RE: Which Fertilizer?
When you get the soil test back, its usually cheapest to apply fertilizers in Non-Mixed form (Like 0-0-60) potash - like 1sagittarius suggested. Keep in mind that 100 lbs of 0-0-60 would equal 60 lbs of Potassium (K). Likewise - you can get other mixes like 7-52-0 MAP, Etc. A mix can run you 20-30% more on cost (generally speaking).