bluuebunny/crossref_metadata_2025_split huggingface dataset:
Corn Root Distribution and Yield Response to Subsoiling for Paleudults Having Different Aggregate Sizes
Authors: Vepraskas M. J. , Wagger M. G. 
Published: July 2010

AbstractChisel plowing loosens dense root‐restricting layers within 0.25 m of the soil surface, while subsoiling can be used to routinely loosen dense layers down to a depth of approximately 0.45 m. Selecting one tillage method over the other to maximize yield is problematic because the lower depth of a root‐restricting layer is often difficult to determine precisely if the layer contains structural aggregates. We hypothesized that the ability of roots to penetrate dense soil layers is related to the size of aggregates in the dense layers. Therefore, this study compared root distributions for chisel plowed and subsoiled tillage treatments and related them to soil properties and corn (Zea mays L.) grain yield for soils having dense layers that varied in their aggregate size. Yields and root distributions were determined for the two tillage treatments on eight Typic and Arenic Paleudults. Each site had a dense, high‐strength soil layer below the depth of chiseling. Subsoiling significantly (P = 0.10) increased yields over chisel plowing at five sites. At four of these sites, the proportion of roots between depths of 0.3 and 1.0 m in the chiseled treatment was low (≤0.20) due to the root‐restricting layer extending below the depth of chiseling. Although all sites had pan‐like layers, which were characterized on the basis of bulk‐density and cone‐index measurements, only layers whose ped meanweight diameter was ≤1.2 mm resulted in root proportions being ≤0.20 in the chiseled treatment. These virtually nonaggregated layers also tended to have low amounts of plant‐available water (<0.12 m3 m−3). To adequately characterize root‐restricting layers that reduced yield in these soils, some measure of subsurface aggregation or a correlated property such as plant‐available water or texture had to be evaluated along with bulk density or cone index.
Nitrogen Mineralization Potentials of Shrub‐Steppe Soils with Different Disturbance Histories
Authors: Bolton H. , Wildung R. E. , Smith J. L. 
Published: July 2010

AbstractDisturbance of shrub‐steppe soils and changes in the dominant plant cover may alter soil N‐cycling processes. The mineralization of organic N to plant‐available forms is an important component of the N cycle in shrub‐steppe soils. Therefore, the soil N‐mineralization potential (No) was determined for two arid ecosystems, an undisturbed perennial shrub‐steppe and an annual grassland, which was initially shrub‐steppe and has been an annual grassland since farming disturbance in the 1940s. The soils at both study sites are similar and are classified as coarse‐silty, mixed, mesic Xerollic Camborthids. Soils were sampled at 0‐ to 5‐, 5‐ to 10‐, and 10‐ to 15‐cm depths, before plant growth in the spring, underneath big sagebrush (Artemisia tridentata Nutt.) bluebunch wheatgrass [Elytrigia spicata (Pursh) D.R. Dewey], Sandberg bluegrass (Poa secunda J.S. Presl), and soil crust at the perennial site and underneath downy brome (Bromus tectorum L.) at the annual grassland site. The 0‐ to 5‐cm soil depth from underneath all plants had the highest No. The No at the 0‐ to 5‐cm soil depth was influenced by plant type and decreased in the order P. secunda, B. tectorum, A. tridentata, E. spicata, and soil crust. The No decreased with soil depth until the 10‐ to 15‐cm soil depth, when all soils had the same value. The production of plant‐available N will, therefore, be largely limited to the soil surface, and losses from the first 5 cm of soil will be detrimental to both ecosystems. Spatial distribution of these plant species in the arid ecosystem result in “islands” where enhanced N mineralization occurs. When plant cover was used to compute a site‐specific No for the perennial shrub‐steppe and the annual grassland, a similar value was obtained indicating similar dynamics of soil N processes at these two sites.
Coupled Water and Heat Transport in Ridged Soils
Authors: Benjamin J. G. , Ghaffarzadeh M. R. , Cruse R. M. 
Published: July 2010

