In the spring of 2014, we conducted a survey of Iowa crop producers to (1) learn about common nutrient management practices, and (2) to elicit farmers' subjective beliefs about the weather and crop growth uncertainty they face when making nutrient management decisions. The survey is part of a larger study that seeks to uncover the subjective or perceived relationship between nitrogen application practices, e.g., quantity, timing, application method, and crop yield outcomes. This paper provides a rationale for measuring subjective beliefs in the context of decision making under uncertainty and discusses specific design elements of the 2014 survey instrument. We provide summary statistics for the information that was gathered and discuss lessons learned from the pilot study.