Performance of the Hybrid-Maize Model in Simulating Soil Water Dynamics of Corn Growing Season.

The Hybrid-Maize model (www.hybridmaize.unl.edu) simulates corn yield potential as well as yield under water limiting conditions including deficit irrigation or rainfed conditions. Hybrid-Maize simulates soil water balance for each 10 cm layer down to the rooting depth in daily time steps. Soil water balance is calculated in a tipping bucket mode, i.e., water distributes uniformly within a 10 cm depth up to the field capacity; extra water beyond field capacity moves down to the next layer. Several pedo-transfer functions were used for conversions between volumetric soil water content and soil water pressure and estimation of hydraulic conductivity in unsaturated conditions. The model estimates soil evaporation and crop transpiration separately. Crop water uptake and water loss through transpiration is simulated using the Ohm law analogy, i.e., the difference between water vapor sucking power of the atmosphere and soil water pressure drives water through crop’s roots and canopy up to the atmosphere. While potential ET (ET_pot) is determined by weather parameters adjusted for canopy coverage, the capacity of soil supply of water determines the actual crop evapotranspiration (ET_act). Whenever ET_act becomes smaller than ET_pot, crop is under water stress, resulting in reduction in photosynthesis. The extent of photosynthesis reduction is linearly proportional to the difference of ET_act with ET_pot. We conducted field experiments of different irrigation levels using subsoil drip irrigation (SDI) and standard center pivot. Soil water content was monitored continuously at different depths throughout the season. We will report the performance of the Hybrid-Maize model in simulating soil water dynamics throughout the corn growing season and corn yield in both irrigation systems.