Iowa Soils Research Articles

Direct observations of NOxemissions over the San Joaquin Valley using airborne flux measurements during RECAP-CA 2021 field campaign

Abstract. Nitrogen oxides (NOx) are principle components of air pollution and serve as important ozone precursors. As the San Joaquin Valley (SJV) experiences some of the worst air quality in the United States, reducing NOx emissions is a pressing need, yet quantifying current emissions is complicated due to a mixture of mobile and agriculture sources. We performed airborne eddy covariance flux measurements during the Re-Evaluating the Chemistry of Air Pollutants in California (RECAP-CA) field campaign in June 2021. Combining footprint calculations and land cover statistics, we disaggregate the observed fluxes into component fluxes characterized by three different land cover types. On average, we find emissions of 0.95 mg N m−2 h−1 over highways, 0.43 mg N m−2 h−1 over urban areas, and 0.30 mg N m−2 h−1 over croplands. The calculated NOx emissions using flux observations are utilized to evaluate anthropogenic emissions inventories and soil NOx emissions schemes. We show that two anthropogenic inventories for mobile sources, EMFAC (EMission FACtors) and FIVE (Fuel-based Inventory for Vehicle Emissions), yield strong agreement with emissions derived from measured fluxes over urban regions. Three soil NOx schemes, including the MEGAN v3 (Model of Emissions of Gases and Aerosols from Nature), BEIS v3.14 (Biogenic Emission Inventory System), and BDISNP (Berkeley–Dalhousie–Iowa Soil NO Parameterization), show substantial underestimates over the study domain. Compared to the cultivated soil NOx emissions derived from measured fluxes, MEGAN and BEIS are lower by more than 1 order of magnitude, and BDISNP is lower by a factor of 2.2. Despite the low bias, observed soil NOx emissions and BDISNP present a similar spatial pattern and temperature dependence. We conclude that soil NOx is a key feature of the NOx emissions in the SJV and that a biogeochemical-process-based model of these emissions is needed to simulate emissions for modeling air quality in the region.

Occurrence and spatial distribution of individual polychlorinated biphenyl congeners in residential soils from East Chicago, southwest Lake Michigan

We report individual polychlorinated biphenyl congeners and the sum of all congeners (ΣPCB) in residential soils of East Chicago, Indiana. ΣPCB in soils ranged from 20 to 1700 ng/g dry weight (DW), with a geometric mean of 120 ng/g DW. These values are significantly higher than other locations, but similar or lower to locations nearby well-known PCB contamination sites. No PCB spatial distribution pattern was observed. PCB concentrations increase with total organic carbon in the soils and proximity to Indiana Harbor and Ship Canal (IHSC), where sediments are contaminated with PCBs. Most samples are similar in their PCB distribution and Aroclor 1254 yielded the highest similarity to all the samples. A fifth of the samples highly resemble other PCB profiles such as EPA background and Cedar Rapids Iowa soils, and volatilization from Lake Michigan, whereas volatilization from IHSC could not explain the PCBs found in soils. IHSC was expected to be the main source of PCBs in the nearby soils. It is possible that soils are impacted by variety of known and unknown sources, including volatilization from Lake Michigan, resulting in a regional PCB signal. Although PCB concentrations are higher than other locations, samples were below the current US EPA non-cancer residential soil level remediation goal for dioxin TEQ.

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.

Identification and Characterization of a Potential Antibiotic Producing Strain of Pantoea ananatis.

Antibiotic resistance continues to be a significant public health challenge. Soil bacteria represent a potential source of yet to be discovered antimicrobials. The screening of Iowa (United States) soils yielded the identification of a strain of Pantoea ananatis (MMB-1), which displayed an antimicrobial-producing phenotype against a bacterium (Bacillus subtilis) representative of Gram-positive bacteria. Crude, organic, extracts of MMB-1 retained the anti-microbial activity. The draft genome of strain MMB-1 contains a total of 4,634,340 bp, and 4,624 protein-encoding genes. Consistent with phenotypic observation, the genome of MMB-1 encodes for a number of putative secondary metabolite biosynthetic gene clusters, including those known to be involved in the production of the antibiotics lankacidin C and bottromycin. This study increases our overall understanding of Panteoa as a group, and is also consistent with the notion that members of this genus have significant potential as useful natural product producers.

