How to Collect Data on Agricultural Nutrient Management Practices: Survey Results from Iowa

Oregon Convention Center 

In response to the 2008 Gulf Hypoxia Action Plan, the Iowa Department of Agriculture partnered with the Iowa State University to create the Iowa Nutrient Reduction Strategy (INRS) to assess and reduce nutrient loadings in Iowa waters and the Gulf of Mexico. In this presentation we will discuss how survey sampling methodologies can be used efficiently to reach such goal of nutrient reduction plans based on the finite sample data collected in Iowa. The two-stage procedure employed initiates with a sampling methodology of randomly selecting 150 individuals out of 580 agricultural retailers across all eight MLRAs(Major Land Resource Areas) using the Local Pivotal Method(LPM) to ensure a balanced sampling scheme. Once data are collected, the average, as well as the standard errors for the percentage of total land where different categories of nutrients are used, is also being extrapolated to the entire state to help policymakers chalk out their nutrient-reduction plans for the succeeding crop years using stratified sampling. To wrap up, We will present some of the findings regarding land use for different nutrients for all these years, and their uncertainty estimates for visualization.

Nutrient reduction plans

Balanced sampling

Local Pivotal Method

Stratified sampling 

Survey Research Methods Section