Compost As a Nutrient Substitute for Golf Course Fairways.

Composted biosolids have yet to be accepted as a nutrient source in the turfgrass industry.  The perceived variability in nutrient release rates sidelines this potential organic substitute.  Eagle's Pride golf course, located between the cities of Tacoma and Olympia, Washington, is managed in part by civilian operators from Joint Base Lewis McChord (JBLM).  Base personnel also manage the on-site composting facility, Earthworks – which composts biosolids and yard debris.  To assess the use of the composted biosolids (Earthworks) as a nutrient source on Eagle's Pride fairways, a two-year study was initiated in the spring of 2015.  The goals of this study are to: (i) compare turfgrass responses, in a field-scale environment, between a composted biosolid and slow-release fertilizer treatment, and (ii) evaluate soil N dynamics between the organic and inorganic treatment.  24 experimental plots were established on three fairway sites (total plots = 72).  Applications of a slow-release inorganic fertilizer, sand topdressing, and composted bio-solids were made in the spring and fall of 2015 and 2016 (fall 2016 upcoming).  The slow-release inorganic nitrogen (N) was applied at a rate of 97 kg N ha^-1, the sand topdressing at a rate of 33,033 kg ha^-1, and the composted bio-solid at 46, 953 kg (wet) ha^-1 which is 50 kg N ha^-1.  To determine the effects on the turfgrass sward, collections of biomass, percent cover, and tissue N concentration were collected in three week increments just after the application.  To evaluate differences in soil N dynamics, soil samples were collected on the same three week schedule, and were analyzed for pH, NO^-3, NH⁴⁺, total N, and total C.