Dynamic Character of Equipment Fluid Injury on a Hybrid Bermudagrass Green.

Lubricants, fuels, and hydraulic oils (HO) injure turf.  Research was conducted to characterize turf injury resulting from these fluids.  Effect of fluid type on injury area (IA, cm²), rate of injury healing (d^-1), shoot necrosis (%), and pixel intensity of necrotic shoot images (%) was studied on a hybrid bermudagrass green (Cynodon dactylon [L.] Pers. var. dactylon x Cynodon transvaalensis Burt-Davy ‘Tifeagle’).  Gasoline and brake fluid caused 100% shoot necrosis 1 d after treatment; motor oil caused 73% necrosis.  Petroleum HO, vegetable HO, and diesel fuel averaged 35% necrosis.  At 7 d IA was ≈100% necrotic.  Necrotic shoot color differed between fluids (p < 0.0001), ranging from ‘blanched almond’ (FFEBCD) to ‘rosy brown’ (BC8F8F).  Necrotic shoots caused by lower viscosity fluids had lighter color (p < 0.0001).  Diesel fuel caused the largest IA (49.2 cm² at 7.4 d) but healed at the fastest rate (-0.09 d^-1); calculated healing was 194 d (Δ IA = -82% at 139 d).  Motor oil injury healed at the slowest rate (-0.02 d^-1); calculated healing was 1004 d (Δ IA = -14% at 139 d).  Kinematic viscosity correlated with time to maximum IA expansion (R²_adj = 0.945) and calculated healing time (R²_adj = 0.943) but not IA (R²_adj = 0.194).  Injury from higher viscosity fluid began healing later and had longer recovery times.  Viscosity appeared to influence injury but constituents that determine fluid properties may ultimately be responsible for observed effects.