On-Farm Evaluation Tools and Approaches to Quantify Risks in Nitrogen Management.

Adaptive management principles can be used to address the complexities of managing nitrogen (N) fertilizer management for corn (Zea mays L.) production. While specific approaches vary substantially, the general strategies used to quantify the uncertainly in N management are often focused on plant, soil or canopy sensor diagnostic tools and evaluation methods to quantify various types of risks. In general, the risk related to N management can defined as the expected likelihood of a specific management practice to deviate from the optimal or target corn N status, which results in economic or environmental loss or increase in the uncertainty when making N management decisions. We will present results of three state-wide on-farm studies conducted to quantity management, soil, and weather factors that affected 1) the risk of economic yield loss from farmers’ reduced N applications; 2) the risk and frequency of identifying areas with deficient N status within production corn fields across Iowa; and 3) the ability to calibrate late-season N diagnostic tools using observations from different on-farm evaluation studies. Similar approaches for quantifying various risks in N management should help in development of better decision management aid tools and recommendation systems for farmers, agronomists, and policy makers.