bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simple Linear Model for Calibration of Time Domain Reflectometry Measurements on Solute Concentration
Authors: Kim D. J. , Vanclooster M. , Feyen J. , Vereecken H. 
Published: July 2010

AbstractThe lack of an adequate method for calibration of time domain reflectometry (TDR) measurement on bulk soil electrical conductivity is a limiting factor, especially for field‐scale solute transport study. This study investigated an appropriate calibration method that can be applied to horizontally positioned TDR probes in situ. A nonlinear model (RM) has been proposed assuming a two‐pathway conductance. Using the quadratic form, the RM equated electrical conductivity in the immobile phase of soil solution (ECws) in a series‐coupled pathway with electrical conductivity in the mobile phase of soil solution (ECwc) in a continuous pathway. We related bulk soil electrical conductivity (ECa) to electrical conductivity of soil water (ECw), assuming constant ECws during breakthrough. This resulted in a linear relationship between ECa and ECw. The linear relation, termed here simple linear model (SLM), was tested using experimental data obtained from soil columns. Laboratory breakthrough experiments were performed on short and large columns by applying a pulse input of solute. At the end of breakthrough, separate calibration experiments were performed using a step input of solute. Both RM and SLM were compared with the step input calibration method (SIM) as a reference method. Results show that the SLM is better than RM in terms of mass recovery. In addition, parameters of the solute transport model were not affected within 20% of uncertainty in the slope coefficient of the SLM when compared with the reference method. Advantages of the SLM are that it has an identical equation form to the SIM but less effort is required, especially for soil columns showing preferential flow, and it can be readily applied to field conditions.
Tillage and Crop Residue Effects on Carbon Dioxide Evolution and Carbon Storage in a Paleustoll
Authors: Dao Thanh H. 
Published: July 2010

AbstractCultivation, high temperatures, and a semiarid climate accelerate organic carbon (OC) loss and weaken soil structure in the Southern Plains. Our hypothesis was that differences in soil C storage attributable to tillage method are related to differences in soil respiration and microbial biomass dynamics. Carbon dioxide fluxes following wheat (Triticum aestivum L.) harvest were determined in Bethany silt loam (fine, mixed, thermic Pachic Paleustoll). Treatments were moldboard plowing (MP) and no‐till (NT) at two residue rates (0 and 4 Mg ha−1). Soil respiration was measured from 1 August to 30 September using closed chambers. Peak CO2‐C flux densities reached 1.3 g m−1 d−1 in NT for 2 d and stabilized at 0.4 g m−1d−1. The CO2‐C evolution peaked at 4.1 and 2.9 g m−1d−1 in MP with and without buried residues, respectively. After 3 d, they decreased to a steady state of 0.4 g m−1d−1. Daily average temperatures in the 0‐ to 0.2‐m depth were 0.5 to 3.4°C higher under MP than NT, increasing microbial adenosine triphosphate (ATP), biomass C, and CO2‐C fluxes. The proportion of soil OC respired in the 60‐d period was twice as great under MP than NT, accounting for 0.42 to 0.58% and 0.19 to 0.22%, respectively. After 11 yr, NT soil OC showed increases of 65, 17, and 7% over the MP for the 0‐ to 0.05‐m, 0.05‐ to 0.1‐m, and 0.1‐ to 0.2‐m depths, respectively. Tillage and residue incorporation enhanced C mineralization and atmospheric fluxes, suggesting that tillage intensity should be decreased to reduce C loss.
Controlled Environment Potentionstat to Study Solid‐Aqueous Systems
Authors: Peterie Robert A. , Sims Ronald C. , Grossl Paul R. 
Published: July 2010

AbstractWe designed a redox apparatus that controls electropotenial (Eh), pH, and temperature. The apparatus is fully automated and can be assembled from equipment found in most soil analytical laboratories. The reactor can maintain environmental conditions used to evaluate the chemical fate of contaminants under natural conditions (natural attenuation) or adjust them to a new steady state to evaluate the effect of engineered remediation on a subsurface system. It can operate within a wide range of redox potential values (−400 to 400 mV) and at any pH value. The stability and accuracy of the instrument was tested by performing Eh‐pH titrations on MnO2 suspensions. Results indicated that Eh could be controlled within 1 to 2 mV, pH within 0.05 to 0.1 unit, and temperature within 0.1°C for weeks or months.
Diffusion Methods for Automated Nitrogen‐15 Analysis using Acidified Disks
Authors: Khan S. A. , Mulvaney R. L. , Brooks P. D. 
Published: July 2010

