Simon J. van Donk

Effect of Growth Promotants on the Occurrence of Endogenous and Synthetic Steroid Hormones on Feedlot Soils and in Runoff from Beef Cattle Feeding Operations

Supplements and growth promotants containing steroid hormones are routinely administered to beef cattle to improve feeding efficiency, reduce behavioral problems, and enhance production. As a result, beef cattle manure will contain both synthetic steroids as well as a range of endogenous steroids including androgens, estrogens, and progestogens. A two-year controlled study was conducted in which beef cattle were administered steroid hormones via subcutaneous implants and feed additives and the occurrence of 16 endogenous and synthetic steroid hormones and metabolites was evaluated in runoff from beef cattle feedlots and in manure and soil collected from feedlot surfaces. Samples were extracted and analyzed using liquid chromatography tandem mass spectrometryfor metabolites of the synthetic androgen trenbolone acetate, 17α-trenbolone, 17β-trenbolone, for the nonsteroidal semisynthetic estrogen agonist, α-zearalanol, and the synthetic progesterone melengesterol acetate, as well as a wide range of endogeneous estrogens, androgens, and fusarium metabolites. Synthetic steroids including trenbolone metabolites and melengestrol acetate were detected in fresh manure and in feedlot surface soils from cattle administered synthetic steroids at concentrations up to 55 ± 22 ng/g dry weight (dw) (17α-trenbolone) and 6.5 ± 0.4 ng/g dw (melengesterol acetate). Melengesterol acetate was detected in 6% of runoff samples from feedlots holding cattle administered synthetic steroids at concentrations ranging up to 115 ng/L. The presence of melengesterol acetate in runoff from beef cattle feeding operations has not been previously reported. Synthetic steroids were not detected in manure or runoff from control cattle. A wide range of endogenous hormones were detected in runoff and feedlot surface soils and manure from cattle given synthetic steroids and from control cattle, with no statistically significant differences in concentration. These results indicate that runoff from confined animal production facilities is of environmental and public health concern regardless of the use of growth promotants.

Effect of composting on the fate of steroids in beef cattle manure.

In this study, the fate of steroid hormones in beef cattle manure composting is evaluated. The fate of 16 steroids and metabolites was evaluated in composted manure from beef cattle administered growth promotants and from beef cattle with no steroid hormone implants. The fate of estrogens (primary detected as estrone), androgens, progesterone, and the fusarium metabolite and implant α-zearalanol was monitored in manure compost piles. First-order decay rates were calculated for steroid half-lives in compost and ranged from 8 d for androsterone to 69 d for 4-androstenedione. Other steroid concentration data could not be fit to first-order decay models, which may indicate that microbial processes may result in steroid production or synthesis in composting systems. We demonstrate that composting is an effective strategy to remove steroid hormones from manure. Total steroid hormone removal in composted beef cattle manure ranged from 79 to 87%.

Economic Return versus Crop Water Productivity of Maize for Various Nitrogen Rates under Full Irrigation, Limited Irrigation, and Rainfed Settings in South Central Nebraska

AbstractField research was conducted at the University of Nebraska-Lincoln South Central Agricultural Laboratory (SCAL) located near Clay Center, NE, in the growing seasons of 2011 to 2014. A partial economic analysis was conducted for maize (Zea mays L.) at nitrogen (N) fertilizer treatments of 0, 84, 140, 196, and 252  kg ha−1 under full irrigation (FIT), limited irrigation (75% FIT), and rainfed settings for all growing seasons and then compared to crop water productivity (CWP) measured as crop water use efficiency (CWUE) and irrigation water use efficiency (IWUE). Nitrogen fertilizer increased CWUE and IWUE in all growing seasons. The CWUE values ranged from 0.90 to 2.81  kg m−3 and the IWUE values ranged from −1.01 to 3.24  kg m−3. Operational costs and net income varied among treatments and across years. Irrigation and N fertilizer rate had an interacting effect (P0.05<0.05) on both gross and net income in 2011, 2012, and 2013. Net income was maximized under rainfed settings with a N fertilizer rate...

Influence of Soil Properties and Test Conditions on Sorption and Desorption of Testosterone

In this study, batch sorption and desorption experiments were conducted for testosterone using four agricultural soils and five clay minerals. Significant differences in sorption behavior were observed between abiotic and biotic systems. The Freundlich sorption coefficient Kf (µg per g)/(µg per mL) ranged from 8.53 to 74.46 for soils and from 35.28 to 1243 for clays. The maximum sorption capacity (µg per g) of soils ranged from 25.25 to 440.61 for soils and 168.46 to 499.84 for clays. Correlation of sorption model parameters with soil properties indicated that both clay content and soil organic matter are important variables in predicting testosterone sorption behavior. Observed testosterone desorption from agricultural soils ranged from approximately 14 to 100 percent after 3 desorption cycles, and the desorption percentage decreased as the initial testosterone concentration decreased. Temperature, ionic strength, the water/soil ratio and soil depth were determined to influence sorption and desorption of testosterone. Desorption significantly increase with the soil depth and with the increase in the water to soil ratio. Temperature had an inverse effect on the sorption capacity of the soils tested. Thermodynamic calculations showed that the enthalpy change of the soils tested were the range of 12.9-20.7 kJ per mol, indicating weak interaction between testosterone and soil. Our results suggest that additional studies on how soil particles with different size fractions affect hormones fate and transport are needed in order to determine the potential risk of testosterone leaching or runoff.

