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 [Buch loe 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. Exper iments were conducted between 1993 and 1995 to determine (i) vertical rooting patterns in the greenhouse and field and (ii) relationships am ong rooting parameters, soil water depletion (SWD), and turfgrass wilt ing 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 greenho use, total root length (TRL) of tall fescue between 0 and 120 cm was 1 80 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 ra tio (SRR) 29 to 63% lower than ratios of warm-season grasses. When sam pled to a 90-cm depth in a silt loam soil (fine, montmorillonitic, mes ic Aquic Arquidolls) in the field, tall fescue exhibited 39 and 140% g reater TRL than warm-season grasses in 1993 and 1994, respectively. Zo ysiagrass 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 durin g five 7- or 12-d precipitation-free periods in the field indicated th at tall fescue extracted over 50% more water than bermudagrass and zoy siagrass at 90 cm. Buffalograss extracted 66% more water than zoysiagr ass at 90 cm during one of these periods. Wilting of warm-season grass es at the end of dry down in the field was correlated with RLD at 30 t o 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 buffalogra ss and Midlawn bermudagrass were important components of leaf wilt res istance during drought. Shallow rooting resulted in poor drought avoid ance in Meyer zoysiagrass.