Central Iowa Research Articles

Establishment of Alleycropped Hybrid Aspen “Crandon” in Central Iowa, USA: Effects of Topographic Position and Fertilizer Rate on Aboveground Biomass Production and Allocation

Hybrid poplars have demonstrated high productivity as short rotation woody crops (SRWC) in the Midwest USA, and the hybrid aspen “Crandon” (Populus alba L. × P. grandidenta Michx.) has exhibited particularly promising yields on marginal lands. However, a key obstacle for wider deployment is the lack of economic returns early in the rotation. Alleycropping has the potential to address this issue, especially when paired with crops such as winter triticale which complete their growth cycle early in the summer and therefore are expected to exert minimal competition on establishing trees. In addition, well-placed fertilizer in low rates at planting has the potential to improve tree establishment and shorten the rotation, which is also economically desirable. To test the potential productivity of “Crandon” alleycropped with winter triticale, plots were established on five topographic positions with four different rates of fertilizer placed in the planting hole. Trees were then harvested from the plots after each of the first three growing seasons. Fertilization resulted in significant increases in branch, stem, and total aboveground biomass across all years, whereas the effects of topographic position varied by year. Allocation between branches and stems was found to be primarily a function of total aboveground biomass.

The Effect of Wind-Turbine Wakes on Summertime US Midwest Atmospheric Wind Profiles as Observed with Ground-Based Doppler Lidar

We examine the influence of a modern multi-megawatt wind turbine on wind and turbulence profiles three rotor diameters (\(D\)) downwind of the turbine. Light detection and ranging (lidar) wind-profile observations were collected during summer 2011 in an operating wind farm in central Iowa at 20-m vertical intervals from 40 to 220 m above the surface. After a calibration period during which two lidars were operated next to each other, one lidar was located approximately \(2D\) directly south of a wind turbine; the other lidar was moved approximately \(3D\) north of the same wind turbine. Data from the two lidars during southerly flow conditions enabled the simultaneous capture of inflow and wake conditions. The inflow wind and turbulence profiles exhibit strong variability with atmospheric stability: daytime profiles are well-mixed with little shear and strong turbulence, while nighttime profiles exhibit minimal turbulence and considerable shear across the rotor disk region and above. Consistent with the observations available from other studies and with wind-tunnel and large-eddy simulation studies, measurable reductions in wake wind-speeds occur at heights spanning the wind turbine rotor (43–117 m), and turbulent quantities increase in the wake. In generalizing these results as a function of inflow wind speed, we find the wind-speed deficit in the wake is largest at hub height or just above, and the maximum deficit occurs when wind speeds are below the rated speed for the turbine. Similarly, the maximum enhancement of turbulence kinetic energy and turbulence intensity occurs at hub height, although observations at the top of the rotor disk do not allow assessment of turbulence in that region. The wind shear below turbine hub height (quantified here with the power-law coefficient) is found to be a useful parameter to identify whether a downwind lidar observes turbine wake or free-flow conditions. These field observations provide data for validating turbine-wake models and wind-tunnel observations, and for guiding assessments of the impacts of wakes on surface turbulent fluxes or surface temperatures downwind of turbines.

