For additional information on pH meters www.hydroponicsales.com/files/phl.htm The have a graph of how the effect of soil pH affects a plants absorbsion of minor chemicals. They also have a statement that litmus papers are not accurate enough for plant pH measurements. www.geneg.com/catalog/en/ksmm.htm Shows a Kelway and states it has a + or - 0.2% accuracy The one offered by Veseys seeds is 1/2 the price. http://www.frostproof.com Has a $14.50 pH analyzer, made in Ft. Lauderdale, Fl. Found info "soil ph meter" on a Yahoo search Check it out yourself Byron