Turfgrass Fertilizers: N P K
Turfgrass fertilizers usually contain three plant nutrients: nitrogen, phosphorus
(designated on labels as available phosphate, or P 2 O 5 ), and potassium
(designated as water soluble potash, or K 2 O). These three nutrients are
represented on the fertilizer container as three numbers, indicating the percentages
by weight of nitrogen, phosphate, and potash—always in that order (Figure 3). The
three numbers are referred to as the fertilizer grade.
When nitrogen, phosphorus, and potassium are all present in the container, the
fertilizer is called a complete fertilizer. Sometimes one or two of these nutrients
are not present, and the missing nutrient(s) are simply listed as “0” in the grade.
Occasionally, turfgrass fertilizers contain other nutrients such as sulfur, iron,
and/or calcium. These are usually listed on the label but are not part of the
A fertilizer grade is used to determine the percentage by weight of plant nutrients
in the product. For example, a 100-lb bag of fertilizer with a grade of 30-0-10
contains 30 lb of nitrogen, no phosphate, and 10 lb of potash. A 50-lb bag of the
same product would yield 15 lb nitrogen, no phosphate, and 5 lb of potash. Knowing
the fertilizer grade is important in determining how much fertilizer to apply to
Sometimes, a fertilizer ratio is specified on soil test reports or in fertilizer
recommendation sheets. The fertilizer ratio indicates the proportion of nitrogen,
phosphate, and potash in the product. For example, an 18-6-6 fertilizer contains
three parts nitrogen to one part phosphate to one part potash. Thus, this fertilizer
has a 3-1-1 fertilizer ratio.
Reference: Penn State College of Agricultural Sciences