Soil quality response to long-term tillage and crop rotation practices

Soil quality is influenced by inherent and anthropogenic factors. This study was conducted to provide multiple groups guidance on how to achieve and maintain improved soil quality/health. Our hypothesis was that tillage intensity was the primary anthropogenic factor degrading soil quality, and our objective was to prove that hypothesis through an intensive 2005 sampling of a central Iowa, USA field study. Chisel plow, disk tillage, moldboard plow, ridge-till and no-till treatments, used for 31 years in a two-year, corn (Zea mays L.)/soybean [Glycine max (L.) Merr.] (C/S) rotation or for 26 years of continuous corn (CC) production, were evaluated by measuring 23 potential soil quality indicators. Soil samples from 0 to 5- and 5 to 15-cm depth increments were collected from 158 loam or clay loam sampling sites throughout the 10-ha study site. Nine of the indicators were evaluated by depth increment using the Soil Management Assessment Framework (SMAF) which has scoring functions for 13 soil biological, chemical, and physical measurements and can be used to compute individual indicator indices and an overall soil quality index (SQI). Water-stable aggregation (WSA), total organic carbon (TOC), microbial biomass carbon (MBC), and potentially mineralizable nitrogen (PMN) were all significantly lower for the 0 to 5-cm and generally lower for 5 to 15-cm increments after long-term moldboard plowing and its associated secondary tillage operations. This presumably reflected greater physical breakup and oxidation of above- and below-ground plant residues. Bray-P concentrations in moldboard plow plots were also significantly lower at both depth increments. Between soil texture groups, significant differences were found for WSA, Bray-P, TOC and MBC at both depth increments and for both cropping systems. When combined into an overall SQI, both soil texture groups were functioning at 82–85% of their potential at 0–5-cm and at 75% of their potential at the 5–15-cm depth. Our hypothesis that moldboard plowing would have the greatest negative effect on soil quality indicators was verified. Based on this assessment, we recommend that to achieve and maintain good soil health, producers should strive to adopt less aggressive tillage practices.

Field-Level Financial Assessment of Contour Prairie Strips for Enhancement of Environmental Quality

The impacts of strategically located contour prairie strips on sediment and nutrient runoff export from watersheds maintained under an annual row crop production system have been studied at a long-term research site in central Iowa. Data from 2007 to 2011 indicate that the contour prairie strips utilized within row crop-dominated landscapes have greater than proportionate and positive effects on the functioning of biophysical systems. Crop producers and land management agencies require comprehensive information about the Best Management Practices with regard to performance efficacy, operational/management parameters, and the full range of financial parameters. Here, a farm-level financial model assesses the establishment, management, and opportunity costs of contour prairie strips within cropped fields. Annualized, depending on variable opportunity costs the 15-year present value cost of utilizing contour prairie strips ranges from $590 to $865ha(-1)year(-1) ($240-$350ac(-1)year(-1)). Expressed in the context of "treatment area" (e.g., in this study 1ha of prairie treats 10ha of crops), the costs of contour prairie strips can also be viewed as $59 to about $87 per treated hectare ($24-$35ac(-1)). If prairie strips were under a 15-year CRP contract, total per acre cost to farmers would be reduced by over 85%. Based on sediment, phosphorus, and nitrogen export data from the related field studies and across low, medium, and high land rent scenarios, a megagram (Mg) of soil retained within the watershed costs between $7.79 and $11.46mg(-1), phosphorus retained costs between $6.97 and $10.25kg(-1), and nitrogen retained costs between $1.59 and $2.34kg(-1). Based on overall project results, contour prairie strips may well become one of the key conservation practices used to sustain US Corn Belt agriculture in the decades to come.

How Many Measurements of Soil Moisture within the Footprint of a Ground‐Based Microwave Radiometer Are Required to Account for Meter‐Scale Spatial Variability?

Validation of ground‐based microwave remote sensing measurements with point measurements of soil moisture remains an important task. The number of point measurements needed to characterize the mean soil moisture of an area on the order of tens of square meters, and the manner in which these observations should be made remain unknown. We conducted a field experiment in central Iowa to characterize the spatial process of soil moisture and sampling strategies for estimating the mean soil moisture of an area that represents the footprint of a ground‐based microwave radiometer. We determined the spatial dependence of the moisture content of bare soil at this scale, which allows the determination of the mean soil moisture from point measurements. This spatial dependence can be described by an exponential variogram model. The parameters of this model vary according to mean moisture conditions. The accuracy of the estimate of mean soil moisture depends on the number of point measurements, what sampling technique is used, and mean moisture conditions. When we use spatial dependence, we increase the accuracy and precision of our estimates of the mean. Lattice and stratified sampling schemes require fewer measurements than random sampling when a higher level of accuracy in the estimate of mean soil moisture is desired. Practically, if measurements of soil moisture are made in random locations and spatial dependence is not used, we found that approximately 20 measurements within a 7 by 9 m footprint would estimate the mean to within close to 0.01 m3 m−3 of the true value for the entire range of soil moisture conditions that we observed.

