University fertilizer recommendations are embedded in Wisconsin nutrient management standards. Potato growers are concerned that reducing their phosphorus (P) application rates to meet the standard could possibly reduce potato yield and quality. The objectives of the study were to evaluate the effect of P rate and timing, and use of Avail^® (P fertilizer enhancer) on potato yield and quality, and to determine if in-season leaf P concentration is correlated with final yield. The treatments were applied as starter fertilizer at rates of 73 and 146 kg P₂O₅ ha-1 each with and without Avail^®. Sidedress P was applied at 73 kg P₂O₅ ha-1 (prior to first flower). There were 12 locations in Wisconsin (8 coarse- and 4 fine-textured soils) in 2006-2007. Leaf samples were taken at sidedress and then at two, four, and six weeks after sidedress and were analyzed for total P. Harvested tubers were graded for size and quality. Comparing rates, the high rate of starter P fertilizer had a higher total yield at three of six locations in 2006, significant differences were found at one location. Sidedress P had a higher total yield compared to starter P at two of the six locations for 2006, though differences were not significant. Avail^® coated starter fertilizer had the highest total yield at five of six locations in 2006, significant differences were found at two locations. Specific gravity was unaffected by any treatment for all locations. Petiole data showed there were some significant correlations between tissue P concentration and total yield for 2006, this occurred at two locations and during different dates. Avail^® fertilizer was more influential on total yield than was rate or timing for 2006. Results from 2007 are unavailable at this time.