Mailbag

On April 21, we sent a message on the Internet asking on-line users at Iowa State to tell us about their experiences in cyberspace. Below are a few of the responses we received. For more on what the Internet can do for you, read the cover story, The Inter-What?, beginning on page 10

Front Lines

Change. Six letters. One word. The topic for an entire magazine. In the case of this issue of ethos, yes. This issue is about changes. Changes in technology (the Internet). Changes on campus (the renovation of Botany Hall and the argument over USSA). Changes in children\u27s literature (political correctness). And changes involving this magazine (expansion and retirement)

Human resources\u27 role in successful mergers and acquisitions

In comparing the success of AOL Time Warner\u27s merger and Hewlett-Packard Compaq\u27s merger, it\u27s easy to see who came out the winner. In comparing their merger strategies, including their focus on HR issues, it\u27s also easy to see why mergers and acquisitions need to be analyzed well in advance and include due diligence, including cultural due diligence, integration planning, and analysis of HR issues, including communication and employee retention. If more companies who are considering merging with or acquiring another company would put as much time as they do money into the merger, and analyze some of the key people-related issues, more mergers would have the fighting chance HP Compaq achieved

Composting and time of application affect corn (Zea mays L.) grain yield and dry matter response to deep-bedded swine (Sus scrofa L.) manure

Swine production in hoop structures is a relatively new deep-bedded husbandry system in which a solid manure/bedding pack accumulates. Currently, no guidelines are available to producers as to the optimal time (fall or spring) and form (composted or fresh) for applying hoop manure for the greatest crop performance and environmental protection. The main objective of this research was to test the effects of composting and time of application on corn (Zea mays L.) dry matter production and grain yield. Two field plot experiments were conducted near Boone, Iowa, each during two growing seasons. Results indicated no difference in grain yields among the fall applied hoop amendments, but inconsistent yield results from the spring applied fresh manure. Parameters used to indirectly monitor plant and soil N status suggested that spring-applied fresh manure did not supply plants with N as effectively as the other hoop amendment treatments. However, an experiment designed to closely examine the temporal relationship between soil N derived from spring applied fresh and composted manure and plant N uptake indicated no treatment differences. Analyses of corn growth responses to the spring applied hoop amendments suggested that fresh hoop manure may sometimes exhibit phytotoxic effects on corn seedlings and that composted manure may aid in drought tolerance relative to the effects of spring-applied fresh hoop manure. Mean N supply efficiency, defined as N fertilizer equivalency as a percentage of the total N applied, was greatest for fall-applied composted manure (34.7%), intermediate for fall-applied fresh manure (24.3%) and spring-applied composted manure (25.0%), and least for spring-applied fresh manure (10.9%). Based on these results, the optimum management strategies would be to apply fresh manure in the fall rather than composting it for spring application, and to compost fresh manure removed from hoops in the spring for fall application. These results are based on agronomic production only; economic and environmental impacts of N losses associated with the time and form of application could affect these recommendations

Soil Oxygen Dynamics: Patterns and Lessons from Six Years of High Frequency Monitoring

Soil oxygen (O2) is a fundamental control on terrestrial biogeochemical cycles including processes producing and consuming greenhouse gases (GHG), yet it is rarely measured. Instead, soil O2 is assumed to be proportional to soil moisture and physical soil properties. For example, soil O2 is often inferred from a 25-year old steady-state diffusion model; however, few data exist to test this model in stochastic systems. The variability of soil O2 may be particularly important to GHG emissions from aquatic-terrestrial interface zones because of the convergence of variable hydrology and rapid biogeochemical processing. Our objective is to gain a better understanding of soil O2 variation and its role in controlling GHG emissions across aquatic-terrestrial interface zones. Specifically, we hypothesize that in aquatic-terrestrial interface ecosystems, soil moisture predicts O2 concentration under stable conditions, but under dynamic conditions (e.g., water table fluctuations or precipitation) heterogeneous distributions of water-filled soil pore space complicate this prediction. Furthermore, we hypothesize that GHG emissions will correspond to variation in soil O2. Twenty-four near-continuous (30-minute frequency) soil O2 and moisture sensors were monitored for more than six years. The sensors were installed at 10 cm of depth across an aquatic-terrestrial interface of a constructed wetland in April 2012 and removed in July 2018. Diurnal, precipitation and drainage events, seasonal, and longer-term patterns were in soil O2 observed. Drought conditions (2012) resulted in minimal soil O2 variation; however, a diurnal pattern of lower soil O2 during the day was observed. When precipitation increases within and among sensor soil O2 variation increases. The relationship between soil moisture and soil O2 was non-linear during periods of soil drainage and precipitation. Commonly, a rapid (change of 10% over <24 hours) increase in soil O2 occurred during soil drainage near a common threshold. As soil moisture increased due to precipitation, soil O2 decreased slower than predicted by simple diffusion models. Soil O2 was an important predictor of weekly methane and nitrous oxide emissions correspond to variation in soil O2. These soil O2 data will be useful for understanding multiple soil biogeochemical functions

