Evaluation of Algae-Based Fertilizers Produced from Revolving Algal Biofilms on Kentucky Bluegrass

The revolving algal biofilm (RAB) system is a wastewater treatment method that is effective at removing nutrients from wastewater, and as a result produces algae that could be used as a sustainable fertilizer source. A two-year greenhouse study was conducted to investigate if algae-based fertilizers produced from the RAB wastewater treatment system could be used as an effective and sustainable turfgrass fertilizer. Fertilizer treatments included pure algae (PA), algae + cellulosic filler (Blended), Milorganite, urea, and a nontreated control. Overall, in terms of percent green cover (PGC), Blended and PA performed similar to Milorganite and outperformed urea and the nontreated control. At the conclusion of the study, Blended was the only treatment to have an increased PGC relative to urea, which was a 29% increase. On average throughout the duration of the study, Blended and PA resulted in similar dark green color index (DGCI) relative to Milorganite and urea, and outperformed the nontreated control. Blended, PA, and Milorganite resulted in 50% and 111% greater total root length compared to urea and the nontreated control, respectively. Furthermore, Blended and Milorganite resulted in 107% and 136% greater root surface area and root volume, respectively, compared to urea and the nontreated control. Pure algae resulted in 58% greater root surface area relative to urea and the nontreated control. Blended and Milorganite increased the longest root by 22% compared to urea. Additionally, Blended and Milorganite resulted in 114% and 110% greater root and shoot biomass relative to the nontreated control, respectively. Blended and PA had a similar longest shoot length to Milorganite and urea. Overall, Blended and PA performed similar or better compared to Milorganite and urea in terms of turfgrass shoot growth, cover, color, and rooting. Thus, algae-based fertilizers (PA and Blended) produced from the RAB system should be considered an effective, sustainable turfgrass fertilizer.