bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calibrating the Root Zone Water Quality Model
Authors: Hanson Jonathan D. , Rojas K. W. , Shaffer Marvin J. 
Published: July 2010

AbstractTechniques to reliably calibrate computer models are needed before the models can be applied to help solve natural resource problems. The USDA‐ARS Root Zone Water Quality Model (RZWQM) is a comprehensive simulation model designed to predict hydrologic and chemical response, including potential for ground‐water contamination, of agricultural management systems. RZWQM Version 3.2 was calibrated and evaluated at sites in Iowa, Minnesota, Missouri, Nebraska, and Ohio as part of the Management Systems Evaluation Areas (MSEA) project and at a site near Sterling in northeastern Colorado. Soil horizon description and a description of the physical and hydraulic properties of the soil were required to initialize the model. Calibration for nutrient cycling involved adjusting the model coefficients for mineralization, infiltration, and denitrification. Initial N pool sizes were estimated using medium to long‐term computer simulations. Maximum N uptake rate, plant respiration, specific leaf area, and the effect of age at the time of propagule development and senescence were used to calibrate the plant production and yield component. To match the observed results for soil water, N, and plant growth, an iterative approach for calibrating the model was followed. When done methodically, total biomass estimates were within 5%, yield estimates were within l0%, and N uptake was within 20% of field measurements. Calibration of the C and N dynamics module produced results that were generally within 20 to 50 kg ha−1 of measured values for soil profile NO−3‐N. Independent evaluations of the calibrated model focused on four indicator output variables related to plant growth—total biomass, yield, N uptake, and N in the soil profile. Predictions matched the observed data in most cases. The crop model is very sensitive to plant N content. Even small errors in simulating N uptake levels can result in substantial errors in estimates of yield and total aboveground biomass. The model predicted biomass and yield well on irrigated and most dryland management systems and adequately simulated crop variables at various positions along the landscape.
Plant Production Model Evaluation for the Root Zone Water Quality Model (RZWQM 3.2) in Ohio
Authors: Landa Feliks M. , Fausey Norman R. , Nokes Sue E. , Hanson Jonathan D. 
Published: July 2010

AbstractThe Ohio Management Systems Evaluation Areas (MSEA) project focused on developing and evaluating improved agricultural management systems and predictive models. The Root Zone Water Quality Model (RZWQM) is an environmental model for simulating water, chemical, and biological response of agricultural management systems. This paper presents calibration and evaluation of the generic plant production model of RZWQM, as well as some evaluation results for the nitrate and soil water content predictions. Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] biomass data collected at the Ohio MSEA from 1991 to 1993 were used for evaluation. Data from 1992 were used in calibrating RZWQM, and data from two other years (1991 and 1993) at the same site were used for validation. Crop growth predictions were compared with observed values of leaf, stem, and seed biomass collected throughout the growing season. Leaf and stem biomass predictions generally fell within 1 SD of the observed values, but for all years there were dates when predictions were outside of the observed range. RZWQM predicted seed biomass or yield adequately for all 3 years, with predictions falling within 1 SD of the observed values. Soil water content estimates for corn were higher than observed values late in the season, perhaps because of underestimates of evapotranspiration due to errors in leaf area predictions. The model overpredicted nitrate concentrations for the corn plot late in the season. Nitrate concentrations for the soybean plot were generally underpredicted. These differences may be due to underestimates of the fast humus pool of the nutrient model and of the N2 fixation rate for soybean. More evaluation is needed to refine the nitrate and soil water content predictions.
Testing CERES–Wheat with Free‐Air Carbon Dioxide Enrichment (FACE) Experiment Data: CO2 and Water Interactions
Authors: Tubiello Francesco N. , Rosenzweig Cynthia , Kimball Bruce A. , Pinter Paul J. , Wall Gerald W. , Hunsaker Douglas J. , LaMorte Robert L. , Garcia Richard L. 
Published: July 2010

