Southern Iowa Research Articles

Cold tolerance and overwintering survival of Aphelinus certus (Hymenoptera: Aphelinidae), a parasitoid of the soybean aphid (Hemiptera: Aphididae) in North America.

Broad-spectrum insecticides are the main control measure of the invasive and economically damaging soybean aphid (Aphis glycines) in North America, although biological control by resident natural enemies can also greatly diminish population levels. One such natural enemy is the accidentally introduced Eurasian parasitoid Aphelinus certus (Hymenoptera: Aphelinidae), though its impact appears to be limited by low rates of parasitism early in the growing season. We tested the hypothesis that A. certus might experience high overwintering mortality. In the laboratory, we used thermocouple thermometry to measure the supercooling points of diapausing parasitoids and assessed parasitoid survival after exposure to ecologically relevant durations of low temperature. We found A. certus to be freeze-intolerant with a median supercooling point of -28°C. When exposed to temperatures of 0°C for up to 7 months, adults emerged only after exposures of at least 60 days and survival decreased with durations beyond 150 days. We also conducted in-field studies at sites from northern Minnesota to southern Iowa to determine if diapausing A. certus could overwinter above and below the snowpack. Survival was negatively correlated with increasing latitude and was greater for parasitoids placed on the ground than 1 meter off the ground, likely due to the warmer and stabler temperatures of the subnivean microclimate. Our results suggest that A. certus is capable of overwintering in the region inhabited by soybean aphid but may experience substantial mortality even under ideal conditions. Climate change is predicted to bring warmer, drier winters to the North American Midwest, with decreased depth and duration of snow cover, which may further reduce overwintering survival.

ACCESS TO HOSPITAL-BASED PALLIATIVE CARE SERVICES FOR OLDER ADULTS IN IOWA

Abstract Background U.S. Medicare covers many palliative services; however, Iowa’s rurality and high rate of older adults (OAs) aged 65 or over make it unclear whether older Iowans have equitable service access. Hospital-based palliative care services (HBPCSs) include curative treatment, whereas other providers of palliative care may not. Thus, this study only examined OAs’ geographic access to HBPCSs in Iowa. Methods This study used the American Hospital Association and U.S. Census Bureau estimate in 2017. The geographical distribution of hospitals and HBPCSs was examined using a county-level approach, considering rural/urban status (using the Office of Management and Budget’s definitions) and OA population proportion. Results Of the 99 counties in Iowa, 89 were rural. Of the 116 hospitals statewide, one urban county and nine rural counties had no hospital. A total of 52 hospitals provided HBPCSs in 43 counties across nine urban and 34 rural counties. HBPCSs were primarily located in central Iowa, with northern and southern Iowa having the lowest access to HBPCSs. The OA population ratio was higher in counties without HBPCSs (19%) than HBPCSs (15.7%). All 54 counties with over a 20% OA population were concentrated in rural counties, while only 37% of these rural counties had HBPCSs. Conclusion This study suggests a regional imbalance of HBPCS providers for OAs in Iowa. Results showed that rural communities with a high ratio of OAs lack HBPCSs and suggest HBPCSs should be expanded at hospitals in northern and southern Iowa counties where many OAs live.

