Central Iowa Research Articles

Measured and Simulated Carbon Dynamics in Midwestern U.S. Corn‐Soybean Rotations

AbstractCorn (Zea mays L.) and soybean (Glycine max [L.] Merr.) production dominate Midwestern U.S. agriculture and impact the regional carbon and nitrogen cycles. Sustaining soil carbon is important for corn‐soybean production (CS); however, quantifying soil carbon changes requires long‐term field measurements and/or model simulations. In this study, changes in soil organic (SOC), inorganic (SIC), and total (TC) carbon; pH; total nitrogen (TN); and net ecosystem production (NEP) were measured in a conventional corn‐soybean rotation in central Iowa. Soil samples (n = 42; 0–120 cm depth) were collected from two adjacent fields in 2005 and 2016. Eddy‐flux stations set up in the fields continuously monitored NEP from 2005–2016, and net biome production (NBP) was calculated using yield records. The DayCENT model was used to simulate the effects of conventional management practices on soil carbon and calibrated with field‐measured NEP and SOC. Measured soil TC (0–120 cm) decreased by −14.19 ± 6.25 Mg ha−1, with highest reductions in SOC and SIC (p < 0.05) at 0–15 and 90–120 cm, respectively. Measured TN decreased by −0.7 ± 0.29 Mg ha−1 with N‐accumulation at 60–90 cm (p < 0.05). Eddy‐flux NBP decreased by −13.19 ± 0.05 Mg ha−1. Soil and eddy‐flux records show a carbon reduction by −1.14 ± 0.63 and −1.20 ± 0.06 Mg ha−1 yr−1, respectively. The validated DayCENT model suggests that all SOC pools declined. We postulate that conventional CS production has adverse effects on C and N dynamics in Midwestern United States.

Multifactor Models for Improved Prediction of Phenological Timing in Cold-climate Wine Grapes

An accurate predictive model for estimating the timing of seasonal phenological stages of grape (Vitis L.) would be a valuable tool for crop management. Currently the most used index for predicting the phenological timing of fruit crops is growing degree days (GDD), but the predictive accuracy of the GDD index varies from season-to-season and is considered unsatisfactory for grapevines grown in the midwestern United States. We used the methods of multiple regression to analyze and model the effects of multiple factors on the number of days remaining until each of four phenological stages (budbreak, bloom, veraison, and harvest maturity) for five cold-climate wine grape cultivars (Frontenac, La Crescent, Marquette, Petit Ami, and St. Croix) grown in central Iowa. The factors (predictor variables) evaluated in models included cultivar, numerical day of the year (DOY), DOY of soil thaw or the previous phenological stage, photoperiod, GDD with a base temperature of 10 °C (GDD 10), soil degree days with a base temperature of 5 °C (SDD 5), and solar accumulation. Models were evaluated for predictive accuracy and goodness of fit by calculating the coefficient of determination (R2), the corrected Akaike information criterion (AICc), and the Bayesian information criterion (BIC); testing for normal distribution of residuals; and comparing the actual number of days remaining until a phenological stage with the number of days predicted by models. The top-performing models from the training set were also tested for predictive accuracy on a validation dataset (a set of data not used to build the model), which consisted of environmental and phenological data recorded for one popular Midwest cultivar (Marquette) in 2019. At all four phenological stages, inclusion of multiple factors (cultivar and four to six additional factors) resulted in predictive models that were more accurate and consistent than models using cultivar and GDD 10 alone. Multifactor models generated from data of all five cultivars had high R2 values of 0.996, 0.985, 0.985, and 0.869 for budbreak, bloom, veraison, and harvest, respectively, whereas R2 values for models using only cultivar and GDD 10 were substantially lower (0.787, 0.904, 0.960, and 0.828, respectively). The average errors (differences from actual) for the top multifactor models were 0.70, 0.84, 1.77, and 3.80 days for budbreak, bloom, veraison, and harvest, respectively, and average errors for models that included only cultivar and GDD 10 were much larger (5.27, 2.24, 2.79, and 4.29 days, respectively). In the validation tests, average errors for budbreak, bloom, veraison, and harvest were 1.92, 1.31, 0.94, and 1.67 days, respectively, for the top multifactor models and 10.05, 2.54, 4.23, and 4.96 days, respectively, for models that included cultivar and GDD 10 only. Our results demonstrate the improved accuracy and utility of multifactor models for predicting the timing of phenological stages of cold-climate grape cultivars in the midwestern United States. Used together in succession, the models for budbreak, bloom, veraison, and harvest form a four-stage, multifactor calculator for improved prediction of phenological timing. Multifactor models of this type could be tailored for specific cultivars and growing regions to provide the most accurate predictions possible.

