Using Ammonium Sulfate Fertilizer as an Organic Mulch Fire Retardant (A Research Note)

"The multiple benefits of organic mulches in landscape environments are well documented. The few problems associated with mulch use can be minimized or avoided with proper management. For example, development of nitrogen deficiency can be reduced by the addition of small amounts of nitrogen fertilizer to the mulch. Rates of 2-3 lbs nitrogen per 100 sq ft of mulch are recommended. Another problem, particularly in the West with dry summer months, is the fire potential. Several California cities and highway departments report regular mulch fires, particularly where located near traffic, from discarded cigarettes. An inexpensive method of reducing organic mulch inflammability, by the addition of fertilizer-grade ammonium sulfate, (NH4)2SO4, has been suggested in the literature. In the 1930s, this chemical was reported by the U.S. Department of Agriculture, Forest Products Laboratory, as the least expensive flame retardant of 136 chemicals tested. The purpose of this paper is to report the results of trials to test the fire retardant abilities of various ammonium sulfate applications to organic mulches used in the landscape." [Abstract]