Resistivity Arrays as an Early Warning System for Monitoring Runoff Holding Ponds

Monitoring wells are installed to intercept contaminants inadvertently discharged from inground structures designed to retain salt-affected wastewaters; however, several difficulties with collection and data interpretation limit their effectiveness. Therefore, improved monitoring methods are needed. The objective of this study was to evaluate the effectiveness of resistivity array technology as an early warning system to monitor for unintended basin discharge. Subsurface resistivity arrays were installed at two Nebraska sites: a beef cattle feedyard located at the U.S. Meat Animal Research Center, Clay Center, Nebraska (FyA) and a commercial cattle feeding operation (FyB). Monitoring well data did not identify any unintended discharge events during the study period. However, the resistivity array (RA) system detected a discharge event that was localized in the non-saturated zone adjacent to the pond at FyB within one day following a precipitation event. Monitoring the unsaturated portion allows the RA system a capacity beyond traditional monitoring wells, which can only intercept discharge carried in groundwater. Also, the RA system effectively measured a larger area (i.e., a virtual curtain) compared to the point measure typical of monitoring wells. Therefore, RA technology provides broader coverage and is more tolerant to placement issues for intercepting discharge. Finally, the capacity to automate the RA system provides a means to continuously monitor unintended subsurface discharge from runoff holding ponds. This continuous monitoring system is more likely to detect discharge events than the bi-annual sampling typically required for monitoring wells. Automatic and continuous monitoring provides feedyard operators options to better manage environmental impacts associated with runoff holding ponds

Energy and Nutrient Recovery fromCattle Feedlots

Selective harvesting of manure can benefit cattle producers by creating a product of value. A tool that identifies locations of manure accumulation has been developed using a subsurface sensor (Dualem-1S, Milton, ON) and software designed for salt mapping (ESAP, Riverside, CA). The combination allowed the development of models to estimate higher heating value (HHV) of feedlot manure across a feedlot pen. Soil sample data from cattle feedlots in Texas and Nebraska were analyzed for volatile solids (VSs) then combined with the Dualem-1S apparent soil conductivity (ECa) data to produce models having correlations between associated ECa values and VS (r2 = 0.869, VS). A corresponding model is under development to estimate the moisture content of the collectable solids. The combined models allow real-time spatial estimates of HHV within a feedlot pen. These methods will allow direct harvesting of VS for use as a recoverable energy source through direct combustion or cocombustion

Greenhouse Gas Emissions from Beef Feedlot Surface Materials as Affected by Diet, Moisture, Temperature, and Time

A laboratory study was conducted to measure the effects of diet, moisture, temperature, and time on greenhouse gas (GHG) emissions from feedlot surface materials (FSM). The FSM were collected from open-lot pens where beef cattle were fed either a dry-rolled corn (DRC) diet containing no wet distillers grains with solubles (WDGS) or a DRC diet containing 35% WDGS. The FSM were collected, air-dried or mixed with 3.0 L of water to represent dry or wet conditions, and then incubated at temperatures of 5°C, 15°C, 25°C, or 35°C. Static flux chambers were used to quantify GHG emissions over a 14-day period. Flux data for each diet × moisture combination were analyzed using repeated measures in time. The largest GHG emissions occurred under wet conditions at temperatures of 25°C and 35°C. Flux values for these conditions typically were significantly greater than measurements obtained on the same day at 5°C and 15°C. Mean emissions under wet conditions for CO2, CH4, and N2O were 35, 121, and 278 times greater, respectively, than emissions from dry FSM. The 0% WDGS diet produced mean CO2 and N2O flux measurements that were 1.8 and 1.5 times greater, respectively, than those obtained for the 35% WDGS diet. The 35% WDGS diet, in contrast, produced a mean CH4 emission rate that was 6 times greater than the 0% WDGS diet. Management for GHG mitigation should include design and/or maintenance of pen drainage to speed drying as well as the use of modified animal diets

EMISSION OF VOLATILE ORGANIC COMPOUNDS FROM LAND-APPLIED BEEF CATTLE MANURE AS AFFECTED BY APPLICATION METHOD, DIET, AND SOIL WATER CONDITION

