SUNFLOWER SIMULATION USING THE EPIC AND ALMANAC MODELS

Modeling of sunflower (Helianthus annuus L.) is challenging because the crop species combines high yield potential with great adaptability. This paper surveys recent modeling-related research on sunflower phenology, growth, and yield. Simulations of sunflower by two closely related models, EPIC and ALMANAC, are described. Phenology was predicted with growing degree days with a 6-degrees-C base temperature (GDD6) SUMmed from sowing to maturity, assuming anthesis occurred when 0.62 of the total GDD6 had accumulated. Growth simulation involved leaf area index (LAI) development, light interception, and radiation-use efficiency (RUE). Inclusion of a vapor pressure deficit (VPD) effect appeared to make RUE more general. A modified harvest index approach was used to simulate seed yields. The EPIC and ALMANAC models gave reasonable yield simulations over a wide range of environments and management options. The models should be valuable both for assessing the impacts of different management schemes and for identifying subject areas where additional basic research is needed.