Laboratory and greenhouse studies were conducted to determine the mobility and bioactivity of thiobencarb on a Pahokee muck, Everglades muck, and Immokalee sand. On all soils > 93% of thiobencarb remained in the upper 1 cm after leaching during unsaturated flow. During saturated flow the retardation factor (RT) of thiobencarb on an Immokalee sand was 68, 20, 2, and 1 with 0, 25, 50, and 75% by volume methanol in 0.01 N CaCl2, respectively. There was a significant log-linear relationship (r2 = 0.97) between the Freundlich adsorption values (Kf) estimated from RT values and the percentage by volume methanol of the leachate. In general, thiobencarb in combination with overhead irrigation reduced lettuce vigor and plant dry weight on an Immokalee sand more than with subsurface irrigation.

Laboratory studies were conducted to characterize the adsorption-desorption and degradation of thiobencarb in soil. Thiobencarb adsorption on soil was correlated with soil organic carbon (r = 0.97) and values (ml g−1) for the following soils were: Pahokee muck 339, Everglades muck 169, and Immokalee sand 14. The adsorption values (ml g−1) per unit of organic carbon were Immokalee sand 1195, Pahokee muck 765, and Everglades muck 539. In desorption studies, thiobencarb Kf values increased 80 ml g−1 from the first to the third desorption step in the muck soils, but were similar in three desorptions from the sand. The half-lives of thiobencarb averaged 16, 18, and 24 days on surface samples of Pahokee muck, Everglades muck, and Immokalee sand, respectively, across the range of 25 to 35 C and 10 to 100 kPa soil water tension. Half-lives were generally longer with water contents equivalent to 100 kPa than 10 kPa soil water tension and incubated at 25 than 35 C. The relative percentages of extractable 14C, bound 14C, and 14CO2 from 14C-thiobencarb-treated soil were dependent on soil type, soil water content, incubation temperature, and time.

There are limited PRE herbicide options available to provide residual weed control in sweet corn grown on organic soils in the Everglades Agricultural Area (EAA). Field studies were established to determine the efficacy of PRE applied saflufenacil + dimethenamid-P at six rates ranging from 10 + 88 to 319 + 2802 g ai ha−1 on weed control and sweet corn tolerance on organic soils in the EAA in 2011 and 2012. Saflufenacil + dimethenamid-P is a premix recently labeled for PRE weed control in field corn at 50 + 438 to 90 + 788 g ha−1 depending on soil texture. There was no phytotoxic effect of PRE applied saflufenacil + dimethenamid-P on sweet corn. At 42 d after treatment, common lambsquarters, common purslane, and spiny amaranth were controlled 90% with saflufenacil + dimethenamid-P at 58 + 508, 71 + 622, and 58 + 512 g ha−1, respectively. Sweet corn yield at 95% of the weed-free yield was estimated to be obtained at 69 + 606 g ha−1 of saflufenacil + dimethenamid-P. Our results show that saflufenacil + dimethenamid-P at 69 + 606 to 71 + 622 g ha−1 controlled three common weeds and maintained acceptable sweet corn yield. Labeled rates of saflufenacil + dimethenamid-P for field corn on mineral soils were adequate for weed control in sweet corn on organic soils.