Land application of beef cattle manure may result in the emission of volatile organic compounds (VOC). This study was conducted to evaluate the effects of diet, land application method, soil water condition, and time since manure application on VOC emissions. Manure was collected from feedlot pens where cattle were fed diets containing 0%, 10%, or 30% wet distillers grains with solubles (WDGS). The effects of manure application method (surface-applied or incorporated) and soil water condition (saturated or wet) on VOC emissions were measured over a 48 h period. Heptanoic, hexanoic, isobutyric, and isovaleric acids contributed 23.5%, 17.6%, 9.26%, and 3.39% (0.034, 0.258, 0.030, and 0.014 g m-2 min-1), respectively, to total odor activity values (OAV). The aromatics indole and skatole contributed 14.7% and 8.84%, (0.005 and 0.0004 g m-2 min-1), respectively, to total OAV. Dimethyl disulfide (DMDS) contributed 9.50% (0.013 g m-2 min-1) and dimethyl trisulfide (DMTS) contributed 5.68% (0.030 g m-2 min-1) to total OAV. Emissions of the sulfur compounds (DMDS and DMTS) were substantially greater for the 30% WDGS diet. With the exception of heptanoic acid, flux measurements were greater from the plots where manure was surface-applied than from the plots where manure was incorporated. Emissions of each VOC were greater on the first day following manure application when a saturated soil water condition was present. VOC flux values were found to rapidly decrease following manure application. Effective best management practices for reducing VOC emissions are to incorporate manure soon after application and to delay land application when there is a high probability of rainfall

Soil-Crop Dynamic Depth Response Determined from TDR of a Corn Silage Field Compared to EMI Measurements

Electromagnetic induction (EMI) techniques have been used to monitor bulk seasonal soil-crop apparent electrical conductivity (ECa) dynamics. Interpreting this information can be complicated by changes in the soil profile such as water content or nutrient leaching. Time domain reflectometry (TDR) measures localized soil EC; therefore, TDR can provide clarification to where in the soil profile the EC changes are taking place. The objective of this study was to determine whether surface or deep EC changes were driving the response measured by EMI during the crop season of a field amended with animal manure. Results indicate that seasonal soil-crop EC dynamics measured by EMI are primarily driven by surface (,0.2 m) changes as opposed to deeper (.0.9 m) changes. These changes appear to be the result of surface ionic dynamics caused by crop-soil interactions and not soil volumetric water content (hv), since no significant correlations were detected between hv and ECa for any treatment, depth or dipole orientation. These findings are consistent with others who reported the EMI signal was driven primarily by changes in nitrate concentration and not by soil water content. The results of this study clarify our understanding of the soil dynamics that drive the ECa response of a manure amended field. The ability to non-intrusively measure nutrient mineralization and crop uptake provides researchers with a powerful tool for understanding soil-crop interactions. Understanding the soil-crop dynamic will facilitate development of management practices for amending soil with manure while protecting the environment from unintended contamination

Soil-Crop Dynamic Depth Response Determined from TDR of a Corn Silage Field Compared to EMI Measurements

Electromagnetic induction (EMI) techniques have been used to monitor bulk seasonal soil-crop apparent electrical conductivity (ECa) dynamics. Interpreting this information can be complicated by changes in the soil profile such as water content or nutrient leaching. Time domain reflectometry (TDR) measures localized soil EC; therefore, TDR can provide clarification to where in the soil profile the EC changes are taking place. The objective of this study was to determine whether surface or deep EC changes were driving the response measured by EMI during the crop season of a field amended with animal manure. Results indicate that seasonal soil-crop EC dynamics measured by EMI are primarily driven by surface (,0.2 m) changes as opposed to deeper (.0.9 m) changes. These changes appear to be the result of surface ionic dynamics caused by crop-soil interactions and not soil volumetric water content (hv), since no significant correlations were detected between hv and ECa for any treatment, depth or dipole orientation. These findings are consistent with others who reported the EMI signal was driven primarily by changes in nitrate concentration and not by soil water content. The results of this study clarify our understanding of the soil dynamics that drive the ECa response of a manure amended field. The ability to non-intrusively measure nutrient mineralization and crop uptake provides researchers with a powerful tool for understanding soil-crop interactions. Understanding the soil-crop dynamic will facilitate development of management practices for amending soil with manure while protecting the environment from unintended contamination

