Papers by James C. Ascough II
Transactions of the ASABE, 2012
ABSTRACT
Journal of Consulting Psychology, 1962
... Bender Gestalt Pascal-Suttell scores sig-nificantly differentiated between normal and organic... more ... Bender Gestalt Pascal-Suttell scores sig-nificantly differentiated between normal and organic groups (Fisher's exact test) in valida-tion (p .0006) and cross-validation (p .043). Page 3. 432 JAMES C. ASCOUGH AND RICHARD H. DANA ...
Agronomy Journal, 2014
The semiarid U.S. Great Plains experiences a large variation in crop yields due to variability in... more The semiarid U.S. Great Plains experiences a large variation in crop yields due to variability in rainfall, soil, and other factors. We analyzed (24-yr) yields from a no-till rotation of winter wheat (Triticum aestivum L.)-corn (Zea mays L.) or sorghum [Sorghum bicolor (L.) Moench]-fallow at three sites, each with three soil types along a catena in Colorado. We investigated: (i) effects of soil organic carbon (SOC), length of slope (SL), and other soil properties on yields; and (ii) degree in which variability in annual yields are explained with water variables of rainfall during the fallow, vegetative and reproductive stages, and soil water at planting. Wheat and corn/sorghum yields were strongly related to soil properties (R 2 = 0.84; 0.97, respectively). Wheat yield regression had only SOC as a significant variable, whereas corn/sorghum had SOC and SL. Water factors explained 37 to 73% of annual variability in wheat yields at the site by soil level, 19 to 63% when pooled over soils within sites, and 35 to 40% pooled over all. For corn, the corresponding percentages were 16 to 64%, 26 to 57%, and 40 to 45%, respectively. Fallow rain made the highest contribution to R 2 in wheat whereas reproductive rain did for corn/sorghum. We conclude SOC is a stand-in for long-term effects of water availability on production, but other natural factors greatly influence the annual yield variability. Combining mean yields determined from soil properties with CV of pooled annual yields, we can estimate mean and standard deviation of yields.
Transactions of the ASAE, 1997
International Symposium on Erosion and Landscape Evolution (ISELE), 18-21 September 2011, Anchorage, Alaska, 2011
Newly developed erosion prediction models require detailed input parameters including those descr... more Newly developed erosion prediction models require detailed input parameters including those describing cropping systems. Each model exhibits a different level of complexity for crop growth modeling, and many plant parameters for these models are difficult to obtain. Furthermore, numerous parameters require interpretation from other measurable plant characteristics. We developed a database containing measurable plant characteristics to supply users of these new erosion prediction technologies with the necessary parameters. The new database supports the Revised Universal Soil Loss Equation (RUSLE) and the Water Erosion Prediction Project (WEPP) erosion prediction models. The Crop Parameter Intelligent Database System (CPIDS) was developed to assist crop database builders and users of RUSLE and WEPP in interpretation of plant characteristics and selection of plant parameters. CPIDS is a Microsoft® Windows™-based program, currently running on a personal computer (PC) under Windows 3.1™, Windows 95™ and Windows NT 4.0™.
Soil tillage practices can affect soil hydraulic properties and processes dynamically in space an... more Soil tillage practices can affect soil hydraulic properties and processes dynamically in space and time with consequent and coupled effects on chemical movement and plant growth. This literature review addresses the quantitative effects of soil tillage and associated management (e.g., crop residues) on the temporal and spatial variability of soil hydraulic properties. Our review includes incidental management effects, such as soil compaction, and natural sources of variability, such as topography. Despite limited research on space-time predictions, many studies have addressed management effects on soil hydraulic properties and processes relevant to improved understanding of the sources of variability and their interactions in space and time. Whether examined explicitly or implicitly, the literature includes studies of interactions between treatments, such as tillage and residue management. No-tillage (NT) treatments have been compared with various tillage practices under a range of conditions with mixed results. The trend, if any, is for NT to increase macropore connectivity while generating inconsistent responses in total porosity and soil bulk density compared with conventional tillage practices. This corresponds to a general increase in ponded or near-zero tension infiltration rates and saturated hydraulic conductivities. Similarly, controlled equipment traffic may have significant effects on soil compaction and related hydraulic properties on some soils, but on others, landscape and temporal variability overwhelm wheel-track effects. Spatial and temporal variability often overshadows specific management effects, and several authors have recognized this in their analyses and interpretations. Differences in temporal variability depend on spatial locations between rows, within fields at different landscape positions, and between sites with different climates and dominant soil types. Most tillage practices have pronounced effects on soil hydraulic properties immediately following tillage application, but these effects can diminish rapidly. Long-term effects on the order of a decade or more can appear less pronounced and are sometimes impossible to distinguish from natural and unaccounted management-induced variability. New standards for experimental classification are essential for isolating and subsequently generalizing space-time responses. Accordingly, enhanced methods of field measurement and data collection combined with explicit spatio-temporal modeling and parameter estimation should provide quantitative predictions of soil hydraulic behavior due to tillage and related agricultural management. Published by Elsevier B.V.
