Comprehensive nitrogen budgets for controlled tile drainage fields in eastern ontario, Canada

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Excessive nitrogen (N) loading from agricultural subsurface tile drainage contributes to water quality degradation.
• Controlled tile drainage (CTD) is a practice implemented to mitigate N losses and enhance crop productivity.

Purpose of the Study:

• To conduct a multi-year, field-scale N budget analysis comparing CTD and free-draining systems.
• To quantify N inputs and outputs in agricultural fields under corn-soybean rotation in eastern Ontario, Canada.

Main Methods:

• Field-scale N accounting of major inputs and outputs over multiple cropping seasons.
• Comparison of N losses via tile drainage, gaseous emissions, and lateral seepage between CTD and free-draining systems.
• Assessment of changes in residual soil N and plant N uptake.

Main Results:

• CTD significantly reduced N losses from tile drainage compared to free-draining fields.
• CTD resulted in greater predicted gaseous N emissions and observed lateral seepage N losses.
• Plant N uptake increased under CTD, likely leading to higher grain yields for both corn and soybean.
• Mass balance residual terms were systematically negative, indicating potential unmeasured N losses, slightly more so for CTD.

Conclusions:

• CTD effectively decreases nitrogen losses through subsurface tile drainage and enhances crop yields.
• The study highlights that CTD may increase N losses via alternative pathways, including gaseous emissions and groundwater seepage.
• Optimizing CTD management is crucial to balance N loss reduction with potential increases in other N loss pathways.