A County-Level Assessment of Manure Nutrient Availability Relative to Crop Nutrient Capacity in Iowa: Analysis of Spatial and Temporal Trends

During the twentieth century, agricultural production strived to achieve increased food production in order to satisfy both local and export demands. In many cases, this led to increased farm sizes and an operational separation of crop and livestock production. Society fears that the trend of increasing centralization and industrialization of agriculture, specifically animal agriculture, has resulted in concentration of waste products associated with their production (manures, wash-down water, process waters, etc.) over relatively small geographic regions that are spatially segregated from crop production areas. Since the distance that manure can be economically hauled for land application has practical limits, this could lead to over-application, of manures near animal feeding facilities, potentially increasing nutrient losses to ground and surface waters. A statewide analysis of crop and animal production in Iowa suggests that about 25% of current nitrogen and phosphorus requirements for crop production could be supplied from manures and litters, while around 40% of the required potassium could be provided. However, neither livestock nor crop production is uniformly distributed across all counties. This unequal distribution suggests that a more disaggregated analysis of crop nutrient requirements and manure nutrient supply is necessary to estimate the risks of excess nutrient loss to the environment. Results indicated that in general all counties had sufficient nutrient utilization capacities to value manure as a resource; however, counties in Northwest Iowa are becoming progressively more manure rich, while counties in Southwestern and Central Iowa are becoming progressively more manure poor. This separation of crop and livestock production is becoming more pronounced, indicating that solids separation and nutrient (especially phosphorus) recovery systems that can concentrate manure nutrients for transport could become more important to help counties maintain nutrient balance and to return manure nutrients to the soil if these trends persist

A Generic Framework for Engineering Graph Canonization Algorithms

The state-of-the-art tools for practical graph canonization are all based on the individualization-refinement paradigm, and their difference is primarily in the choice of heuristics they include and in the actual tool implementation. It is thus not possible to make a direct comparison of how individual algorithmic ideas affect the performance on different graph classes. We present an algorithmic software framework that facilitates implementation of heuristics as independent extensions to a common core algorithm. It therefore becomes easy to perform a detailed comparison of the performance and behaviour of different algorithmic ideas. Implementations are provided of a range of algorithms for tree traversal, target cell selection, and node invariant, including choices from the literature and new variations. The framework readily supports extraction and visualization of detailed data from separate algorithm executions for subsequent analysis and development of new heuristics. Using collections of different graph classes we investigate the effect of varying the selections of heuristics, often revealing exactly which individual algorithmic choice is responsible for particularly good or bad performance. On several benchmark collections, including a newly proposed class of difficult instances, we additionally find that our implementation performs better than the current state-of-the-art tools