The accuracy of the plusoptiX A08 photoscreener in detecting risk factors for amblyopia in central Iowa

To evaluate the accuracy of the plusoptiX A08 photoscreener in detecting risk factors for amblyopia in children aged 0-5 years in central Iowa. The medical records of consecutive patients seen at 1 practice during a 2-month period were retrospectively reviewed. All patients were screened with the plusoptiX A08 photoscreener and received a comprehensive pediatric ophthalmology examination. Photoscreening results, according to our age-based criteria, were compared with the comprehensive examination findings. Patients were considered to have amblyopia or amblyogenic risk factors in the comprehensive examination based on the American Association for Pediatric Ophthalmology and Strabismus referral criteria guidelines. A total of 290 children were examined during the study period. Of these, 190 (66%) patients were found to have amblyopia or amblyogenic risk factors during the pediatric ophthalmology examination on the basis of American Association for Pediatric Ophthalmology and Strabismus guidelines. The plusoptiX A08 offered an overall testability rate of 98%, sensitivity of 87%, specificity of 88%, positive predictive value of 93%, and negative predictive value of 78%. The sensitivity for detection of strabismus ≤20(Δ) was 52%. The plusoptiX showed a high sensitivity for the detection of refractive amblyogenic risk factors and had a high successful testability rate in infants; however, it had low sensitivity for detecting strabismus ≤20(Δ). We postulate that sensitivity for detecting amblyogenic risk factors can be improved by combining the use of this instrument with a cover or stereo test.

First Report of Soybean Vein Necrosis Disease Caused by Soybean vein necrosis-associated virus in Wisconsin and Iowa.

Several viral diseases of soybean (Glycine max) have been identified in the north-central U.S. soybean production area, which includes Wisconsin and Iowa (2). Previously, Soybean vein necrosis disease (SVND) caused by Soybean vein necrosis-associated virus was reported in Arkansas, Tennessee, and other southern states (4). In September 2012, soybean plants with symptoms similar to those reported for SVND (4) were observed in fields across Wisconsin and Iowa. Symptoms included leaf-vein and leaf chlorosis, followed by necrosis of the leaf veins and eventually necrosis of the entire leaf. Six samples with symptoms indicative of SVNaV were collected from research plots located at the West Madison Agricultural Research Station located in Madison, WI. An additional three samples were collected from three locations in central Iowa. Total RNA extracted from each sample using the Trizol Plus RNA purification kit (Invitrogen, Carlsbad, CA) was used to generate complementary DNA (cDNA) using the iScript cDNA synthesis kit (Bio-Rad Laboratories, Hercules, CA) following the manufacturers' suggested protocols. The resulting cDNA was used as template in a PCR with SVNaV-specific primers, SVNaV-f1 and SVNaV-r1 (3). PCRs of two of the six Wisconsin samples and two Iowa samples were positive. Amplification products were not detected in the other five samples. The amplification products from the four strongly positive samples were purified using the Wizard SV Gel and PCR Purification Kit (Promega, Madison, WI) following the manufacturer's suggested protocol and were subjected to automated sequencing (University of Wisconsin Biotechnology Center or Iowa State University, DNA Sequencing Facilities). BLASTn (1) alignments of the 915-bp consensus sequence revealed 98% and >99% identity of the Wisconsin and Iowa samples, respectively, with the 'S' segment of the SVNaV 'TN' isolate (GenBank Accession No. GU722319.1). Samples from the same leaf tissue used above, were subjected to serological tests for SVNaV using antigen coated-indirect ELISA (3). Asymptomatic soybeans grown in the greenhouse were used as a source of leaves for negative controls. These tests confirmed the presence of SVNaV in eight symptomatic soybean leaflets collected in Wisconsin and Iowa. The asymptomatic control and one Iowa sample, which was also PCR-negative, were also negative by serological testing. Six additional samples from soybean fields in as many Wisconsin counties (Fond Du Lac, Grant, Green, Juneau, Richland, Rock) tested positive for SVNaV using specific primers that amplify the 'L' segment (4). The sequenced amplification products (297-bp) showed 99 to 100% homology to the L segment of the TN isolate (GU722317.1). To our knowledge, this is the first report of SVNaV associated with soybean and the first report of SVND in Wisconsin and Iowa. Considering that little is known about SVNaV, it is assumed that it is like other Tospoviruses and can cause significant yield loss (4). Soybean is a major cash crop for Wisconsin and Iowa, and infection by SVNaV could result in potential yield loss in years where epidemics begin early and at a high initial inoculum level.

