EPA has proposed a rule that would bring more dairy farms under regulation and restrict manure application more closely to a crop's need of phosphorous. This paper uses whole farm modeling applied to survey data to assess the impact of proposed regulations on dairy farms in the Cornbelt, upper-Midwest, and Northeast regions. Results show that the proposed rule affects 2.7 percent of surveyed dairy farms (over 200 milk cows) in these regions and causes income losses for 40 percent of farms spreading slurry manure on crops.