The primary objectives of this research were to determine SWAT model predicted reductions in four... more The primary objectives of this research were to determine SWAT model predicted reductions in four water quality indicators (sediment yield, surface runoff, nitrate nitrogen (NO 3 -N) in surface runoff, and edge-of-field erosion) associated with producing switchgrass (Panicum virgatum) on cropland in the Delaware basin in northeast Kansas, and evaluate switchgrass break-even prices. The magnitude of potential switchgrass water quality payments based on using switchgrass as an alternative energy source was also estimated. SWAT model simulations showed that between 527,000 and 1.27 million metric tons (Mg) of switchgrass could be produced annually across the basin depending upon nitrogen (N) fertilizer application levels (0-224 kg N ha K1 ). The predicted reductions in sediment yield, surface runoff, NO 3 -N in surface runoff, and edge-of-field erosion as a result of switchgrass plantings were 99, 55, 34, and 98%, respectively. The average annual cost per hectare for switchgrass ranged from about $190 with no N applied to around $345 at 224 kg N ha K1 applied. Edge-of-field break-even price per Mg ranged from around $41 with no N applied to slightly less than $25 at 224 kg N ha K1 applied. A majority of the switchgrass produced had an edge-of-field break-even price of $30 Mg K1 or less. Savings of at least 50% in each of the four water quality indicators could be attained for an edge-of-field break-even price of $22-$27.49 Mg K1 .
Sustainable resource management is one of the most complex concerns today. Society has spent bill... more Sustainable resource management is one of the most complex concerns today. Society has spent billions on conserving productive and marginal soils in cultivation yet it is unclear whether these efforts buy sustainability. Further study about which soils need conservation merits consideration.
Environmental Modelling & Software, 2014
ABSTRACT
Sustainable agriculture is a complex problem that demands consideration of many interrelated fact... more Sustainable agriculture is a complex problem that demands consideration of many interrelated factors, processes, and institutions. Unfortunately, current definitions of sustainability are expansive, and use as a guide for strategic planning or decision making is clouded by ambiguity and a plethora of definitions. Regardless of how sustainability is defined, agricultural producers are interested in developing and evaluating agricultural management systems that are both environmentally sound and economically profitable. There has been a proliferation of decision analysis and economic indicator tools developed to aid producers; however, the tools rarely are used due to excessive complexity or a failure to capture important criteria (e.g., economic, ecological/environmental and social factors) that better represent how producers define "sustainability." In this paper, we adapt the payoff matrix approach from the financial risk arena to develop a comparable framework for agroecosystem risk. The payoff matrix concept utilizes the probability function for management alternatives to represent multiple pieces of information; a matrix of these vectors allows for development of many types of decision rules (e.g., minimax regret or maximin strategies) that can represent alternative value systems. Instead of a payoff matrix, we create an "impact matrix" that contains a vector of plausible environmental indicators and outcomes for agricultural systems. The result of this research is a tool that allows indicators to be incorporated in an index that can be adapted to different situations, and thus used in a variety of contexts while remaining simple to understand.
Agricultural Systems, 2006
The root zone water quality model (RZWQM) was developed primarily for water quality research with... more The root zone water quality model (RZWQM) was developed primarily for water quality research with a generic plant growth module primarily serving as a sink for plant nitrogen and water uptake. In this study, we coupled the CERES-Maize Version 3.5 crop growth model with RZWQM to provide RZWQM users with the option for selecting a more comprehensive plant growth model. In the hybrid model, RZWQM supplied CERES with daily soil water and nitrogen contents, soil temperature, and potential evapotranspiration, in addition to daily weather data. CERES-Maize supplied RZWQM with daily water and nitrogen uptake, and other plant growth variables (e.g., root distribution and leaf area index). The RZWQM-CERES hybrid model was evaluated with two well-documented experimental datasets distributed with DSSAT (Decision Support System for Agrotechnology Transfer) Version 3.5, which had various nitrogen and irrigation treatments. Simulation results were compared to the original DSSAT-CERES-Maize model. Both models used the same plant cultivar coefficients and the same soil parameters as distributed with DSSAT Version 3.5. The hybrid model provided similar maize prediction in terms of yield, biomass and leaf area index, as the DSSAT-CERES model when the same soil and crop parameters were used. No overall differences were found between the two models based on the paired t test, suggesting successful coupling of the two models. The hybrid model offers RZWQM users access to a rigorous new plant growth model and provides CERES-Maize users with a tool to address soil and water quality issues under different cropping systems.
