Reducing Nitrate in Groundwater with Slow-Release Fertilizer

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7/1/2010 - 6/30/2012

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  • Matthew Burke, UW-Madison
  • Birl Lowery, UW-Madison
  • Meghan Buckley, UW-Stevens Point

Nitrate concentrations persist as a groundwater contaminant in the Central Sands Region of Wisconsin. This water quality problem has been linked to irrigated potato production systems, which is a major land use in the Central Sands. Since potato is both a high value crop and a high nitrogen (N) demand crop, N inputs typically exceed recommended rates. Little effort has been devoted to promoting the use of slow-release N fertilizers, which slowly exposes N to the root zone. Preliminary data suggests that ESN® shows promise for improving yields, reducing N applications, and possibly reducing nitrate losses to groundwater. The objectives of this proposed research are to evaluate nitrate leaching in potato production systems under different N management practices and to develop a partial N budget for these systems. These objectives will be achieved through a replicated, large- plot field study that will utilize groundwater water monitoring equipment. Groundwater monitoring wells and suction cup samplers will be used to monitor nitrate concentrations in groundwater and in the vadoze zone below potato production using different N management practices. Four N management treatments will be studied: High input (HI), controlled input (CI), reduced input (RI), and no input (NI). The HI treatment will include N application as a standard in-season application rate of N. The CI treatment will include the recommended rate of N as ESN® and RI will be a reduced rate of ESN®. Agronomic components such as yield, total N uptake, and petiole nitrate concentrations will be evaluated. This study will provide, for the first time, field level data that would support the use of slow-release fertilizers for potato production systems in Wisconsin. Results from this research have the potential to decrease nitrate fluxes to groundwater in the Central Sands and other sand plains in Wisconsin and surrounding states.

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