Impacts of Soil NOx Emission on O3 Air Quality in Rural California.

Nitrogen oxides (NOx) are a key precursor in O3 formation. Although stringent anthropogenic NOx emission controls have been implemented since the early 2000s in the United States, several rural regions of California still suffer from O3 pollution. Previous findings suggest that soils are a dominant source of NOx emissions in California; however, a statewide assessment of the impacts of soil NOx emission (SNOx) on air quality is still lacking. Here we quantified the contribution of SNOx to the NOx budget and the effects of SNOx on surface O3 in California during summer by using WRF-Chem with an updated SNOx scheme, the Berkeley Dalhousie Iowa Soil NO Parameterization (BDISNP). The model with BDISNP shows a better agreement with TROPOMI NO2 columns, giving confidence in the SNOx estimates. We estimate that 40.1% of the state's total NOx emissions in July 2018 are from soils, and SNOx could exceed anthropogenic sources over croplands, which accounts for 50.7% of NOx emissions. Such considerable amounts of SNOx enhance the monthly mean NO2 columns by 34.7% (53.3%) and surface NO2 concentrations by 176.5% (114.0%), leading to an additional 23.0% (23.2%) of surface O3 concentration in California (cropland). Our results highlight the cobenefits of limiting SNOx to help improve air quality and human health in rural California.

The Effects of Soil Depth on the Structure of Microbial Communities in Agricultural Soils in Iowa, USA.

This study investigated the differences in microbial community abundance, composition and diversity throughout the depth profiles in soils collected from corn and soybean fields in lowa, USA using 16S rRNA amplicon sequencing. The results revealed decreased richness and diversity in microbial communities at increasing soil depth. Soil microbial community composition differed due to crop type only in the top 60 cm and due to location only in the top 90 cm. While the relative abundance of most phyla decreased in deep soils, the relative abundance of the phylum Proteobacteria increased and dominated agricultural soils below the depth of 90 cm. Although soil depth was the most important factor shaping microbial communities, edaphic factors including soil organic matter, soil bulk density and the length of time that deep soils were saturated with water were all significant factors explaining the variation in soil microbial community composition. Soil organic matter showed the highest correlation with the exponential decrease in bacterial abundance with depth. A greater understanding of how soil depth influences the diversity and composition of soil microbial communities is vital for guiding sampling approaches in agricultural soils where plant roots extend beyond the upper soil profile. In the long term a greater knowledge of the influence of depth on microbial communities should contribute to new strategies that enhance the sustainability of soil which is a precious resource for food security.IMPORTANCE Determining how microbial properties change across different soils and within the soil depth profile, will be potentially beneficial to understanding the long-term processes that are involved in the health of agricultural ecosystems. Most literature on soil microbes has been restricted to the easily accessible surface soils. However, deep soils are important in soil formation, carbon sequestration, and in providing nutrients and water for plants. In the most productive agricultural systems in the USA where soybean and corn are grown, crop plant roots extend into the deeper regions of soils (> 100 cm), but little is known about the taxonomic diversity or the factors that shape deep soil microbial communities. The findings reported here highlight the importance of soil depth in shaping microbial communities, provide new information about edaphic factors that influence the deep soil communities and reveal more detailed information on taxa that exist in deep agricultural soils.

Maize Response to Sulfur Fertilizer in Three Iowa Soils

ABSTRACT Maize (Zea mays L.) yield increases from sulfur (S) fertilizer have recently been documented in Iowa, but responses have not been consistent. The objective for this study was to evaluate the response of juvenile maize to S applied as ammonium sulfate (AMS), ammonium thiosulfate (ATS), and S-enhanced mono-ammonium phosphate (MAPS). Clarion loam (Typic Haplaquolls), Fayette silt loam (Typic Hapludalfs), and Muscatine silt loam (Aquic Hapludolls) were collected from eroded hillslopes in Iowa, and amended with 0, 22, 34, and 45 kg S ha−1. Maize (Pioneer 36N71) seedlings were planted in pots, placed in a controlled-climate chamber, and harvested after 21 days. Fertilizer S increased maize shoot dry matter (DM) when AMS was applied to Clarion loam, and when S from any source was applied to Muscatine silt loam. Sulfur fertilizer had no effect on DM accumulation in Fayette silt loam. Whole-plant S concentrations were generally higher than the control for all S sources. The agronomic efficiency of S (DM yield per unit applied) was greatest for the Muscatine soil, and was not related to S source or application rate. Early season growth of maize in Iowa may benefit from S fertilizer application, but the response may be site-specific.