Modeling the performance of runoff control systems on open beef feedlots in Iowa

Runoff from open feedlots has the potential to cause degradation of surface and groundwater if handled improperly. Due to this pollution potential, the United State Environmental Protection Agency (US EPA) regulates runoff control systems on concentrated animal feeding operation (CAFO) sized feedlots. For the first time, the 2003 effluent limitation guidelines allowed consideration of alternative manure treatment systems for National Pollutant Discharge Elimination System (NPDES) permitted CAFO operations. Concentrated animal feeding operations that utilize alternative manure treatment systems under an NPDES permit are required to demonstrate, through modeling, that their alternative runoff control system had an equal or lesser nutrient mass release than a conventional manure management system would. This permitting requirement renewed interest in the modeling of traditional containment systems and generated interest in modeling alternative technology systems. One possible alternative technology systems being considered are vegetative treatment systems (VTS). A VTS is defined as a runoff control system that uses a series of treatment components, at least one of which uses vegetation, to treat open lot runoff. In particular, much of the VTS research thus far has focused on vegetative treatment areas (VTA\u27s). A VTA is an area planted to permanent vegetation that reduces pollutant transport via sedimentation, filtration, and infiltration of the feedlot runoff. This modeling requirement led to the development of the Iowa State University (ISU) - Effluent Limitations Guidelines (ELG) model and the ISU - VTA model, which predict the performance of traditional containment systems and of vegetative treatment area systems, respectively. This thesis reviews the accuracy of the ISU-ELG model by comparing the modeled runoff control performance of a traditional containment system to that predicted by the Soil-Plant-Air-Water (SPAW) model. Specifically, the criterion used to determine if a particular day is a dewatering day, i.e., suitable for land application of basin effluent, is investigated to determine its effect on basin performance, with the objective of verifying that the ISU-ELG model is providing a reasonable prediction of the runoff control provided by a containment basin in Iowa. The ISU-ELG model is based on a model developed by Koelliker et al. (1975) to predict the performance of a holding basin at controlling feedlot runoff and uses a set of general criteria to determine if land application is acceptable, while the SPAW model uses a soil moisture criterion to determine if conditions are acceptable for land application. The results show that the ISU-ELG model over-predicts performance of traditional containment systems in comparison to the SPAW model at all five Iowa locations investigated. For wetter areas in Iowa, the number of drying days has a large affect on basin performance, whereas for the drier northwest region of Iowa this affect is limited. Possible methods of improving the ISU-ELG model predictions include adding a soil moisture accounting function to model moisture levels in the land application area or calibrating the number of drying days required before land application can commence. In addition to modeling traditional containment systems, this thesis also examines possible methods of modeling VTA\u27s, as previous research has shown that the ISU-VTA model greatly over-predicts VTA performance. In this study, two different approaches, both using the SPAW model, were investigated to determine their ability to predict hydraulic performance of the vegetative treatment areas (VTA\u27s). Three of the four locations used in this study had a high water table; this water table elevation limited the space available in the soil profile to infiltrate and store water. For these locations, the performance of the VTA was limited by the storage available in the soil profile and SPAW simulations provided a realistic prediction of the monitored results. Modeling results verified that for these locations VTA performance was limited by the space available in the soil profile. Modeling statistics were calculated to determine the model\u27s ability to predict VTA performance. For the four locations investigated, Nash-Sutcliffe efficiencies ranged from 0.45 to 0.99 while the percent bias of the model ranged from -3% to 100%. The results show that the SPAW pond module can be used to determine if VTA performance will be limited by presence of a high water table. Additionally, these methods provided insight into possible modifications to improve the performance of the ISU-VTA model

A Runoff and Sediment Routing Model for Open Lot Beef Feeding Facilities

Feedlot runoff is a potential environmental contaminant and requires proper management to minimize impact on water quality. In designing runoff management systems, accurately assessing the amount of runoff that will be generated is of foremost importance. Along with overall quantity of runoff, the temporal pattern, both throughout the year and within an individual storm event, can have important implications for sizing control system components, in determining the performance the control system achieves, and in the overall pollution potential of the feedlot. This review summarizes the hydraulic properties of the feedlot surface, specifically focusing on variables that impact the total volume of effluent generated and the resulting amount of sediment transported. The work cumulates in development of a feedlot runoff routing model, presented as a series of equations that are implemented within the updated Iowa State University-Vegetative Treatment Area model, with a sediment transport/erosion component. Overall, the results indicated that a curve number of 91 was best for estimating runoff volumes, but substantial variation about this value could occur. The calibrated model was able to accurately estimate average total solids concentrations of lots of different size, shape, and surface condition under different hydraulic situations (R2 = 0.92 for calibration and the slope of the measured vs. modeled data was not different than one during model validation). Most calibration and validation feedlots were earthen, had the majority of runoff from rainfall events, had mounds within the pen, and were scraped only once or twice per production cycle; thus model performance may be limited for other situations. The feedlot runoff and sediment routing components were used to assess the impact of various feedlot design characteristics, including feedlot area, aspect ratio, and slope, on solids transport from the feedlot surface. This model can be used to evaluate the risk that feedlot runoff poses to water quality for prioritizing feedlots that are in need of enhanced runoff control systems, and to evaluate the hydraulic and sediment loadings that a runoff control system is required to handle

Evaluating solids, phosphorus, and nitrogen cycling and transport in vegetative treatment systems used for runoff control on beef feedlots

