The soil test is a few years old, but showed 4.3% om, 36 ppm P, 248 ppm K, 1.2 ppm Zn, and a pH of 6.8. This is bordeline high levels of potassium according to Iowa State soils lab. A leaf analysis of peaches (next row over in the same orchard) in 2011 showed the following ppm: P 2720, K 20600, Mg 5184, Ca 17720, Mn 36, Fe 121, Cu 29, Zn 90, and total N 2.2.
The provided no interpretation of the results, but from what I have tried to figure out, the magnesium was maybe a little high, P, K, Ca were OK.
The soil is a fairly heavy clay loam, and its on a good slope but these pears are near the bottom and the soil is definitely wetter there (this spring especially). I notice that a couple of peaches near the bottom are not doing well (peaches really don't like wet feet). Red Sensation and Concorde pears seem to be totally unaffected; they are a little further up the hill, and have dark green leaves. The trees that have the blackening problem (Crisp 'n' sweet as well as Comice) have lighter green leaves; don't know if this is just the variety or indicates a nutrition problem.
This is a new orchard, trees planted on CRP land in spring 2009. The same problem afflicted potomac pear trees 2 years in a row, (and they were even further up the hill, but also had light green leaves) and they just generally seemed sick, so I replaced them this spring.
Turkey Creek Orchard
Solon, Iowa (zone 5A)