2012 Annual Report 1a.Objectives (from AD-416): The first objective is to develop new modules to partition carbon, nitrogen, phosphorous, and potassium in individual leaves, modules for simulation of leaf growth and reproductive stages and organs in corn crop. The second objective is to develop algorithms to calculate the effects of nutrient and water stress on leaf addition rates. The third objective is to determine variety related parameters for the corn and potato models. 1b.Approach (from AD-416): The corn model MAIZSIM and potato model SPUDSIM are under development. These models require additional modules and algorithms to improve in order to accurately simulate these crops under arid conditions of the northwestern United States. The collaborator using the data collected under irrigated conditions of the arid northwest will develop new modules and algorithms and integrate with the MAIZSIM and SPUDSIM models. These models will be validated against field data collected under a range of environmental, soil, and management conditions using several cultivars. They will also identify and develop cultivar specific parameters. 3.Progress Report: Accurate simulations of non-linear temperature effects on crop growth and yield are critical for assessing the climate impacts and developing adaptive crop management solutions to climate change. We improved MAIZSIM for realistic, mechanistic simulation of non-linear temperature responses in leaf growth, final leaf size, and phenology. We developed new algorithms based on controlled experimental data from Soil Plant Atmosphere Research facilities (SPAR) growth chambers and previously published data in the literature. These new algorithms have been implemented and tested in MAIZSIM. The improved MAIZSIM provides realistic simulations of biomass accumulation, leaf area growth, and phenology of corn grown in diverse environmental conditions including several locations in the U.S., Europe, and Africa. A manuscript has been written and submitted to a journal from this work. In association with the Agricultural Model Improvement Program (AgMip) activities, we have also been contributing to the MaizeMIP panel since April 2012. The cooperator from the University of Washington and a scientist from Crop Systems and Global Change Laboratory (CSGCL) are both part of the expert panel for this project that seeks to compare and improve the current state of major maize crop models (e.g., MAIZSIM, CERES-Maize, HybridMaize, APSIM, CropSyst, EPIC, etc.). We have provided a description of MAIZSIM phenology module to the panel and participated in the WebEx conference on maize phenology modeling. The next scheduled topics of the panel discussions include modeling carbon assimilation, allocation, and leaf growth. We are currently working on. 1)improving MAIZSIM for modeling yield components during reproductive stage,. 2)enhanced coupling of leaf expansion and carbon balance, and. 3)testing model performance for a wide range of climate and soil conditions at diverse locations.