2010 Annual Report 1a.Objectives (from AD-416) 1) Evaluate interactions among nitrogen, carbon, soil water, and crop growth response across a range of soil types in a production field; and. 2)Evaluate field scale decision support system for nitrogen and crop management. 1b.Approach (from AD-416) Field scale studies will be developed to evaluate nitrogen response to varying soil water regimes across a production field and the carbon dynamics in response to nitrogen management. Corn-soybean rotations will be evaluated over three growing seasons. Water, CO2, nitrogen and light exchanges will be measured at several field locations within the field. 3.Progress Report This agreement with a local producer, supports the objectives of the parent project and focuses on the exchanges of nitrogen, carbon, and water relative to crop growth patterns. Intensive studies have been conducted over a number of years to quantify the interactions of nitrogen, carbon, and water in both corn and soybean production systems. There have been continued refinements in the approach to quantify the exchanges of energy (water), carbon (photosynthesis), and nitrogen (crop growth) for both crops. There is a linkage between carbon and water exchanges that is not constant throughout the day and is mediated by the availability of nitrogen in the crop plant. Patterns of carbon and water vapor exchanged throughout the day reveal where the plant is less efficient in the photosynthetic process and the degree of stress the plant is undergoing throughout the season. These relationships are linked to surface temperature patterns and to growth rates as determined by remote sensing methods. These seasonal patterns for both crops have provided new insights into how plants respond to soil water conditions during the growing season and have provided evidence of how crop growth efficiency can be enhanced through management. There are weekly exchanges of information about the progress in the field experiments during the summer growing season and monthly meetings to discuss the changes in the field experiments during the winter period.