Crop Wind Energy Experiment (CWEX): Observations of Surface-Layer, Boundary Layer, and Mesoscale Interactions with a Wind Farm

Perturbations of mean and turbulent wind characteristics by large wind turbines modify fluxes between the vegetated surface and the lower boundary layer. While simulations have suggested that wind farms could significantly change surface fluxes of heat, momentum, momentum, moisture, and CO2 over hundreds of square kilometers, little observational evidence exists to test these predictions. Quantifying the influences of the “turbine layer” is necessary to quantify how surface fluxes are modified and to better forecast energy production by a wind farm. Changes in fluxes are particularly important in regions of intensely managed agriculture where crop growth and yield are highly dependent on subtle changes in moisture, heat, and CO2. Furthermore, speculations abound about the possible mesoscale consequences of boundary layer changes that are produced by wind farms. To address the lack of observations to answer these questions, we developed the Crop Wind Energy Experiment (CWEX) as a multiagency, multiuniversity field program in central Iowa. Throughout the summer of 2010, surface fluxes were documented within a wind farm test site and a 2-week deployment of a vertically pointing lidar quantified wind profiles. In 2011, we expanded measurements at the site by deploying six flux stations and two wind-profiling lidars to document turbine wakes. The results provide valuable insights into the exchanges over a surface that has been modified by wind turbines and a basis for a more comprehensive measurement program planned for the summer in 2014.

Changes in hydrology and streamflow as predicted by a modelling experiment forced with climate models

Changes in precipitation and temperature have direct effects on crop water use, water stress, crop yield, evapotranspiration, water nutrient dynamics and other indicators. This study, built on a modelling framework with the Soil and Watershed Assessment Tool (SWAT) model for the Raccoon River Watershed in central Iowa, a typical US Midwestern agricultural watershed, examines the watershed response to changes in meteorological inputs from an ensemble of ten global climate models under the A1B scenario. Changes in climate were directly applied to observations (the delta change method) assuming that the estimates of climate change are reliable even if the simulated current climate may be biased. The ensemble average for the mid-century (1946–1965) predicted 0.7% increase in daily precipitation (monthly variation from −11.3% to +19.5%) and 2.78 °C increase in average temperature over the entire watershed. These predictions were translated through a well-calibrated SWAT modelling setup into 22% decrease in snowfall, 16% decrease in surface runoff, 18% decrease in baseflow, 8% increase in evapotranspiration and 17% decrease in total water yield. The spatial impact at the subwatershed level revealed a wide variation (but no defined trend) with decrease in water yield that ranged from 10% to 23%. Flow near the watershed outlet (Van Meter, Iowa) is expected to decline by 17% on an average annual basis with the highest impact occurring during summer months with a maximum 39% reduction in August. Changes in climate were found to have a clear and significant impact signal of decreasing streamflow at the watershed outlet with far-reaching implication for drinking water supplies for the central Iowa communities. Copyright © 2013 John Wiley & Sons, Ltd.

A hybrid dual‐source scheme and trapezoid framework–based evapotranspiration model (HTEM) using satellite images: Algorithm and model test

Satellite remote sensing techniques are widely considered as the most promising way to estimate evapotranspiration (ET) over large geographic extents. In this study, a hybrid dual‐source scheme and trapezoid framework–based evapotranspiration model (HTEM) is developed to map evapotranspiration from satellite imagery. It adopts a theoretically determined vegetation index/land surface temperature trapezoidal space to decompose bulk radiative surface temperature into component temperatures (soil and canopy) and uses a hybrid dual‐source scheme of the layer approach and patch approach to partition net radiation and estimate sensible and latent fluxes separately from the soil and canopy. The proposed model was tested at the Soil Moisture‐Atmosphere Coupling Experiment (SMACEX) site in central Iowa, USA, for 3 days during the campaign in 2002 using Landsat Thematic Mapper/Enhanced Thematic Mapper Plus (TM/ETM+) data, and at the Weishan flux site in the North China Plain during the main growing season of 2007 with Moderate Resolution Imaging Spectroradiometer Terra images. Results indicate that HTEM is capable of estimating latent heat flux (LE) with mean absolute percentage errors of 6.4% and 11.2% for the SMACEX and the Weishan sites, respectively. In addition, the model was found to be able to give reasonable evaporation and transpiration partitioning at both sites. Compared with other models, HTEM generally produced better sensible and latent flux estimates at the two sites and had comparable abilities in estimating net radiation and ground heat flux. Sensitivity analysis suggests that HTEM is most sensitive to temperature variables and less sensitive to other meteorological observations and parameters.