AbstractStudy of ridge‐tillage effects on the soil environment has been impeded by the lack of models to adequately describe water and heat movement in the ridge system. The ridge system introduces many nonuniform characteristics into the field problem, such as variable solar radiation across the soil surface, unevenly distributed surface mulches, and variable water and heat transport properties caused by ridge construction or wheel traffic. A finite‐element model was developed to simulate coupled water and heat flow in ridge systems. The finite‐element solution scheme was chosen because of the ease by which nonuniform soil transport properties and nonuniform boundary conditions can be included in the problem specifications. Model predictions of soil water and temperature were compared with field measurements for two ridge configurations. Predicted and measured average daily temperatures over a 10‐d period were within 1 °C and water contents were within 0.02 m3 m−3 for 80% of the measurements.
Organic Selenium Distribution in Selected California Soils
Authors: Abrams M. M. , Burau R. G. , Zasoski R. J. 
Published: July 2010

AbstractThe distribution of organic Se was determined in seven soils from central California. Six of these soils (one Typic Pelloxerert, three Typic Torriorthents, one Vertic Torriorthent, and one Entic Chromoxerert) were in a toposequence from an area thought to be relatively high (>1000 µg total Se kg−1) in native Se. The seventh soil, Yolo (a Typic Xerorthent), thought to be low in native Se, was included for comparison. Three of the soils in the toposequence had total Se levels less than 1000 µg kg−1; the basin soil (Tachi; Typic Pelloxerert) had less than the Yolo soil. A solution of 0.1 M NaOH/0.1 M Na4P2O7 (alkaline pyrophosphate) extracted an average of 12% of the total Se, but this ranged from 5 to 32%. Organic Se accounted for 50% or more of the NaOH‐Na4P2O7 extractable Se in all but the poorly drained Ciervo clay (Typic Torriorthent), which had about 40% in an organic form. Extracted organic Se compounds were fractionated into humates and hydrophobic and hydrophilic fulvates. Selenium associated with hydrophobic fulvates was high in the soils of intermediate toposequence elevation. Selenomethionine was identified by gas chromatography/mass spectrometry in the hydrophilic fulvate fraction of the Yolo soil and in three soils from the toposequence. The high percentage of extractable Se associated with organic matter in these soils represents a pool of potentially plant‐available Se.
Procedure for Determining Sodium‐Calcium Selectivity in Calcareous and Gypsiferous Soils
Authors: Amrhein C. , Suarez D. L. 
Published: July 2010

AbstractA procedure to determine the exchanger‐phase composition (and thus the Na/Ca selectivity) of calcareous and gypsiferous soils was developed and tested on three soils and three phyllosilicate minerals. The procedure corrects for anion exclusion and mineral weathering by measuring the Cl, SO4, and HCO3 in the soil solution and in the extracting solution. Anion exclusion was found to be significant in the montmorillonite system, but generally less than 10% of the cation‐exchange capacity in the soil, illite, and vermiculite systems. Mineral weathering contributed significantly to the total extracted Ca. Thus, exchangeable‐Ca values were overestimated by 30 to 500% in the gypsiferous soils and 3 to 20% in the calcareous soils when weathering was neglected. The proposed method allows the determination of cation‐exchange capacity, exchangeable‐cation composition, and anion exclusion at any solution composition, concentration, and pH.
Ethylene Accumulation in Soil in Response to Organic Amendments
Authors: Arshad Muhammad , Frankenberger W. T. 
Published: July 2010

AbstractOne of the major factors affecting ethylene (C2H4) accumulation in soil is the availability of organic substrates. Various organic compounds were screened for their stimulatory effect on C2H4 accumulation in soil. Since L‐methionine (L‐met), a sole precursor of C2H4 synthesis in plants, is also an excellent precursor for microbial biosynthesis of C2H4, all the compounds tested were added on a C‐equivalent basis with respect to 1 g L‐met kg−1 soil. Incubation was carried out under ambient conditions (24 ± 3 °C) for 14 d and the soil was maintained at field capacity (−33 kPa). Among the 63 compounds tested, the majority of amino acids, organic acids, carbohydrates, proteins, alcohols, and met analogs promoted C2H4 generation to a greater degree than did the unamended soil. Use of 1‐aminocyclopropane‐1‐carboxylic acid (acc) enhanced C2H4 synthesis much more than any other treatment (2400‐fold over the unamended nonsterile control). Of the five vitamins tested, inositol was the most effective in promoting C2H4 production. L‐Ethionine (L‐eth) was an excellent precursor among the five met analogs. Nonbiological production of C2H4 was observed only upon treatment with L‐met, L‐cysteine, acc, ethanol, and L‐eth, which were 7.9, 19.0, 3.0, and 4.2% and 2.1‐fold, respectively, of the total C2H4 detected under nonsterile amended conditions. Since the majority of these compounds are excreted by plant roots, the rhizosphere may be an active site for C2H4 generation.
Unbuffered and Buffered Salt Methods for Exchangeable Cations and Effective Cation‐Exchange Capacity
Authors: Amacher M. C. , Henderson R. E. , Breithaupt M. D. , Seale C. L. , LaBauve J. M. 
Published: July 2010

