Are you looking for the biggest numbers on the fertilizer bag (eg. 28-1-10)?
Did you know that cool season grass like Kentucky Blue requires just as much potassium (the last number on the fertilizer bag) as it does nitrogen (the first number on the fertilizer bag) in a growing season? Therefore the first and last number should be as close as possible to ensure a balanced feeding. Looking for high nitrogen numbers may in some cases cause unhealthy growth leaving the plant susceptible to certain species of insects and particularly diseases. Using water insoluble organic i ingredients allows to use smaller numbers and still provide essential quantities of nutrients for healthy balanced plant growth.
Source: Turf Revolution – Follow this link for more tips.