Using biodiversity to link agricultural productivity with environmental quality: Results from three field experiments in Iowa

AbstractAgriculture in the US Corn Belt is under increasing pressure to produce greater quantities of food, feed and fuel, while better protecting environmental quality. Key environmental problems in this region include water contamination by nutrients and herbicides emitted from cropland, a lack of non-agricultural habitat to support diverse communities of native plants and animals, and a high level of dependence on petrochemical energy in the dominant cropping systems. In addition, projected changes in climate for this region, which include increases in the proportion of precipitation coming from extreme events could make soil and water conservation in existing cropping systems more difficult. To address these challenges we have conducted three cropping systems projects in central Iowa: the Marsden Farm Cropping Systems experiment, the Science-based Trials of Row-crops Integrated with Prairies (STRIPs) experiment, and the Comparison of Biofuel Systems (COBS) experiment. Results from these experiments indicate that (1) diversification of the dominant corn–soybean rotation with small grains and forage legumes can permit substantial reductions in agrichemical and fossil hydrocarbon use without compromising yields or profitability; (2) conversion of small amounts of cropland to prairie buffer strips can provide disproportionately large improvements in soil and water conservation, nutrient retention, and densities of native plants and birds; and (3) native perennial species can generate large amounts of biofuel feedstocks and offer environmental benefits relative to corn- and soybean-based systems, including greater carbon inputs to soil and large reductions in nitrogen emissions to drainage water. Increasing biodiversity through the strategic integration of perennial plant species can be a viable strategy for reducing reliance on purchased inputs and for increasing agroecosystem health and resilience in the US Corn Belt.

Thirty-year tillage effects on crop yield and soil fertility indicators

Long-term studies are crucial for quantifying tillage effects on productivity and soil fertility. Moldboard plow, chisel plow, spring disk, ridge-tillage, and no-tillage systems were evaluated after 32 years of a corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] rotation and 27 years of continuous corn in central Iowa, U.S.A. Productivity was quantified using yield, while soil fertility status was evaluated by collecting four, 5-cm diameter soil cores to a depth of 0.9m from each treatment, dividing them into four depth increments (0–15-, 15–30-, 30–60-, and 60–90-cm), analyzing them for bulk density (BD), NO3-N, NH4-N, electrical conductivity (EC), pH, Mehlich-3 extractable P, K, Ca, Mg and DTPA-extractable Cu, Fe, Mn, and Zn, and interpreting the data using Iowa State University (ISU) guidelines. Production costs for each tillage and cropping system were also computed. To account for genetic and agronomic changes during the 30-year study period, yields were examined for establishment, maintenance, and intensification/recovery phases. Rotated corn yield averaged 8.6, 8.8, and 11.6Mgha−1 and soybean yield averaged 2.7, 3.2, and 3.4Mgha−1, respectively, for each of the phases. Continuous corn from 1988 to 2006 averaged 7.5 and 10.1Mgha−1 for the maintenance and intensification/recovery phases, respectively. Fixed plus variable machinery costs for corn ranged from 233 to 354 USD ha−1, while for soybean they ranged from 194 to 280 USD ha−1. Net returns to land, labor and management ranged from 233 to 269, 560 to 620, and 437 to 483 USD ha−1 for continuous corn, rotated corn, and rotated soybean, respectively. Based on 9-year (2003–2011) average grain prices and yields from this study, the corn–soybean rotation was twice as profitable as continuous corn. Soil-test P and K measurements, as well as calculated P and K removal, suggest that nutrient mining occurred during the course of this study. The soil-test data also indicate that further studies are needed regarding plant availability of subsoil K and its impact on fertilizer recommendations. Overall, we conclude that with good nutrient management and crop rotation, yield and soil fertility differences between no-tillage and more intensive tillage systems can be minimized and that no-till production can be profitable on glacial till derived soils.