AbstractThis study was conducted to determine if a single unbuffered salt extractant for exchangeable bases and Al could be used in place of a buffered salt extractant for exchangeable bases and an unbuffered salt extractant for exchangeable Al. Barium chloride and a mixed NH4Cl‐BaCl2 extractant were compared with NH4OAc for determining exchangeable bases and with KCl for determining exchangeable Al in soils. In general, BaCl2 extracted less exchangeable K than either NH4OAc or NH4CL‐BaCl2. The NH4CL‐BaCl2 extractant was equivalent overall to NH4OAc for extracting exchangeable bases and to KCl for extracting exchangeable Al, although less K was extracted by NH4Cl‐BaCl2 at low levels of K for some Coastal Plain soils. The NH4Cl‐BaCl2 extractant can be used by soil‐test or soil‐characterization labs as a simple one‐step extractant in place of NH4OAc and KCl for the determination of exchangeable cations and effective cation‐exchange capacity of soils.
Soybean Yield Response to Various Depths of Erosion on a Fragipan Soil
Authors: Rhoton F. E. 
Published: July 2010

AbstractErosion of soils with limited profile thickness can reduce soil productivity to the point that crop yields are no longer profitable. The intention of this study was to determine the effects of progressive erosion on the productivity of a fragipan soil. Soybean [Glycine max (L.) Merr.] was the indicator crop. Twelve experimental plots were installed at each of the three differentially eroded sites on a Grenada silt loam (fine silty, mixed, thermic Glossic Fragiudalf). Average depth to fragipan ranged from 16 to 63 cm. Soil P and K levels were adjusted to 140 and 280 kg ha−1, respectively, on one‐half of the plots, and pH was adjusted up to 6.5. The remaining plots received no lime or fertilizer. No significant differences were found for yield between the two fertility treatments. Average grain yields for the 3‐yr study were 2417, 1953, and 1877 kg ha−1 at the slight, moderate, and severely eroded sites, respectively. The lowest yields, for these same plots were 2286, 1773, and 1549 kg ha−1 recorded in 1986, when soil water content during pod‐fill stage was least. Depth to fragipan accounted for 56, 60, and 67% of the variability in grain yields for 1984, 1985, and 1986, respectively. A yield‐depth‐to‐fragipan curve derived from these data showed that the greatest grain‐yield reduction per increment of soil loss occurred as soil depth decreased from 60‐ to 50‐cm. This indicates that, to maintain productivity on these soils, management systems should be designed to preserve a minimum soil thickness above the fragipan of ∼60 cm.
Bare Fallowing on Sandy Fields of Niger, West Africa
Authors: Payne W. A. , Wendt C. W. , Lascano R. J. 
Published: July 2010

AbstractAn experiment was conducted in three rainfall zones of Niger, West Africa, to evaluate the potential of mulched and nonmulched bare fallow to conserve water in deep, sandy soils. Water content of adjacent bare and cropped experimental plots was monitored with a neutron probe at three sites during the 1985 growing season and the subsequent dry season. Experimental sites, with soil type and 1985 rainfall, were near the villages of Chikal (Ustic Torripsamment; 233 mm) N'Dounga (Psammentic Paleustalf; 344 mm), and Kala Paté (Alfic Ustipsamment; 428 mm). Cropped plots were managed using traditional low‐input practices. Bare plots were weeded using a traditional, shallow cultivating hoe. At the end of the growing season, portions of the bare and cropped plots were mulched with millet stalks at a rate of 25 Mg ha−1. At the end of the dry season, no significant increases in profile water storage were detected in mulched treatments. Increased soil water storage in the upper 1.65 m of bare fallowed plots toward the end of the dry season was 16.5 ± 10.5 mm at Chikal, and 40.6 ± 17.9 mm at N'Dounga. No increase in storage was observed in bare fallowed plots at Kala Paté. Mean increases in storage efficiency at Chikal and N'Dounga were 7.1% and 11.8%, respectively. Position of the zero‐flux boundary during the dry season and profile water distribution toward the end of the dry season indicate that drainage was substantial at all sites. However, large losses due to evaporation are also possible, due to high evaporative demand during the dry season. Data obtained in this study suggest that bare fallowing, with and without dry‐season mulching, is an inefficient means of water conservation for these soil systems. A possible application of bare fallow is in sandy soils underlaid by laterite in high‐risk, low‐rainfall zones of the Sahel if accompanied by adequate erosion prevention.
Low‐Molecular‐Weight Organic Acids in Selected Forest Soils of the Southeastern USA
Authors: Fox T. R. , Comerford N. B. 
Published: July 2010

