Keith County, Nebraska, Map Series

KEITH COUNTY--LIST OF MAPS AND THEIR AUTHORS Topography--U. S. Geological Survey Index of 7.5\u27 Topographic Quadrangles and Township Boundaries--R. F. Diffendal, Jr. Generalized Soils Map--M. Kuzila and J. Culver Approximate Loess Thickness--R. F. Diffendal, Jr. Bedrock Geologic Map--R. F. Diffendal, Jr. Volcanic Ash Localities--R. F. Diffendal, Jr. Ogallala Vertebrate Faunal Sites--R. F. Diffendal, Jr. Ogallala Group Outcrops--R. F. Diffendal, Jr. White River Group Outcrops--R. F. Diffendal, Jr. Conservation and Survey Division Test Hole Locations--R. F. Diffendal, Jr. Oil and/or Gas Test Hole Locations--R. F. Diffendal, Jr. Mineral Resources Localities--R. F. Diffendal, Jr. Locations of Registered Irrigation Wells--R. F. Diffendal, Jr. Configuration of Top of Bedrock--R. F. Diffendal, Jr. Configuration of Top of White River Group (= Brule Fm.)--R. F. Diffendal, Jr. Configuration of Top of Cretaceous--H. M. DeGraw Configuration of Top of Niobrara Fm.--H. M. DeGraw Configuration of Base of Greenhorn Limestone--H. M. DeGraw Configuration of Top of Permian System--R. R. Burchett Structural Contours on Top of Stone Corral--R. R. Burchett Structural Contours on Top of Pennsylvanian System--R. R. Burchett Depth to Precambrian Surface--M. P. Carlson Configuration of Top of Precambrian--R. R. Burchett and M. P. Carlson Geothermal Projected Temperatures on Top of Dakota Group--D. Eversoll and W. Gosnold Bouguer Gravity Anomaly Map--R. R. Burchett and T. Eversol

Keith County, Nebraska, Map Series

KEITH COUNTY--LIST OF MAPS AND THEIR AUTHORS Topography--U. S. Geological Survey Index of 7.5\u27 Topographic Quadrangles and Township Boundaries--R. F. Diffendal, Jr. Generalized Soils Map--M. Kuzila and J. Culver Approximate Loess Thickness--R. F. Diffendal, Jr. Bedrock Geologic Map--R. F. Diffendal, Jr. Volcanic Ash Localities--R. F. Diffendal, Jr. Ogallala Vertebrate Faunal Sites--R. F. Diffendal, Jr. Ogallala Group Outcrops--R. F. Diffendal, Jr. White River Group Outcrops--R. F. Diffendal, Jr. Conservation and Survey Division Test Hole Locations--R. F. Diffendal, Jr. Oil and/or Gas Test Hole Locations--R. F. Diffendal, Jr. Mineral Resources Localities--R. F. Diffendal, Jr. Locations of Registered Irrigation Wells--R. F. Diffendal, Jr. Configuration of Top of Bedrock--R. F. Diffendal, Jr. Configuration of Top of White River Group (= Brule Fm.)--R. F. Diffendal, Jr. Configuration of Top of Cretaceous--H. M. DeGraw Configuration of Top of Niobrara Fm.--H. M. DeGraw Configuration of Base of Greenhorn Limestone--H. M. DeGraw Configuration of Top of Permian System--R. R. Burchett Structural Contours on Top of Stone Corral--R. R. Burchett Structural Contours on Top of Pennsylvanian System--R. R. Burchett Depth to Precambrian Surface--M. P. Carlson Configuration of Top of Precambrian--R. R. Burchett and M. P. Carlson Geothermal Projected Temperatures on Top of Dakota Group--D. Eversoll and W. Gosnold Bouguer Gravity Anomaly Map--R. R. Burchett and T. Eversol

