Belfrey
Senior Member
Yes, I did sample from the surface and below the roots of my spoiled corn crop. Aluminum anomalies were from the surface soil.
Aluminum toxicity acts primarily on the root meristem of the corn - so if it was only abnormal at the surface and not in the root zone, then that's not your problem. The reason I was asking about whether the pH was measured from the same surface sample as your soluble aluminum result is that soil pH varies with depth - typically, it's most acidic at the surface (and thus, that's where there will be more soluble Al), particularly with agricultural soils to which amendments have been applied.