Improving Water and Nitrogen Use Efficiency Under Changing Weather Variability in the Central Sands

Wisconsin Central Sands (WCS) potato and vegetable producers are facing increasing pressure to adopt farming practices – specifically irrigation and nitrogen (N) management – to minimize their impact on regional water resources. However, we have an incomplete understanding about water and N management effectiveness under more challenging and variable future weather. The primary goal of proposed research is to determine how future nitrogen (N) fertilizer and irrigation management in the Wisconsin Central Sands (WCS) can be modified to minimize irrigation water use and N losses to groundwater from maize and potato crops while maintaining production. This improved guidance will account for seasonal variations of NO3-N in applied irrigation water, an increased frequency of weather variability and extremes, and a projected trend of higher temperatures that will increase crop demand for water.

The specific objectives include:
(1) Quantify spatiotemporal variability of nitrate in precipitation and irrigation water applied to potato and maize in the WCS;
(2) Utilize field measurements in the WCS to parameterize and improve simulation of N cycling, water balance, and productivity of potato and maize in the Agro-IBIS agroecosystem model to link irrigation and N fertilizer management choices to water use and NO3-N leaching;
(3) Use Agro-IBIS to identify irrigation and fertilizer management strategies that maximize water use efficiency (WUE) and N use efficiency (NUE) for potato and maize under more challenging growing conditions (e.g., weather) in the future. This research will help inform policy decision-making and support the development of improved nutrient management plans that account for N-credits associated with irrigation management. Ultimately, these data could help optimize economic returns while reducing the amount of NO3-N lost to the groundwater system by maximizing nitrogen and water use efficiencies.