Root Depth Development of Warm-Season Turfgrass for Lower Latitudes.

Water availability is becoming increasingly limited for irrigating landscapes, particularly in urbanized areas, where water use restrictions are often imposed.  Better knowledge of drought-resistance mechanisms in turfgrasses would improve management strategies and speed progress in the development of drought-resistant cultivars. The objective of the present study is to identify those species or genotypes with greater root depth development and potential better drought avoidance in warm-season turfgrasses utilized in lower latitudes. Twenty six genotypes were evaluated from the following species:  zoysiagrass (Zoysia spp), carpetgrass (Axonopus fissifolius), centipedegrass (Eremochloa ophiuroides), bermudagrass (Cynodon spp), and St. Augustinegrass (Stenotaphrum secundatum). Plants were grown in clear acrylic tubes set inside of 7.6 cm PVC pipes in Gainesville, FL and watered to sustain growth. The tubes measured 121.9 cm length by 6.4 cm diameter. Tubes were filled with an 80% USGA-spec sand and 20% peat mix. Soilless 5 cm plugs of each genotype were planted into the tubes and arranged in a randomized complete block design with four replications.  Root depth measurements were initiated eight days after planting and subsequently recorded three times per week. Twenty-three days after planting species differed for their root depth (P<0.0001). Regression analysis was used to estimate the rate of root depth development (RRDD) corresponding to the slope of the linear function between time and depth of the deepest visible root. Root depth growth was linear for all the genotypes through time and regression coefficients ranged from 0.9276 to 0.9974. The highest rate of root depth development was for an experimental common bermudagrass, UFCD347; its daily rate of root depth growth was 6.50 cm. The lowest rate was for an experimental zoysia genotype, UFZ374; its daily root depth growth was 2.68 cm. Results indicate that variability exists between species for RRDD.