Improving the effectiveness of saturated riparian buffers for removing nitrate from subsurface drainage.

A saturated riparian buffer (SRB) is an edge-of-field conservation practice that reduces nitrate export from agricultural lands by redistributing tile drainage as shallow groundwater and allowing for denitrification and plant uptake. We propose an approach to improve the design of SRBs by analyzing a tradeoff in choosing the SRB width, and we apply the approach to six sites with SRBs in central Iowa. A larger width allows for more residence time, which increases the opportunity for removing nitrate that enters the buffer. However, because the SRBs considered here treat only a portion of the tile flow when it is large, for the same difference in hydraulic head, a smaller width allows more of the total tile flow to enter the buffer and therefore treats more of the drainage. By maximizing the effectiveness of nitrate removal, defined as the ratio of total nitrate removed by the SRB to total nitrate leaving the field in tile drainage, an equation for the optimal width was derived in terms of soil properties, denitrification rates, and head difference. All six sites with existing SRBs considered here have optimal widths smaller than the current width, and two are below the minimum width listed in current design standards. In terms of uncertainty, the main challenges in computing the optimal width for a site are estimating the removal coefficient for nitrate and determining the saturated hydraulic conductivity. Nevertheless, including a width that accounts for site conditions in the design standards would improve water quality locally and regionally.

Inverse modeling of NH3 sources using CrIS remote sensing measurements

Spatiotemporal uncertainty in emissions in the US hinders prediction of environmental effects of atmospheric . We conducted 4D-Var inversions using CrIS remote-sensing observations and GEOS-Chem to estimate monthly emissions over the contiguous US at the 0.25°× 0.3125° resolution in 2014, finding they are 33% higher than the prior emissions which likely underestimated most agricultural emissions, especially intense springtime fertilizer and livestock sources over the Central US. However, decreases were found in the Central Valley, southern Minnesota, northern Iowa and southeastern North Carolina during warm months. These updates increased the correlation coefficient between modeled monthly mean and surface observations from 0.53 to 0.84, and reduced the normalized mean bias of annual mean simulated and wet by a factor of 1.3 to 12.7. Our satellite-based inversion approach thus holds promise for improving estimates of and reactive nitrogen deposition throughout the world where measurements are scarce.

Yearling Muskellunge Poststocking Behavior and Survival in Two Central Iowa Reservoirs with Contrasting Habitat Availability

AbstractMuskellunge Esox masquinongy is a prized sport fish throughout much of North America. Due to the species’ popularity among anglers and limited natural recruitment in reservoirs, Muskellunge are commonly stocked to maintain populations. However, little is known about their poststocking behavior and survival in reservoirs. We used radiotelemetry to evaluate behavior and survival of spring‐stocked yearling Muskellunge in two Iowa reservoirs that differed in habitat availability (Big Creek Lake: limited habitat; Brushy Creek Lake: abundant habitat). Hatchery‐reared Muskellunge were implanted with radio transmitters (n = 15–16 fish·lake−1·year−1; 61 fish total) and stocked in both lakes during May 2017 and 2018; fish were tracked daily for 1 week, every other day for the second week, and then weekly until December. Telemetry data were used to evaluate depth and vegetation use, selection of littoral substrate and coarse woody habitat (CWH) complexities, movement, home ranges, and survival. Muskellunge depth use generally increased with time poststocking and was greater in Brushy Creek Lake than in Big Creek Lake. Movement rates were greatest during the first week poststocking and declined thereafter, with greater rates and home ranges in Big Creek Lake. Muskellunge in both systems selected for fine substrates while avoiding coarse substrates. Muskellunge in Brushy Creek Lake were more commonly associated with CWH and aquatic vegetation compared to those in Big Creek Lake. Muskellunge in Big Creek Lake selected for complex CWH, while those in Brushy Creek Lake used CWH classes in proportion to their availability. Cormack–Jolly–Seber daily apparent survival estimates were lowest for the first 4 d poststocking and ranged from 0.59 to 0.99, after which survival increased from May to September before declining in October and November. Results of this study provide a greater understanding of the poststocking success of yearling Muskellunge and suggest that Muskellunge behavior and survival are dependent on habitat complexity, with weaker habitat selection but higher survival in complex systems.

