Early season losses of fertilizer nitrogen during corn production

Fertilizer nitrogen (N) usually is applied to Iowa cornfields before planting in late April or early May. Although it is well established that some of this N can escape from fields before the corn (Zea mays L.) begins rapid growth in June, the practical importance of these early season losses of N has not been established. This dissertation focused on learning more about the importance of early season N losses during corn production in Iowa. Three studies were conducted. The first involved a survey-type approach using the late-spring test for soil nitrate and the end-of-season test for cornstalk nitrate in hundreds of fields managed by farmers. The tests were performed over an eight-year period, and both tests showed a strong negative correlation between mean annual nitrate concentrations and March--May rainfall. The second involved coordinated field trials and laboratory incubations to characterize effects of the organic and inorganic N fractions of animal manure on N supplies for crop growth. The results indicate that early season losses of inorganic N should be considered a major factor determining the effects of the manure. The third study involved use of precision farming technologies in field-scale trials to evaluate the importance of N losses when farmers apply N only in the fall. The importance was evaluated by applying extra N in strips and measuring crop responses to this N. Large responses to the extra N were detected, and these responses suggest that losses of fall-applied N resulted in severe N deficiencies and costly yield reductions. The results of each study provided compelling evidence that early season losses of N are important during corn production in Iowa and that these losses could be substantially reduced by delaying N fertilization until plants are growing. The benefits of this change would include greater profits for producers and less environmental degradation associated with losses of N from fields. The results suggest that these benefits could be obtained if farmers used the new soil and tissue tests in organized programs designed to evaluate and improve the outcomes of N management on their fields

Modeling Lake Temperature Response to Climate Change in the Alaskan Arctic

This thesis study focuses on simulating lake temperature and ice duration for four lakes at the Arctic Long-Term Ecological Research site, near the Toolik Field Station in Alaska. Model projections were driven by the representative global climate model outputs under different carbon emission scenarios. Results show that my simple lake model can reproduce historical lake temperature and ice duration observations, indicating the reliability of the model for future projections. Model projections show that JuneSeptember lake temperatures would increase by 4.3-5.8 °C from the historical period with most progressive carbon emission scenarios, but by 0.7-2.2 °C in the conservative scenarios. Results also indicate that in all carbon emission scenarios, the ice-off period would increase in duration by at least 10 days by 2100, but by as much as 25-30 days in the most progressive scenarios. In addition, while the timing of mixed lake conditions would shift with the timing of ice-off, the duration of mixing and onset of stratification would be unaffected by warming temperatures. This study provides important knowledge for modeling and predicting lake thermal processes for the Arctic region

Interview with Bill Westenbarger

Bill Westenbarger speaks about growing up in Mount Vernon, and being a farm machinery implement dealer. Westenbarger also talks about how farming has changed over the years, including a sharp drop in farming that occurred in 1978 and marked the end of \u27big farming\u27 in the Mount Vernon area.https://digital.kenyon.edu/ffp_interviews/1020/thumbnail.jp

Estimating the Size of Georgia\u27s Resident Canada Goose Population

Canada geese (Branta canadensis) are an important waterfowl species in Georgia, and are hunted across the state. To meet management objectives, managers need to understand the impacts of hunting regulations on the population of interest. Therefore, reliable population estimates are necessary. Population size can be estimated by various methods, including aerial surveys, ground surveys, or population indices such as the Lincoln Estimator. I used annual estimates of resident Canada goose harvest in Georgia from the U.S. Fish and Wildlife Service’s Harvest Information Program along with banding and recovery data from the Bird Banding Laboratory in a bias-adjusted version of the Lincoln Estimator. Because of annual variation in the population estimates among years, I compared various trendlines across years, and the top three models generated an average 2018 population estimate of 231,274 resident Canada geese in Georgia

Prospectus, March 21, 2001

https://spark.parkland.edu/prospectus_2001/1009/thumbnail.jp

Early season losses of nitrogen

It is generally recognized that spring rainfall can result in losses of fertilizer nitrogen (N) from soils, but there is little agreement concerning the importance of these losses. Surveys of nitrate concentrations in Iowa cornfields over the past decade provide new information on this matter. The surveys were conducted as part of the N-Check Program, in which the late-spring test for soil nitrate and the end-of-season test for cornstalk nitrate were used to assess N-sufficiency levels in fields managed by producers

Effects of Hydrilla Control on Wintering Waterfowl at Lake Seminole, Georgia

Hydrilla (Hydrilla verticillata) is an exotic, submergent plant that clogs waterways in the southeastern United States yet appears to be beneficial to migratory waterfowl. We studied the effects of hydrilla control on wintering waterfowl populations at Lake Seminole, GA. We applied fluridone (Sonar®) in a low-dose injection system starting May 2000 in the Spring Creek arm of the reservoir. We used aerial photography and ground-truthing methods to quantify coverage of vegetation types and open water pre- and post-treatment for the entire reservoir. We flew weekly aerial surveys to document waterfowl numbers and distribution across the reservoir between 1 November and 15 March during 1998-1999 and 2001-2002 for pre- and post-treatment estimates. Application of Sonar® in the Spring Creek arm reduced hydrilla coverage in the reservoir from approximately 35% to 24%. Average number of ducks per flight before treatment (mean = 2864, SE = 304) did not differ from after treatment counts (mean = 2774, SE = 273) for the reservoir. However, the distribution of ducks changed, with use decreasing 12% in Spring Creek arm. Distribution of ducks before and after treatment revealed that ducks selected hydrilla greater than its availability. Our results indicate that biologists in the Southeast can reduce coverage of hydrilla using Sonar® applied in a low-dose injection system; however, waterfowl distribution may change following treatment

Prospectus, October 18, 2000

https://spark.parkland.edu/prospectus_2000/1027/thumbnail.jp

Estimating the Accuracy and Precision of Nitrogen Management During Corn Production

The advent of variable-rate fertilizer applicators has created a need for fertilizer N recommendations that address spatial variability within cornfields. These recommendations must include assessments of where variable-rate applications are likely to be profitable and where they are not. They also must indicate how rates should vary with soil type within fields when variable-rate applications are used