Effect of Nitrogen Application Timing on Corn Production Using Subsurface Drip Irrigation

The use of subsurface drip irrigation (SDI) in row-crop agriculture is increasing because of potential increases in water and nutrient use efficiency. Research-based information is needed to manage N applications through SDI systems in field corn (Zea mays L.) production. This study was conducted to assess the effect of different in-season SDI system N application timings on corn production and residual soil NO3-N at the University of Nebraska-Lincoln West Central Research and Extension Center in North Platte, Neb, on a Cozad silt loam (fine-silty, mixed, mesic Fluventic Haplustoll). We evaluated the effect of three N application timing methods (varying percentages of the total N rate [48% of total N] applied at the V10, VT, and R3 growth stages, in addition to uniform N applications [52% of total N] over all treatments at preplant, planting, and V14 growth stage) at two N application rates (University of Nebraska-Lincoln [UNL] recommended rate and the UNL rate minus 20%) on corn grain and biomass yield and end-of-study distribution of residual soil NO3-N. In 2006, there were no significant differences in corn grain yields between the two N application rates. In 2007, the grain yield under the UNL recommended N rate was significantly higher (190 kg ha−1) than the UNL-minus-20% N rate. The average grain yield for this study was close to the predicted yields (based on average 5-year historic yields + a 5% yield increase), indicating that corn production under SDI is satisfactory. In 2006 and 2007, grain yield and biomass production for the N application timing treatments were not significantly different (P > 0.05). The application of 13% of the total N at as late as R3 did not result in decreased yields. The lack of response to different N application timing treatments indicates that there is flexibility in N application timing for corn production under SDI. The distribution of NO3-N in the 0- to 0.9-m and 0.9- to 1.8-m soil profiles was not significantly different among all the treatments.

Effect of rainfall timing and tillage on the transport of steroid hormones in runoff from manure amended row crop fields

Runoff generated from livestock manure amended row crop fields is one of the major pathways of hormone transport to the aquatic environment. The study determined the effects of manure handling, tillage methods, and rainfall timing on the occurrence and transport of steroid hormones in runoff from the row crop field. Stockpiled and composted manure from hormone treated and untreated animals were applied to test plots and subjected to two rainfall simulation events 30days apart. During the two rainfall simulation events, detection of any steroid hormone or metabolites was identified in 8-86% of runoff samples from any tillage and manure treatment. The most commonly detected hormones were 17β-estradiol, estrone, estriol, testosterone, and α-zearalenol at concentrations ranging up to 100-200ngL-1. Considering the maximum detected concentrations in runoff, no more than 10% of the applied hormone can be transported through the dissolved phase of runoff. Results from the study indicate that hormones can persist in soils receiving livestock manure over an extended period of time and the dissolved phase of hormone in runoff is not the preferred pathway of transport from the manure applied fields irrespective of tillage treatments and timing of rainfall.

Effect of Amount and Timing of Subsurface Drip Irrigation on Corn Production

Subsurface drip irrigation (SDI) has the potential of being a more efficient irrigation system compared to systems such as center pivot and furrow irrigation. The objective of this study was to determine the effect of the amount and timing of irrigation, using SDI, on corn (Zea mays) production. A field study was conducted at North Platte, Nebraska in 2007 and 2008, using two SDI systems. The study was replicated eight times on the older SDI system (SDI1) and four times on the newer SDI system (SDI2). On SDI1, there were nine treatments to impose different irrigation regimes, ranging from dryland to fully irrigated. Five of the nine treatments allowed water stress only after tasseling and silking. On SDI2, there were eight treatments that were very similar to the nine on SDI1.

Effects of nitrogen application frequency via subsurface drip irrigation on corn development and grain yield

ABSTRACT Subsurface drip irrigation (SDI) has not only potential for water conservation, but also for improving nutrient use efficiency. Two nitrogen (N) application frequencies (every week versus every two weeks, via SDI) were compared in 2012 and 2013 on a Cozad silt loam in North Platte, Nebraska. The weekly treatment was fertigated every week for seven weeks in a row; the bi-weekly treatment was fertigated in weeks 1, 3, 5 and 7. Both treatments received the same total amount of N. There was a positive grain yield response to N application, but no advantage was found to a greater frequency of N application. Corn (Zea mays L.) grain yields and other indicators of corn growth and development (canopy-intercepted light, vegetation indices, indicators of chlorophyll content of corn plant leaves) were not affected by N application frequency.

