A few growers place charcoal in the bottom of containers to absorb excess salts and maintain sweet soil, if plants are grown more than a few months.
People who put charcoal in the bottom of their pots test their soil for sweetness and salt
( z1 test :ARG0 ( z2 person :ARG0-of ( z3 put :ARG1 ( z4 charcoal ) :ARG2 ( z5 bottom :part-of ( z6 pot :poss z2 ) ) ) ) :ARG1 ( z7 soil :part-of z2 ) :ARG2 ( z8 and :op ( z9 sweet ) :op ( z10 salt ) ) )