Cover crop mixtures versus single species: Water quality and cash crop yield

Cover crops promote environmental health and agricultural production, but most research in the Midwest focuses solely on winter cereal rye (<i>Secale cereal</i> L.) (CR). We evaluated cover crop mixtures compared to single species in terms of cover crop biomass (<i>n</i> = 32 site-years), cash crop yield (<i>n</i> = 32), and subsurface water quality (<i>n</i> = 17) spanning six sites and seven years in Iowa. Before soybeans (<i>Glycine max</i> [L.] Merr), the single species was CR and the mixture species were CR, radish (<i>Raphanus sativus</i>), and rapeseed (<i>Brassica napus</i>). Before corn (<i>Zea mays</i> L.), the single species was oats (<i>Avena sativa</i>) and the mixture species were oats, radish, and hairy vetch (<i>Vicia villosa</i>). Before soybeans, average fall growth of CR in the single species was significantly greater than or similar to the mixture. Fall growth before corn with oats was significantly less than or similar to the oat mixture. Before soybeans/during soybean growth, both cover crop treatments had significantly lower spring nitrate-nitrogen (NO₃-N) concentrations in soil pore water than the control, and single species had lower concentrations than mixtures. Even with mostly winterkill cover crops before corn, spring NO₃-N concentrations of soil pore water were significantly lower in the single species treatment than in the no cover treatment. Cover crop treatments had no influence on corn yield overall and slight negative influence on soybean yield at two of the sites. We propose the following to increase diversity of cover crops in the Midwest: CR before soybeans, oats and/or an oat mixture before corn, and introducing brassicas and hairy vetch in southern Iowa. In this project, these diverse species were possible after broadcast seeding in late August, and that would be our planting recommendation to promote fall growth.

Increased abundance and productivity of a grassland bird after experimental control of invasive tall fescue

Tall fescue (Schedonorus arundinaceus) is a widespread invasive grass in the United States that degrades habitat quality for biodiversity. Herbicide followed by seeding of native plants reduces tall fescue and is predicted to restore habitat quality over time, but little is known about short‐term (1–2 year) impacts on native species. We conducted a landscape‐scale controlled experiment to assess the short‐term effects of herbicide and seeding on the reproduction of an obligate grassland bird, the dickcissel (Spiza americana). In 2014, four sites in southern Iowa were each subdivided into three patches (mean 7 ha). One patch in each site was treated with glyphosate herbicide (spray‐only), one with herbicide and native seeding (spray‐and‐seed), with the third serving as a control. Two sites were grazed by cattle from April to July and two sites were ungrazed. We monitored dickcissel reproduction in 2016, finding that they were more abundant, built more nests, experienced less cowbird parasitism, had increased nest survival, and produced more fledglings on spray‐only and spray‐and‐seed treatments compared to control patches. Dickcissels nested infrequently on grazed sites—especially grazed control patches. We did not detect any impacts on clutch size, provisioning rates, or nestling mass, but Araneae (spiders) and Lepidoptera larvae (caterpillars) may have been smaller on sprayed patches. Positive responses by dickcissels were likely due to successful reduction of tall fescue and improved access to suitable nest sites through increased vegetation heterogeneity. Our results indicate that using herbicide and seeding to restore tall fescue‐dominated sites improves habitat quality for this grassland bird, shortly after restoration.

Evaluating Causal Factors That Influence the Spatial and Temporal Variability of Streambank Erosion in Iowa

Highlights Critical shear stress and erodibility were quantified for Iowa streambanks at regional and seasonal scales. Variations in critical shear stress and erodibility were apparent across landform areas. Values of critical shear stress in northern Iowa were less than those in southern Iowa. Seasonal variations in critical shear stress and erodibility are due to soil moisture and freeze-thaw cycles. Abstract. Streambank erosion exhibits high variability both spatially and temporally, and few studies have attempted to characterize the causal factors of the variability at regional and seasonal scales. This study combines geotechnical field measurements with historical trends of soil moisture and temperature to quantify the spatial and temporal variability of critical shear stress and erodibility in streambanks of the Major Land Resource Areas of Iowa (MLRAs). The data suggest that till-derived soils in north-central and northeast Iowa lack cohesion compared to loess-derived soils in southern Iowa. Thus, critical shear stress values from the northern parts of the state were significantly less than those from western and southern Iowa. A multivariate regression equation was developed using properties of texture and bulk density to quantify critical shear stress values for all stream bank soil series in the state. The cumulative distribution functions of these values visually reflect the separation between the critical shear stress values of the different MLRAs, with the loess-derived soils in western and southern Iowa having similar, overlapping patterns, in contrast to MLRAs in north central and northeast Iowa with the till-derived soils. Temporally, the critical shear stress reaches minimum values during March when soil moisture is high and there are several freeze-thaw events. This is most apparent with bank soils in eastern Iowa. Keywords: Cohesion, Critical shear stress, Erodibility, Sediment, Streambank erosion.