The Comparison of Three Environmental Metrics for Cr, Pb, and Zn in the Agricultural Region of the Mid-Continent of USA

The chemical and physical properties of soil are critical factors that affect human health. The current geochemical study is designed to evaluate the concentrations of heavy metals (Cr, Pb, and Zn) in the soil in Iowa (IA), Kansas (KS), and Nebraska (NE). The basic descriptive statistical results suggest that there are some limited levels of the heavy metals in the soils that come from anthropogenic inputs. The results of three environmental metrics, the enrichment factor (EF), geoaccumulation (Igeo), and potential ecological risk (PERI), have been calculated, evaluated, and compared. EF values show that soils contain minimal enrichment of Cr, Pb, and Zn in the study area. In addition, PERI values presented low risk with Cr, Pb, and Zn. However, Igeo values showed no contamination of Cr, Pb, and Zn in the study area. These results suggest that the elevated levels of these heavy metals are dominated by the historic agricultural inputs derived from long-term anthropogenic applications, especially in the regions with extensive human activities, which means that soil is the sink for heavy metals released into the environment.

Distribution of Natural and Anthropogenic Sources, and Mapping of As, Co, and Hg by Three Ecological Risk Indices in the Mid-continent of the USA

Three indicators are employed including the Enrichment factor (EF), geoaccumulation (I geo), and potential ecological risk assessment (PERI) to measure the degree of contamination of As, Co, and Hg in soils. The objective of this investigation is to evaluate the concentration of As, Co, and Hg in the soils of Iowa (IA), Kansas (KS), and Nebraska (NE). Study of the spatial distribution of chemicals was carried out as part of the investigation, which leads to the suggestion of the potential source of the elements. EF, I geo and PERI indexes, As and Co contain minimal enrichment, and Hg is high. EF of As and Hg are similarly classified with minimal contamination as well as EF of Co in NE. EF can be ordered Hg > As > Co. PERI values of As and Co are classified as a low risk. PERI values of Hg are higher than As and Co. I geo values of As and Co indicate uncontaminated to moderately contaminated soil. I geo of Hg is highest of three chemicals order Hg > As > Co. However, I geo degree of As is approximately similar in the three states and it is higher than Co, which indicate as uncontaminated to moderately contaminated. PERI show serious ecological risk pollution of Hg in the soils. These investigations indicate minimal to moderate soil contamination with As and Co in the three states. The spatial distribution is widespread and continuous. Point source maps are compared with this present product. The nature of the spatial distribution correlates with the major human activity on the land, agriculture. The As, Co, and Hg chemistry of the soil is due to the intense fertilization that accompanies such successful agriculture, which originates from anthropogenic sources that require continuous monitoring.

The Comparison of Three Environmental Metrics for Cd, Cu, and Ni in the Agricultural Region of the Mid Continent of USA

