Evaluation of Lawn and Native Grasses Under Deficit Irrigation.

Increasing water shortage has led to the need for drought tolerant cool-season species in arid climates. Native grasses are believed to conserve more water because they are better adapted for their particular environment. A study was conducted in 2014 and 2015 at the University of California, Riverside turfgrass research facility to compare four blends of southern California native grasses (Delta Native Mow free Mix, Delta Native Biofiltration Mix, Stover Native All-Purpose Mix, Stover Native Fine Fescue Mix), six tall fescue varieties (‘Spyder LS’, ‘Titanium LS’, ‘PPG-TF105’, ‘PPG-TF142’, ‘PPG-TF145’, ‘PPG-TF156’), two native bentgrass varieties (Delta Native Bentgrass, Stover Native Bentgrass) and five non-native cool-season mixes (Delta Bolero Plus Mix 90/10, Delta 90/10 Fescue/Blue Mix, Cutting Edge Sun & Shade Mix, Pearl’s Premium Ultra Low Maintenance Lawn Seed-Sunny Mix, New Millenia Dwarf Fescue Blend) under deficit irrigation and when mowed at two different heights (5 and 10 cm). Plots were seeded 10 May 2013 and were established under non-limiting water conditions during the summer season. Irrigation replacement was reduced to 60% reference evapotranspiration (ET₀) starting on June 1 2014 and 2015 and until October 2014 and 2015. Visual quality and digital image analysis (DIA) to calculate dark green color index (DCGI) and percent ground cover (%GC) were collected every other week from the beginning of drought stress until the end of October. Analysis of variance showed that mowing height and seed variety had an effect on turf visual quality. One month after the beginning of the study in both years, quality dropped below an acceptable level of 6 and never recovered. Higher mowing height showed the highest quality at the beginning of the study but, as deficit irrigation progressed, mowing height did not have a beneficial effect on visual quality. The highest visual quality was achieved by non-native tall fescues while native mixes were rated the lowest.