Drainage N Loads Under Climate Change with Winter Rye Cover Crop in a Northern Mississippi River Basin Corn-Soybean Rotation

To help reduce future N loads entering the Gulf of Mexico from the Mississippi River 45%, Iowa set the goal of reducing non-point source N loads 41%. Studies show that implementing winter rye cover crops into agricultural systems reduces N loads from subsurface drainage, but its effectiveness in the Mississippi River Basin under expected climate change is uncertain. We used the field-tested Root Zone Water Quality Model (RZWQM) to estimate drainage N loads, crop yield, and rye growth in central Iowa corn-soybean rotations. RZWQM scenarios included baseline (BL) observed weather (1991–2011) and ambient CO2 with cover crop and no cover crop treatments (BL_CC and BL_NCC). Scenarios also included projected future temperature and precipitation change (2065–2085) from six general circulation models (GCMs) and elevated CO2 with cover crop and no cover crop treatments (CC and NCC). Average annual drainage N loads under NCC, BL_NCC, CC and BL_CC were 63.6, 47.5, 17.0, and 18.9 kg N ha−1. Winter rye cover crop was more effective at reducing drainage N losses under climate change than under baseline conditions (73 and 60% for future and baseline climate), mostly because the projected temperatures and atmospheric CO2 resulted in greater rye growth and crop N uptake. Annual CC drainage N loads were reduced compared with BL_NCC more than the targeted 41% for 18 to 20 years of the 21-year simulation, depending on the GCM. Under projected climate change, average annual simulated crop yield differences between scenarios with and without winter rye were approximately 0.1 Mg ha−1. These results suggest that implementing winter rye cover crop in a corn-soybean rotation effectively addresses the goal of drainage N load reduction under climate change in a northern Mississippi River Basin agricultural system without affecting cash crop production.

Temporal changes in soil hydraulic conductivity in saturated and unsaturated fields

Soil hydraulic conductivity ( $$K$$ ) is an important soil property that exhibits relatively large uncertainty. The temporal variability of $$K$$ is often ignored when calculating water movement in soil. Various factors such as tillage, rain, temperature, wetting/drying, soil surface crusting, solution concentration, and biological activity can influence field $$K$$ . We investigated soil $$K$$ in a central Iowa field as a function of time and tillage by using tension infiltrometer measurements with pressure head tension settings of 0 cm and − 3 cm. No clear relationship was found between bulk density ( $$\rho_{\text{b}}$$ ) and $$K$$ . Path analysis was conducted to assess the contribution ratios and causal relationships between factors affecting $$K$$ . The $$K$$ values were influenced by physical impacts such as tillage, precipitation, and surface crusting with contributions of 24%, − 32%, and 49%, respectively, and with error of 60%. Soil surface crusting had a particularly large impact on saturated $$K$$ . The maximum volume fraction influenced $$K$$ . Earthworm activity that impacted the soil pore structure was also noticed in the field. Owing to this biological mechanism, no relationship was observed between $$\rho_{\text{b}}$$ and $$K$$ . It is important to recognize the multiple combined effects of soil physical processes and biological activities when documenting $$K$$ in field soils.

Riparian Land-Use, Stream Morphology and Streambank Erosion within Grazed Pastures in Southern Iowa, USA: A Catchment-Wide Perspective

Factors influencing streambank erosion at the field/reach scale include both watershed and riparian land-uses, stream hydrology and channel morphology at the catchment scale. This study assesses the relationship of riparian land-uses, stream morphologic characteristics and catchment scale variables to streambank erosion within grazed riparian pastures in the Southern Iowa Drift Plain. Thirteen cooperating beef cow–calf farms and their catchments ranging from 2.5 to 12.9 km2 in the Rathbun Lake watershed in South Central Iowa (USA) were chosen to conduct this study. Results suggest that the integration of stream morphologic characteristics and riparian land-uses at both the reach and catchment scale are necessary to explain the current level of streambank erosion measured at the reach scale. Larger catchment size or catchments with more total channel length were found to experience more bank erosion at the reach scale. A significant positive relationship between percent sand-and-silt in the bank soil and bank erosion rates implies that bank soils with less cohesiveness are more erodible. Catchment-scale assessments of the thirteen watersheds showed that within the 50 m corridor on both sides of the stream, 46 to 61% of riparian area was devoted to agricultural use and only 6 to 11% was in ungrazed perennial vegetation, much of it enrolled in the USDA Conservation Reserve Program. Overall, this and previous Rathbun watershed studies have shown that intensive agricultural use of riparian areas over such extents of time and scale could be directly (in field scale) and/or indirectly (watershed scale) related to excessive amounts of streambank erosion (ranging from 8.6 to 38.3 cm/yr) to receiving streams and lakes leading to their impairment and reduction in ecological services. Exclusion of cattle grazing in the riparian areas along buffered stream lengths (2.1% of the total watershed area) of the Rathbun watershed would reduce this impact. This approach could also be applicable to other similar watersheds with extensive land-use under grazed management.