Grassland-to-cropland conversion increased soil, nutrient, and carbon losses in the US Midwest between 2008 and 2016

After decades of declining cropland area, the United States (US) experienced a reversal in land use/land cover change in recent years, with substantial grassland conversion to cropland in the US Midwest. Although previous studies estimated soil carbon (C) loss due to cropland expansion, other important environmental indicators, such as soil erosion and nutrient loss, remain largely unquantified. Here, we simulated the environmental impacts from the conversion of grassland to corn and soybeans for 12 US Midwestern states using the EPIC (Environmental Policy Integrated Climate) model. Between 2008 and 2016, over 2 Mha of grassland were converted to crop production in these states, with much less cropland concomitantly abandoned or retired from production. The net grassland-cropland conversion increased annual soil erosion by 7.9%, nitrogen (N) loss by 3.7%, and soil organic carbon loss by 5.6% relative to that of existing cropland, despite an associated increase in cropland area of only 2.5%. Notably, the above estimates represent the scenario of converting unmanaged grassland to tilled corn and soybeans, and impacts varied depending upon crop type and tillage regime. Corn and soybeans are dominant biofuel feedstocks, yet the grassland conversion and subsequent environmental impacts simulated in this study are likely not attributable solely to biofuel-driven land use change since other factors also contribute to corn and soybean prices and land use decisions. Nevertheless, our results suggest grassland conversion in the Upper Midwest has resulted in substantial degradation of soil quality, with implications for air and water quality as well. Additional conservation measures are likely necessary to counterbalance the impacts, particularly in areas with high rates of grassland conversion (e.g. the Dakotas, southern Iowa).

Moderate Grazer Density Stabilizes Forage Availability More Than Patch Burning in Low-Stature Grassland

Spatially patchy fire creates landscape-level diversity that in turn stabilizes several rangeland ecosystem services, including forage production and habitat availability. To enhance biodiversity and livestock production, efforts are underway to restore fire regimes in rangelands throughout the Great Plains. However, invasive species such as tall fescue Schedonorus arundinaceus syn. Festuca arundinacea, initially introduced for forage production, hamper prescribed fire use. Grazer density, or stocking rate, modulates the effect of patchy fire regimes on ecological patterns in invaded, semi-natural rangeland pastures. We compare three diversity–stability responses—temporal variability in aboveground plant biomass, portfolio effects among plant functional groups, and beta diversity in plant functional group composition—in pastures managed with two different fire regimes through three periods of heavy, light, and moderate stocking rate in southern Iowa, USA. Pastures were either burned in patches, with one-third of the pasture burned each year, or completely burned every third year. The period of moderate grazer density had the least temporal variability in aboveground plant biomass, regardless of fire regime. We also found statistical evidence for a portfolio effect under moderate stocking, where diversification of plant communities through varying cover of functional groups can stabilize communities by reducing year-to-year variability. Beta diversity among plant functional groups was greatest during the moderate grazer density period as well. The short stature of tall fescue prevented the patch-burning regime to create contrast in vegetation structure among patches, and there was no difference in any diversity–stability mechanism response across the two different patterns of burning. Although longitudinal, these data suggest that temporal variability in aboveground plant biomass declines with diversity–stability mechanisms that underlie ecosystem function. Our results also support a decades-old principle of range management: moderate grazing intensity enhances diversity and stability, which has been shown to buffer forage shortfalls during drought.