Spatial Variations in Nutrient and Microbial Transport from Feedlot Surfaces

Nutrient and microbial transport by runoff may vary at different locations within a beef cattle feedlot. If the areas making the largest contributions to nutrient and microbial transport can be identified, it may be possible to institute site‐specific management practices to reduce runoff nutrient and microbial transport. The objectives of this study were to: (1) measure selected feedlot soil properties and nutrient and microbial transport in runoff from various feedlot locations, (2) compare the effects of unconsolidated surface materials (USM) (loose manure pack) and consolidated subsurface materials (CSM) (compacted manure and underlying layers) on nutrient and microbial transport, and (3) determine if nutrient and microbial transport in runoff are correlated to selected feedlot soil characteristics. Simulated rainfall events were applied to 0.75 m wide by 2 m long plots. No significant differences (P \u3c 0.05) in feedlot soil characteristics or nutrient transport in runoff were found between USM and CSM. However, concentrations of E. coli were significantly greater in the USM than the CSM. Pen location was found to significantly influence feedlot soil measurements of Bray‐1 P, calcium, chloride, copper, electrical conductivity (EC), loss on ignition, organic N, phosphorus, potassium, sodium, sulfur, total N (TN), water‐soluble P, and zinc. Runoff measurements of dissolved phosphorus (DP), EC, and NH4-N were significantly influenced by pen location and were correlated to selected feedlot soil characteristics. Thus, it may be possible to estimate DP, EC, and NH4-N in runoff from selected feedlot soil parameters

Nutrient and Microbial Transport from Feedlot Surfaces

Nutrient and microbial transport by runoff may vary at different locations within a beef cattle feedlot. If the areas making the largest contributions to nutrient and microbial transport can be identified, it may be possible to institute site-specific management practices to reduce runoff nutrient and microbial transport. The objectives of this study were to: a) measure selected feedlot soil properties, and nutrient and microbial transport in runoff from various feedlot locations b) compare the effects of unconsolidated surface materials (USM) (loose manure pack) and consolidated subsurface materials (CSM) (compacted manure and underlying layers) on nutrient and microbial transport, and c) determine if nutrient and microbial transport in runoff are correlated to selected feedlot soil characteristics. Simulated rainfall events were applied to 0.75-m wide by 2-m long plots. No significant differences (P \u3c 0.05) in feedlot soil characteristics or nutrient transport in runoff were found between USM and CSM. However, concentrations of E. coli were significantly greater in the USM than the CSM. Pen location was found to significantly influence feedlot soil measurements of Bray 1-P, calcium, chloride, copper, electrical conductivity (EC), loss on ignition, organic-N, phosphorus, potassium, sodium, sulfur, total N (TN), water soluble P, and zinc. Runoff measurements of dissolved phosphorus (DP), EC, and NH4-N were significantly influenced by pen location and were correlated to selected feedlot soil characteristics. Thus, it may be possible to estimate DP, EC, and NH4-N in runoff from selected feedlot soil parameters

Energy and Nutrient Recovery fromCattle Feedlots

Selective harvesting of manure can benefit cattle producers by creating a product of value. A tool that identifies locations of manure accumulation has been developed using a subsurface sensor (Dualem-1S, Milton, ON) and software designed for salt mapping (ESAP, Riverside, CA). The combination allowed the development of models to estimate higher heating value (HHV) of feedlot manure across a feedlot pen. Soil sample data from cattle feedlots in Texas and Nebraska were analyzed for volatile solids (VSs) then combined with the Dualem-1S apparent soil conductivity (ECa) data to produce models having correlations between associated ECa values and VS (r2 = 0.869, VS). A corresponding model is under development to estimate the moisture content of the collectable solids. The combined models allow real-time spatial estimates of HHV within a feedlot pen. These methods will allow direct harvesting of VS for use as a recoverable energy source through direct combustion or cocombustion

Energy and Nutrient Recovery fromCattle Feedlots

Selective harvesting of manure can benefit cattle producers by creating a product of value. A tool that identifies locations of manure accumulation has been developed using a subsurface sensor (Dualem-1S, Milton, ON) and software designed for salt mapping (ESAP, Riverside, CA). The combination allowed the development of models to estimate higher heating value (HHV) of feedlot manure across a feedlot pen. Soil sample data from cattle feedlots in Texas and Nebraska were analyzed for volatile solids (VSs) then combined with the Dualem-1S apparent soil conductivity (ECa) data to produce models having correlations between associated ECa values and VS (r2 = 0.869, VS). A corresponding model is under development to estimate the moisture content of the collectable solids. The combined models allow real-time spatial estimates of HHV within a feedlot pen. These methods will allow direct harvesting of VS for use as a recoverable energy source through direct combustion or cocombustion