Use phosphorus as an example. You can
see that when a soil has a pH of 6.5 to 7.5, the
available phosphorus in the soil will be absorbed
into the plants. When I studied this chart, I also
learned that a soil with a pH above 7.5 is just as
bad as a soil that has below 6.5 pH. The horizontal
graph section for phosphorus becomes more narrow
outside of the 6.5 to 7.5 range.