Tuesday, November 14, 2006
141-2

Simulation of Soybean Leaf Area Index and Dry Matter Accumulation Under Non-limiting Conditions.

Tri D. Setiyono1, Albert Weiss2, James Specht3, Kenneth G. Cassman3, and Achim Dobermann4. (1) Dept of Agronomy and Horticulture, Univ of Nebraska at Lincoln, P. O. Box 830915, Lincoln, NE 68503, (2) School of Natural Resources, Univ of Nebraska at Lincoln, P.O. Box 830728, Lincoln, NE 68583, (3) Dept of Agronomy and Horticulture, Univ of Nebraska at Lincoln, P. O. Box 830915, Lincoln, NE 68503, (4) Deptt of Agronomy and Horticulture, Univ of Nebraska at Lincoln, P. O. Box 830915, Lincoln, NE 68503

Development and evaluation of a new soybean simulation model that incorporates some existing and  somr new approaches will be presented. Under non-limiting conditions, when agronomic management is optimized toward achieving yield potential, soybean growth is primarily determined by solar radiation, temperature, daylength, and relative humidity. A long-term field experiment (1999-2005) was conducted at Lincoln, NE, where agronomic management (planting date and density, water, nutrient, and pest management) was optimized to achieve yields near the yield potential. Yield (at 13% moisture) obtained in the experiment ranged from 4.3 to 5.9 Mg ha-1. Phenology and growth data were used for model development and evaluation. The phenology component was simulated as a function of temperature and photoperiod (SOYDEV). Leaf area expansion was simulated using a logistic curve accounting for genetic potential for a given cultivar as well as response to population density and environmental factors. Apparent leaf photosynthesis rate (gross photosynthesis and photorespiration) was simulated in an hourly time step as a function of solar radiation, temperature, ambient CO2 concentration, and phenology. Single-leaf photosynthesis was converted into canopy photosynthesis using a multi-layer canopy approach accounting for sunlit and shaded leaves fractions, including vertical leaf area distribution. Respiration (maintenance and growth) and partitioning were simulated using approaches similar to the WOFOST model, but with modification in specific leaf area index and partition coefficients between root and shoot.

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