AbstractDynamic crop‐growth models are used to project the effects of rising atmospheric CO2 concentration and associated climate change on crop yields. Such model predictions are largely untested in the field, for lack of experimental data. We tested the CERES‐Wheat model, modified to include leaf‐level photosynthesis response to elevated CO2, using field data from 2 yr of Free‐Air Carbon Dioxide Enrichment (FACE) experiments with spring wheat (Triticum aestivum L. cv. Yecora Rojo) in Maricopa, AZ. Two irrigation treatments (well‐watered, WW; water‐deficit stressed, WS) and two atmospheric CO2 concentrations (ambient, 350 (μmol mol−1; elevated, 550 (μmol mol−1) were simulated. The model was evaluated using measurements of crop phenology, aboveground dry matter (DM) production, grain yield, and evapotranspiration (ET). Model calculations of crop phenology were within 2 to 3 d of observed values under WW, ambient CO2 conditions in both years. The model did not simulate the accelerated crop phenology (5–8 d at physiological maturity) observed in the WW and elevated CO2 treatments, indicating the need to include effects of increased stomatal resistance on canopy temperature. Simulations of DM and grain yield were within 10% of measured values, except for a tendency to overcalculate DM response to CO2 by 10 to 15% in Year 1 for WS treatments. The model undercalculated cumulative ET under WW conditions by 15%; model sensitivity analyses suggest that simulation of potential evapotranspiration (PET) was too low for this arid site. The model reproduced measured dynamics of CO2‐water interactions. Simulated reductions in water loss due to elevated CO2 were about 4%, in agreement with measurements. The model simulated larger increases in DM production and yield due to elevated CO2 under WS than under WW conditions. In Year 1, simulated crop response to CO2 was 2% larger (measured: 3%) under WS than under WW conditions; in Year 2, it was 11% larger (measured: 9%). The ability to simulate CO2‐water interactions, though it needs to be further evaluated with additional experimental datasets, is an important attribute of models used to project crop yields under elevated CO2 and climate change.
Estimation of Nitrogen Fixed by Legumes in Long‐Term vs. Short‐Term Cropping Systems
Authors: Papastylianou Ioannis 
Published: July 2010

AbstractA critical evaluation of legumes should consider both the above‐and belowground contribution to N2 fixation. Based on the amount of N in crops and correcting for the changes of soil N as a result of cropping, 15 equations are presented for estimation of the apparent net amount of atmospheric N2 fixed by legumes grown in short‐ and long‐term cropping systems. In the final equation, all components of a legume‐cereal rotation system were considered. In estimating N2 fixation, including in the equation the non‐N2–fixing crop that follows the legume in the rotation is an innovation of the method, in addition to the system approach concept. The validity and accuracy of each equation in estimating N2 fixation by legumes is discussed. An example is provided using data from long‐term vetch‐barley (Vicia sativa L.‐Hordeum vulgare L.) rotation studies in Cyprus. The estimated amount of apparent net N2 fixation by vetch was 184 kg N ha−1, a quantity twice that usually estimated using only the aboveground vetch production. This result shows the importance of calculating apparent net N2 fixation by considering above‐ and belowground system components.
Spring‐Applied Nitrogen and Productivity of Cool‐Season Grass Seed Crops
Authors: Young William C. , Chilcote David O. , Youngberg Harold W. 
Published: July 2010

AbstractUnderstanding effects of spring N rates and application timing on seed yield and yield components of cool‐season grass seed crops will help improve N fertilization management. We tested effects of 90, 120, 150, 180, and 210 kg N ha−1, applied at the double‐ridge (DR) stage of development on seed yield and yield components of Chewing's fescue [Festuca rubra L.subsp. fallax (Thuill.) Nyman; syn. F. rubra var. commutata Gaudin], tall fescue (F. arundinacea Schreb.), and orchardgrass (Dactylis glomerata L.) in 1985 and 1986. In a second study, effects of 120 kg N ha−1, applied either at DR, at spikelet initiation (SI), or equally split between the two stages, were tested. Soil type for both experiments was fine‐silty, mixed, mesic Aquultic Argixerolls. Chewing's fescue seed yield was not affected by N rates in 1985 and was the greatest at 90 kg N ha−1 in 1986. Averaged across years, orchardgrass seed yield was the greatest at 120 kg N ha−1. Nitrogen rates did not affect seed yield of tall fescue. Seed yield of all species was most closely correlated with the number of seeds produced per unit area. Seed number per unit area was primarily correlated with the number of seeds produced per panicle in all species; in orchardgrass, the number of panicles per unit area also contributed to total number of seeds produced. Seed yields of all three species were the greatest when N was applied at DR. Split application was not better than application of all N at DR or SI. We concluded that in western Oregon spring application of 90 kg N ha−1 for Chewing's fescue and tall fescue and 120 kg N ha−1 for orchardgrass should be adequate for seed production. For all species, spring N should be applied in one application at DR.
A Comparative Study of Interpolation Methods for Mapping Soil Properties
Authors: Kravchenko Alexandra , Bullock Donald G. 
Published: July 2010

