Tissue tests as "postmortem types of analyses"

Soil nutrient analyses—soil tests—are used to determine if certain elements are required as fertilizer. If an element is required as fertilizer, the soil test will be interpreted to make a recommendation for the quantity of the element required.

That doesn’t work for leaf nutrient analyses—tissue tests. I’ve explained this in many ways. One was not finding yesterday’s gas mileage useful in choosing how I’m going to drive today. That’s similar to something I read this year.

In Chapter 1 of Soil Testing and Plant Analysis, 3rd Ed. I came across this quote:

Total plant analysis and plant sap analysis (rapid tissue tests) are postmortem types of analyses that help explain what was wrong that year on that soil but do not quantitatively predict fertilizer needs.

That’s from “Chapter 1: The Principles of Soil Testing” by Peck and Soltanpour.