Nitrogen Management and Water Productivity of Limited Irrigation Corn.

In an era of water scarcity, irrigators must employ strategies to maximize crop yields when water is limited. When irrigation water supply cannot meet the full evapotranspiration (ET) demand of the crop, limited irrigation is a strategy that manages drought stress as a function of crop growth stage. The interacting effects of nitrogen fertilizer rate and timing and limited irrigation are not well understood, yet such information is key to optimizing crop water productivity in water scarce environments. This study uses a combination of greenhouse and field studies to evaluate the interaction of crop water and nitrogen status on growth and productivity of maize. A greenhouse study with two irrigation regimes (100% and 60% ET) and three nitrogen treatments (2997, 1685, and 375 mg N per pot) evaluated growth and water productivity of maize biomass. When irrigated at full ET, water productivity was greatest for the 2997 mg N per pot treatment and declined with lower N treatments.  However, when water was limited, the water productivity was greatest for the 1685 mg N per pot treatment. An oversupply of N resulted in reduced water productivity, suggesting a need for careful N management in order to maximize productivity when water is limited. In the field, a randomized complete block study was implemented to study the effects of full irrigation (100% ET), deficit irrigation (60% ET), and growth-stage timing irrigation (75% ET), along with various levels of applied nitrogen. Results from the field study will evaluate water productivity for both biomass and grain yields.