of the toposequence, but these evaluations have to be made in detail from deep pits, particularly in borderline situations.
Influence of Soil Properties on the Statistical Characterization of Dry Aggregate Strength
Authors: Perfect E. , Kay B. D. , da Silva A. P. 
Published: July 2010

AbstractDry aggregate strength measurements, important in tillage and erosion studies, are often analyzed statistically using the Weibull model. The parameters of this model, α and β, characterize the absolute strength and the spread of strengths, respectively. Information is lacking on the influence of soil properties on values of α and β. We measured dry aggregate strength as the specific rupture energy (E in J g−1) of 40 aggregates in two size classes (4–8 and 8–16 mm) from 36 locations along a 500‐m transect across four soil types with a wide range of physical and chemical properties (e.g., 8.0–72.6% sand content). Estimates of α and β were obtained by fitting Weibull's model to these data using nonlinear regression. The α and β values were lognormally and normally distributed, respectively. The mean log(α) was ‐2.4 and the mean β was 1.3. Multiple regression analysis was used to relate log(α) and β to soil properties. The resulting regression equations explained 93% of the variation in log(α) and 60% of the variation in β. The log(α) increased with decreasing aggregate size and sand content and increasing organic matter content. The β increased (indicating a narrower range of strength values) with decreasing log(α) and aggregate size. The regression equations were validated by predicting the cumulative relative frequency distribution of E for aggregates from a different site where independent measurements of E were available for comparison. A good agreement (R2 ≥ 0.91) was obtained between predicted and observed values of E.
Spring Wheat Straw Production and Composition as Influenced by Topsoil Removal
Authors: Tanaka D. L. 
Published: July 2010

AbstractWind and water erosion have resulted in reduced crop productivity and created soil management problems. Management of crop residues can be effective for soil erosion control, but influences of soil erosion on crop residue production is unknown. The purpose of this study was to determine total residue production and residue N and P concentration and content for 8 yr as influenced by topsoil removal and additions of N and P fertilizer for a spring wheat (Triticum aestivum L.)‐fallow system. Total straw production for the first increment of P increased ≈ 14% for 0.00‐ and 0.06‐m soil removal treatments compared with ≈ 33% for 0.12‐ and 0.18‐m soil removal treatments. Total straw production was increased more than total grain production with the addition of N and P fertilizer. Total straw production for 0.12‐ and 0.18‐m soil removal treatments needed at least 20 kg P ha−1 and 35 kg N ha−1 to equal or exceed that for 0.00‐m soil removal treatment with no fertilizer additions. Total straw N content decreased 33% as soil removal increased from 0.00 to 0.18 m. While total straw P content was considerably less than total straw N content, both decreased about 32% for 0.18 m compared with 0.00‐m soil removal treatments. Greater total straw N and P content for the 0.00‐m soil removal treatment was due to greater total straw production as well as greater N and P concentrations. Consequently, cycling of N and P may be reduced for eroded soils due to low quantities of residue as well as low N and P concentrations in the residues.
Aboveground Net Primary Productivity and Nutrient Content of Fertilized Plantation Sweetgum
Authors: Nelson L. E. , Shelton M. G. , Switzer G. L. 
Published: July 2010

AbstractSweetgum (Liquidambar styraciflua L.) is a commercially desirable species that can be successfully established in plantations, and information is needed concerning its genotypic variation and response to fertilization. This study evaluates various aspects of productivity and nutrition for two half‐sib seed sources in a 9‐yr‐old sweetgum plantation that was refertilized in 1981 with a total of 0, 100, 200, or 400 kg N ha−1. Foliar and litter samples were collected in the year preceding and for 3 yr following N application, and tree diameter and height were measured annually. Aboveground net primary productivity (AGNPP) of the unfertilized controls averaged 6.7 Mg ha−1 from 1981 to 1983. By contrast, maximum AGNPP for treatments receiving N were 11, 16, and 16 Mg ha−1 in 1981, 1982, and 1983, respectively. Fertilization resulted in large increases in foliar biomass and leaf area index (LAI); values were highest in 1982, and then declined in 1983. Most responses peaked at the highest application rate, but differences between 200 and 400 kg N ha−1 were generally small. Estimated apparent recovery of applied N in aboveground tissues was 75% for the 100 kg N ha−1 rate in the first and second years; however, in the third year following fertilization only 47% was accounted for. The response of the two half‐sib seed sources differed, especially in terms of woody biomass.
Effects of Incubation and pH on Soil Solution and Exchangeable Cation Ratios
Authors: Curtin D. , Smillie G. W. 
Published: July 2010