Intraseasonal Changes in Switchgrass Nitrogen Distribution Compared with Corn

Incorporating perennial, bioenergy crops like switchgrass (Panicum virgatum L.) into agricultural landscapes can provide harvestable biomass while improving ecosystem functions, but clear plant N management recommendations for switchgrass remain elusive. Delaying harvest until spring can reduce plant N concentration ([N]) but also harvestable yield, creating a tradeoff between feedstock quality and quantity. This study investigated internal changes in the temporal and spatial distribution of N in switchgrass tissues. Above‐ and belowground switchgrass biomass was harvested at five dates annually from field plots in central Iowa for 2 yr. The [N] of aboveground tissues decreased during the growing season, with no further change over winter. The [N] of belowground biomass tissues found within the upper strata (0–45 cm) of the soil profile increased significantly from July to October (P = 0.0050), suggesting seasonal N translocation. Plots harvested at peak biomass, before senescence, yielded significantly less the following season (P < 0.0001), suggesting that this harvest strategy would not be sustainable in the long term. Although delaying harvest to after frost reduced the harvested biomass, less N was removed with the harvest, more was stored in belowground tissues, and yields were more similar between years. A postfrost switchgrass harvest would remove much less N during a 2‐yr period compared with continuous corn (Zea mays L.) with 50% stover removal (57.7 vs. 432.2 kg N ha−1). Results provide values of N stocks and fluxes in switchgrass tissues, showing the tradeoffs between feedstock quality and quantity.

Migration, Acculturation, and Environmental Values: The Case of Mexican Immigrants in Central Iowa

Human–environment geography and geographic research on migration have largely been treated as separate scholarly spheres. Meanwhile, even as recent immigration exerts dynamic changes on American culture, relatively little scholarly work addresses immigrants’ attitudes toward environmental issues. In this article, we address the following questions: How do Mexican immigrants perceive and understand the environment and environmental problems? How do environmental values shift or become modified during the process of acculturation in the United States? To answer these questions, we use the results of surveys conducted with Mexican immigrants and their kin in central Iowa. We develop an interdisciplinary theoretical framework based on a modified concept of “environmentality” that incorporates insights from research on environmental values, immigration and acculturation, political ecology, and environmental justice. Based on this analysis, we find that immigrants become socialized to new norms, in part, through environmental practices. They are readily accepting of some U.S. norms around environmental thought and behavior (especially with respect to maintaining public spaces) but critical of others (e.g., the excessive materialism of American consumerism and its impacts on the environment and society). Immigrants draw on their experience of life in Mexico as they acculturate to find the right balance between protecting the environment and looking after human needs.

Climatic and Environmental Trends Observed During Epidemic and Non-epidemic Years of Soybean Sudden Death Syndrome in Iowa

Soybean yield losses due to sudden death syndrome (SDS) have varied from year to year in Iowa since the disease was first reported in 1993. An SDS epidemic in 2010 resulted in significant yield losses and raised numerous concerns by farmers and agronomists regarding the potential for future outbreaks. Since infection and SDS development is highly dependent on temperature and soil moisture, our hypothesis was that SDS epidemics occur in years with above-average rainfall and below-average temperatures. To test this hypothesis, environmental conditions in southeast and central Iowa were compared among epidemic and non-epidemic years. Mean total precipitation and number of days with precipitation during each month of the growing season (April through August) tended to be greater in epidemic years (10.4 to 26.3 inches, 10 to 15 days) than non-epidemic years (8.9 to 15.4 inches, 9 to 12 days). Soil temperatures in April through July averaged less in epidemic years (9.0 to 24.7°C) than non-epidemic years (10.4 to 26.6°C). The widespread 2010 SDS epidemic in Iowa likely resulted from the concurrence of several weather conditions that were particularly favorable for disease. To reduce risk of yield losses in future years, soybean farmers should use an integrated disease management for SDS, focusing on using resistant varieties, avoiding soil compaction, and avoiding planting in cool wet soils. Accepted for publication 31 January 2013. Published 29 May 2013.