Estimating Near Real-Time Hourly Evapotranspiration Using Numerical Weather Prediction Model Output and GOES Remote Sensing Data in Iowa

This study evaluates the applicability of numerical weather prediction output supplemented with remote sensing data for near real-time operational estimation of hourly evapotranspiration (ET). Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR) systems were selected to provide forcing data for a Penman-Monteith model to calculate the Actual Evapotranspiration (AET) over Iowa. To investigate how the satellite-based remotely sensed net radiation ( R n ) estimates might potentially improve AET estimates, Geostationary Operational Environmental Satellite derived R n (GOES- R n ) data were incorporated into each dataset for comparison with the RAP and HRRR R n -based AET evaluations. The authors formulated a total of four AET models—RAP, HRRR, RAP-GOES, HRRR-GOES, and validated the respective ET estimates against two eddy covariance tower measurements from central Iowa. The implementation of HRRR-GOES for AET estimates showed the best results among the four models. The HRRR-GOES model improved statistical results, yielding a correlation coefficient of 0.8, a root mean square error (mm hr−1) of 0.08, and a mean bias (mm hr−1) of 0.02 while the HRRR only model results were 0.64, 0.09, and 0.04, respectively. Despite limited in situ observational data to fully test a proposed AET estimation, the HRRR-GOES model clearly showed potential utility as a tool to predict AET at a regional scale with high spatio-temporal resolution.

Putting Knowledge into Practice: Low-Income Women Talk about Food Choice Decisions

Insights into barriers and facilitators for healthy eating are needed to improve low-income women’s diets and to decrease disease risk. The study objectives were to explore women’s qualitative perceptions of influences on their food choices such as food security, their knowledge of nutrition-related health risk factors and self-efficacy for diet change, and their dietary intakes in practice. Thirty-six women, aged 19–50, who were eligible to receive income-based assistance were recruited in central Iowa. Focus group discussions on defining healthy foods, influences on food choice, and nutrition information sources were analyzed using a socioecological model framework. Demographics, nutrient intake estimates, food security status, health behaviors, and self-efficacy for nutrition behavior change were collected by survey. Most participants were White (61%), single (69%), food insecure (69%), and living with children (67%). Few women met dietary recommendations. Barriers to healthy eating include cost, convenience/preparation time, family taste preferences, and limitations of federal food assistance programs. Facilitators are high self-efficacy for nutrition change and health knowledge on average. These results challenge the strategy of using nutrition education to improve healthy eating and instead show that intervention messaging should focus on limited, achievable steps to improve dietary choices that fit within cost, convenience, and taste constraints.

Subsurface nutrient export from a cropped field to an agricultural stream: Implications for targeting edge-of-field practices

It is understood that the major transport pathways for the soluble nutrients nitrate (NO3-N) and orthophosphorus (OP) from cropped fields to streams in the U.S. Cornbelt are tile drainage and groundwater seepage. The relative contribution of each, however, has not been well quantified and can vary between fields and watersheds. In this study, we used intermittent grab sample water quality monitoring and tile flow measurements, and the groundwater model MODFLOW to source dissolved nutrients from a cropped field to a low-order stream in the intensively-drained and cropped Des Moines Lobe landform of north central Iowa. Based on monitoring of eight tile outlets, nine groundwater wells and the receiving stream over a two-year period, nutrient loads from tiles were found to contribute approximately 98 % of the nitrate load to Hardin Creek. The loading pattern for OP was also dominated by discharge from constructed drainage, with 99.7 % sourced back to field tiles. Results from the farm field fit within the scaling pattern observed within the Des Moines Lobe region of Iowa showing that water yields and NO3-N loads are dominated by tile drainage at the field and local watershed scale. Loads dominated by tile flows suggest edge-of-field interception and treatment of tile water for mitigation of stream nutrients. Study results are consistent with local and regional assessments showing tile drainage to be an important pathway for both water and nutrients in the stream network of the US Cornbelt.

