Reducing nitrogen loss with managed drainage and polymer-coated urea.

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Continuous corn production with high nitrogen (N) fertilizer rates poses a risk of nitrate-nitrogen (NO-N) loss via tile drainage, especially in dry years.
• Claypan soils exacerbate NO-N loss potential by impeding N leaching below tile drains.

Purpose of the Study:

• To evaluate if managed subsurface drainage (MD) with controlled-release N fertilizer reduces annual NO-N loss compared to free drainage (FD) with noncoated urea.
• To quantify the impact of MD on water drainage and NO-N loss under varying environmental conditions.

Main Methods:

• A 4-year study comparing MD and FD systems with different N fertilizer types.
• Monitoring of water drainage volumes and NO-N concentrations in tile effluent.
• Analysis of N uptake by corn and soil N concentrations.

Main Results:

• MD reduced annual water drainage by over 73% in two of the four years due to dry conditions.
• MD decreased annual NO-N loss by 78-85% in two of the four years.
• The effectiveness of MD was most pronounced during dry growing seasons followed by wet non-cropping periods.

Conclusions:

• Managed subsurface drainage (MD) is effective in reducing nitrate-nitrogen loss in tile drainage, particularly under specific climate conditions.
• While MD showed significant reductions, high soil N concentrations may have influenced fertilizer source effectiveness.
• MD presents a viable strategy for mitigating agricultural N pollution in water bodies.