Analyses of Vehicle Trajectories and Speed Profiles Along Horizontal Curves

Vehicle speed and lane position are two of the many possible factors that lead to crashes on horizontal curves. Vehicle position and speed through horizontal curves are of great relevance to many areas of traffic engineering, including countermeasure design, design consistency, and policy. This article discusses the results of an exploratory analysis of vehicle trajectories and speed profiles at two horizontal curves located in central Iowa. The sites include an urban and rural curve. Data were collected at five stations within the horizontal curves in both directions of travel using pneumatic road tubes set up in a Z-configuration. Overall, vehicles were found to cut the horizontal curve in the inside and outside travel lanes. However, the trajectories were seen to be different at the two curve sites. Vehicle mean speed profiles indicated that the curve site selected for evaluation operate differently and are reflected in the speed profiles. Speed deviations of individual vehicles as they traversed the curve were evaluated. More vehicles were found to adjust their speeds and lateral position in the vicinity of the center of the curve, and then at the end of the horizontal curve.

Assessment of owner willingness to treat or manage diseases of dogs and cats as a guide to shelter animal adoptability

To determine community approaches to medical and behavioral diseases in dogs and cats. Cross-sectional descriptive study. 97 companion animal veterinarians and 424 animal owners. Companion animal veterinarians in central Iowa ranked medical or behavioral diseases or conditions by what they thought most clients would consider healthy, treatable, manageable, or unhealthy (unmanageable or untreatable). In a parallel survey, cat- or dog-owning households in central Iowa responded to a telephone survey regarding the relationship of their animal in the household, owner willingness to provide medical or behavioral interventions, and extent of financial commitment to resolving diseases. One hundred twenty common health or behavioral disorders in cats and dogs were ranked by veterinarians as healthy, treatable, manageable, or unhealthy (unmanageable or untreatable) on the basis of their opinion of what most clients would do. Findings were in congruence with animal owners' expressed willingness to provide the type of care required to maintain animals with many acute or chronic medical and behavioral conditions. In general, owners indicated a willingness to use various treatment modalities and spend money on veterinary services when considering current or previously owned animals as well as hypothetical situations with an animal. Past experiences with veterinary care in which an animal did not recover fully did not diminish the willingness of respondents to use veterinary services again in the future. These results provide a baseline indication of community willingness to address medical or behavioral conditions in dogs and cats. These considerations can be used in conjunction with Asilomar Accords recommendations to assess adoptability of cats and dogs in animal shelters.

A New Plant Record for Iowa: Lactuca hirsuta (Asteraceae)

A new record of a native vascular plant, Lactuca hirsuta Muhlenberg ex Nuttall var. sanguinea (Bigelow) Fernald, is reported for Iowa. A specimen was collected in 1983 by the author during a study of the Swaledale railroad prairie in Cerro Gordo County, north central Iowa (Eddy 1988). The plant was inexplicably excluded in the species catalogue when a Swaledale railroad flora was published in 1988; thus, this “new” Iowa record in 2013 was collected 30 years prior. The voucher specimen was “re-discovered” by Dr. Neil A. Harriman at the University of Wisconsin-Oshkosh (OSH), and its identification verified.

Swine Manure Rate, Timing, and Application Method Effects on Post-Harvest Soil Nutrients, Crop Yield, and Potential Water Quality Implications in a Corn-Soybean Rotation

