ROOTED INRESEARCH SOD PRODUCTION ON COMPOST
By Mike Fidanza, PhD
With this issue’s Rooted in Research article, let’s take a look back at a sod study from the early 1990s. Te research was conducted by Dr. John Cisar (Professor at the University of Florida’s Ft. Lauderdale Research and Education Center from 1986 to 2014), and Dr. George Snyder (Professor at the University of Florida’s Belle Glade Research and Extension Center from 1967 to 2002). Dr. Cisar (
cisarturfdoc@gmail.com) and Dr. Snyder (
phdlaboratory@hotmail.com) remain active in numerous consultative activities for the turfgrass industry.
Te primary objective of that research was to determine if municipal solid waste compost would be suitable for growing sod over a plastic barrier, and the study was conducted at Ft. Lauderdale in 1990. Te compost was provided by the municipality of Pompano Beach, FL. It started with urban or municipal solid waste that was mechanically mixed and aerated to form windrows for a 21-day period. Te result was a composted material that was passively aged indoors for three months. Further processing included the removal of any hazardous and toxic materials. Glass, plastics, and small metallic components were crushed and included in the compost. However, final processing involved screening through 6 mm (.25 inch) sieves, and the finished compost met Florida’s regulations for heavy metal content. Te final organic matter content was 12 percent, pH of 7.1, and 0.006 percent N, 0.0003 percent P, and 0.03 percent K.
Test plots measured 3 x 10 ft. (approximately 1 x 3 m), and the compost was spread 2 inches (5 cm) thick onto thin polyethylene black plastic. Bahiagrass (‘Argentine’) and St. Augustinegrass (‘Floratam’) were sprigged and bermudagrass (‘Tifway’) was seeded in early May, grown through the season, and harvested in late October. All three turfgrass species were evaluated for visual quality, percent cover, tear resistance (i.e., sod shear strength), and root weight.
So, what were the results of this study? All three turfgrasses successfully produced sod grown in compost over plastic in five months. Initially, the compost had higher than desired soluble salts (EC = 2.85 dS•m-1
[2 H2 O:1 soil extract)]),
but standard irrigation and fertilization practices lowered the salts to 0.34 dS•m-1
by six weeks after establishment.
So, with all three turfgrass species, visual quality and percent plot area covered were not compromised, and in fact improved, when grown in compost over plastic.
Of note, “sod strength” as measured by tear resistance was statistically similar for bahaigrass or bermudagrass grown on compost over plastic or grown conventionally (Figure 1). However, St. Augustinegrass grown in compost over plastic measured higher sod strength compared to conventionally grown sod (Figure 1). It was observed that this increase in sod strength was due to the rooting stability facilitated by the plastic liner.
Figure 1. Tear resistance (sod tear resistance force measured in kg) for sod from those turfgrasses grown on compost over plastic compared to standard or conventionally grown sod; average of three replications; same letters indicate treatments are not statistically different at p < 0.10.
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TPI Turf News July/August 2023
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