Date of Graduation

5-2018

Document Type

Thesis

Degree Name

Master of Science in Horticulture (MS)

Degree Level

Graduate

Department

Horticulture

Advisor/Mentor

Richardson, Michael D.

Committee Member

Savin, Mary C.

Second Committee Member

Karcher, Douglas E.

Keywords

COI; Earthworm; Sand Topdressing; Turfgrass

Abstract

As earthworms feed, they can egest soil and nutrient-rich aggregates (casts) on the soil surface. In low-cut turfgrass systems, such as golf course greens, tees, and fairways, surface casting can result in a muddy playing surface, ball roll issues, weed and pest invasion, reduced aesthetics, surface softening, and reduced photosynthesis. Because the use of pesticides for earthworm control is illegal in the U.S., earthworm casting must be managed through cultural practices. Sand topdressing is one method of earthworm control studied for use on golf courses, with the supposition being that the abrasive sand particles will deter the soft-bodied earthworms from remaining in the system; however, effects have been varied. Because treatment effects may vary depending on earthworm species composition, earthworm identification may be a critical step in establishing a casting control plan.

The objectives of this study were to 1) test the effect of heavy (2.54 cm yr⁻¹) or light (0.64 cm yr⁻¹) sand topdressing treatments and the effect of native soil (Captina silt loam; fine-silty, siliceous, active, mesic Typic Fragiudults) and sand-capped rootzones on casting activity of earthworms in ‘Patriot’ bermudagrass (Cynodon spp.), 2) to assess the relationships between soil moisture content and soil temperature on earthworm casting activity, and 3) determine earthworm species composition on golf course turf in Arkansas and Oklahoma.

Results indicate that light topdressing on a native soil rootzone may reduce casting activity, while topdressing rate in a sand-capped rootzone may not significantly impact casting activity. Soil moisture was not a significant predictor of earthworm casting activity. Soil temperature was a significant predictor of earthworm casting activity and explained 10-34% of the variation in casting activity between the four treatment combinations.

Diplocardia spp. were predominant across three sampling locations, and Amynthas spp. were present across all five sampling locations. The dominance of Diplocardia spp. in the turfgrass systems in this study is counter to expectations, as previous reports on earthworm composition in turfgrass systems have primarily reported non-native European and Asian earthworm species.

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