Quantifying the Extent of Eroding Streambanks in Iowa

AbstractStreambank erosion is a major source of sediment to rivers and it is important to find locations where severely eroding streambanks are occurring in watersheds. In this study, a new approach to mapping eroding streambanks at a regional scale was conducted using high‐resolution Light Detection and Ranging (LiDAR) elevation data. By calibrating field mapping studies to LiDAR derivative data, the extent of severely eroding streambanks in third‐ to sixth‐order streams and rivers found in Iowa was estimated. Study results suggest that over 35,200 km of streambanks may be severely eroding, or approximately 41% of all third‐ to sixth‐order streambanks. The extent of streambank erosion was not uniform across the state with more erosion occurring in hillier western and southern Iowa compared to flatter and more recently glaciated northern Iowa. Streambank erosion was related to greater bank heights and was more prevalent (as a percent of the total stream length) in larger fifth‐ and sixth‐order rivers. Overall, despite limitations in the study related to the collection and extrapolation of the LiDAR dataset, study results provide new evidence for the magnitude of the streambank erosion problem in Iowa and likely apply to similarly glaciated regions of the United States Midwest.

Erosion and sediment delivery in southern Iowa watersheds: Implications for conservation planning

Soil sediment export from agricultural watersheds is a major environmental concern and is a primary contributor to nonpoint source sediments in streams. The purpose of this study was to quantify total suspended solid (TSS) export and current sediment delivery ratios (SDRs) in four southern Iowa watersheds and evaluate how existing and potential best management practices (BMPs) have affected SDRs. Our study updated estimates of SDRs that were previously developed using mid-20^th century data and largely unknown methods. We estimated TSS export using continuous turbidity measurements and total phosphorus (P) data and measured discharge data to calculate TSS loads. By comparing annual TSS export to watershed-scale soil erosion estimated with the Revised Universal Soil Loss Equation (RUSLE) model, we calculated annual SDRs for the study watersheds and found that current SDRs were significantly lower than previous estimates. This new analysis provides an exceptional story of conservation progress in our study watersheds over the past four decades. Further, they are likely a worst-case scenario for sheet and rill eroded sediment export since TSS export does not distinguish among other sediment sources, such as stream bank and gully erosion. Based on the extent of BMP implementation in the watersheds and the potential for future BMPs determined using the Agricultural Conservation Planning Framework (ACPF) toolbox, we found that there is only limited potential for further reducing TSS export using additional in-field practices. Hence, we believe that further work toward reducing TSS export in these Iowa watersheds should be shifted to reducing contributions from other TSS sources including from streambed, bank, and gully erosion.

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.

Trophic dynamics of a reservoir fishery following an introduction of a top predator: Insights from stable carbon and nitrogen isotopes

AbstractTrophic dynamics and conceptual niche spaces of top piscivores were assessed using stable isotope analysis following the introduction of hybrid striped bass Morone saxatilis (Walbaum) × Morone chrysops (Rafinesque) into an established reservoir fishery devoid of gizzard shad, Dorosoma cepedianum (Lasueur). Hybrid striped bass were initially stocked into Three Mile Lake, Iowa as an attempt to biologically control pervasive yellow bass, Morone mississippiensis Jordan &amp; Eigenmann, populations. From the analyses, it concluded that hybrid striped bass predominately targeted prey fish located in the littoral habitats of the reservoir and did not selectively consume yellow bass as intended. Bayesian isotope mixing models described the diets of hybrid striped bass to include a variety of prey fish, predominantly consisting of young bluegill Lepomis macrochirus and yellow bass. Food resource overlap among hybrid striped bass, largemouth bass, Micropterus salmoides Lacépède, and walleye, Sander vitreus (Mitchill), appeared substantial based on the isotopic niche overlap model. Results from this case study, in conjunction with the hindsight that yellow bass populations became prolific even with stockings of hybrid striped bass, suggest that their use to control yellow bass populations may not be a viable management strategy in southern Iowa.

