NU Water-Related Research in Nance County

It has been established with a degree of confidence that the temperature of the earth’s atmosphere has increased by about 0.3 to 0.6 degrees C in the late 19th century (IPCC, 1997). Global warming can have substantial impact on agricultural production, water resources, and their interactions, by influencing microclimatic variables that drive plant physiological functions, such as surface air temperature, solar radiation, humidity, wind speed, rainfall frequency and amount, as well as hydrological balances, including evapotranspiration. Knowledge and analyses of long-term historical trends in agro-meteorological and hydrological parameters can aid in water resources design, planning, and man-agement. Historical trends in these variables can also help to relate agro-ecosystem production to climate change. We assessed the long-term trends in climatic variables. We quantified reference evapo-transpiration from solar and net radiation, vapor pressure deficit, wind speed, relative humidity, and air temperature from 1893 to 2008 using measured and estimated climatic data. Both alfalfa-reference and grass-reference evapotranspiration values were computed on a daily time step. We present historical trends in air temperature, relative humidity, preci-pitation, solar radiation, and evapotranspiration from 116 years of climatic observations and modeling results in the Central Platte Valley, Nebraska.

Conclusions from this project are:

• Missing long-term climatic variables from 1893 to 1986 were reliably estimated for reference ET calculations.
• Annual total rainfall amount showed an increasing trend over 116 years.
• Both grass and alfalfa-reference ET fluctuated from year to year, but slightly decreased over the years.
• Solar radiation slightly decreased due to increased rainfall/cloud cover.
• Average vapour pressure deficit (VPD) did not change considerably.
• Aridity index trend indicates a general tendency for Central City, NE area to shift toward more humid conditions, more so in the last 10 years.

The role of the faculty and staff in this unit is to prevent or solve problems using research based information. Faculty and staff subscribe to the notion that their programs should be high quality, ecologically sound, economically viable, socially responsible and scientifically appropriate. Learning experiences can be customized to meet the needs of a wide range of business, commodity, or governmental organizations based upon the many subject matter disciplines represented. As part of the University of Nebraska, the Northeast Center faculty and staff consider themselves to be the front door to the University in northeast Nebraska. Through well targeted training backgrounds and continuous updating via the internet and other telecommunications technologies, faculty and staff have the most current information available to help their clientele.

The Haskell Ag. Lab is a University of Nebraska research farm located 1.5 miles east of the Dixon County Fairgrounds in Concord. This 320 acre farm was donated to the University of Nebraska by the C.D. Haskell family of Laurel in 1956. A number of demonstrations and projects are going on at the Haskell Ag. Lab, including a riparian buffer strip demonstration and a study to evaluate the effect of irrigation on soybean aphid population dynamics. Other studies focus on:

Subsurface Drip Irrigation: In the spring of 2007 a new subsurface drip irrigation system was installed on a 4 acre portion of the farm with sandy loam soils. The initial objective of the research is to collect field data to document crop water use rates for new corn varieties. Specifically, the work will concentrate on varieties that have different drought resistance ratings to improve the accuracy of the information provided to producers via the High Plains Regional Climate Center. In 2007, two varieties were planted and five irrigation treatments were imposed ranging from dryland to full irrigation. The data will also be used to develop improved local crop production functions for use in the Water Optimizer spreadsheet.

Hormones in Livestock Waste: This project will evaluate the fate of both naturally occurring and synthetic hormones that are associated with solid waste harvested from beef cattle feeding facilities. The research involves: 1) tracking the fate of hormonal compounds from the feedlot into surface run-off that would make its way into a liquid storage lagoon; 2) establishing stockpiled and composted sources of the solid manure removed from the feedlot; and 3) applying stockpiled and composted manure to cropland areas under different tillage systems and native grasses. Once the manure is applied the runoff potential will be evaluated using a rainfall simulator. Research will then focus on whether plants that could be a source of food for wildlife and/or domestic animals take up the hormones. (More information about this project is available; see projects listed under Dan Snow.)

The hydrologic properties of channel sediments have an important role in controlling hydrologic process in streams. This study focused on the water exchange between a stream and an aquifer induced by groundwater withdrawal, with the purpose of investigating the interbedded feature of channel sediments and to evaluate its effects on the calculation of streamflow depletion. Field work was conducted at nine study sites between Kearney and Columbus during the summers of 2005 and 2006. Direct-push techniques were used to produce electrical conductivity logs and to collect sediment cores. Permeameter tests were conducted on the sediment cores. Stream-aquifer simulation models were used to evaluate streamflow depletion for various types of channel sediments.

Sediment core samples were categorized into four groups:

• sand and gravel,
• sand and gravel with interbedded silt and clay layers,
• fine sand with silt or clay layers, and
• silt and clay with some sand and gravel.

In general coarse sediments occur in the western part of the study area, and the amount of fine sand, silt and clay increases eastward along the river. However, the sediments in the top two meters are about the same for all the sites, consisting mainly of sand and gravel.