BUFF-BREASTED SANDPIPER DENSITY AND NUMBERS DURING MIGRATORY STOPOVER IN THE RAINWATER BASIN, NEBRASKA

The Buff-breasted Sandpiper (Tryngites subruficollis) is a shorebird of conservation concern whose migration patterns and population size are poorly known. We conducted surveys in the Eastern Rainwater Basin, Nebraska, in 2004 and 2005 using distance sampling. This survey produced density estimates of 0.09 birds per ha in 2004 and 0.04 birds per ha in 2005. Because the study area was explicitly defined by soil characteristics, we were able to extrapolate from density estimates to produce predictions of overall numbers in the study area. We produced minimum estimates of the numbers of Buff-breasted Sandpipers stopping over in the region—43 300 in 2004 and 22 924 in 2005. When we restricted our predictions to only the area adjacent to roads, numbers of birds ranged from 13 488 to 41 513, depending on the area used. These predictions indicate two important findings—that 1) the current estimate of the world population of Buff-breasted Sandpipers of 15 000 to 20 000 individuals is too low, and 2) the Eastern Rainwater Basin appears to be a primary spring stopover site for the species in the North American Great Plains. Tryngites subruficollis es un ave playera con estatus de conservación preocupante, de la cual se conoce poco sobre sus patrones migratorios y tamaños poblacionales. Realizamos muestreos en el este de la Cuenca de Rainwater en Nebraska en los años 2004 y 2005 utilizando el método de muestreo que considera las distancias. Este muestreo produjo estimaciones de densidad de 0.09 individuos por ha en 2004 y de 0.04 individuos por ha en 2005. Debido a que el área de estudio fue definida explícitamente por las características del suelo, fuimos capaces de extrapolar las estimaciones de densidad para predecir los números totales en el área de estudio. Produjimos estimaciones mínimas del número de individuos de T. subruficollis que realizan paradas migratorias en la región—43 300 en 2004 y 22 924 en 2005. Al restringir las predicciones sólo a las ´áreas adyacentes a los caminos, el número de aves varió entro 13 488 y 41 513, dependiendo del área utilizada. Estas predicciones señalan dos hallazgos importantes—que 1) la estimación actual de la población mundial de T. subruficollis de 15 000 a 20 000 individuos es muy baja y que 2) el este de la Cuenca de Rainwater parece ser uno de los puntos de parada migratoria más importantes para esta especie en la región de las grandes planicies de Norte América

Large-scale on-farm implementation of soil moisture-based irrigation management strategies for increasing maize water productivity

Irrigated maize is produced on about 3.5 Mha in the U.S. Great Plains and western Corn Belt. Most irrigation water comes from groundwater. Persistent drought and increased competition for water resources threaten long-term viability of groundwater resources, which motivated our research to develop strategies to increase water productivity without noticeable reduction in maize yield. Results from previous research at the University of Nebraska-Lincoln (UNL) experiment stations in 2005 and 2006 found that it was possible to substantially reduce irrigation amounts and increase irrigation water use efficiency (IWUE) and crop water use efficiency (CWUE) (or crop water productivity) with little or no reduction in yield using an irrigation regime that applies less water during growth stages that are less sensitive to water stress. Our hypothesis was that a soil moisture-based irrigation management approach in research fields would give similar results in large productionscale, center-pivot irrigated fields in Nebraska. To test this hypothesis, IWUE, CWUE, and grain yields were compared in extensive on-farm research located at eight locations over two years (16 site-years), representing more than 600 ha of irrigated maize area. In each site-year, two contiguous center-pivot irrigated maize fields with similar topography, soil properties, and crop management practices received different irrigation regimes: one was managed by UNL researchers, and the other was managed by the farmer at each site. Irrigation management in farmer-managed fields relied on the farmers' traditional visual observations and personal expertise, whereas irrigation timing in the UNL-managed fields was based on pre-determined soil water depletion thresholds measured using soil moisture sensors, as well as crop phenology predicted by a crop simulation model using a combination of real-time (in-season) and historical weather data. The soil moisture-based irrigation regime resulted in greater soil water depletion, which decreased irrigation requirements and enabled more timely irrigation management in the UNL-managed fields in both years (34% and 32% less irrigation application compared with farmer-managed fields in 2007 and 2008, respectively). The average actual crop evapotranspiration (ETC) for the UNL- and farmer-managed fields for all sites in 2007 was 487 and 504 mm, respectively. In 2008, the average UNL and average farmer-managed field had seasonal ETC of 511 and 548 mm, respectively. Thus, when the average of all sites is considered, the UNL-managed fields had 3% and 7% less ETC than the farmer-managed fields in 2007 and 2008, respectively, although the percentage was much higher for some of the farmer-managed fields. In both years, differences in grain yield between the UNL and farmer-managed fields were not statistically significant (p = 0.75). On-farm implementation of irrigation management strategies resulted in a 38% and 30% increase in IWUE in the UNL-managed fields in 2007 and 2008, respectively. On average, the CWUE value for the UNL-managed fields was 4% higher than those in the farmer-managed fields in both years. Reduction in irrigation water withdrawal in UNL-managed fields resulted in $32.00 to$74.10 ha in 2007 and $44.46 to$66.50 ha in 2008 in energy saving and additional net return to the farm income. The results from this study can have significant positive implications in future irrigation management of irrigated maize systems in regions with similar soil and crop management practices