AbstractDiffusion methods are often employed to speciate inorganic N in soil extracts or water for N‐isotope analysis with automated mass spectrometers. Diffusion is usually carried out in a plastic specimen container with an acidified filter disk to collect the diffused NH3. Owing to the small size of the container and the limited surface area of the acidified disk, a diffusion period of 6 to 14 d is generally required, and even then recovery may be incomplete. Simple diffusion methods were developed that use two acidified disks in a 473‐mL (1‐pint) wide‐mouth Mason jar. Diffusions with MgO to recover NH4‐N, or with MgO plus Devarda's alloy to recover (NH4 + NO3)‐N or (NH4 + NO3 + NO2)‐N, were performed from 5 to 100 mL of either 2 or 4 M KCl. Quantitative recovery of 150 µg of N was achieved in 1 to 7 d at 20 to 25°C, and in 2 to 14 h by heating on a hot plate at 45 to 50°C. Isotopic analyses of labeled soil extracts were accurate to within 5%, as determined by isotope‐dilution calculations. Incomplete diffusion led to <2% error in analysis of NH4‐N, whereas serious error occurred in analysis of (NH4 + 15NO3)‐N.
Soil Organic Matter Dynamics after Addition of Nitrogen‐15‐Labeled Leucaena and Dactyladenia Residues
Authors: Vanlauwe B. , Sanginga N. , Merckx R. 
Published: July 2010

AbstractQuantification of the movement of residue N through various biologically meaningful soil organic matter (SOM) fractions is essential in low‐input tropical cropping systems for the development of management practices aimed at optimizing N‐use efficiency. The flow of N derived from 15N‐labeled leucaena [Leucaena leucocephala (Lam.) de Wit] and dactyladenia [Dactyladenia barteri (Hook f ex Oliv.) Engl.] leaf residues was followed through the SOM of different particle‐size fractions during 858 d. A bioassay study with maize (Zea mays L.) was carried out to assess the availability of residue‐derived N (RDN) incorporated in the particle‐size fractions. At 53 d after residue application (DAA), most of the RDN was found in the fraction between 0.250 and 2 mm (O250) in the leucaena treatment and in the fraction >2 mm and the surface litter (O2000 + SL) in the dactyladenia treatment. The RDN content of all fractions <0.250 mm was significantly higher in the leucaena than in the dactyladenia treatment up to 471 DAA. The proportion of the total amount of RDN recovered in the fractions <2 mm shifted toward the smaller particle‐size classes near the end of the experiment. Highly significant (P < 0.001) relationships between RDN present in the particulate organic matter (POM) and uptake of RDN by maize indicated the relatively high availability of RDN in the POM. Fractionating the SOM pool into different particle‐size classes yielded useful information on the relative contributions of the different SOM fractions to N turnover and availability. This information is needed in identifying SOM pools with direct relevance to plant nutrition in low‐input cropping systems.
Improving the Berthelot Reaction for Determining Ammonium in Soil Extracts and Water
Authors: Rhine E. D. , Mulvaney R. L. , Pratt E. J. , Sims G. K. 
Published: July 2010

AbstractColorimetric methods based on the Berthelot reaction are used widely for quantitative determination of NH4‐N in biological and environmental samples. Studies to evaluate phenol and salicylate, the most commonly used chromogenic substrates, revealed minor interferences by metallic cations, whereas up to a threefold shift in absorbance was observed with 38 diverse N‐containing organic compounds. Interferences differed markedly between phenol and salicylate. The possibility of a simple correction was precluded by the fact that interferences were both positive and negative, and depended on the temperature during color development and the concentration of NH4‐N. Fourteen compounds were evaluated as alternatives to phenol and salicylate, of which the Na salt of 2‐phenylphenol (PPS) proved to be the most promising. Using PPS, macro‐ and microscale batch methods and an automated flow‐injection method were developed. These methods are simple, convenient, and sensitive. Using the PPS microscale method, for which the limit of detection is 0.17 mg NH4‐N L−1, recovery of NH4‐N added to soil extracts ranged from 98 to 104%, with a coefficient of variation of 1.4 to 2.7%. As with phenol and salicylate, precipitation of metal hydroxides was observed. Precipitation was controlled by chelation with citrate rather than ethylenediaminetetraacetic acid (EDTA), which suppressed color development by preventing monochloramine formation. Compared with Berthelot methods that use phenol or salicylate, interference by amino acids was decreased by up to 10‐fold. Interference by other organic N compounds was virtually eliminated.
Design of Porous Media for Optimal Gas and Liquid Fluxes to Plant Roots
Authors: Jones Scott B. , Or Dani 
Published: July 2010