Quantifying soil carbon change in a long‐term tillage and crop rotation study across Iowa landscapes

AbstractThe dominant cropping system of corn and soybean in the midwestern United States, coupled with use of conventional tillage (CT), has contributed to soil organic carbon (SOC) loss since the conversion of grassland to row crops. This study, conducted at seven sites in Iowa from 2002 to 2014, included five tillage systems: conservation tillage (no tillage [NT], strip‐tillage [ST]) and CT (chisel plow [CP], deep rip [DR], and moldboard plow [MP]) as main treatment and three crop rotations (corn–soybean [C‐S], corn–corn–soybean [C‐C‐S], and continuous corn [C‐C]) as subtreatments in a completely randomized block design with four replications. The objective was to quantify the effect of different tillage intensities and crop rotations on SOC change in different regions in Iowa. The average SOC gain in northern Iowa with NT and ST was 0.33 Mg ha−1 yr−1 over 12 yr with C‐S and C‐C‐S and 0.28 Mg ha−1 yr−1 over 7 yr in the C‐C rotations. The average SOC loss with CP, DR, and MP was −0.34 Mg ha−1 yr−1 with C‐S and C‐C‐S and −0.36 Mg ha−1 yr−1 with C‐C over the same periods. In southern Iowa, NT and ST gained 0.36 Mg ha−1 yr−1 with C‐S and C‐C‐S and 0.33 Mg ha−1 yr−1 with C‐C, whereas CP, DR, and MP on average lost −0.36 Mg ha−1 yr−1 with C‐S and C‐C‐S and −0.34 Mg ha−1 yr−1 with C‐C. The findings also showed that most SOC change (gain or loss) occurred at the top 0–30 cm with no evidence of significant SOC translocation to lower depths.

Total phosphorus export from Iowa agricultural watersheds: Quantifying the scope and scale of a regional condition

Total phosphorus (TP) export in rivers contributes to development of hypoxic conditions in receiving waterbodies and is typically sourced to agricultural nonpoint sources. Systematic quantification of TP loads and yields at a regional scale is not often reported but TP yields are known to vary considerably. In this study, TP yields from 46 Iowa watersheds were evaluated for the period from 2000 to 2017 to evaluate long-term patterns of TP export and quantify the contribution of Iowa-sourced TP loads to the Gulf of Mexico. Using two common load estimation programs, annual mean and median TP yields ranged from 0.44 to 7.71 kg/ha and 0.32 to 3.75 kg/ha, respectively. Highest median yields were found in western and southern Iowa. The weighted average TP yield for Iowa was 1.70 kg/ha and, on average, Iowa’s TP export contributes approximately 15% of the TP load to the Gulf of Mexico. Reducing TP export will require improved quantification and differentiation of sources of TP loads in Midwestern rivers and a commitment to find strategies that reduce both TP and NO3-N loss from agricultural lands in a complementary and additive approach.

Shifting Cattle Producer Beliefs on Stocking and Invasive Forage: Implications for Grassland Conservation

To advance the dialogue to define sustainable working landscapes, it is essential to include the perceptions, knowledge, and factors guiding decision making. We surveyed livestock producers in the Grand River Grasslands region of southern Iowa and northern Missouri, United States, to gain insight into key factors shaping decision making and perspectives on effective management practices in the eastern Great Plains, focusing in particular on demographic and social change and producer willingness to reduce stocking rate as a conservation practice. First, a longitudinal evaluation of livestock producer demographics in 2007 and 2017 revealed individuals were older and were renting grazing land to a greater extent than in 2007. Second, when making land management decisions, producers in 2017 focused on economic concerns more than environmental concerns compared with more balanced views in 2007. For those who prioritized the environment over economics, this prioritization was related to both higher levels of education and a willingness to reduce stocking rate (livestock production) if there is a positive conservation outcome. In contrast, a lower willingness to reduce stocking was associated with increasing rental acreage and prevalence of an invasive cool-season grass that responds favorably to heavy grazing (tall fescue, Schedonorus arundinaceus Schreb.). Regardless, about 37% of cattle producers representing ∼40% of the land area surveyed were at least moderately willing to reduce stocking rates to achieve a conservation outcome. In conclusion, our findings suggest that producers’ need to gain income from livestock may limit the willingness to enact a conservation practice similar to reduced stocking rates. However, there is clearly conservation receptiveness from a segment of the producer community, which indicates potential for improved conservation.