AbstractBioavailability of nutrients is dependent on their concentration in the soil solution and on exchange equilibria between solution and adsorbed nutrient species. Elucidation of these nutrient supply relationships has been hampered by the fact that soil solution is not only difficult to extract, but its composition may change significantly during storage or incubation of field‐moist soil prior to solution extraction. The objectives of this study were to evaluate the effects of liming on the exchange relationships of the major cations (Ca, Mg, K, and Na) and to determine the causes of incubation‐induced changes in their solution concentrations. For periods of up to 1 yr, soil solution was extracted from soils treated in the laboratory with CaCO3 and incubated at approximately field capacity. Solution samples were also obtained from field‐limed soils (lime applied 17 yr previously) after 1 and 10 wk of incubation in field‐moist condition. The concentrations of cations in solution increased substantially during incubation. These increases were balanced by NO−3, indicating that the changes in cation solubility were microbially mediated. In contrast to cation concentrations, cation ratios (i.e., Mg/Ca, Na adsorption ratio, K adsorption ratio) were little affected by incubation. These ratios were directly related to the composition of the exchange phase and were strongly influenced by liming. Protons generated by mineralization of organic N during incubation displaced exchangeable Ca, Mg, K, and Na in ratios that maintained the equilibrium between solution and exchangeable phases. The results suggest that a reasonable approximation of soil solution cation ratios can be obtained from exchangeable cation data.
Maize Temporal Yield Variability under Long‐Term Manure and Fertilizer Application: Fractal Analysis
Authors: Eghball B. , Power J. F. , Binford G. D. , Baltensperger D. D. , Anderson F. N. 
Published: July 2010

AbstractLong‐term experiments offer unique possibilities to study the effects of management practices on crops and soils with time. Characterizing temporal variability of grain yield provides an opportunity to distinguish between the effects of environment vs. management practices on grain yield, an important parameter. A long‐term study was established in 1912 in western Nebraska as part of a rotation study. In 1953, each plot was divided into manure (27 Mg ha−1 annually) and no‐manure sections to which fertilizer treatments of 0, 45, 90, 135, 180 kg N ha−1, and 135 kg N + 80 kg P ha−1 were applied annually. Grain yield data from 1953 to 1993 for these treatments were used for fractal analysis and determination of fractal dimension (D), which is an indication of pattern of variation. A D value close to 1 indicates dominance of long‐term variation (or trend), while a D value close to 2 indicates dominance of short‐term (year‐to‐year) variation. Grain yield increased with increasing N application rate without manure, but no response to fertilizer application was observed where manure had been applied. Fractal dimensions ranged from 1.942 to 1.996, indicating significant domination of short‐term variation of grain yield in the past 41 yr in all treatments. There was no significant difference between D values for manure or fertilizer treatments. Soil fertility amendments did not alleviate year‐to‐year variability observed in the corn (Zea mays L.) yield. Environmental factors like hail, fall freezing, and temperature variation during the growing season had a significant effect on the grain yield over the years. Although management practices can reduce temporal grain yield variability in some crops, variations in environmental factors in this study were great enough to dominate the yearly maize grain yield regardless of soil fertility amendments.
Tillage Effects on Thermal Conductivity of Two Soils in Northern British Columbia
Authors: Azooz R. H. , Arshad M. A. 
Published: July 2010