AbstractThe selection of plant growth media remains an empirical endeavor often focusing on available materials rather than on the physical principles that govern water retention and flow. Apparent water‐ and O2‐induced stresses affecting plant growth experiments in microgravity (10−3–10−6 g0) have prompted the need for refinement of selection criteria for optimal growth media. The objective of this work was to develop a comprehensive approach for selecting the physical characteristics of plant growth media that optimize the dynamic availability of liquids and gases to plant roots. Physically based models describing the relationship between content and fluxes of liquids and gases were written in terms of media parameters and were used to cast a multi‐objective optimization problem. Plant physiological target values, growth container design, and other system considerations provided constraints for the optimization problem. The optimized media parameters designated a pore‐size distribution (psd) that is scaled to a corresponding particle‐size distribution (PSD) by inversion of the Arya and Paris model. The iterative process resulted in an average scaling of psd to PSD and led to the synthesis of an optimal medium. Sand and glass bead mixtures were well matched to the optimized media characteristics resulting from the optimization procedure. This methodology is amenable to horticultural, greenhouse, and research applications where optimal porous media design is of value.
Inexpensive Automated Paging System for Use at Remote Research Sites
Authors: Sargent S. L. , Dey W. S. , Keefer D. A. 
Published: July 2010

AbstractThe use of a flow‐activated automatic sampler at a remote research site required personnel to periodically visit the site to collect samples and reset the automatic sampler. To reduce site visits, a cellular telephone was modified for activation by a datalogger. The purpose of this study was to demonstrate the use and benefit of the modified telephone. Both the power switch and the speed‐dial button on the telephone were bypassed and wired to a relay driver. The datalogger was programmed to compare values of a monitored environmental parameter with a target value. When the target value was reached or exceeded, the datalogger pulsed a relay driver, activating power to the telephone. A separate relay activated the speed dial, dialing the number of a tone‐only pager. The use of this system has saved time and reduced travel costs by reducing the number of trips to the site, without the loss of any data.
Nitrous Oxide Emission From Long‐Term Manured Soils
Authors: Chang C. , Janzen H. H. , Cho C. M. 
Published: July 2010

AbstractLand‐applied manure is a significant source of N2O, but current estimates of emission are based on laboratory studies or field measurements from short‐term application studies. Manure is often repeatedly applied to the same field for long periods, however. Our objectives were to determine annual N2O emission from a Typic Haploboroll soil that received 21 annual applications of solid feedlot manure at rates of 0, 60, 120, and 180 Mg ha−1 (wet weight), and to relate the emission rates to environmental conditions. Nitrous oxide fluxes from soil were measured weekly from 10 Nov. 1993 until 27 Oct. 1994. Annual N2O emission increased with manuring rate and reached 56 kg N ha−1 yr−1 at the highest manuring rate (<1 kg N ha−1 in the control). The N2O emission rate was not related to any single environmental factor, apparently because the N2O emission rate is not only controlled by rates of N2O production, but also by its rate of diffusion. The N2O emission rates were highest in early spring, but fluxes of N2O were also significant in winter, perhaps associated with freeze‐thaw events. The N2O emission rates observed in our study are similar to N‐fertilizer or combining N‐fertilizer and manure application, but they are higher than other short‐term studies with similar manure. These results probably reflect the accumulation of NO3 and organic matter from repeated manuring and suggest that the N2O emission from long‐term manured soils may be underestimated by quantifying fluxes from short‐term manuring studies.
A Volumetric Inorganic Carbon Analysis System
Authors: Wagner S. W. , Hanson J. D. , Olness Alan , Voorhees W. B. 
Published: July 2010