<abstract> <bold><sc>Abstract. </sc></bold>Management practices for applying liquid swine manure to minimize surface runoff water pollution and improve crop production can be evaluated by conducting long-term field studies. This article documents results from a six-year (1996-2001) central Iowa field study that evaluated the effects of swine manure application management practices on soil nutrients, organic matter, pH, crop yield, and discusses potential water quality implications. Swine manure management practices included single-rate (SR) and double-rate (DR) nitrogen (N) based application rates (168 and 336Â kg N ha^-1, respectively), three timings (fall injection [FI], winter broadcast [WB], and spring injection [SI]), and two methods (broadcast and injection) of liquid swine manure. Analysis of these practices involved comparing levels of residual soil total phosphorus (P) as Bray-1 available P (RSP), residual soil nitrate-nitrogen (RSN), percent organic matter (OM%), pH, carbon:nitrogen (C:N) ratio, and crop yields (kg ha^-1) in a corn-soybean rotation cropping practice. Manure application rates were based on standard crop-available N levels as applied to corn plots and were adjusted for environmental losses. Soil samples were collected immediately prior to commencing the study and after harvest each year and analyzed for RSP, RSN, OM%, pH, and C:N ratio at selected depths in the top 0.30 m of the soil profile. Deep soil core (0-1.22 m) samples also were collected after harvest in 1996 and 2000 and analyzed for RSN as a function of depth in the soil profile. When averaged over the six project years and manure application times for corn plots, these findings showed that DR application plots had significantly higher accumulation of RSP and RSN (32.6% and 36.5%, respectively) versus SR application plots in the top 0.30 m of the soil profile. The RSP for the SI (38.2%) and WB (32.8%) treatments was significantly higher than for the FI treatment on corn plots. The RSN accumulation also was found to be significantly higher for the SI (33.4%) and WB (17.4%) treatments than for the FI treatment on corn plots. The 0-1.22 m deep soil core analysis indicated a higher RSN accumulation in up to 88% of the 1.22 m soil profile depth range for the DR and SI treatments. When averaged across the six years and application rates, corn yield was significantly higher for SI plots (9,596 kg ha^-1) versus FI plots (9,236 kg ha^-1). The reduction in FI plot corn yield results may have been due largely to excessive leaching of nutrients through the soil profile from post-harvest rainfall during the fall-spring duration. Swine manure SI plots with the higher DR application rate produced the highest average corn yield (10,093 kg ha^-1). When averaged over project years and application times, the SI treatment showed an increase of 4.0% in corn yield over the FI treatment. While there were short-term significant increases in OM% for the SI1 treatment during 1996 and 1997, there were no significant cumulative differences in OM% as well as pH and C:N ratio in the soil profile after six years of N management practices at the study site. Although no manure was applied to soybean plots, residual effects of N management practices using the WB and SI application methods in the DR treatment plots during corn years significantly increased average values of RSP, RSN, and soybean yield. Results of this study indicate that long-term application of higher liquid swine manure rates during winter and spring application times resulted in significantly higher post-harvest accumulation of residual P and N in the soil profile. These results also show that incorporation of swine manure during the spring application time produced significantly higher corn yields compared with fall and winter application times. Overall results suggest that while residual soil P and N content may be significantly higher from spring versus fall manure application times, these nutrient runoff losses and the potential threat to surface water quality may be substantially lower during spring and summer compared with fall and winter due to effects from crop nutrient uptake, microbial activity, leaching, and evapotranspiration during the growing season.

Changes in yield and nitrate losses from using drainage water management in central Iowa, United States

Drainage water management (DWM) is a potentially valuable management practice for reducing NO₃ losses to surface waters in areas of artificial drainage. But the practice is essentially untested in Midwest United States conditions and its water quality and crop yield benefits uncertain. This paper reports results from applying DWM to a 22 ha (54 ac) production field in central Iowa as part of a five-state Conservation Innovative Grant effort to document the impact of DWM across the Midwest. Three of nine plots in an existing tile drainage research site were retrofitted with control structures so that the drainage level could be controlled. Water flow from the tile in each plot, NO₃ concentration in the drainage, and crop yield were measured over a four year period from 2006 to 2009. The field was in a two year corn (<i>Zea mays</i> L.)–soybean (<i>Glycine max</i> [L.] Merr.) rotation with nitrogen (N) fertilizer applied before the corn crop only. During four years of monitoring tile flow, there was a significant (<i>p</i> = 0.05) 21% decrease in tile flow, no significant decrease in NO₃ concentration, and a significant 29% reduction in NO₃ load leaching from the DWM treatment compared to conventional drainage. No yield benefits from DWM were observed for the two year average for corn (2006 and 2008), but a significant yield increase of 8% was observed for the two year average for soybean (2007 and 2009). For the four years monitored in this study, it is unclear if the yield increase for soybean versus no increase for corn was due to weather patterns or because corn and soybean responded differently to the raised water table caused by DWM.