Runoff from open lot animal feeding operations has been recognized as a potential pollutant to receiving surface waters. This effluent is known to contain nutrients such as nitrogen and phosphorus, as well as other potential pollutants such as organic matter, solids, and pathogens. Increased environmental awareness has prompted the need for improved feedlot runoff control. As a result, open feedlots of all sizes are looking for cost effective alternatives to handle feedlot runoff. Vegetative treatment systems (VTSs) have been proposed as a potential option to control this runoff, enhance environmental security, and protect water quality. Although previous research has shown that vegetative treatment systems can be effective in plot-scale and limited field-scale studies, questions about their performance on commercial operations remain. In addition the sustainability and the mechanisms by which treatment is occurring are still uncertain. Answering questions about the mechanisms these systems use to provide treatment offers the possibility of improvements in future designs and will increase our ability to effectively operate and manage existing systems. Thus, the objectives of this research was to evaluate solids, phosphorus, and nitrogen transport and cycling within the vegetative treatment system to better understand that fate of these contaminants, and in doing so to improve the design and management of vegetative treatment systems. This dissertation will consist of work on each of these areas, solids, phosphorus, and nitrogen transport and cycling, as they, along with hydrology, are the keys to understanding vegetative treatment system performance and sustainability. The first section, on solids transport consists of three manuscripts. The first manuscript, Using total solids concentration to estimate nutrient content of feedlot runoff effluent from solids settling basins, vegetative infiltration basins, and vegetative treatment areas, relates nutrient content in feedlot runoff from solid settling basins, vegetative infiltration basins, and vegetative treatment areas to the solids content within the effluent. This analysis serves the purpose of demonstrating that managing and understanding the sedimentological connections within the treatment system provides a great deal of insight into transport of other parameters (particularly nitrogen, phosphorus, and organic matter). Specifically, this work demonstrates that if detailed models of sediment export from the feedlot and through the treatment system can be developed, then this information can be used in predicting the movement of other parameters of concern. The second manuscript, A review of settling characteristics of solids in runoff from beef feedlots reviews the sediment characteristics that are required to perform detailed modeling of solids transport within the treatment system. Specifically, the manuscript reviews the physical characteristics (particle size, density, and settling rates) of particles transported in runoff from beef feedlots, addressing how these properties differ between various feedlots with different surface conditions (concrete and earthen) and at different locations. The review focuses on the implications these settling properties have for designing successful sedimentation systems and in predicting the actual performance of settling basins. The third manuscript, Development of a runoff and sediment routing model for open lot beef feeding facilities describes the development of a hydraulic and sediment routing model designed to predict solids transport from feedlot surfaces. This model can be used for prioritizing feedlots that are in need of enhanced runoff control systems, evaluating the hydraulic and sediment loadings that a feedlot runoff control systems are required to handle, and for exploring how different feedlot sizes, layouts, and designs impact solids transport. The second section, on phosphorous fate and cycling in the vegetative treatment areas, consists of a series of three manuscripts that utilize different monitoring procedures and assays to assess mechanisms of phosphorus treatment and its fate within the vegetative treatment area. The first manuscript uses a phosphorus mass balance approach to project phosphorus accumulation in the soil and compares the projected increases to monitored trends in soil test phosphorus at six vegetation areas in Iowa. The manuscript provides a preliminary phosphorus balance at six vegetative treatment areas focusing on how phosphorus is partitioning between soil, water, and vegetation. The second manuscript builds on this work by utilizing a sequential fractionation procedure, the Hedley method, to better understand the accumulation patterns of phosphorus within the soil and thereby obtain the relative stability of the accumulated phosphorus. Results of the fractionation procedure were interpreted based on the concept that a maximum soil phosphorus retention capacity existed; however, none of the soils as of yet exhibited a phosphorus accumulation pattern indicative of saturation, although in many cases, specific pools, mostly organic phosphorus pools, did appear saturated. The third manuscript utilizes a phosphorus sorption experiment to evaluate how the soil\u27s phosphorus retention properties had been modified by five years of use as vegetative treatment areas. Specifically, the experiment evaluated how continued use of the vegetative treatment area modified the soil properties and the impact this had on the estimated phosphorus sink capacity of the soil. This experiment provides an evaluation of whether the life expectancy model developed previously by Baker et al. (2010) provides a useful estimation of vegetative treatment area phosphorus saturation life and explores what mechanisms may be allowing further phosphorus accumulation. Finally, the third section, on nitrogen transport and cycling, contains two manuscripts. The first manuscript, Vegetative treatment system impacts on groundwater quality, discusses groundwater concentrations up-gradient, within, and down-gradient of six vegetative treatment system on beef feedlots in Iowa. The manuscript provides statistical comparisons and trend analysis to evaluate impacts the system may be having. Nitrate leaching in the vegetative treatment system is also estimated. The second and final manuscript, The impact of vegetative treatment area use on soil biologically available carbon and nitrogen pools, reports the results of a long-term carbon and nitrogen fractionation procedure to evaluate if accumulation of labile carbon and nitrogen is occurring and if this organic matter is nitrogen enriched. A final conclusions manuscript, Vegetative treatment systems: design, management, and siting recommendations provides recommendations on what is required to construct successful vegetative treatment systems and which areas require future research so that designs can be refined and ensure appropriate nutrient cycling and retention

