In Vitro Pesticide Degradation in Turfgrass Soil Incubated under Open and Sealed Conditions

Degradation of selected pesticides was conducted in a turfgrass soil from a golf course under open (i.e., allowing gas exchange with atmosphere) and sealed systems. The time required for 50% of the initial dose of fenitrothion ( O , O ‐dimethyl O ‐4‐nitro‐ m ‐tolyl phosphorothioate), diazinon ( O , O ‐dimethyl O ‐2‐isopropyl‐6‐methylpyrimidin4‐yl phosphorothioate), iprodione [3‐(3,5‐dichlorophenyl)‐ N ‐isopropyl‐2,4‐dioxo‐imidazolidine‐1‐carboxamide], mecoprop [(RS)‐2‐(4‐chloro‐ o ‐tolyloxy)propionic acid], and asulam (4‐aminophenylsulfonyl‐carbamate) to dissipate (half‐life, t 1/2 ) was less than 2 wk under both conditions. The t 1/2 values of dithiopyr ( S , S ′‐dimethyl 2‐difluoromethyl‐4‐isobutyl‐6‐trifluoro‐methylpyridine‐3,5‐dicarbothioate) were 324 and 185 d under the open and sealed conditions, respectively. The t 1/2 values of isoprothiolane (di‐isopropyl 1,3‐dithiolan‐2‐ylidene‐malonate), flutolanil (α,α,α‐trifluoro‐3′‐isopropoxy‐ o ‐toluanilide), and benefin ( N ‐butyl‐ N ‐ethyl‐α,α,α‐trifluoro‐2,6‐dinitro‐ p ‐toluidine) under the open conditions were 154, 336, and 47 d, respectively. The t 1/2 values of these pesticides increased slightly under the sealed conditions. The t 1/2 values of terbutol (2,6‐di‐ tert ‐butyl‐4‐methylphenyl N ‐methycarbamate) and one of the major degradation products, N ‐demethyl‐terbutol (2,6‐di‐ tert ‐butyl‐4‐methylphenyl carbamate), were 182 and 291 d under the open conditions and increased by six‐ and threefold under the sealed conditions, respectively. The degradation system under the sealed conditions could characterize the persistence of terbutol and N ‐demethyl‐terbutol, which were the most persistent in the field.