Field Experiment and Modeling Comparison of Corn Root Distribution, Water Uptake and Yield Under Deficit Irrigation.

Deficit irrigation has effects on crop root distribution, water uptake from different depths, and grain yield. It is critical to have reliable simulations on crop growth and development when crop experiences water stress. A combination of field experiment and crop modeling was conducted to evaluate those effects. A corn deficit irrigation field experiment was conducted in 2013 and 2014 in Lincoln, Nebraska. The treatment included 100% irrigation based on water depletion of the top 30 cm soil, and corresponding 75%, and 50% of that amount, and rainfed. We monitored soil water dynamics at four depths (30, 60, 90, and 120 cm), crop growth and development (including phenology, LAI, biomass, and final grain yield) at different stages. We also used the Hybrid-Maize model (http://hybridmaize.unl.edu/) to simulate the same variables and processes. Before early July 2013 and 2014 (shortly before silking), there was no difference in crop development and growth among the four treatments due to sufficient soil water recharge at planting and plentiful rainfall in the early growing season. After that, irrigation started, and soil water uptake at different depths started to differentiate among the different irrigation treatments. A significant amount of soil water was taken up from as deep as 120 cm shortly before silking, not only from rainfed and deficit treatments but also from fully irrigated treatment. Measured corn LAI and total biomass were consistently lower than model simulations. The crop phenology of model simulations was similar compared to field measurements in 2013 and 2014. Results of two years and their implications to modeling of root distribution, crop water uptake from different depths and crop yield will be presented and discussed at the conference.