AbstractOrganic acids can form stable complexes with metals and therefore can affect metal solubility and speciation. The low‐molecular‐weight aliphatic organic acids extracted in water and present in soil solution from O, A, Bh and Bt horizons from a group of forested Utlisols, Entisols and Spodosols were identified by high performance liquid chromatography (hplc). Oxalic acid was found in all samples and was present generally in the highest concentrations. Oxalate concentrations in soil solution ranged from 25 to 1000 µM and were greater in the Bh and Bt horizon soils than in the A horizon soil. High concentrations of formic acid were also identified in most soils, ranging from 5 to 174 µM in soil solution. Trace amounts of citric, acetic, malic, lactic, aconitic, and succinic acids were detected in some samples. In a greenhouse pot study, the concentrations of low‐molecular‐weight organic acids in the rhizosphere of slash pine (Pinus elliottii Engelm.) seedlings growing in A, Bh, and Bt horizons from an Ultic Haplaquod were compared with the concentrations in the nonrhizosphere soil. The observed concentrations were approximately an order of magnitude greater than in native soils. Oxalate was the only low‐molecular‐weight organic acid identified in the non‐rhizosphere soil. The suite of organic acids identified in the rhizosphere was more complex than in the bulk soil. In the rhizosphere, high concentrations of both oxalate and formate were detected, along with trace amounts of citric, acetic, and aconitic acids. Since oxalate forms stable complexes with Al, the presence of large concentrations of oxalate may affect P availability in these soils.
Dicyandiamide Influence on Uptake of Preplant‐Applied Fertilizer Nitrogen by Rice
Authors: Wilson C. E. , Wells B. R. , Norman R. J. 
Published: July 2010

AbstractA field study was conducted to determine the influence of dicyandiamide (dcd) on fertilizer N recovery from soil and rice (Oryza sativa L.) when 15N‐labeled urea was applied preplant (20 g N m−2). Microplots consisted of polyvinyl chloride pipes, 20.3 cm in diameter, driven into the soil. ‘Newbonnet’ rice was seeded, thinned to five plants per microplot, and flooded when the plants were at the four‐ to five‐leaf stage of development. Soil and plant samples were analyzed for N every 7 d for 49 d following application (plant samples beginning at 35 d) and then every 14 d. Prior to flooding, urea with dcd reduced nitrification. With dcd, 51 and 8% of the applied N was recovered at flooding as NH4 and NO3, respectively, compared with 8 and 23%, respectively, without dcd. Dicyandiamide, by maintaining more fertilizer N in the NH4 form, appeared to cause greater immobilization of the fertilizer N than when dcd was not applied (19 and 15% of applied N, respectively). More fertilizer N was recovered in the shoots and roots (17.2 and 2.9% of applied N, respectively) when urea was applied with dcd than when used alone (9.7 and 1.9%, respectively). However, fertilizer N recovered in the panicles and grain yield were not significantly different between treatments. Fertilizer N recovered in the total plant increased significantly from 35 to 42 d, after which no further changes occurred. However, total plant N and native soil N uptake increased significantly throughout the growing season.
Phosphorus Release in Sodium Ion Dominated Soils
Authors: Gupta Raj K. , Singh R. R. , Tanji K. K. 
Published: July 2010

