Agricultural conservation planning framework: 1. Developing multipractice watershed planning scenarios and assessing...

Area of Science:

• Environmental science
• Agricultural science
• Hydrology

Background:

• Nutrient discharge from agricultural watersheds contributes to hypoxia in the Gulf of Mexico.
• The Iowa Nutrient Reduction Strategy targets a 40% reduction in nitrogen (N) and phosphorus (P) loss from agriculture.
• Small watersheds (hydrologic unit code 12) require targeted conservation strategies.

Purpose of the Study:

• To identify and evaluate conservation practice scenarios for reducing nutrient discharge in two midwestern watersheds.
• To assess the potential of various conservation practices to meet a 40% nitrate-nitrogen (NO-N) reduction target.
• To develop a spatial approach for watershed-scale conservation planning.

Main Methods:

• Development of databases integrating soil, land use, and topographic data (LiDAR).
• Application of terrain analysis and geographic criteria to identify conservation practice locations (e.g., grassed waterways, wetlands, buffers).
• Scenario development and assessment using a spreadsheet model to estimate nutrient removal efficiency for a 40% NO-N reduction target.

Main Results:

• Identified planning scenarios achieving targeted NO-N reduction with less than 5% cropland removal.
• Cover crops and nutrient removal wetlands were key components in successful scenarios.
• The approach demonstrated the feasibility of achieving significant nutrient reductions through strategic placement of conservation practices.

Conclusions:

• Spatial data and conservation planning tools can effectively identify strategies to reduce watershed nutrient loads.
• Targeted conservation can achieve substantial nutrient reductions without significantly impacting agricultural production.
• This methodology provides a transferable tool for local watershed management and planning.