Nutrient export to groundwater across a land use and historical climate gradient

Groundwater inputs to streams are important to intermittent stream function and can be a source of nutrients such as nitrogen and phosphorus. The amount of nutrients within groundwater are an important factor for downstream processes, including eutrophication far from the groundwater source. We asked whether land use and precipitation affect nutrient export patterns to groundwater. Soil samples were taken from sites across a variable precipitation gradient in Kansas with three land uses: agriculture, native prairie, and restored prairie. By analyzing the relative concentrations of nitrogen and phosphorus in the water after leaching the soil samples in mesocosms, we can tell how water quality is affected by land use and precipitation patterns, especially in intermittent streams

Seasonal Salinization Decreases Spatial Heterogeneity of Sulfate Reducing Activity

This work is licensed under a Creative Commons Attribution 4.0 International License.Evidence of sulfate input and reduction in coastal freshwater wetlands is often visible in the black iron monosulfide (FeS) complexes that form in iron rich reducing sediments. Using a modified Indicator of Reduction in Soils (IRIS) method, digital imaging, and geostatistics, we examine controls on the spatial properties of FeS in a coastal wetland fresh-to-brackish transition zone over a multi-month, drought-induced saltwater incursion event. PVC sheets (10 × 15 cm) were painted with an iron oxide paint and incubated vertically belowground and flush with the surface for 24 h along a salt-influenced to freshwater wetland transect in coastal North Carolina, USA. Along with collection of complementary water and soil chemistry data, the size and location of the FeS compounds on the plate were photographed and geostatistical techniques were employed to characterize FeS formation on the square cm scale. Herein, we describe how the saltwater incursion front is associated with increased sulfate loading and decreased aqueous Fe(II) content. This accompanies an increased number of individual FeS complexes that were more uniformly distributed as reflected in a lower Magnitude of Spatial Heterogeneity at all sites except furthest downstream. Future work should focus on streamlining the plate analysis procedure as well as developing a more robust statistical based approach to determine sulfide concentration

Seasonal Salinization Decreases Spatial Heterogeneity of Sulfate Reducing Activity

Evidence of sulfate input and reduction in coastal freshwater wetlands is often visible in the black iron monosulfide (FeS) complexes that form in iron rich reducing sediments. Using a modified Indicator of Reduction in Soils (IRIS) method, digital imaging, and geostatistics, we examine controls on the spatial properties of FeS in a coastal wetland fresh-to-brackish transition zone over a multi-month, drought-induced saltwater incursion event. PVC sheets (10 - 15 cm) were painted with an iron oxide paint and incubated vertically belowground and flush with the surface for 24 h along a salt-influenced to freshwater wetland transect in coastal North Carolina, USA. Along with collection of complementary water and soil chemistry data, the size and location of the FeS compounds on the plate were photographed and geostatistical techniques were employed to characterize FeS formation on the square cm scale. Herein, we describe how the saltwater incursion front is associated with increased sulfate loading and decreased aqueous Fe(II) content. This accompanies an increased number of individual FeS complexes that were more uniformly distributed as reflected in a lower Magnitude of Spatial Heterogeneity at all sites except furthest downstream. Future work should focus on streamlining the plate analysis procedure as well as developing a more robust statistical based approach to determine sulfide concentration

Variation in Stream Chemistry Across the Kansas Precipitation Gradient

How do stream order, land use, and stream position within the precipitation gradient across Kansas affect stream chemistry? Land use will drive changes in stream chemistry that are biologically driven (e.g., DOC, NO3-), whereas stream order or position in the precipitation gradient will have a greater affect on conservative (e.g., Cl- or Na+). Take home message is stream order was the most consistent factor for explaining variation in stream chemistry. Land use never explained the highest amount of variation in stream chemistry. Stream chemistry did not vary between Central and Eastern Kansas streams