Ok, now it comes back. When I was gardening in Germany I got into several discussions with local farmers about the need for fertilization of the land, and how much of what to use. There, as here, the "storebought" fertilizers were listed by the amount of Nitrogen, Potassium and Phosphorous they contained, or "N-P-K". I've forgotten what the numbers mean, but they would come in like "12-12-12" or "40-8-12" with the numbers signifying the amount of each element. The topsoil over there, having been farmed for centuries, is usually deficient in Nitrogen and Potassium.

Ok, now I gotta go back and look all that stuff up...