County-Level Assessment of Manure Nutrient Availability Relative to Crop Nutrient Capacity in Iowa

During the twentieth century, agricultural production strived to achieve increased food production in order to satisfy demands. This led to increased farm sizes and an operational separation of crop and livestock production. Society fears that the trend of increasing industrialization of animal agriculture has resulted in concentration of waste products associated with their production over relatively small geographic regions that are spatially segregated from crop production areas. A county level analysis of manure nutrients relative to crop nutrient capacity was conducted to assess the prevalence of these issues in Iowa. Results indicated that in general all counties had sufficient nutrient utilization capacities to value manure as a resource; however, counties in Northwest Iowa are becoming progressively more manure rich, while counties in Southwestern and Central Iowa are becoming progressively more manure poor. This separation of crop and livestock production is becoming more pronounced, indicating that nutrient (especially phosphorus) recovery systems that can concentrate manure nutrients for transport could become more important in maintaining county nutrient balances

Spin-Orbit Coupling and Magnetic Anisotropy in Iron-Based Superconductors

We determine theoretically the effect of spin-orbit coupling on the magnetic excitation spectrum of itinerant multi-orbital systems, with specific application to iron-based superconductors. Our microscopic model includes a realistic ten-band kinetic Hamiltonian, atomic spin-orbit coupling, and multi-orbital Hubbard interactions. Our results highlight the remarkable variability of the resulting magnetic anisotropy despite constant spin-orbit coupling. At the same time, the magnetic anisotropy exhibits robust universal behavior upon changes in the bandstructure corresponding to different materials of iron-based superconductors. A natural explanation of the observed universality emerges when considering optimal nesting as a resonance phenomenon. Our theory is also of relevance to other itinerant system with spin-orbit coupling and nesting tendencies in the bandstructure.Comment: 15 pages, 9 figure

Narasin as a Manure Additive to Reduce Methane Production from Swine Manure

Animal production systems are an important source of anthropogenic methane emissions. Production of methane results from microbial activity by anaerobic bacteria populations within the stored manure that breaks down organic material and converts it to biogas. Swine manures obtained from three deep pit storages in Central Iowa were dosed with Narasin, an ionophore, to evaluate its inhibitory effects on methane and biogas production. Four Narasin dosing rates were evaluated, these included 0 (Control), 7.5, 15, and 30 mg Narasin/kg of manure. Overall, the results indicated that Narasin had an inhibitory effect on methane and biogas production, with greater inhibition being seen at higher dosing rates. The inhibitory effect weakened with time such that after 120 days of incubation there was no statistical difference in cumulative methane production between samples dosed with Narasin and the control. Two additional treatments, based on the addition of an easily available carbohydrate, sugar, were also evaluated. Sugar (10 g per kg of manure) was added to manure both with (15 mg Narasin/kg) and without (0 mg Narasin/kg manure) Narasin amendment. The addition of sugar was performed to evaluate the impact an easily available substrate had on the inhibitory effects of Narasin. The results suggested that methane production was initially increased by the addition of sugar, but that the increased methane production lasted for less than 6 days, at which point cumulative methane production was similar to the control. When treated with both Narasin and sugar the inhibitory effect did not impact the gas production during the sugar digestion phase, but did result in reduced methane and biogas production thereafter. Overall the results indicated that Narasin can be an effective pit additive but further study is needed to recommend dosing frequency and to evaluate how the continuous addition of manure impacts Narasin effectiveness. Thus, this paper will describe a scaled up lab experiment that will be used to evaluate the effect of dosing frequency of Narasin to determine how producers could most effectively use it at the farm scale