Effects of evapotranspiration based irrigation, double mowing, and wetting agent on an Agrostis stolonifera var. palustris putting green

State of Michigan legislators recommend the amount of irrigation water should be equal to total evapotranspiration (ET) since the last irrigation. To the common citizen this recommendation makes sense and is good policy, however, the legislation makes no differentiation between turfgrass species, mowing height, and soil type. The demand for optimum Agrostis stolonifera var. palustris (creeping bentgrass) putting greens requires golf courses' to manage inputs closely. Challenges include low mowing heights, summer heat stress, traffic, along with limitations in viable irrigation sources in order to manage creeping bentgrass. A factorial field experiment was designed on a Crenshaw putting green during the summers of 2010-2012 in East Lansing, MI comparing irrigation and mowing frequencies with and without a wetting agent. Daily irrigation replenishment of 30, 60, and 90% evapotranspiration (ET) measurements were compared for irrigation use efficacy while maintaining quality playing conditions and turfgrass health. Daily single and double mowing frequencies were compared for long-term aesthetics, pest populations, and playability when mowed at 0.3175 cm (0.125 in). Monthly applications of a wetting agent (RevolutionRTM) were compared to untreated plots. Playability and overall aesthetics were characterized by weekly measurements of ball roll distance, percent volumetric water content (%VWC), and visual quality ratings (1-9). Disease differences among treatments were measured on an incidental basis. Annual soil measurements included percent organic matter (%OM), water drop penetration (WDP) test, and total microbial biomass (TMB).;Cumulative effects were averaged at the conclusion of the study, and data presented no significant differences among irrigation or wetting agent treatments for ball roll distance. Three year ball roll distance averages were significantly increased from 284.5 to 317.5 cm (112 to 125 inches) for single versus double mowed plots, respectively. Values for percent volumetric water content (%VWC) averaged 23.3, 33.1, and 35.6 for 30, 60, and 90% ET levels, respectively. Data of 60 and 90% were statistically similar, and were significantly greater than 30% ET in %VWC. Overall, double mowing and wetting agent application data presented no significant differences among treatments for %VWC. Visual quality averaged 5.6, 7.9, and 8.1 for 30, 60, and 90% ET levels, respectively. 60 and 90% were statistically similar in visual quality, and were significantly greater than 30% ET. Visual quality increased significantly from 6.7 to 7.9 with use of a wetting agent. Double mowing data presented no significant difference among treatments for visual quality. No significant differences in TMB were observed in soils treated with 30, 60 , or 90% ET daily irrigation from 2010 to 2012, with levels ranging from 29.9 to 60.1 &mgr;g g dry soil -1 (Table 26). Daily double mowing and wetting agent application did not significantly affect TMB. However, during the driest season of 2012, TMB was significantly increased with the use of wetting agent at 30% ET replenishment. Data obtained from water drop penetration (WDP) tests resulted in significantly lower hydrophobicity in soil at the 0-1 cm depth below plant and/or thatch with wetting agent applications in all years (8-18 seconds). No differences were observed at sampling depths below 1 cm, and in response to irrigation or mowing treatments. Soil hydrophobicity reductions were more responsive to wetting agent applications than irrigation or mowing treatment effects.