What is required for incorporation of fertilizer or manure?

• A. Surface broadcast only.
• B. Incorporate to 2 inches depth.
• C. No incorporation required.
• D. Tillage that mixes the material into the soil to an average minimum depth of 4 inches, covering at least 80% of the applied material.

Answer: (D)

The main idea here is protecting water quality and improving nutrient use by getting fertilizer or manure into the soil rather than left on the surface. The best practice is tillage that blends the material into the soil to an average depth of four inches and ensures about 80% of the applied material is incorporated. This depth places nutrients in the root zone where plants can take them up and reduces losses from ammonia volatilization, surface runoff, and erosion. Surface broadcasting or no incorporation leaves nutrients exposed to weather and is more prone to loss. Shallow incorporation, such as two inches, isn’t sufficient to reliably protect against those losses, so the four-inch depth with wide coverage is the effective standard.