Editor’s Note: This is a combination of two smaller excerpts from Acres U.S.A. original book, Eco-Farm, An Acres USA Primer, written by Acres U.S.A. founder Charles Walters. Copyright 1979, 2009. #122. Softcover. 462 pages. $30.00 regularly priced.
By Charles Walters
All of the confusion [in labeling fertilizer] is further complicated by the nature of the weighted N-P-K formula system. A bag might say 0-0-60. Does this mean that in a 100-pound bag there are 60 pounds of K, the rest being inert filler? Not exactly.
The fact is that farmers get a lot of things they may not even want when they buy 0-0-60,18-46-0,17-17-17, or whatever.
As an example, take ammonium nitrate—or 33.5-0-0. Here’s how they compute the formula. Ammonium nitrate of course is NH4NO3. Each of the elements in this affair has a Mendeleyeff atomic weight. N has an atomic weight of 14. O has an atomic weight of 16. There are two Ns in the formula, or 2N. There are four Hs, or 4H. There are three 0s, or 3O.