Effects Of Deficit Irrigation On Corn Root Distribution, Water Uptake and Yield: A Combined Study Of Field Experiment and Modeling.

Deficit irrigation can save water. Its effects on crop root distribution, water uptake from different depths, and grain yield are less known. We used a combination of field experiment and crop modeling to evaluate those effects. A corn deficit irrigation field experiment was conducted in 2013 in Lincoln, Nebraska. The treatment includes 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 to simulate the same variables and processes. Before early July 2013 (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 is expected to reach maturity in September, 2013. Results of the entire season 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.