Enrichment factor (EF), potential ecological risk assessment (PERI), and geoaccumulation (I geo) were employed to measure degree the of contamination Cd, Cu, and Ni in soils in Iowa (IA), Kansas (KS, and Nebraska (NE). Cd and Cu were measured as minimal enrichment and low risk using EF and PERI indexes. This study aims to study the regional distribution of chemical elements to determine the source of the elements and which evaluation tools may be applied to determine the quality and the health of the soil. The presence of significant concentrations of different biologically active chemical substances, such as agricultural additives can affect the status and functioning of the soil microbial biogenesis, soil fertility, and human health. Nevertheless, Cd measured uncontaminated to moderately contaminated while Cu, and Ni indicated uncontaminated (I geo ≤ 0) in the soil. EF of Cd is the highest EF of three heavy metals, Cd > Cu > Ni. The highest value of EF of Cd is observed in KS (1.65) followed by NE (1.25) and IA (1.22). However, enrichment degree of Cu is approximately similar in IA (1.11) and KS (1.01) while enrichment degree of Ni is lowest and its average in NE (1.07), IA (0.76, KS (0.82), and NE (0.92). Igeo showed high value Cd estimated at 0.36 in KS followed by 0.29 in NE and 0.18 in IA, which indicate to the possibility of the soil contamination with the Cd originated from human inputs. In addition, high value of Cu in IA in the soil is sourced from human applications as well. PERI showed serious ecological risk pollution of Ni in the soils of IA, KS, and NE. According to the evaluating standard of PERI, Ni is classified as a very high risk in IA (2784.5), in KS (1883.1), in NE (1154.6) while Cd and Cu are estimated as low risk of soil contamination. Keywords : soil chemistry, chemical elements, soil contamination, PERI, EF, I geo, geochemical mapping, Regional Geochemical Mapping (RGM). DOI: 10.7176/JEES/10-6-09 Publication date: June 30 th 2020

Thermal property values of a central Iowa soil as functions of soil water content and bulk density or of soil air content

AbstractSoil thermal properties play important roles in dynamic heat and mass transfer processes, and they vary with soil water content (θ) and bulk density (ρ b). Both θ and ρ b change with time, particularly in recently tilled soil. However, few studies have addressed the full extent of soil thermal property changes with θ and ρ b. The objective of this study is to examine how changes in ρ b with time after tillage impact soil thermal properties (volumetric heat capacity, C v, thermal diffusivity, k, and thermal conductivity, λ). The study provides thermal property values as functions of θ and ρ b and of air content (n air) on undisturbed soil cores obtained at selected times following tillage. Heat pulse probe measurements of thermal properties were obtained on each soil core at saturated, partially saturated (θ at pressure head of −50 kPa) and oven‐dry conditions. Generally, k and λ increased with increasing ρ b at the three water conditions. The C v increased as ρ b increased in the oven‐dry and unsaturated conditions and decreased as ρ b increased in the saturated condition. For a given θ, a larger ρ b was associated with larger thermal property values, especially for λ. The figures of C v, k and λ versus θ and ρ b, as well as C v, k and λ versus n air, represented the range of soil conditions following tillage. Trends in the relationships of thermal property values with θ and ρ b were described by 3‐D surfaces, whereas each thermal property had a linear relationship with n air. Clearly, recently tilled soil thermal property values were quite dynamic temporally due to varying θ and ρ b. The dynamic soil thermal property values should be considered in soil heat and mass transfer models either as 3‐D functions of θ and ρ b or as linear functions of n air.Highlights Thermal property values for a range of θ and ρ b were measured on undisturbed soil cores. Freshly tilled soil thermal property values were quite dynamic temporally. The thermal property values of a tilled soil were described as 3‐D surfaces with θ and ρ b. The thermal property values of a tilled soil varied linearly with n air.

Dedicated Bioenergy Crops and Water Erosion.

Information on the water quality impact of perennial warm-season grasses (WSGs) when grown in marginal lands as dedicated energy crops is limited. We studied how WSGs affected runoff, sediment, and nutrient losses and related near-surface soil properties to those of no-till corn ( L.) on an eroded soil in southwestern Iowa and a center pivot corner in east-central Nebraska. The experiment at the eroded soil was established in 2012, and treatments included 'Liberty' switchgrass ( L.) and no-till continuous corn. The experiment at the pivot corner was established in 2013 with 'Liberty' switchgrass, 'Shawnee' switchgrass, low-diversity grass mixture, and corn. We simulated rainfall at 63.5 ± 2.8 mm h for 1 h to portray 5-yr return periods and measured water erosion in spring 2017. Time to runoff start and runoff depth did not differ between WSGs and corn. On the eroded soil, sediment and nutrient losses did not differ between treatments. At the pivot corner, sediment (0.71 vs. 0.15 Mg ha) and PO-P (0.037 vs. 0.006 kg ha) losses were five times higher in corn than in WSGs. Near-surface soil properties did not differ on the eroded soil, but at the pivot corner, wet aggregate stability was four times higher and residue cover was 34% higher in WSGs than in corn. Water-stable aggregates were negatively correlated with NO-N and PO-P losses. Overall, WSGs can improve water quality in marginally productive croplands, but their effectiveness appears to be site specific.