AbstractThe choice of an optimal interpolation technique for estimating soil properties at unsampled locations is an important issue in site‐specific management. The objective of this study was to evaluate inverse distance (InvD) weighting, ordinary kriging (KO), and lognormal ordinary kriging (KOlog) to determine the optimal interpolation method for mapping soil properties. Relationships between statistical properties of the data and performance of the methods were analyzed using soil test P and K data from 30 agricultural fields. For InvD weighting, we used powers of 1, 2, 3, and 4. The numbers of the closest neighboring points ranged from 5 to 30 for the three methods. The results suggest that KOlog can improve estimation precision compared with KO for lognormally distributed data. The criteria helpful in deciding whether KOlog is applicable for the given data set were the Kolmogorov‐Smirnov goodness‐of‐fit statistic, coefficient of variation, skewness, kurtosis, and the size of the data set. Careful choice of the exponent value for InvD weighting and of the number of the closest neighbors for both InvD weighting and kriging (KO or KOlog) significantly improved the estimation accuracy (P≤ 0.05). However, no a priori decision could be made about the optimal exponent and the number of the closest neighbors based on the statistical properties of the data. For the majority of the data sets, kriging with the optimal number of the neighboring points, a carefully selected variogram model, and appropriate log‐transformation of the data performed better than InvD weighting. Correlation coefficients between experimental data and estimated results of kriging were higher than those of InvD for 57 out of a total of 60 data sets, kriging mean absolute errors were lower for 44 data sets, and kriging mean errors were lower than those of InvD weighting for 31 data sets.
Soil Management and Supplemental Irrigation Effects on Potato: II. Root Growth
Authors: Opena Geraldine B. , Porter Gregory A. 
Published: July 2010

AbstractThis study was conducted to determine if supplemental irrigation and/or application of soil amendments rich in organic matter can improve root growth of potato (Solanum tuberosum L.). Root length density (RLD) and root dry matter production of potato were studied under two levels of supplemental irrigation (nonirrigated check vs. moderate irrigation) and two levels of soil amendments [none vs. amended with compost and manure from beef cattle (Bos taurus L.)] during 1993 and 1994. Amendments significantly increased RLD during both growing seasons and these increases occurred consistently throughout each growing season. Irrigation effects were not observed in 1993, while irrigation significantly increased RLD during 1994. Approximately 85% of the root length was concentrated in the upper 30‐cm layer of the soil. The supplemental irrigation and soil amendment treatments did not affect the proportional distribution of roots among the soil layers. Root‐to‐shoot ratio was not affected by irrigation or amendment during either growing season. The RLD and leaf area index (LAI) at all four sample dates during 1994 were significantly correlated with final tuber yields, indicating that growth patterns early in the season were important in establishing the productivity of the potato crop. Root length density tended to have a higher correlation with yields than did LAI (r = 0.58* to 0.80** vs. 0.51* to 0.68**).
The Effect of Logging and Slash‐Burning on Soil Structure
Authors: Dyrness C. T. , Youngberg C. T. 
Published: July 2010