AbstractTillage management practices may affect crop growth, in part by altering soil thermal properties. Effects of long‐term conventional (CT), no tillage (NT), and modified no tillage (NTR: NT with surface residue pushed away from a 7.5‐cm zone over the seed rows) systems on soil thermal conductivity (K) and water content (θ) were evaluated on Donnelly silt loam and sandy loam (Typic Cryoboralfs). Measured K (M1) was compared with calculated K using the McInnes equation (M2) and a modified McInnes equation (M3, which included additional soil properties). The K in both soils increased with an increase in soil θ; the differences among the tillage systems decreased as the soil dried. Soil K for the silt loam was 0.81 (θ = 0.13 m3 m−3), 0.83 (θ = 0.14 m3 m−3), and 0.84 W m−1 K−1 (θ = 0.15 m3 m−3) in CT, NTR, and NT, respectively, at 25 d after planting in 1992 (a dry year). It was 1.13 (θ = 0.42 m3 m−3), 1.53 (θ = 0.50 m3 m−3) and 1.55 W m−1 K−1 (θ = 0.57 m3 m−3) in CT, NTR, and NT, respectively, at 47 d after planting in 1993 (a wet year). Soil K for sandy loam was significantly lower than for silt loam. Soil K measured by M1 and calculated by both the M2 and M3 methods were highly correlated. However, the calculated K values were somewhat improved, although not significantly, with the M3. Mean K was lower by 0.133 W m−1 K−1 in M2 and by 0.045 W m−1 K−1 in M3 than in M1 under CT on silt loam. Increased soil water storage under long‐term NT produced a greater thermal contact area and, consequently, a significantly greater K under NT and NTR than CT.
Carbon Sequestration in an Aggrading Forest Ecosystem in the Southeastern USA
Authors: Huntington Thomas G. 
Published: July 2010

AbstractAn analysis of C pools at the Panola Mountain Research Watershed (PMRW) near Atlanta, GA, indicates that aggrading forests in the U.S. Southeast are an important regional C sink. The forests in this area were cut in the early 1800s and the land was cultivated until the early 1900s, when farming was abandoned and forest regeneration began. Cultivation resulted in extensive erosion, which depleted soil C pools. The rate of soil C sequestration during the 70‐yr period of forest regeneration was estimated to be between 0.34 (standard error [SE] = 0.12) and 0.79 (SE = 0.19) Mg C ha−1 yr−1. There is a large potential for continued C accumulation in the soil at PMRW based on the difference between current measured soil C pools of 82 Mg C ha−1 at PMRW and 122 Mg C ha−1 at the nearby “undisturbed” Fernbank Forest in Atlanta, GA. The rate of C sequestration in biomass at PMRW was 1.47 Mg C ha−1 yr−1 for the regeneration period, bringing the ecosystem total to between 1.81 and 2.26 Mg C ha−1 yr−1. Carbon sequestration in temperate forest ecosystems partially mitigates the effects of increased atmospheric loading of CO2.
Mineralization, Nitrification, and Denitrification in Histosols of Northern Minnesota
Authors: Zanner C. W. , Bloom P. R. 
Published: July 2010

AbstractWater content and temperature are influences on N mineralization, nitrification, and denitrification rates in drained Histosols. To look at possible differences in these rates and to enable comparisons to mineral soils, we collected soil samples from two Minnesota Histosols planted in cultivated wild rice (Zizania palustris L.), incubated amended subsamples at 4, 7, 10, 16, and 22°C, and monitored changes in NH4‐N with time. Amendments used were plus or minus NH4 and plus or minus nitrapyrin. Net mineralization rates for Soil 1 (plus‐nitrapyrin treatment) increased from 0.30 to 2.0 mg N kg−1 dry soil d−1 from 4 to 22°C. Nitrification and denitrification occurred simultaneously, with lower denitrification than nitrification rates. Nitrification rates (determined from the zero‐order plots of the disappearance of NH4‐N with time in the plus‐NH4 samples) increased from 4 to 22°C (Soil 1, 17–99 mg N kg−1 d−1; Soil 2, 11–40 mg N kg−1 d−1). Soil 1 nitrified faster than most mineral soils; Soil 2 was comparable with many mineralsoils. Denitrification rates for Soil 1, determined from the decrease in total inorganic N (NH4‐N + NO3‐N; plus‐NH4 samples), increased from 9 mg N kg−1 d−1 at 4°C to 53 mg N kg−1 d−1 at 22°C. There were no differences between the two experimental water contents (corresponding to soil water pressure heads of ‐25 and −50 cm) for any of these rates. The high water‐holding capacity of Histosols increases the potential for simultaneous nitrification and denitrification and will result in removal of native and applied NH4 from the system, thus affecting N use efficiency of both wild rice and upland crops grown on Histosols.