Characterizing Putting Green Root Zones in Tennessee

Author

Maureen M. KahiuFollow

Date of Award

12-2025

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Plant, Soil and Environmental Sciences

Major Professor

James T. Brosnan

Committee Members

Brandon Horvath, Micah S. Woods, Jordan C. Booth

Abstract

Organic matter mineralization to inorganic nitrogen (N) occurs in turfgrass soils. A benchmarking study was conducted to understand organic matter content in creeping bentgrass (CBG; Agrostis stolonifera L.) and ultradwarf bermudagrass (UDBG; C. dactylon (L.) Pers. x C. transvaalensis Burtt-Davy) putting green root zones in Tennessee. Soil organic matter (SOM; passed through sieve with 2 mm openings) content throughout a 10 cm core was quantified, along with total organic material (TOM; non-disturbed cores) within each sample. Assessments of TOM were also made at 0-2 cm, 2-4 cm and 4-6 cm, profile depths; TOM values from UDBG greens were greater than those from CBG at all profile depths. While TOM and SOM were associated (R² = 0.62), removing verdure for SOM assessments reduced the amount of organic material in each sample 38% and increased variability.

Laboratory and glasshouse studies were conducted to evaluate the rate of mineralization in root zones containing three different SOM contents: (low 6.4 g kg ^-1 to 12.6 g kg ^-1), medium (12.7 g kg ^-1 to 19.4 g kg ^-1), and high (19.5 g kg ^-1 to 25.6 g kg ^-1). When incubated at 25 °C under dark conditions, inorganic N increased 36 mg kg^-1 in cores from the high SOM group indicating the potential for as much as 50 kg N ha^-1 to become available within the root zone during similar environmental conditions in the field.

However, no differences in SOM, TOM, soil inorganic N, clipping volume, or turfgrass quality were detected among four different N fertilizer regimes evaluated in the field: 0, 5, 10 kg N ha^-1 wk^-1, and a growth-potential based regime that determined N rates based on 7-d clipping volume and air temperature data. Each year, total soil inorganic N increased during the first 28 d of the experiment and decreased thereafter. The 10 kg N ha^-1 wk^-1 fertilizer regime resulted in the greatest foliar N content (3.8%) than those from non-treated plots (3.3%). Overall, these studies found that mineralization can provide inorganic N to turfgrass root zones but is dependent on various factors such as existing SOM content and air temperature.

Recommended Citation

Kahiu, Maureen M., "Characterizing Putting Green Root Zones in Tennessee. " PhD diss., University of Tennessee, 2025.
https://trace.tennessee.edu/utk_graddiss/13607