Lawn fertilizers are typically high in nitrogen and would supply your lawn with that portion of the recommendation. The K number 30, representing 30 percent potassium, could be supplied by a second fertilizer product - a "single element fertilizer" containing just potash. At larger garden centers and feed stores you can find a selection of these fertilizers. Look for "muriate of potash," which is 0-0-60. This product is usually sold in small bags. You will have to do some arithmetic to figure out the rate at which it should be applied.
Read about how to understand soil test results and recommended fertilizer rates at:
Soil Test Results
Fertilizing plants stimulates them to put on new growth. If you fertilize too late in the season, that new growth does not have enough time to harden off before winter. In Minnesota, fertilizer can be applied to shrubs and trees until early autumn, when they begin to shut down for the winter. At the following link is a calendar for tree and shrub maintenance:
Seasonal Care for Trees and Shrubs
Take a look at the lawn care calendar at the following link, as a guide for when you should be doing various lawn care chores:
Lawn Care Calendar
