Agricultural conservation practices in Iowa watersheds: comparing actual implementation with practice potential

As part of the solution to reduce the size of the Gulf of Mexico hypoxia, the state of Iowa has created the Iowa Nutrient Reduction Strategy (INRS) to reduce total nitrogen and phosphorous loads by 45% by 2035. A major component of the strategy is implementation of conservation practices to reduce loads of non-point source pollution from agricultural lands. To identify potential locations for conservation practices in Iowa watersheds, the Agricultural Conservation Planning Framework (ACPF) is being used. In addition, the location of existing implemented practices are being identified by the Iowa Best Management Practices Mapping Project (IBMP). From these two products, a methodology was developed to compare the differences between actual implementation and practice placement potential. The compared conservation practices are grassed waterways, wetlands and ponds, and water and sediment control basins (WASCOBs). The comparison is performed in three hydrologic unit code 12 (HUC-12) watersheds in three distinct landform regions of Iowa. Analyses show that grassed waterways are widely implemented (at least 78% of the potential) in the three watersheds. For ponds and wetlands, the majority of the existing structures were smaller than the ACPF potential wetlands (average drainage area between 7 and 20 ha compared to between 89 and 109 ha). WASCOB implementation was only present in one watershed, most likely due to regional differences in conservation preferences. Coupled together the IBMP and ACPF will be important for stakeholders of watersheds in planning future investment and advancing towards a more systems-based approach to conservation.