Milorganite doesn't have any potassium, one analysis I found for alfalfa pellets gave them as 3% K. U of Wisconsin basic soil test is $15 for pH, lime requirement, organic matter, phosphorous (P), and potassium (K). If you have weak scapes I would check to make sure you don't need to add more potassium.
The jar with soil and layers of sediment test tells you your soil texture, whether clayey, sandy, sandy-loam etc. It won't tell you the level nutrients in the soil.
Some of the soil test kits for nutrient levels are better than others. I did find a review of them somewhere once, I can try and find it again if you prefer to go that route over the lab test. The advantage with the lab test is that if you need to add lime (never do that without a soil test) they will tell you how much to apply.
