HOW TO READ THE BAG
So far we have considered the nutrient content of fertilizer materials in percentages. If you want to apply 4 pounds of actual nitrogen to 1,000 square feet of lawn, it is easy to figure that this can be supplied by 100 pounds of a 4 per cent material or 25 pounds of a 16 per cent material.
The problem seems more confusing when mixed fertilizers are used because the bags carry three figures instead of one. However, remember that these are still percentages. Thus a 1086 fertilizer contains 10 pounds of nitrogen (N), eight of phosphorus (P) and six of potash (K) in every 100 pounds of fertilizer.
When I first began using commercial fertilizers, figuring percentages was easy: everything was packed in 100 pound bags. This was hard on the back, of course. We had no handy small cartons, no 50
or 3 5pound bags, but at least we knew, without figuring, that a 100pound bag of 5105 would supply 5 pounds of nitrogen, 10 of phosphorus and 5 of potash.
Today it takes a wizard to figure out actual weights and percentages. Despite the need for doing a little paper work, the gardener who wants to be careful with his pennies should take time to work out costs.
COST PER POUND
The most important figure is the cost per pound of nitrogen. A product which contains 40 per cent or 40 units of nitrogen and costs $20 per 100 pounds sounds expensive by the pound (50 cents per unit). It would, however, be cheaper than sheep manure which sells for $2.10 for a 50pound bag but contains only between 1 per cent and 2 per cent nitrogen. Compare the 50 cents per unit cost of nitrogen in the first product with the costbetween $2 and $4of each nitrogen unit in the second product, sheep manure.
Another way to figure costs is by the total plant food in a product A dried sheep manure, for example, that contains 211 units of the "big three" nutrients, usually sells for $2.10 for a 50pound bag; this sounds cheap, yet the cost per nutrient unit is over $1. A mixed ureaform fertilizer analyzing at 2055 and selling for $9.95 for a 50pound bag would at first glance seem many times costlier, yet the cost for all the units is less than 67 cents per unit.
In figuring fertilizer costs you should give some thought to the form in which the plant food occurs. While urea would be cheaper on a costperunit basis, it is inferior to ureaform as a longlasting turf fertilizer that provides an eightmonth feeding period and greater safety in application.