Emissions from Swine Manure Treated with Current Products for Mitigation of Odors and Reduction of NH3, H2S, VOC, and GHG Emissions

Odor and gaseous emissions from the swine industry are of concern for the wellbeing of humans and livestock. Additives applied to the swine manure surface are popular, marketed products to solve this problem and relatively inexpensive and easy for farmers to use. There is no scientific data evaluating the effectiveness of many of these products. We evaluated 12 manure additive products that are currently being marketed on their effectiveness in mitigating odor and gaseous emissions from swine manure. We used a pilot-scale system simulating the storage of swine manure with a controlled ventilation of headspace and periodic addition of manure. This dataset contains measured concentrations and estimated emissions of target gases in manure headspace above treated and untreated swine manure. These include ammonia (NH3), hydrogen sulfide (H2S), greenhouse gases (CO2, CH4, and N2O), volatile organic compounds (VOC), and odor. The experiment to test each manure additive product lasted for two months; the measurements of NH3 and H2S were completed twice a week; others were conducted weekly. The manure for each test was collected from three different farms in central Iowa to provide the necessary variety in stored swine manure properties. This dataset is useful for further analyses of gaseous emissions from swine manure under simulated storage conditions and for performance comparison of marketed products for the mitigation of gaseous emissions. Ultimately, swine farmers, the regulatory community, and the public need to have scientific data informing decisions about the usefulness of manure additives.

Seasonal variations in export of antibiotic resistance genes and bacteria in runoff from an agricultural watershed in Iowa

Seasonal variations of antimicrobial resistance (AMR) indicators in runoff water can help improve our understanding of AMR sources and transport within an agricultural watershed. This study aimed to monitor multiple areas throughout the Black Hawk Lake (BHL) watershed (5324 ha) in central Iowa during 2017 and 2018 that consists of both swine and cattle feeding operations as well as known areas with manure application. The measured indicators included plate counts for fecal indicator bacteria (FIB) E. coli, Enterococcus, antibiotic resistant fecal indicator bacteria (ARBs) tylosin resistant Enterococcus, tetracycline resistant Enterococcus, and antibiotic resistance genes (ARGs): ermB, ermF (macrolide), tetA, tetM, tetO, tetW (tetracycline), sul1, sul2 (sulfonamide), aadA2 (aminoglycoside), vgaA, and vgaB (pleuromutilin). Both the plate count and the ARG analyses showed seasonal trends. Plate counts were significantly greater during the growing season, while the ARGs were greater in the pre-planting and post-harvest seasons (Wilcoxon Rank-Sum Test p < 0.05). The ermB gene concentration was significantly correlated (p < 0.05) with E. coli and Enterococcus concentrations in 2017, suggesting a potential use of this ARG as an indicator of environmental AMR and human health risk. Flow rate was not a significant contributor to annual variations in bacteria and AMR indicators. Based on observed seasonal patterns, we concluded that manure application was the likely contributor to elevated ARG indicators observed in the BHL watershed, while the driver of elevated ARB indictors in the growing season can only be speculated. Understanding AMR export patterns in agricultural watersheds provides public health officials knowledge of seasonal periods of higher AMR load to recreational waters.

Long-term nitrate removal in three riparian buffers: 21 years of data from the Bear Creek watershed in central Iowa, USA

Riparian buffers are a conservation practice that increases vegetation diversity on the agricultural landscape while providing environmental benefits. This study specifically focused on the ability of riparian buffers to remove nitrate from shallow groundwater. There are many studies that assessed nitrate removal within buffers, but not many have a long-term, continuous data set that can analyze for variation in nitrate removal rates over time. Here we report on 21 years of nitrate well data, from 1996 through 2017, for three buffers in the Bear Creek watershed in central Iowa. These buffers are named using abbreviations to help keep landowners anonymous (e.g. RN, RS, and ST). Studied buffers RS and ST showed greater nitrate reduction (or removal) after 10 and 6 years of its establishment, respectively. Buffer RN did not experience a significant nitrate removal increase with time, but instead had higher nitrate removal rates when compared to buffers RS and ST of 10.3 g NO3−-N m−1 day−1 from the start of this study. From this data, we suggest that past land management played a major role in the responses observed. RN had previously been established in cool-season grasses for grazing before being converted to a buffer, while RS and ST had been managed in a corn and soybean rotation. RN was thought to have higher denitrification immediately with increased labile soil carbon input and enhanced soil aggregation due to the grassland perennials, while buffer vegetation establishment increased soil carbon inputs and soil aggregation over time for RS and ST. These nitrate removal trends would not have been observed without access to long-term, continuous data. This study highlighted the importance of long-term data sets and the need to assess conservation practices over time to determine their longevity and efficiency with time.