Identifying Opportunities to Conserve Farm Ponds on Private Lands: Integration of Social, Ecological, and Historical Data

In some landscapes, effective conservation of wildlife habitat requires extending beyond the boundaries of reserves and addressing stewardship of private lands. This approach could be especially valuable for the conservation of farm ponds, which are abundant and serve key agricultural functions on private lands. Though farm ponds also provide wildlife habitat, little is known about how they are managed or how values and beliefs of their owners relate to their quality. To address this knowledge gap, we collected data on pond habitat quality and management using historical aerial imagery and high-resolution Google Earth satellite imagery of the Grand River Grasslands of southern Iowa and Northern Missouri. We also collected spatially congruent social data using a mail back survey sent to 456 landowners in the region (32.7% response rate). We used mixed-effects linear regression to link indicators of habitat quality to the survey results. We found that many ponds were permanent, accessible to cattle, in early successional states, and had little wetland vegetation, indicating a scarcity of suitable habitat for wildlife. At the same time, 35–57% of survey respondents said they would be willing to change their management to benefit aquatic organisms. Our analyses indicated that higher cover of cattails correlated with ownership by respondents who regarded row crops or income from agriculture as less important and ponds tended to be temporary if owned by respondents who had many ponds. Moving forward, large landowners and those willing to manage their land to benefit wildlife may constitute a core set of future partners for conservation efforts focused on improving pond habitat in the region.

Nitrogen Fertilizer Suppresses Mineralization of Soil Organic Matter in Maize Agroecosystems

The possibility that N fertilizer increases soil organic matter (SOM) mineralization and, as a result, reduces SOM stocks has led to a great debate about the long-term sustainability of maize-based agroecosystems as well as the best method to estimate fertilizer N use efficiency (FNUE). Much of this debate is because synthetic N fertilizer can positively or negatively affect SOM mineralization via several direct and indirect pathways. Here, we test a series of hypotheses to determine the direction, magnitude, and mechanism of N fertilizer effect on SOM mineralization and discuss the implications for methods to estimate FNUE. We measured the effect of synthetic N fertilizer on SOM mineralization via gross ammonification at two long-term experiments in central and southern Iowa, USA with replicated plots of continuous maize that received one of three ‘historical’ N fertilizer rates (zero, moderate or high) from 1999-2014. In 2015, prior to our measurements, we split the historical N fertilizer rate plots into two subplots that received either the site-specific agronomic optimum N rate or zero N fertilizer. At the onset of rapid maize N uptake, N fertilizer reduced gross ammonification by 13-21% (2-5 kg NH4-N ha-1 d-1). A companion laboratory experiment rejected the hypothesis that differences in net primary productivity between fertilized and unfertilized treatments explained the negative effect of N fertilizer on SOM mineralization. Moreover, the NH4+ pool size was negatively correlated with the gross ammonification rate (r2 = 0.85, p < 0.001). Thus, we conclude that NH4+-N fertilizer had a direct suppressive effect on SOM mineralization. These results demonstrate that the direct effect of N fertilizer on microbial activity can exceed the indirect effects of N fertilizer via large changes in NPP that alter organic matter inputs, soil temperature and moisture content. The magnitude of this effect and specificity to NH4+-N has significant implications for fertilizer management as well as the measurement and modeling of agroecosystem N dynamics including FNUE.