AbstractCalcareous sodic soils having high sodicity and high pH often maintain high solution P concentration. The effect of high exchangeable Na, high pH, and alkali anions and carbonates on the release of inorganic P was investigated in soils representing the three major benchmark sodic soil series found in the Indo‐Gangetic plains of India. Sodium saturation of the exchange complex, high pH, carbonate ions, and low electrolyte level shifted the solid P‐solution P equilibrium in favor of maintenance of high P concentrations in aqueous solutions. In the sodic soil environment, release of P can be accounted for by the dissolution of various forms of Ca‐P compounds at high alkalinity and pH. Cultivation of alkali soils improves the organically bound P forms. Together or in combination, high sodicity, high pH, and the presence of carbonate ions at low salinity markedly increased P desorption and P availability in sodic soils.
Mineralization of Nitrogen from Nitrogen‐15 Labeled Crop Residues and Utilization by Rice
Authors: Norman R. J. , Gilmour J. T. , Wells B. R. 
Published: July 2010

AbstractThe availability of N from the residues of the previous crop to the subsequent rice (Oryza sativa L.) crop is largely unknown. The objectives of this study were to (i) measure the mineralization of N from 15N‐labeled rice, soybean (Glycine max L.), and wheat (Triticum aestivum L.) residues and the uptake by a subsequent rice crop; and (ii) compare the 15N tracer method with the standard fertilizer‐N response method used in field studies to quantify the N contribution from the crop residue to the next crop. Nitrogen mineralization from decomposing crop residues was measured by soil sampling prior to seeding the rice crop and after seeding by plant sampling the rice at maturity. The minimum estimate of the amount of residue N mineralized from the time of residue incorporation until rice harvest was 9, 52, and 38% of the rice, soybean, and wheat residue N, respectively. The amount of residue N recovered in the rice crop was 3, 11, and 37% of the rice, soybean, and wheat residue N, respectively. The lower the C/N ratio and the higher the amount of N in the residue, the lower was the amount of residue N recovered in the soil organic fraction at harvest and the higher was the amount of residue N mineralized. The 15N tracer method compared favorably with the fertilizer N response method when the uptake efficiency of the fertilizer N was taken into account.
Soil‐Geomorphic Relations on the Blue Ridge Front: II. Soil Characteristics and Pedogenesis
Authors: Graham R. C. , Buol S. W. 
Published: July 2010

AbstractSoils along two mountain slope transects in mica gneiss and schist terrane were studied to better understand soil distribution and genesis on the Blue Ridge Front landscape in North Carolina. Soils may form entirely in residuum or colluvium, but on most slope positions they have developed in both materials. The colluvial/residual nature of soils is related to geomorphic position and has a strong influence on soil properties and the evolution of the soils. Soils on upper slopes have a significant residual component as a result of weathering into the parent rock. Low slope positions are sites of accumulation, resulting in deep soils formed in colluvium. Dystrochrepts, or very weakly expressed Hapludults, have developed entirely in colluvium, whereas soils with at least a partial component of residuum are Hapludults. Soils on landscape positions down wearing into fresh mica gneiss or schist are in the micaceous mineralogy class, whereas those in highly weathered colluvium and in very stable residuum (i.e., nearly level summit positions) have been depleted of mica and are in the oxidic class. A conceptual model relating slope processes to pedogenesis is proposed in which colluvial transport interrupts the orderly in situ progression of residual soil development. The genesis and distribution of soils are best understood when studied in landscape contexts, rather than at the level of individual pedons or classification units.
Water Balance Estimation Model: Field Test and Sensitivity Analysis
Authors: Chopart J. L. , Vauclin M. 
Published: July 2010

AbstractA simplified, capacity‐based simulation model has been developed to predict components of the field water balance. This requires only daily information such as the atmosphere evaporative demand and soil‐wetting events, maximum available soil water storage, and root growth characteristics, as well as crop and soil parameters. Actual evapotranspiration was modeled using Eagleman's parameterization. The model was tested for upland rice grown on a 3500‐m2 field plot, and on an undisturbed lysimeter. The predicted actual evapotranspiration (AET) and drainage (D) at the bottom of the soil profile matched the lysimeter data. Also, the model predicted reasonably well the field soil water content data, which were obtained at 15 sites. In the latter case, the root mean square error was about 16% for the seasonal AET, and 19% for D. Errors were within the limits of experimental uncertainties expected when such measurements are analyzed by Darcy's law. The results of a sensitivity analysis with respect to changes in parameter inputs show that the model is physically realistic. However, the sensitivity depends strongly on the supply of water in the soil. This clearly justifies the need to simulate the root‐zone water balance as a time‐dependent process, especially if there is a practical interest in accurate prediction during drought periods.