AbstractMeasurement of soil organic carbon (OC) is slow and expensive when inorganic carbon (IC) is present. Our objective was to develop an automated volumetric IC analysis system, thus allowing OC to be determined by difference. The system was developed by combining a pressure transducer with a personal computer (PC), data acquisition board, and appropriately developed software. The volumetric system was compared with combustion, neutralization, and sum of Ca + Mg techniques for samples containing up to 60 g kg−1 IC. Correlations between methods showed linear agreement (r2 ≥ 0.994). The volumetric system was more precise for relatively low IC amounts (2.0 g kg−1) and could process 20 samples h−1.
Subalpine Loamy Spodosols in Taiwan: Characteristics, Micromorphology, and Genesis
Authors: Li Shin‐Yi , Chen Zueng‐Sang , Liu Jen‐Chyi 
Published: July 2010

AbstractFour subalpine loamy Spodosols with illuvial clay in the spodic horizons were selected for study to understand their characteristics, micromorphology, and genesis. These Spodosols, located in central Taiwan, are covered by coniferous vegetation, receive high levels of precipitation, and occupy gentle slope positions at elevations >2400 m. Soil textures, which range from loam to clay, are finer than those of Spodosols formed in temperate regions. The pedogenic products in the soils of the study area are mainly organo‐metallic complexes or illuvial clay mixed with organo‐metallic complexes in the spodic horizons. Typical micromorphological features in the spodic horizons of these Spodosols revealed infillings of organo‐Fe complexes, argillans, or argiferrans along the irregular voids. The four selected pedons have loose spodic horizons where illuvial clay also has accumulated. The large amounts of spodic materials and illuvial clays in the spodic horizons indicate that podzolization and clay accumulation were the two dominant pedogenic processes. Some of the illuvial clay translocated into the spodic horizons is mixed with organo‐Fe (or ‐Al) complexes along the irregular voids of the spodic horizons. This may also have resulted in a lack of well‐oriented clay in these horizons despite the occurrence of large amounts of illuviated clays.
Measuring Nutrient Depletion by Roots of Mature Trees in the Field
Authors: Escamilla J. A. , Comerford N. B. 
Published: July 2010

AbstractThe kinetics of ion uptake by roots is of fundamental importance to the study of the mineral nutrition of plants and the definition of an “effective” root system. Our understanding of ion uptake by roots comes from studies of transport phenomena using new, white roots of young plants. Much less is known about nutrient absorption by older roots of perennial plants, where these root may encompass >90% of the fine root system. However, studies of nutrient uptake in situ are complicated because of plant size, age, and access to the root system. This is also true when considering roots of mature trees. The objectives of this study were to: (i) present the design and construction of a system suitable for measuring nutrient uptake by lateral root systems of mature trees in the field, and (ii) test the system under laboratory and field conditions. We developed a system for root regeneration that allows easy access to roots while minimizing disturbance. The design includes: (i) a system for gas supply; (ii) a root chamber; and (iii) a Mariotte flask system. The system was tested under laboratory and field conditions. Laboratory results showed that all components of the nutrient uptake system were inert to P and K. Under field conditions when the chambers were aerated, P and K were absorbed from the nutrient solutions. In comparison, when roots were gassed with N2 (hypoxic conditions), P was still absorbed but K absorption was inhibited.
Recent and Long‐Term Organic Soil Accretion and Nutrient Accumulation in the Everglades
Authors: Craft C. B. , Richardson C. J. 
Published: July 2010

AbstractOrganic soil accretion and nutrient accumulation were measured in the northern, central, and southern Everglades to evaluate the effects of anthropogenic nutrient and hydroperiod alterations on organic C and nutrient storage during the past century. Six soil cores (euic, hyperthermic Typic Medisaprists) were collected from nutrient‐enriched (Water Conservation Area [WCA] 2A) and unenriched locations. Soil depth increments were analyzed for radionuclides (137Cs, 210Pb, 14C), bulk density, and nutrients (C, N, P, S) to estimate recent (30‐yr) and long‐term (100‐yr) organic soil accretion and nutrient accumulation. Since WCA 2A was completely impounded in the early 1960s, organic soil accretion in northern WCA 2A (5.8–6.7 mm yr−1) increased by three to five times compared with before 1960 (1.9 mm yr−1) or with unenriched areas within and outside of WCA 2A (1.4–1.6 mm yr−1). Nutrient accumulation in the enriched area of WCA 2A since 1960 was two (184–223 g C m−2 yr−1, 13.6–16.6 g N m−2 yr−1) to eight (0.40–0.46 g P m−2 yr−1) times higher than before 1960 (110 g C m−2 yr−1, 6.6 g N m−2 yr−1, 0.06 g P m−2 yr−1) or in unenriched areas (65–90 g C m−2 yr−1, 4.7–6.4 g N m−2 yr−1, 0.06 g P m−2 yr−1). Unenriched areas of the Everglades possess some of the lowest rates of P accumulation of peatlands in North America. Successful restoration of the Everglades will have to include the elimination of anthropogenic nutrient loadings to limit the P enrichment zone from expanding into existing unenriched interior areas and areas downstream of WCA 2A.
Dichromate Digestion and Simultaneous Colorimetry of Microbial Carbon and Nitrogen
Authors: Doyle Allen , Schimel Joshua P. 
Published: July 2010

