Concerns over high levels of nitrate in groundwater beneath sandy soils in Wisconsin have precipitated development of new management systems for nutrient use and application methods, especially for nitrogen in potato production. We initiated a three year research study on the use of a slow-release fertilizer (NitaminTM) starting in 2004, to evaluate this product as a slow-release supplemental nitrogen (N) fertilizer for potato. The study was conducted at the Hancock Research Farm in Hancock, Wisconsin. The study consisted of a randomized complete block design with five blocks and three treatments. Although not always statistically significant, the slow-release fertilizer increased yield over the conventional fertilizer in all three years (2004, 2005, and 2006). Over the three years slow release fertilizer increased total yields by an average of 2,128 kg per ha compared to the standard fertilizer. There were more cull potatoes for the standard N fertilizer in 2004 but, this was not the case in 2005 where there were more culls with the slow-release fertilizer. The culls in 2006 were the same for both treatments. The US#1 grade potatoes increased with 224 kg per ha of slow-release in 2004 and the % dry matter increased. In 2005 the dry matter was not different for the two fertilizer treatments and US#1 grade potatoes decreased with the 224 kg slow-release compared to the conventional N fertilizer, although the total yield increased with slow-release. The unusual high numbers of culls in 2005 were the result of scab. In 2006 US#1 grade potatoes were increased by the slow release fertilizer but the dry matter content was the same for both treatments.