2008 Annual Report 1a.Objectives (from AD-416) Build a framework for weed emergence models that is integrated with hydrothermal times and summed across soil depths, to generate more realistic weed emergence curves. 1b.Approach (from AD-416) Integrate soil microclimate through soil physical models with depth distributions of seeds. 3.Progress Report The modeling and software development efforts for the NRI project on weed seedling emergence prediction entered its fourth and final year. The necessary preliminary models dealing with light quantity and soil microclimate simulation were completed. These models are now on-line, as is the tillage redistribution model for weed seeds (Solarcalc, SolarCalQ, STM2, and SeedChaser). Models describing weed seed and seedling responses to soil microclimate were completed. Integration of these models with the microclimate software is in progress, with completion expected by October 2008. The research led to an invitation to present results as the keynote address to the Spanish Weed Science Society in November 2007 and a special session of the Ecological Society of America in August 2008. The project is associated with Objective 1 (model development) of the Project Plan for the parent project 3645-21220-003-00D. This project entailed the development of software for simulating soil microclimate, which then is directly used by the weed and crop models created through the parent project.