Applications of WEPS and SWEEP to Non-Agricultural Lands

Soil erosion by wind is a serious problem throughout the United States and the world. Dust from wind erosion obscures visibility and pollutes the air. It fills road ditches where it impacts water quality, causes automobile accidents, fouls machinery, and imperils animal and human health. Dust and specifically particulate matter less than 10 microns (PM10), is regulated by the US-EPA National Ambient Air Quality Standards. The Wind Erosion Prediction System (WEPS) model was developed by the USDA Agricultural Research Service, primarily for the USDA Natural Resources Conservation Service to simulate wind erosion and develop conservation plans on cultivated agricultural lands. WEPS is a process based, daily-time step model that simulates hydrology, plant growth and decomposition, land management, and soil surface erodibility to simulate soil wind erosion loss (total, saltation/creep, suspension, and PM10 sizes) as affected by stochastically simulated local weather. The WEPS erosion sub-model has been developed into a stand-alone companion product that is known as the Single-event Wind Erosion Evaluation Program (SWEEP). SWEEP consists of the stand-alone WEPS Erosion sub-model combined with a user-friendly graphical interface and simulates soil loss and dust emissions from single wind storm events (i.e., one day). In addition to cultivated agricultural lands, wind erosion results in sediment and dust emissions from construction sites, mined and reclaimed land, landfills, and other disturbed lands. Such disturbed lands are often regulated by government agencies. The US-EPA sets limits on pollution levels and establishes permits for pollution release. In addition, state agencies develop State Implementation Plans (SIP’s) and operate permit programs for release of fugitive dust. Although developed for agricultural situations, WEPS and SWEEP are useful tools for simulating erosion by wind for such lands where typical agricultural practices and control methods are not utilized. WEPS is suitable for simulating long term (multiple years) control strategies such as mulching, re-vegetation, and large roughness elements such as burms. SWEEP on the other hand can simulate the potential soil loss for site specific planned surface conditions and control practices for a given date. SWEEP also provides probabilities of dust events given the defined surface conditions for the specified location and date. This paper explores the use of WEPS and SWEEP for developing control strategies for fugitive dust on construction sites and other non-agricultural disturbed lands. Case studies and comparative scenarios with examples of modifying WEPS and SWEEP inputs and management files to simulate common erosion control strategies are presented. Control strategies discussed include the simulation of water and other dust suppressants, wind barriers such as silt and snow fencing and hay bales, anchored and crimped straw mulch, vertical mulches, erosion blankets, re-vegetation, gougers, basin blades, berms, and other roughening practices. For example, dust suppressants are simulated by creating a crusted soil with low loose erodible material on the surface. Example simulations will be demonstrated. The paper describes tools needed to design erosion control plans that are not only cost-effective but also demonstrate regulatory compliance by using a science-based approach to risk assessment.

Feedlot manure handling and application strategies on surface runoff of artificial hormones applied to rowcrop fields

Hormones are essential to the function and propagation of almost all organisms, yet the environmental fate of hormones is not well understood. Because these substances are so common in nature, the question is not whether they will be found, but rather at what concentrations and in what form (biologically active or inactive) will they be found. The objective of this research was to determine the effect of manure handling and application strategies on artificial hormone losses in runoff through the use of simulated rainfall. In 2008, rainfall simulations were conducted at the Haskell Agricultural Laboratory near Concord, NE (Latitude: 42o 23’ 33.6” N; Longitude: 96o 57’ 18.0” W). The soil at the site is of the Nora silty clay loam family. Field slope was approximately 8% and no-till practices and a corn-soybean rotation had been employed for the previous 7 years. The field study consisted of 3 replications of a check (no manure, no tillage); 2 animal treatments (w/hormones, w/o hormones); 2 manure handling practices (stockpile and compost); and two incorporation methods (moldboard plow+disk and disk). Simulated rainfall was applied within 24-hours of manure application and runoff samples were collected at five minute intervals beginning at runoff initiation. Analyses of runoff samples were conducted using liquid chromatography tandem mass spectrometry. Results of the study showed sporadic infrequent detection of very low concentrations artificial hormones among treatments with no distinct pattern. More samples were detected with treated composted manure plots compared to stockpile manure; on the other hand, moldboard plow with disk incorporation detected more samples compared to the other two methods. The mass transport and flow weighted concentrations varied within the range of 1635 µg/ha and 9.75 ng/L for melengestrol acetate to 10.73 µg/ha and 0.14 ng/L for 17a-trenbolone respectively among the treatments. It can be concluded that low levels of artificial hormones and some metabolites were detected in runoff samples after land application and, may be transported to nearby surface water sources.