Transactions of the ASABE, 2007
Alternative agricultural management systems in the semi-arid Great Plains are receiving increasin... more Alternative agricultural management systems in the semi-arid Great Plains are receiving increasing attention. GPFARM is a farm/ranch decision support system (DSS) designed to assist in strategic management planning for land units from the field to the whole-farm level. This study evaluated the regional applicability and efficacy of GPFARM based on simulation model performance for dry mass grain yield, total soil profile water content, crop residue, and total soil profile residual NO 3 -N across a range of dryland no-till experimental sites in eastern Colorado. Field data were collected from 1987 through 1999 from an on-going, long-term experiment at three locations in eastern Colorado along a gradient of low (Sterling), medium (Stratton), and high (Walsh) potential evapotranspiration. Simulated crop alternatives were winter wheat (Triticum aestivum L.), corn (Zea mays L.), sorghum (Sorghum bicolor L.), proso millet (Panicum miliaceum L.), and fallow. Relative error (RE) of simulated mean, root mean square error (RMSE), and index of agreement (d) model evaluation statistics were calculated to compare modeled results to measured data. A one-way, fixed-effect ANOVA was also performed to determine differences among experimental locations. GPFARM simulated versus observed REs ranged from -3% to 35% for crop yield, 6% to 8% for total soil profile water content, -4% to 32% for crop residue, and -7% to -25% for total soil profile residual NO 3 -N. For trend analysis (magnitudes and location differences), GPFARM simulations generally agreed with observed trends and showed that the model was able to simulate location differences for the majority of model output responses. GPFARM appears to be adequate for use in strategic planning of alternative cropping systems across eastern Colorado dryland locations; however, further improvements in the crop growth and environmental components of the simulation model (including improved parameterization) would improve its applicability for short-term tactical planning scenarios.
Encyclopedia of Ecology, 2008
Gut, 2000
C282Y hereditary haemochromatosis is an appropriate condition for population screening. Transferr... more C282Y hereditary haemochromatosis is an appropriate condition for population screening. Transferrin saturation, the best screening test to date, is relatively expensive, labour intensive, and cannot be automated. Unsaturated iron binding capacity is a surrogate marker of transferrin saturation and its measurement can be automated. To evaluate a screening strategy for C282Y hereditary haemochromatosis in a tertiary hospital environment based on unsaturated iron binding capacity as the initial screening test. Measurement of unsaturated iron binding capacity was adapted to the main laboratory analyser. An unsaturated iron binding capacity of less than 30 micromol/l was identified as an appropriate decision point and 5182 consecutive subjects were screened over 28 consecutive days. Of those screened, 697 had an unsaturated iron binding capacity less than 30 micromol/l. Of these, transferrin saturation was greater than 40% in 294. A total of 227 were able to be genotyped for the C282Y mutation. Nine subjects homozygous for C282Y were identified. Based on full cost recovery, affected persons were identified at a cost of Aus$2268.77 per case (approximately US$1496). Automated measurement of unsaturated iron binding capacity enables a cost effective, large scale population screening programme for C282Y hereditary haemochromatosis to be developed.
SSSA Special Publication, 1994
Sustainability, 2014
The fishing industry in Abu-Dhabi, United Arab Emirates (UAE), plays an important role in diversi... more The fishing industry in Abu-Dhabi, United Arab Emirates (UAE), plays an important role in diversifying food sources in order to enhance national food security. The fishing industry is facing an increasing risk that may impact the sustainability (i.e., quantity and quality) of the fish caught and consumed in the UAE. Therefore, the main objective of this study is to analyze common Abu-Dhabi fishing management alternatives using various stochastic dominance techniques (i.e., first/second degree stochastic dominance, stochastic dominance with respect to a function and stochastic efficiency with respect to a function) to assess the risk facing UAE fishermen. The techniques represent a risk assessment continuum, which can provide a ranking of management alternatives to improve decision making outcomes and help maintain long-term UAE fishing sustainability. Data for the stochastic dominance analyses were obtained from a cross-sectional survey conducted through face-to-face interviews of Abu Dhabi, UAE, fishermen. Analysis of fishing methods, trap sizes and trap numbers using stochastic efficiency with respect to a function (SERF) showed that fishermen efficient practices were not the same for risk-neutral
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Papers by James C. Ascough II