Subsoil Potassium in Central Iowa Soils: Status and Future Challenges

Core Ideas Surface and subsurface soil K concentrations are both important. Soil‐test K levels in many central Iowa soils are below recommended levels. A cellulosic‐based bioeconomy will require higher soil‐test K concentrations. Plant‐available K below 15 cm averaged 100 to 110 mg kg‐1 in central Iowa. A reevaluation of plant‐available K within central Iowa soils is needed, especially if crop residues are harvested for animal feed or cellulosic feedstock. This study evaluated plant‐available K concentrations to depths of 120 cm (n = 2433) within soil profiles at 10 experimental sites. Data from 0‐ to 5‐, 5‐ to 15‐, 0‐ to 15‐, 15‐ to 30‐, 30‐ to 60‐, 60‐ to 90‐, and 90‐ to 120‐cm depths were compiled and evaluated. Based on over 400 samples collected from each depth increment below 15 cm, a reference value of 100 mg kg–1 appears common for central Iowa subsoils. Sixty‐four percent of all samples had soil‐test K levels below the 120 mg kg–1 threshold for very low nutrient status for crop production in Iowa. Only 28% of surface soil samples (<15‐cm depth) were considered to have at least optimum nutrient status with concentrations greater than 160 mg kg–1. As K is not an environmentally sensitive nutrient, its management in central Iowa soils has generally been neglected in recent years, particularly when compared with N and P management initiatives. Building awareness of soil K profile concentrations, rather than focusing only on surface concentrations, will be necessary to meet nutrient requirements for 21st century agricultural production.

Evaluation of nitrogen fertilizer additives for enhanced efficiency in corn on Iowa soils

Recent years of high rainfall and prolonged wet soil conditions in Iowa have renewed interest to protect losses of fertilizer nitrogen (N) in corn. This study evaluated effect of N additives and a slow‐release urea product on the soil NO3–N fraction of total inorganic N, mid–vegetative growth N stress, grain yield, and corn nitrogen use efficiency. Earn 1 CEU in Nutrient Management by reading this article and taking the quiz at www.certifiedcropadviser.org/education/classroom/classes/516.

Evaluation of Nitrogen Fertilizer Additives for Enhanced Efficiency in Corn on Iowa Soils

Core Ideas Landscape position was selected and N fertilizer treatments were designed to promote significant denitrification and enhanced potential volatilization. No agronomic benefit was found using urea with nitrification and urease inhibitors or urea with a polymer coating. Lack of response to inhibitor products and coated urea were likely due to rainfall timing and amount shortly after application, reduced volatilization due to high soil retention of NH4, and slowed nitrification rates from cool soil temperatures after application. Recent years of high rainfall and prolonged wet soil conditions in Iowa have renewed interest to protect losses of fertilizer nitrogen (N) in corn (Zea mays L.). This study evaluated effect of N additives and a slow‐release urea product on the soil NO3–N fraction of total inorganic N, mid–vegetative growth N stress, grain yield, and corn nitrogen use efficiency (NUE). Field trials were conducted at two Iowa State University Research Farms in 2013 and 2014. Sites were selected for probable response to applied N with different nitrification product treatments and coated urea (fine‐textured soils that were poorly drained with high organic matter) and urease inhibitor products (incorporated vs. unincorporated). Urea and treated urea were applied at 120 lb N/acre and incorporated and left on the surface. Overall, there was no agronomic benefit from using urea with nitrification inhibitors (Instinct and SuperU), urea with urease inhibitors (Agrotain, SuperU, and Factor), or urea with a polymer coating (Environmentally Smart Nitrogen). Lack of response to nitrification and urease products was potentially due to climatic conditions during the study. Significant rainfall shortly after N application moved urea into the soil profile (minimizing NH3 volatilization) and slowed nitrification rates from cool temperatures early in the season.

