| Jerry, I agree with you completely (on the bag stated formulation), but there is a difference between the reporting of nitrogen and the reporting of phosphorus and potassium.
Nitrogen is reported as percentage nitrogen in the product and further broken down by law into the proportions of nitrate, ammoniacal, and urea sources of N.
Phosphorus is reported as % phosphorus pentoxide (P2O5). Since P makes up only 40% of P2O5, the amount of P in the formula is 40% of the reported number.
Potassium is reported as potassium oxide (K2O). So the K in the formula is about 57% of the reported number.
In 10-10-10 there is 10% by weight nitrogen, 4% by weight phosphorus, and 5.7% by weight potassium.
Pure water MSU is 13-3-15-8Ca-2Mg. So it's really low in P since it's
40% of 3 or about 1.2%. Personally I like that low value because I have good luck with it.
However I do not disagree with your "even" recommendation such as 10-10-10 or 20-20-20 as long as it's known that these numbers don't tell the entire tale.  |