Maize and Sunflower Root Distribution in Response to Deficit Irrigation.

In order to meet world demand for food under anticipated water shortages, we need to increase crop productivity per evapotranspiration (ET). Quantifying root distribution in response to deficit irrigation is crucial to mechanistically understanding ET response under deficit irrigation as well as modeling crop water use. We investigated three dimensional root distributions in maize and sunflower by taking a soil core at the end of the growing season from the row center, half way between row center and middle, and the row middle from plants growing under full irrigation, 70% seasonal ET, and 40% seasonal ET. Interestingly fine root distribution was similar across rows from row center to middle despite the application of drip irrigation in narrow irrigation bands in deficit treatments. Fine root distribution was also similar between treatments while aboveground plant height, leaf area, chlorophyll fluorescence, and gas exchange decreased with increased deficit. Alongside reduced yield but similar WUE with increased deficit, these results suggest that maize and sunflower will mine all available water from the soil profile with aboveground responses controlling plant water use.