Tardigrades of Hardin County, Iowa: Seven New Records from Iowa, USA

Although Iowa was the site of one of the earliest collections of tardigrades in the United States in 1873, only two additional papers on the tardigrades of this state have been published in the intervening 147 years. These earlier papers focused on tardigrades in central Iowa, living in either freshwater algae or in deciduous trees, and reported a total of only five recognized species in four genera. This project expands the known tardigrade diversity of the state through collection of specimens from both deciduous and coniferous trees in northern Iowa. Tardigrades were extracted from 29 moss and lichen samples collected from deciduous and coniferous trees in Hardin County during December 2015. 485 adult specimens and 74 eggs were collected, representing seven species (Milnesium cf. barbadosense, Milnesium burgessi, Milnesium eurystomum, Milnesium swansoni, Ramazzottius sp., Macrobiotus hibiscus, and Paramacrobiotus tonollii). Of these, one is a new species record for the United States (Milnesium cf. barbadosense), and all are new records for the state of Iowa. This is also the first report of a member of the genus Ramazzottius in Iowa. Pseudoplates, tardigrade structures that were only described for the first time in 2016, were also observed in all Milnesium specimens.

Are Visible Fractures Accurate Predictors of Flow and Mass Transport in Fractured Till?

Tracer experiments conducted in the laboratory on undisturbed core samples (<7.3-cm-diameter) have been a standard method for estimating hydraulic and transport properties of fractured till since the 1980s. This study assesses the relationship between visible fractures on the top and bottom of core samples and the resulting hydraulic and mass transport properties of the core. We hypothesized that more visible fractures would indicate the presence of a well-connected fracture network, leading to greater hydraulic conductivity (K) values and earlier chemical breakthrough times. To test this hypothesis, water flow and bromide (Br-) tracer experiments were performed on 10, 16-cm diameter, 16-cm-tall samples of fractured Dows Formation till from central Iowa. Visually identifiable fractures were present on the top and bottom of every sample. Results indicate that the visual identification of fractures does not predict a connected fracture network, as some samples produced breakthrough curves showing rapid first arrival times and shapes characteristic of solute transport in a fractured medium, while others appeared similar to an unfractured medium. No correlation was found between the number of visible fractures and K (Pearson's r=0.25), or Br- first arrival time (r=-0.33), but a strong negative correlation between K and first arrival time (r=-0.92). Results indicate that the sample volume was not large enough to reliably contain a connected fracture network. Thus, testing large volumes of till at the field scale coupled with fracture-flow modeling likely represents the best approach for estimating hydraulic and mass transport properties for fractured till.

Yield and Berry Composition of Cold-climate Grape Cultivars and Advanced Selections in Iowa Climate

Increasing interest in grape (Vitis sp.) and wine production in the upper midwest region of the United States has created a need for science-based information that characterizes the potential of cold-climate cultivars to produce quality grapes with acceptable yields. We evaluated the yield and quality (composition) of grapes from 12 cold-climate, interspecific-hybrid grape cultivars (northern hybrids) grown in a randomized and replicated field plot in central Iowa. The grape trial was planted in 2008, and crop performance of cultivars was evaluated from 2012 through 2017 (yield) and 2014 through 2017 (berry composition). The trial included two established cultivars, five newer cultivars, and five advanced selections. The established cultivars included in the study as controls were Frontenac and St. Croix. The newer cultivars evaluated in this study were Arandell, Corot Noir, La Crescent, Marquette, and Petit Ami, and the advanced selections were MN 1189, MN 1200, MN 1220, MN 1235, and MN 1258. Yield and productivity were characterized by measuring yield per vine, number of clusters per vine, average cluster weight, and pruning weight. The fruit composition indices were soluble solids concentration (SSC), pH, titratable acidity (TA), and sugar:acid ratio (SSC ÷ TA). On the basis of their strong results for both yield and fruit composition measures, ‘Marquette’, MN 1235, and MN 1220 ranked as the top-performing cultivars in Iowa’s climate, followed by Petit Ami and St. Croix. ‘Petit Ami’ had slightly lower yield consistency and slightly lower results for SSC than did the top performing cultivars, and St. Croix had among the highest and most consistent yields of the trial but showed lower results for SSC and sugar:acid ratio than many of the other cultivars. ‘La Crescent’ had midrange yields and high SSC, but the high TA of ‘La Crescent’ fruit resulted in a low sugar:acid ratio at harvest. Two cultivars (MN 1258 and MN 1200) had relatively low yields in Iowa’s climate but achieved good results for composition indices. ‘Frontenac’ had high, consistent yields and achieved high SSC, but the very high TA of ‘Frontenac’ fruit resulted in a very low sugar:acid ratio compared with most other cultivars. The remaining three cultivars (Corot Noir, MN 1189, and Arandell) performed poorly in Iowa’s climate, showing both low yield and undesirable fruit composition indices compared with the other cultivars in the trial. An itemized summary of the relative ratings for yield and fruit composition is provided to aid growers in selection and management of grape cultivars for use in Iowa and other areas of similar climate.

