2/9/2021 - By Xunzhong Zhang, Ph.D.

Our previous studies on bentgrass showed foliar application of Harrell’s pigment source at 5 fl oz/acre and 10 fl oz/acre weekly consistently improved leaf color at all sampling dates, and photochemical efficiency during drought stress. Application of the pigment at 5 fl oz/acre also improved root length, surface area, number of root tips, and root biomass relative to the fertilized control in creeping bentgrass putting greens.

Ultradwarf bermudagrass has been used for putting greens in many areas. We tested the effects of Harrell’s pigment at three rates on leaf color, physiological fitness, and root growth characteristics in ultradwarf bermudagrass putting greens during summer months.

We carried out this trial on the ‘Champion’ ultradwarf bermudagrass putting greens in central Virginia in 2020. We had 4 treatments including control, pigment at 2.5 fl oz/acre, 5.0 fl oz/acre, and 10 fl oz/acre. The pigment was applied weekly from June 11th to September 1st at 2-gal solution/1000 ft². All treatments received the same amount of fertilizers (28-8-18) during the experiment. A randomized block design was used with four replications. We rated leaf color based on scale of 1-9 with 9 indicating dark green, and measured chlorophyll content with CCM-300 chlorophyll meter, and photochemical efficiency with OS-50II chlorophyll fluorometer biweekly. At the end of trial, the roots were washed and root length, root diameter, root surface area, and length density were analyzed using WinRhizo technology. In addition, root viability was analyzed using TTC method. Root viability is a good indicator of root function.

The results of this study showed that foliar application of Harrell’s pigment weekly at all three rates improved leaf color of ultradwarf bermudagrass putting greens. The pigment applied at 10 oz/acre increased leaf chlorophyll content and photochemical efficiency. The pigment at the high rate (10 oz/acre) increased root biomass, root length, surface area, and root volume relative to the control, The pigment application at 10 oz/acre increased root biomass by 57.1%, and root length by 49.6% relative to the control. The pigment application at 2.5 oz/acre and 5 oz/acre improved root viability of ultradwarf bermudagrass putting greens.