Legacy effects of long-term nitrogen fertilizer application on the fate of nitrogen fertilizer inputs in continuous maize

Nitrogen fertilizer management can impact soil organic C (SOC) stocks in cereal-based cropping systems by regulating crop residue inputs and decomposition rates. However, the impact of long-term N fertilizer management, and associated changes in SOC quantity and quality, on the fate of N fertilizer inputs is uncertain. Using two 15-year N fertilizer rate experiments on continuous maize (Zea mays L.) in Iowa, which have generated gradients of SOC, we evaluated the legacy effects of N fertilizer inputs on the fate of added N. Across the historical N fertilizer rates, which ranged from 0 to 269 kg N ha−1 yr−1, we applied isotopically-labeled N fertilizer at the empirically-determined site-specific agronomic optimum rate (202 kg N ha−1 at the central location and 269 kg N ha−1 at the southern location) and measured fertilizer recovery in crop and soil pools, and, by difference, environmental losses. Crop fertilizer N recovery efficiency (NREcrop) at physiological maturity averaged 44% and 14% of applied N in central Iowa and southern Iowa, respectively (88 kg N ha−1 and 37 kg N ha−1, respectively). Despite these large differences in NREcrop, the response to historical N rate was remarkably similar across both locations: NREcrop was greatest at low and high historical N rates, and least at the intermediate rates. Decreasing NREcrop from low to intermediate historical N rates corresponded to a decline in early-season fertilizer N recovery in the relatively slow turnover topsoil mineral-associated organic matter pool (0–15 cm), while increasing NREcrop from intermediate to high historical N rates corresponded to an increase in early-season fertilizer N recovery in the relatively fast turnover topsoil particulate organic matter pool and an increase in crop yield potential. Despite the variation in NREcrop along the historical N rate gradient, we did not detect an effect of historical N rate on environmental losses during the growing season, which averaged 34% and 69% of fertilizer N inputs at the central and southern locations, respectively (69 kg N ha−1 and 185 kg N ha−1, respectively). Our results suggest that, while beneficial for SOC storage over the long term, fertilizing at the agronomic optimum N rate can lead to significant environmental N losses.

Heroism and Comics Form: Feminist and Queer Speculations

Heroism and Comics Form: Feminist and Queer Speculations

Surveillance of Mosquitoes (Diptera: Culicidae) in Southern Iowa, 2016.

The mosquito fauna of Iowa has been extensively investigated over several decades, providing a wealth of information regarding species distributions, relative abundance, temporal activity patterns, and identifying vectors of medical importance. However, these investigations have had unequal coverage, leaving the mosquito fauna in some parts of the state, including southern Iowa, largely uncharacterized. With the heightened public health threat of Zika virus in the summer of 2016, greater emphasis was placed on surveying for two potential Zika virus vectors: Aedes (Stegomyia) albopictus (Skuse) and Aedes (Stegomyia) aegypti (Linnaeus). Southern Iowa became an area of interest due to the range of Ae. Albopictus, potentially extending into this part of the state. Employing CO2-baited Centers for Disease Control and Prevention light traps and BG-Sentinel traps, our targeted trapping efforts in southern Iowa did not yield either Ae. albopictus or Ae. aegypti. However, the geographical expansion of our trapping efforts did lend valuable insights into the mosquito fauna of southern Iowa. Mosquito species such as Aedes atropalpus (Coquillett), Culex erraticus (Dyar and Knab), and several Psorophora species once presumed rare or uncommon in the state were found to be more prevalent in this ecologically diverse region, augmenting our understanding of mosquito distributions in the state. Moreover, these surveillance efforts established baseline data for continued monitoring of the potential introduction and spread of invasive mosquito species in Iowa as part of an integrated mosquito management program.

An Overlooked 1853 List of Iowa Plants by a Pseudonymous Botanist: Who Was “Flores”?

Abstract The Iowa Farmer and Horticulturist was an agricultural and horticultural journal that began publication in 1853 at Burlington, Iowa. An article serialized in its second, third, fourth, and seventh issues listed 252 native plants of horticultural merit that grew in the vicinity; for 79 of the species, it was the first report for Iowa. The author of this article was identified only by the pseudonym “Flores.” The article evinces numerous similarities of topic and phraseology with an address delivered to the Southern Iowa Horticultural Society in October 1852 by Dr. John Henry Rauch (1828–1894). The previous year, Rauch had published the first checklist of the state's flora at the behest of the Iowa State Medical and Chirurgical Society, and it is suggested that he was the author of the 1853 article as well.