Survival of white-tailed deer fawns in central Iowa.

Understanding demographic parameters such as survival is important for scientifically sound wildlife management. Survival can vary by region, sex, age-class, habitat, and other factors. White-tailed deer fawn survival is highly variable across the species’ range. While recent studies have investigated fawn survival in several Midwestern states, there have been no published estimates from Iowa for 30 years. We radio-collared 48 fawns in central Iowa from 2015–2017 to estimate survival, home range size, and habitat composition and identity causes of mortality. Estimated fawn survival (± SE) was similar to other Midwest studies at 30 (0.78 ± 0.07)) and 60 days (0.69 ± 0.08), but considerably lower at 7 months (0.31 ± 0.02). Survival was positively associated with woodland habitat through 30 and 60 days, but not related to habitat at 7 months. Female fawns avoided agricultural habitat in their home ranges. Fawn 95% kernel density home ranges were smaller than in other studies in the Midwest (21.22 ± 2.74 ha at 30 days, 25.47 ± 2.87 ha at 60 days, and 30.59 ± 2.37 ha at 7 months). The large amount of woodland and grassland (>90%) in our study area meant that fawns did not have to travel far to find suitable cover, which may explain their small home ranges. We recorded 21 mortalities, the leading cause of which was disease (n = 9; 56% epizootic hemorrhagic disease [EHD]) followed by suspected predation (4) and harvest (3). The mortality associated with an outbreak of EHD in 2016, all of which occurred after 60 days post-capture, is the most likely explanation for our low survival estimate at 7 months. While predation, usually early in life, is the leading cause of mortality in most studies, sporadic diseases like EHD can be a major source of mortality in older fawns in some years.

The effect of wind direction shear on turbine performance in a wind farm in central Iowa

Abstract. Numerous studies have shown that atmospheric conditions affect wind turbine performance; however, some findings have exposed conflicting results for different locations and diverse analysis methodologies. In this study, we explore how the change in wind direction with height (direction wind shear), a site-differing factor between conflicting studies, and speed shear affect wind turbine performance. We utilized lidar and turbine data collected from the 2013 Crop Wind Energy eXperiment (CWEX) project between June and September in a wind farm in north-central Iowa. Wind direction and speed shear were found to follow a diurnal cycle; however, they evolved differently with increasing wind speeds. Using a combination of speed and direction shear values, we found large direction and small speed shear to result in underperformance. We further analyzed the effects of wind veering on turbine performance for specific values of speed shear and found detrimental conditions on the order of 10 % for wind speed regimes predominantly located in the middle of the power curve. Focusing on a time period of ramping electricity demand (06:00–09:00 LT – local time) exposed the fact that large direction shear occurred during this time and undermined turbine performance by more than 10 %. A predominance of clockwise direction shear (wind veering) cases compared to counterclockwise (wind backing) was also observed throughout the campaign. Moreover, large veering was found to have greater detrimental effects on turbine performance compared to small backing values. This study shows that changes in wind direction with height should be considered when analyzing turbine performance.

Lungworm infection in a central Iowa beef herd

A beef herd presented four calves, aged 8–9 months, in late September for evaluation of respiratory disease of 2 months duration that was non-responsive to antimicrobial treatment. Calves were housed...