Rich - in reviewing your soil test results I see that your soil is very healthy.  The graph at the top shows that Phosphorous, Potassium and Magnesium are all above optimum.   In addition, your CEC (Cation Exchange Capacity) indicates that your soil will readily hold the nutrients you apply and the organic matter in the soil is very good. 

Based on these results, the recommendation is to only add Nitrogen fertilizer which is mobile in the soil (being taken up by the plants and soil over time).  There is no need to add Phosphorous or Potassium since those nutrients will not vary as much as the Nitrogen.  Accordingly, the fertilizer ratio recommendation is 3:0:0 (i.e. Nitrogen only).  If Nitrogen only fertilizer is challenging to find, you could purchase a product with Nitrogen and a small amount of Potassium.  Phosphorous is mainly recommended for newly seeded turf and readily binds with the soil so will not change much in your soil.  This means that the middle number on the bag should be 0.

Whichever product you purchase, you can come back to the MSU soil test site and enter the nutrient bag numbers into the Fertilizer Calculator (found under Tools) and the site will calculate how much of that product you should apply in one year for 100 sq. ft.  Remember to pro-rate the amount if you have more or less than 100 sq. ft.

Good job starting with a soil test to know the health of your soil.  Hope that helps!

Hi Diane -- Thank you for this detailed and helpful information -- much appreciated.

So I understand that the numbers indicate my soil should be healthy, but a third of my 120 dahlias have withered and died this year.  These were all located in soil that had quite a lot of pine bark chips tilled in last fall---something I've never done before.  The other dahlias that are still healthy are largely located in new-soil sections of the garden that do not have any bark chips mixed in.

Could the bark chips be releasing a harmful compound into the soil?

Richard - it might be possible that the area with the mulch tilled in is retaining more water than the other areas.  I would test the different areas by sticking your finger about an inch into the ground and seeing if the soil moisture seems about the same.  

If not moisture, then I am wondering if there is excess Nitrogen in the area with the mulch which is causing the Dahlias not to thrive.  If so, the Nitrogen will go down as the mulch decomposes.  Was there a specific reason that you worked in the mulch?  That is not typically required from year to year.

Another thought is that Dahlias are prone to Verticillium Wilt which is a soil-borne fungi that affects the plants through the roots.  As the fungus travels through the plant, it prevents water-conduction to the tissues and will cause wilting of the upper parts due to water stress.   If this is the cause, unfortunately there is no cure.   See the article below for more info on this fungus.

https://ipm.ucanr.edu/PMG/GARDEN/PLANTS/DISEASES/vertwilt.html

That being said, I am hoping the problem may be more of an issue with too high of Nitrogen or water for the Dahlias in that area.

Hope that helps.

You are most welcome.