Submitted to: Watershed Management Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 6, 1998
Publication Date: N/A
Technical Abstract: Our project addresses one of the most prevalent environmental issues of the Midwest, nitrate-N contamination of surface waters. This investigation has evolved from an on-going water quality assessment study of an agricultural watershed located in Central Iowa. This study documented that N was at or above its maximum contamination limit of 10 ppm in the stream for extended periods for most years of measurement. Our goal is to determine if the late-spring soil nitrate test (LSNT) N fertilizer management program can reduce nitrate contamination of surface waters and maintain economical corn yields at the watershed scale. Project objectives for the LSNT program are to: 1) Quantify the change in nitrate content in stream flow; 2) Develop a N balance; and 3) Determine the economics and farmer-cooperator perspectives. The LSNT method is designed to optimize N fertilizer use through soil tests and better timing of N fertilizer application. With this system N fertilizer is managed in split applications. The first application is a nominal rate shortly before -- or at -- planting; the second occurs soon after late-spring soil sampling. Conventional N fertilizer management consists of a single pre-plant application, which leaves the N at risk to off-site movement for several weeks to months. A variety of soil and corn plant tests will be done during each growing season to monitor their N status. We are also utilizing precision farming technologies to measure crop yields for economic analyses. Water monitoring stations have been established at two watershed subbasins, serving as a paired subbasin approach to evaluate the impact of the LSNT program on water quality as compared to conventional N management systems.