Wisconsin's Role in Great Lakes Restoration - American Water ...

Slow-Release Fertilizer Effect on Groundwater Nitrogen Concentration in Sandy Soils
under Potato Production
**Nicholas J. Bero, University of Wisconsin-Madison, Madison, WI, njbero@wisc.edu
Matt D. Ruark, University of Wisconsin-Madison, Madison, WI mdruark@wisc.edu
Birl Lowery, University of Wisconsin-Madison, Madison, WI blowery@wisc.edu
Current nitrogen (N) fertilizer management practices for potato farming have led to elevated
levels of N in the local groundwater. Slow-release fertilizer, specifically Environmentally Smart
Nitrogen® (ESN) may reduce the amount of N leaching to groundwater; however no field
scale studies have been performed in Wisconsin to validate these assertions. Field
experiments were conducted at the Hancock Agricultural Research Station using Russet
Burbank potato, planted in Plainfield Loamy sand. Four fertilizer rates, 0 N control, 224 kg ha -1
ESN, 280 kg ha -1 ESN, and current University of Wisconsin-Extension recommended 280 kg
ha -1 ammonium sulfate-ammonium nitrate (AS-AN) were used. Day of planting was April 29,
with fertilizer applied twice, once at plant emergence on May 17, and the second application
on June 2, 2010. This study included three replicates to create twelve 15.24 m by 15.24 m
field plots. Three monitoring wells spaced diagonally across plot, were installed in each plot to
sample groundwater for N assessment. Potato plant growth parameters and yields were
measured. Groundwater sampling regime was weekly throughout the growing season and
monthly afterward assessed for nitrate, ammonium and total N. In general, results indicate
that ESN reduced the amount of nitrate leaching to groundwater. Potato growth parameters
and yields were maintained, and demonstrates that use of slow-release ESN fertilizer is a
reasonable alternative to current management practices of AS-AN applications. Fall
application of Br - and Cl - tracers indicated that no cross contamination of N occurred and plot
sizes were large enough to be representative of full scale fields.
** Graduate student presentation
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