How does one "build good soils"? Serious question.
I frequently see soil test reports with a CEC below 7meq. A CEC of 7 is
necessary in order to hold onto sufficient Ca, Mg, and K to provide
minimum optimal levels of those minerals (minimums would be 750 ppm Ca,
100 ppm Mg, 100 ppm K). Those amounts need to be there even if the soil
can't hold onto them. If they are added for the growing season and the
soil can't hold them what the plants don't take up will likely by washed
away by precipitation and irrigation.
How to build CEC? By adding or growing large quantities of organic
matter, or high CEC clay, or humate ore, or biochar. Adding enough
compost may or may not be practical, and in a hot climate may not be
do-able at all. High CEC clay is heavy, and the best, Calcium Bentonite,
is expensive and hard to find. Humate ore is expensive and can only be
used in small quantities. Biochar is often the most practical answer if
it can be obtained or made at a reasonable cost.
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