A Study On Root Morphological and Physiological Characteristics of Warm Season Turf Grass Species As Affected by Mowing Height.

Abstract: Root morphology is considered important in selecting for field drought performance of warm season turfgrass species.  There is considerable variability among turfgrass genotypes in their rooting behavior. A mini-rhizotron camera system was used to study rooting behavior of two commercial warm season turfgrass species from April to June, 2011 and 2012 at the University of Florida turfgrass research center in Citra, FL. Using this technology, we evaluated the effect of mowing height on rooting parameters of two turfgrass species, St. Augustinegrass and hybrid bermudagrass. The experimental design was a randomized complete block design (RCBD) with three replications and three mowing heights treatments for each species. Mowing heights for St. Augustinegrass were 5.0 cm, 7.5 cm and 10.0 cm and for bermudagrass they were 1.3 cm, 3.8 cm, and 6.4 cm. Mowing was performed weekly using a push-mower through the growing season. Root images were taken once every two weeks and were analyzed with Win-rhizotron software (Bartz Technology Corporation, Carpinteria, Canada) for root length, diameter, surface area and volume. In 2011, we found that higher mowing heights promoted increased root length, but reduced average root diameter. For St. Augustinegrass, at the 7.5 cm, and 10.0 cm mowing heights root growth was observed at 30-40 cm, but for the 5.0 cm mowing height root growth was limited above 30 cm.  In bermudagrass, root depth at the 6.4 cm mowing height was observed at 70 cm. In contrast, when bermudagrass was mowed at 1.3 cm and 3.8 cm the maximum root depth was between 30-40 cm. Lower mowing heights were associated with shallower rooting but the average root diameter was comparatively higher with lower mowing heights. Shorter mowing heights in these two warm season species were associated with decreased root growth which may negatively impact their drought tolerance.