Watershed Initiatives

2016 Code of Practice for Nitrogen Fertilization

Purpose: To establish reasonable and practicable guidelines for nitrogen fertilization applications to reduce nitrate loss from farm fields.

Why: Effective management of nutrients on farms in the watershed is one of the keys to enhancing both environmental quality and profitable crop production. Consistent with the Iowa Nutrient Reduction Strategy, this Code of Practice provides information about guidelines adopted by the ACWA members as a condition of membership.



  1. A nutrient budget for nitrogen, phosphorus and potassium shall be developed that considers all potential sources of nutrients including manure, legumes, etc. Nutrient recommendations shall be based on current soil test results, realistic yield goals, environmental impact and producer management capabilities.
  2. Use the standardized county temperature and forecast maps found at http://extension.agron.iastate.edu/NPKnowledge/ as part of the decision-making process for fall fertilizer application.
  3. Delay fall anhydrous applications without a nitrification inhibitor until soil temperatures are:
  4. Regardless of time of year application occurs, encourage use of other nutrient management technologies such as stabilizers, slow release fertilizers, incorporation or injection, soil nitrate testing and other technologies that minimize loss to surface or ground water resources.
  5. If producer is participating with USDA Conservation Programs additional considerations for producer conformance with NRCS 590 Nutrient Management standard shall be followed. For guidance and requirements see standard: Iowa Nutrient Management Conservation Practice Standard Fact Sheet — What's New That Affects You in the Iowa 590 Standard?
  6. Encourage use of other supporting practices where feasible:
    • Tile line denitrification bioreactor
    • Constructed wetland
    • Conservation stream buffer
    • Fall cover cropping system

Download this code of practice (pdf)