Iowa Code Title V. Agriculture [Chs. 159-215A] § 200.20. Phosphoric acid, nitrogen, and potash requirements

a. Phosphatic fertilizer containing less than eighteen percent available phosphoric acid (P₂O₅).

b. Nitrogen fertilizer containing less than fifteen percent total nitrogen (N).

c. Potash fertilizer containing less than fifteen percent soluble potash (K₂O).

d. Mixed fertilizer in which the sum of the guaranteed analysis of total nitrogen (N), available phosphoric acid (P₂O₅), and soluble potash (K₂O) totals less than twenty percent.

a. A specialty fertilizer.

b. A fertilizer designed to be applied and ordinarily applied directly to growing plant foliage to stimulate further growth.