Identification of Soil Microbes Capable of Utilizing Cellobiosan

Approximately 100 million tons of anhydrosugars, such as levoglucosan and cellobiosan, are produced through biomass burning every year. These sugars are also produced through fast pyrolysis, the controlled thermal depolymerization of biomass. While the microbial pathways associated with levoglucosan utilization have been characterized, there is little known about cellobiosan utilization. Here we describe the isolation and characterization of six cellobiosan-utilizing microbes from soil samples. Each of these organisms is capable of using both cellobiosan and levoglucosan as sole carbon source, though both minimal and rich media cellobiosan supported significantly higher biomass production than levoglucosan. Ribosomal sequencing was used to identify the closest reported match for these organisms: Sphingobacterium multivorum, Acinetobacter oleivorans JC3-1, Enterobacter sp SJZ-6, and Microbacterium sps FXJ8.207 and 203 and a fungal species Cryptococcus sp. The commercially-acquired Enterobacter cloacae DSM 16657 showed growth on levoglucosan and cellobiosan, supporting our isolate identification. Analysis of an existing database of 16S rRNA amplicons from Iowa soil samples confirmed the representation of our five bacterial isolates and four previously-reported levoglucosan-utilizing bacterial isolates in other soil samples and provided insight into their population distributions. Phylogenetic analysis of the 16S rRNA and 18S rRNA of strains previously reported to utilize levoglucosan and our newfound isolates showed that the organisms isolated in this study are distinct from previously described anhydrosugar-utilizing microbial species.

Polychlorinated biphenyl congeners in sediment cores from the Upper Mississippi River.

We determined polychlorinated biphenyls (PCBs) and radionuclide (137)Cs in sediment cores from the Upper Mississippi River (UMR) and the Iowa River, Iowa, at their confluence. Vertical distribution of (137)Cs indicated negligible mixing in the UMR core, while the Iowa River core showed signs of mixing. A clear (137)Cs peak was found in the UMR core, which was correlated to 1963. The PCB vertical distribution in UMR core was similar to the historical trend in Aroclor production observed in Great Lakes cores, with a peak close to the (137)Cs peak, suggesting a date near 1960. In general, PCB congener profiles in both cores resembled the Iowa soil background signal. We concluded that despite evidence of mixing in the Iowa River core, both cores retain the PCB signature of historical and regional environmental exposure. Further, our results indicate that this iconic waterway has a long history of PCBs that reflects national production and use.

Phosphorus Sorption Capacity of Six Iowa Soils before and after Five Years of Use as Vegetative Treatment Areas

Abstract. Accumulation of phosphorus in soil is a major factor limiting the operational life (period of time where the soil can serve as an effective phosphorus sink) of land application waste disposal systems. Better evaluation of phosphorus operational life requires improved understanding of how manure application to soil can affect its phosphorus sorption characteristics. In this study, laboratory experiments were conducted to investigate the impact of feedlot runoff effluent application on phosphorus sorption capacities, equilibrium phosphorus concentrations, and phosphorus buffering capacities of six Iowa soils. Soil samples were collected from vegetative treatment areas that had received feedlot runoff application for the previous five years and from a paired grassed area that did not. Subsamples of each soil were incubated with a series of 12 phosphorus solutions ranging in concentration from 0 to 200 mg P/L to determine the sorption characteristics and results fitted to the Langmuir model to determine the phosphorus equilibrium concentration, phosphorus buffering capacity, and maximum phosphorus sorption capacity. Results indicated that vegetative treatment areas generally had elevated phosphorus equilibrium concentrations, indicating an elevated risk of loss of dissolved phosphorus. In most cases, the ability of the soil to sorb phosphorus was significantly increased, as was the remaining phosphorus sorption capacity of the soil. These results indicate that vegetative treatment area life could be greatly extended due to soil property modifications that occur as a result of system operation.

