THE RESEARCH PLAYBOOK

By Jose Diaz , Benjamin Wherley , Ph . D ., and Chase Straw , Ph . D ., Texas A & M University

Thick-cut , plastic grown sod ( PGS ) demand for midseason repair or complete renovation of professional and collegiate sports field venues has increased dramatically . However , published information on best practices for PGS development is lacking . Furthermore , there has been very little prior research done to examine cultural factors relating to rate of establishment and final quality of PGS . Therefore , the objective of this study was to evaluate the influence of cultural practices ( e . g ., mowing frequency , topdressing particle size , and plant growth regulator ) on establishment , tensile strength , and root / rhizome development of plastic-grown ‘ Latitude 36 ’ hybrid bermudagrass sod .

The study was conducted March 2 through June 24 , 2021 in a greenhouse at Texas A & M University in College Station , Texas , using washed ‘ Latitude 36 ’ bermudagrass sod placed in plastic trays . A randomized complete block design with four replications was used to accommodate all cultural practice treatment combinations , including mowing frequency ( one vs . three times a week ), topdressing sand particle size distribution ( medium fine = 0.05 to 0.5 mm vs . medium coarse = 0.5 to 1 mm sand ), and plant growth regulator [ trinexapac-ethyl applied every 14 days at label rate ( Primo Maxx ) vs . no trinexapac-ethyl ]. At the beginning of the study , all treatments received a micronutrient fertilizer application , and trays were fertilized monthly through the study using a 10-20-20 granular fertilizer at rate of 0.67 lb . N / 1,000 sq . ft . Topdressing treatments were applied by hand at a depth of 0.1 inch every 14 days . Trays were irrigated daily with overhead mist irrigation at a depth of 0.25 inches , divided into two split-applications per day .

Visual turf quality ( 1-9 scale , 6 = minimal acceptable ) and light box images were collected every week . Soil volumetric water content for the upper half inch was also measured weekly . At the conclusion of the 16- week study , sod trays were allowed to drain overnight and were weighed to determine final mass . Sod tensile strength was then measured for all treatments using a tensile strength testing device with electric winch and Transcell TI-500E load cell . Root length density attributes for each treatment were also characterized

Plastic-grown ‘ Latitude 36 ’ hybrid bermudagrass sod cross-section .

using WinRhizo to relate to tensile strength differences . Root and rhizome dry mass were determined for two , four-inch-diameter plugs removed from each sod piece .

All treatments maintained excellent visual turf quality throughout the duration of the study ( 8.1 average across all treatments ). The medium-fine sand resulted in higher turf quality ( 8.2 ) than coarse sand when mowing was performed 1x weekly ( 8.0 ). When topdressed with medium-fine sand , the 1x weekly mowing treatment led to significantly higher sod strength ( 344 N ) compared to 3x weekly mowing ( 225 N ). Bi-weekly PGR application resulted in significantly greater root dry weight ( 5.4 g ) compared to non-PGR-treated sod ( 4.1 g ). Trinexapac-ethyl also improved turf quality ( 8.2 vs . 8.0 for treated and untreated sod , respectively ). Final plastic grown sod mass ranged from 1.37 g cm -3 ( coarse sand ) to 1.44 g cm -3 ( medium-fine sand ) but did not statistically differ . Root length density of plastic grown sod in this study was much higher than that of previously published field-grown turf , averaging 70 cm cm -3 , but no differences were seen among treatments .

The study is currently being repeated . At the conclusion of the study , principal components analysis will be utilized to determine the relative contributions of cultural and plant developmental factors to sod strength . SFM

10 SportsField Management | January 2022 sportsfieldmanagementonline . com