Turf and Landscape - Know Your Soluble Fertilizers 1

This is the first in a series on soluble fertilizer sources for use in turf or landscapes.

Ammonium Sulfate is a white crystalline material containing 20-21% N and 24% S. If produced in the pure crystalline form it is seldom marketed. The marketed product may be grayish in color due to carbon contamination during manufacture. Nitrification of ammonium sulfate produces acidity in the soil. Upon conversion to nitrate, the ammonium ion produces 5.35 pounds of acidity per pound of N applied, thus making ammonium sulfate the most acidifying N source available. This acidifying property makes ammonium sulfate the desired N source on alkaline turfgrass soils. When applied on high pH soils, particularly those containing free calcium carbonate, ammonium sulfate should always be watered in to limit volatile loss of N. Ammonium sulfate has a high burn potential with a salt index of 3.25, therefore, it should not be applied at high rates to avoid potential turfgrass burn. Due to limited solubility ammonium sulfate is not often applied in solution form. Ammonium sulfate imparts a dark green color in turfgrasses which tends to last for at least 30 days when applied at recommended rates. Turfgrass responses to ammonium sulfate tend to last for a longer period than for the other soluble N sources, and for this reason ammonium sulfate tends to be the preferred soluble N source of many turfgrass managers.

Reprinted from "Selected Fertilizers Used in Turfgrass Fertilization" by J.B. Sartain & J.K. Kruse, University of Florida Cooperative Extension.