AbstractDichromate digestion is used frequently for analysis of organic C and is followed by manual titration. We sought to automate C detection and to include N in the analysis. We optimized digestion parameters (duration, temperature, acids, and catalysts), compared detection methods [manual and automated titration, colorimetric absorbance of Cr(III) and Cr(VI) and automated colorimetry of Cr(VI)], adapted salicylate‐indophenol colorimetry for N detection, and compared N digestion efficiency with Kjeldahl digestion. Optimal digestion conditions were 144°C internal temperature for 3 h with 2:1 H2SO4/H3PO4 and Ag2SO4. Automated and manual titrations were reliable but the titrant (ferrous ammonium sulfate) precluded N detection. Colorimetric detection of Cr(VI) with s‐diphenylcarbazide was fast and precise, but high blanks and steady decomposition of Cr(VI) necessitated several internal standards. Colorimetric analysis of N was possible after precipitating Ag and it was stable, precise, and accurate. Digestion recovery of yeast extract and soil extract N from birch (Betula papyrifera Marsh.), alder (Alnus tenuifolia Nutt.), and poplar (Populus balsamifera L.) stands was low compared with Kjeldahl N (82, 79, 88, and 78%), but precision of the two digestions was the same. The detection limits were 25 µg C and 2 µg N per digestion (125 mg C and 10 mg N kg‐1 dry soil). While this method is not suitable for work demanding high accuracy, automated C detection combined with N detection provides data acceptable for studies comparing field or laboratory soil treatments.
Modified Iron‐Oxide‐Impregnated Paper Strip Test for Soils Treated with Phosphate Fertilizers
Authors: Habib L. , Chien S. H. , Menon R. G. , Carmona G. 
Published: July 2010

AbstractThe Fe‐oxide‐impregnated paper strip (Pi) test with 0.01 M CaCl2 has been proposed as an improved soil test for evaluating available P from soils treated with phosphate rock (PR) and triple superphosphate (TSP). However, conclusive evidence for this suggestion has not been reported. This study was conducted to evaluate the suitability of the Pi test for both PR and TSP. In a greenhouse study, two acid soils — Hartsells silt loam (fine‐loamy, siliceous, thermic Typic Hapludult) and Hiwassee clay loam (fine, kaolinitic, thermic Rhodic Kanhapludult) — were mixed with ground (0.15‐mm, 100‐mesh) North Carolina (NC) PR or commercial‐grade granular TSP at 0 to 300 mg P kg‐1 soil. The soil samples were preincubated for 2 wk before maize (Zea mays L.) was planted and grown for 5 wk. Prior to planting, soil samples were analyzed by three soil tests: Bray I, Pi test with 0.01 M CaCl2, and Pi test with 0.02 M KCl. The results showed that NC‐PR and TSP were equally effective in increasing dry‐matter yield and P uptake by maize in Hartsells soil. North Carolina phsophate rock was approximately 83 and 91% as effective as TSP in increasing drymatter yield and P uptake, respectively, in Hiwassee soil. When P uptake was plotted against soil test values, both the Bray I and Pi test with CaCl2 underestimated available P from NC‐PR for TSP‐treated soil. Available soil P estimated by the Pi test using KCl instead of CaCl2 was more closely related to P uptake with both NC‐PR and TSP. More P was extracted from NC‐PR by the Pi test with KCl than with CaCl2, whereas no effect was observed for TSP.