Diclosulam persistence in soil and its effect on peanut (Arachis hypogaea L.) and rotation crops

Abstract

The persistence of diclosulam in soil was evaluated in Yoakum and De Leon, TX. During the first year, peanut was planted and diclosulam was applied at 0, 18, 27, 52 and 81 g ai/ha. Soil samples were taken from these treatments at 0, 1, 2, 3, 6 and 12 months after application. Conventional corn, imidazolinone resistant (IR) corn, sorghum and cotton were planted as rotational crops the following year. Data taken from the rotational crops included stand counts, plant heights, fresh weights and dry weights. Sorghum height was significantly decreased from the untreated check at 52 and 81 g/ha in Yoakum. Cotton and sorghum height was also significantly decreased in De Leon. However, differences were not consistent with diclosulam rate. The only significant weight reduction compared to the untreated check was with conventional corn at the highest rate. Soil samples were extracted and analyzed by gas chromatography-mass spectrometry (GC-MS) to determine the amount of diclosulam remaining in soil. The mean recovery was 70 ± 8% and at 0 d after application, the average soil concentration was 126 ± 32 []g/kg in Yoakum and 226 ± 30 []g/kg in De Leon. Diclosulam degraded to levels below the limit of quantitation (LOQ) at the remaining timings. Laboratory data corresponded with the field data, which showed that diclosulam degraded rapidly. Due to peanut injury during the first year of diclosulam use, studies were conducted in growth chambers evaluating the effects of three temperatures (13 C, 18 C, 24 C), four peanut varieties ('FL-458', 'Georgia Green', 'GK-7' and '301-1-8), and five diclosulam rates (0, 7, 13, 27 and 52 g/ha) on peanut germination. Germination counts were taken at 3-d intervals up to 28 d after initiation. Germination results were similar at all five rates and germination increased as temperature increased. The variety, 301-1-8, consistently germinated better at the two highest temperatures while GK-7 and Georgia Green had the lowest percent germination at these temperatures. The varietal response was not affected by diclosulam rate indicating that early peanut injury was possibly due to other undetermined factors.