AbstractThe effects of logging and slash‐burning on soil structure were investigated on three Reddish Brown Latosol soils in the Coast Range of Western Oregon. Soil samples of the surface 2 inches were collected at 50‐foot intervals along randomly located transects within the clear‐cut areas. Soil samples were also collected in the adjacent uncut timber. The condition of the surface soil was noted at 10‐foot intervals along the transects and was recorded as follows: lightly burned, severely burned, disturbed and unburned, or undisturbed. Sixty soil samples from each clear‐cut sampling area were analyzed in the laboratory for mechanical composition, organic matter content, and water stable aggregates.The soil surface conditions after logging and slash‐burning were as follows: lightly burned 44.7%, severely burned 8%, unburned 30.1%, and undisturbed 17.2%. Severe burning was the only treatment that had any significant effects upon soil structure, particle size distribution and soil organic matter content. Analysis of variance revealed that there was a significant decrease in the amount of clay present in the severely burned soils as compared with the soils under undisturbed timber. A 20.6% decrease in the degree of aggregation and a 61.1% decrease in organic matter content were also noted in the severely burned soils as compared with soils in the undisturbed timber. Other treatments had no significant effects upon the soils of the logged area.Since only 8% of the soil surface was severely burned, it is concluded that logging by the high lead method and slash‐burning in the fall after rainfall has occurred have had no appreciable detrimental effects upon soil structure in the area studied.
Soil Nitrogen Complexes: II. Electrophoretic Separation of Organic Components
Authors: Waldron A. C. , Mortensen J. L. 
Published: July 2010

AbstractExtracts of soil organic matter solubilized by 0.1M Na4P2O7 and hydrolyzed by 0.5N NaOH, 6N HCl, and 0.1M Na4P2O7 + 0.5N NaOH were electrically desalted and subjected to continuous flow paper electrophoresis. Determination of organic matter, total nitrogen, α‐amino nitrogen and amino sugar in the collection tubes revealed the presence of nitrogen‐containing components having different electrophoretic mobilities.NaOH and HCl hydrolysates contained several nitrogenous components in which α‐amino nitrogen and amino sugars were detected. These hydrolysates also contained a brown‐colored component which contained most of the organic matter. The Na4P2O7 extract, which exhibited considerable loss of organic nitrogen during desalting, contained one major component in which most of the nitrogen and brown material was contained.A fluorescent component was associated with the brown‐colored component in each extract.
A Glassbead‐Glycerol Model for Non‐Steady‐State Tile Drainage
Authors: Grover Ben L. , Kirkham Don 
Published: July 2010

AbstractThe construction and use of a reduced scale model for studying the falling water table in non‐steady‐state drainage problems are described. A capillary fringe is accounted for in the model. Stratified soils may be simulated. It is concluded that the model can be used to obtain information which is valuable in drainage theory and design.
Soil Moisture Evaluation by Tensiometers
Authors: Perrier Eugene R. , Evans D. D. 
Published: July 2010

AbstractFour different types of tensiometers were compared and found to be quite similar within their range of measurement. Only a slight difference in range was found between the instruments.Moisture desorption curves obtained by plotting tensiometer readings versus soil water content as obtained by sampling were different from those obtained by the porous plate apparatus using cores or disturbed samples. The differences are associated with structural changes resulting from the procesures used in the porous plate technique. The moisture desorption curves obtained with the tensiometers should be reliable if time lag and hysteresis effects are small.
The Effect of Sulfur on the Absorption and Utilization of Molybdenum by Peas
Authors: Reisenauer H. M. 
Published: July 2010

AbstractAn experiment including a factorial combination of 4 rates of S and 3 rates of Mo fertilization was conducted on a low‐S, low‐Mo soil to evaluate the effects of soil S level on the absorption and utilization of Mo by peas. The uptake of soil and fertilizer Mo was markedly reduced by applications of sulfate fertilizer. The higher rates of S fertilization also reduced the apparent efficiency of utilization of Mo by the plant. Higher plant Mo levels were required for maximum yield and N fixation as the SO4‐S content of the plant tissue was increased by S fertilization. Correlation coefficients of 0.78 and 0.94 were obtained with response surface equations for seed yield and vine N content as functions of the Mo and SO4‐S contents of the plant tissues. Maximum pea yields were associated with plant tissue Mo contents of 0.3 to 1.0 ppm. and 200 to 600 ppm. of SO4‐S.
Hydraulic Properties of a Clay Loam Soil and the Field Measurement of Water Uptake by Roots: I. Interpretation of Water Content and Pressure Profiles
Authors: van Bavel C. H. M. , Stirk G. B. , Brust K. J. 
Published: July 2010

