USING TRANSPIRATION TO CHARACTERIZE PLANT HEIGHT IN WINTER-WHEAT IN DIFFERENT ENVIRONMENTS - A SIMULATION STUDY

Winter wheat (Triticum aestivum L.) plant height is an important trait for the diverse environmental conditions found in the Great Plains. It has been related to seedling emergence, lodging, soil erosion, ease of harvest, crop residue and weed control. The hypothesis that transpiration, which integrates atmosphere, soil, and plant processes, could be used to characterize environmental effects on wheat plant height was tested in this research. Data from four commercial winter wheat cultivars (Arapahoe, TAM107, Vista, and Siouxland) and nine environments in Nebraska in 1992 and 1993 were used. The climatic regions represented in this study ranged from sub-humid to semiarid. To test our hypothesis, a spring wheat growth and yield model was modified to predict plant height development (modeled as a sigmoidal function of time) in winter wheat. Daily height increment was based on the ratio of actual to potential transpiration. The model was run for these four cultivars in eight environments. Data from the ninth environment was used to estimate maximum plant height for each cultivar; a necessary input into the model. Modeled plant height predictions were in good agreement with actual measurements for all environments (R(2) = 0.80). Based on these results, we conclude that transpiration was a good indicator of environment for plant height development in winter wheat.