Rooting and Drought Avoidance of Warm‐Season Turfgrasses and Tall Fescue in Kansas

Rooting characteristics of 'Midlawn' bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy], 'Prairie' buffalograss [Buchloe dactyloides (Nutt.) Engelm.], 'Meyer' zoysiagrass (Zoysia japonica Steud.), and 'Mustang' tall fescue (Festuca arundinacea Schreb.) are not well documented, but likely contribute to drought avoidance. Experiments were conducted between 1993 and 1995 to determine (i) vertical rooting patterns in the greenhouse and field and (ii) relationships among rooting parameters, soil water depletion (SWD), and turfgrass wilting in the field. Tall fescue was mowed once weekly at 6.5 cm, whereas warm-season grasses were mowed twice weekly at 4.5 cm. In the greenhouse, total root length (TRL) of tall fescue between 0 and 120 cm was 180 to 270% greater, and its maximum root extension (MRE) was 33 to 60% deeper than warm-season grasses. Tall fescue also had a shoot/root ratio (SRR) 29 to 63% lower than ratios of warm-season grasses. When sampled to a 90-cm depth in a silt loam soil (fine, montmorillonitic, mesic Aquic Arquidolls) in the field, tall fescue exhibited 39 and 140% greater TRL than warm-season grasses in 1993 and 1994, respectively. Zoysiagrass had the lowest root length density (RLD) at 30 to 60 and 60 to 90 cm of any grass studied in the field. Soil water depletion during five 7- or 12-d precipitation-free periods in the field indicated that tall fescue extracted over 50% more water than bermudagrass and zoysiagrass at 90 cm. Buffalograss extracted 66% more water than zoysiagrass at 90 cm during one of these periods. Wilting of warm-season grasses at the end of dry down in the field was correlated with RLD at 30 to 60 (r = 0.74) and 60 to 90 cm (r = 0.66). Deep and extensive rooting of Mustang tall fescue and intermediate rooting of Prairie buffalograss and Midlawn bermudagrass were important components of leaf wilt resistance during drought. Shallow rooting resulted in poor drought avoidance in Meyer zoysiagrass.