AbstractThe distribution of irrigation water in an Adelanto clay loam profile was studied in a field plot by simultaneous, periodic observations of the water content and hydraulic head profiles. Successive measurement series were made with the plot bare and covered, bare, and planted to a sorghum crop (Sorghum vulgare Pers.). From the first two, the in situ and dynamic relations of water content to water pressure and to conductivity were obtained. From the cropped field data, the root‐extraction pattern was derived, using the established hydraulic properties of the profile. The data demonstrate the variability within depths and locations of water retention and conduction properties and the consequent problem of calculating fluxes. The mobile character of soil water is also evident, confirming the inadequacy of static concepts of soil water “constants” for a profile. Calculated root‐extraction rates agreed reasonably with independent lysimetric measurements of the water loss from the surface to the atmosphere.
Variation in the Relative Distribution of Amino Sugars with Depth in Some Soil Profiles
Authors: Stevenson F. J. , Braids O. C. 
Published: July 2010

AbstractIon exchange chromatography of the amino sugars in hydrolysates of several soil profiles revealed that the proportion of the amino sugar material in the form of glucosamine increased dramatically with increasing depth. Little variation was noted in the relative distribution of amino sugars in the surface horizons of the soils examined.
Convective Diffusion in Clay Systems
Authors: Overman Allen R. 
Published: July 2010

AbstractThe theory of convective diffusion has been applied to transport of salt through clay columns. An expression was derived for salt distribution within the column for steady state conditions.Data from the literature were used to test the applicability of the distribution function to clay systems. The observed nonlinearity is described to high precision by the equation. However, some discrepancy occurs between calculated and measured parameters.
Movement of Water and Salt through a Clay‐Water System: Experimental Verification of Onsager Reciprocal Relation
Authors: Letey J. , Kemper W. D. 
Published: July 2010

AbstractEquations that describe the movement of solution and salt through a soil system in which there are both hydrostatic and osmotic pressure gradients are presented. These equations are: JV = − LP ∇P + LPD ∇π, JD = LDP ∇P − LD ∇π, and JS/CS = (−LP + LDP) ∇P + (−LD + LPD) ∇π where JV is the flux of solution, JD the difference in velocity between water and salt, JS is flux of salt, P is pressure, π is osmotic pressure, CS is the average solute concentration, and L is phenomenological coefficients. The Onsager reciprocal relation states that LPD = LDP. This relation was found to be valid for a clay‐water‐salt system.
Specific Character of Boron Adsorption by an Amorphous Soil
Authors: Bingham Frank T. , Page A. L. 
Published: July 2010

AbstractThe adsorption of boron by an allophanic soil as influenced by the presence of sulfate, phosphate, and monosilicic acid was studied at pH 6.0 and 8.5. Amounts of B adsorbed by the soil from a 4.8 mM B solution which contained sulfate or phosphate ions in varying concentrations up to 0.1M were independent of the presence of these anions. Pretreatment of soil by repeated saturation with 1.42 mM Si solution resulted in a slight but progressive decrease in the quantity of B adsorbed subsequently from the 4.8 mM B solution. Apparently, B adsorption by allophanic soils is more or less specific, being essentially independent of the presence of other anions.
Effect of Urea Fertilization on Nitrification in Forest Soils of the Pacific Northwest
Authors: Heilman Paul 
Published: July 2010

AbstractNitrate levels in untreated samples of upper mineral soil from 14 Douglas‐fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) sites incubated at 20C for 21 days varied from 0 to 45 ppm N. No relationship of nitrification to soil pH was evident but N and organic C content appeared to be associated with nitrate production; for nitrate versus total N, r = 0.85, and versus organic C, r = 0.75, while nitrate versus C:N ratio, r = −0.38. Little nitrate was produced in soils with C:N ratios above 27.Treatment of the soils with urea at approximately 400 ppm N increased nitrate levels in similarly incubated samples by an average of 70 ppm N. The increases varied considerably with two soils still containing less than 4 ppm N as nitrate and four with over 100 ppm nitrate N (one exceeded 300 ppm N).N fertilization in the field markedly increased capability of the majority of soils tested to form nitrate following subsequent urea treatment.Low temperature (2.5 and 5C) restricted nitrification whether or not soils were treated with urea. Generally, rate of nitrification in urea‐treated soils increased rapidly with increase in temperature above 5C. The patterns of increase in nitrate with increase in temperature and time suggest that low nitrification capability in some soils results primarily from low population of nitrifying organisms and that nitrate levels following urea treatment are linked to growth of the population of nitrifying organisms in response to a large supply of ammoniacal N.