Necessary Courage: Iowa’s Underground Railroad in the Struggle against Slavery by Lowell J. Soike (review)

Reviewed by: Necessary Courage: Iowa’s Underground Railroad in the Struggle against Slavery by Lowell J. Soike Don Elder Necessary Courage: Iowa’s Underground Railroad in the Struggle against Slavery. Lowell J. Soike. Iowa City: University of Iowa Press, 2013. ISBN 978-1-60938-193-6, 322 pp., paper, $24.95. At the time Abraham Lincoln was elected president in 1860, eighteen of the thirty-three states in the American political union did not allow slavery to exist within their borders. Six of those free states shared a common border with at least one slave state. Of those six, only Iowa was located west of the Mississippi River. Thus, Iowa was strategically positioned to help individuals trying to escape the bonds of slavery in the western region—if residents were willing to break existing laws to aid the fugitives. As it turns out, some Iowans were up to that challenge prior to the Civil War. Lowell J. Soike has at last told their story, never before examined in a monograph-length work. Thoroughly researched and clearly written, Necessary Courage helps to further our understanding of how and why a small but resolute group of Iowans flaunted laws to help slaves have a chance to attain freedom. Soike is uniquely qualified to tell the story of the part that Iowa played in the Underground Railroad. A mandate by the Iowa General Assembly in the late 1990s led to the creation of the Iowa Freedom Trail Grant Project, a program designed to help identify the locations in Iowa associated with the Underground Railroad; Soike headed this project, and Necessary Courage came out of his effort. While he found that many of the physical structures from the antebellum period no longer existed, he learned that there was a wealth of written accounts that pertained to Iowa’s role in the Underground Railroad. These sources form the basis of his story. In Soike’s telling, the Iowans involved in the Underground Railroad had a number of successes in aiding runaway slaves. Many fugitives were rather mundanely shuttled from location to location, but some endeavors involved armed confrontation, and not every escaped slave avoided capture while on Iowa soil. Moreover, Necessary Courage proves that not every Iowan involved in the Underground Railroad was white. Indeed, an African American businessman from Muscatine named Alexander Clark emerges as a hero for his efforts to aid a runaway. Soike also demonstrates that Iowans could indirectly help the Underground Railroad. The story of John Brown is a prime example; Soike points out that Brown spent a long time traveling through Iowa, where he gained financial backing, and in the community of Springdale trained his band for their raid on Harpers Ferry. Soike’s book shows how a wide variety of Iowans helped slaves escape from servitude. Necessary Courage does suffer from a few minor errors. For example, Lecomp-ton, Kansas, is misspelled, as is Platte County, Missouri. But the book’s merits [End Page 175] far outweigh its drawbacks. In an engaging manner, Lowell Soike has brought to life the stories of Iowans who took a stand against what they perceived to be a great injustice and, in the process, became part of one of the most important movements in the Civil War era. Don Elder Eastern New Mexico University Copyright © 2015 Kent State University Press

Modeled nitrous oxide emissions from corn fields in iowa based on county level data.

The U.S. Corn Belt area has the capacity to generate high nitrous oxide (NO) emissions due to medium to high annual precipitation, medium- to heavy-textured soils rich in organic matter, and high nitrogen (N) application rates. The purpose of this work was to estimate NO emissions from cornfields in Iowa at the county level using the DeNitrification-DeComposition (DNDC) model and to compare the DNDC NO emission estimates with available results from field experiments. All data were acquired for 2007 to 2011. Weather Underground Network and the Iowa State University Iowa Soil Properties and Interpretation Database 7.3 were the data sources for DNDC inputs and for computing county soil parameters. The National Agriculture Statistic Service 5-yr averages for corn yield data were used to establish ex post fertilizer N input at the county level. The DNDC output suggested county-wide NO emissions in Iowa ranged from 2.2 kg NO-N ha yr in south-central to 4.6 to 4.7 kg NO-N ha yr in north-central and eastern Iowa counties. In northern districts, the average direct NO emissions were 3.2, 4.4, and 3.6 kg NO-N ha yr for west, central, and east, respectively. In central districts, average NO emissions were 3.5, 3.9, and 3.4 kg NO-N ha yr for west, central, and east, respectively. For southern districts, NO emissions were 3.5, 2.6, and 3.1 kg NO-N ha yr for west, central, and east, respectively. Direct NO emissions estimated by the DNDC model were 1.93% of N fertilizer input to corn fields in Iowa, with values ranging from 1.66% in the northwest cropping district to 2.25% in the north-central cropping district. These values are higher than the average 1% loss rate used in the IPCC Tier 1 approach.