Leaching and Persistence of Sulfentrazone when Mixed with Adjuvants

ABSTRACT: The objective of this work was to study the influence of adjuvants on leaching and persistence of sulfentrazone in a Red-Yellow Ultisol. The soil was stored in PVC columns of 10 cm diameter and 50 cm length. The treatments were composed of sulfentrazone mixed with six adjuvants (Adesil®, Break-Thru®, Assist®, Hoefix®, Fera® and Nortox® Vegetable Oil), a treatment with sulfentrazone without any adjuvant and a treatment without the herbicide. In the treatments with sulfentrazone, the herbicide was applied at a rate of 1.0 kg ha-1 at the top of the columns, and 12 hours after application, the columns were subjected to simulated rainfall (60 mm). To confirm leaching of sulfentrazone, soil samples were collected every 5 cm up to 50 cm in each column and transferred to 300 cm3 pots to conduct a bioassay using the species Sorghum bicolor. At 21 days after emergence (DAE) of sorghum, visual assessment of intoxication was performed and shoot dry matter percentage was determined. To determine the influence of adjuvants on persistence of sulfentrazone in the soil, new sorghum seeds were planted as soon as the sorghum plants from the first planting were cut; also, phytotoxicity scores were assigned and shoot dry matter was determined at 21 DAE. This procedure was repeated up to 173 days after herbicide application, when the plants showed no more visual symptoms of intoxication. The adjuvant Break-Thru® was effective at reducing leaching of sulfentrazone. The presence of adjuvants applied together with sulfentrazone did not influence the persistence of the herbicide in the study soil. Persistence of sulfentrazone lasted for 143 days.

摘要：本研究旨在探究助剂对红黄色老成土（Red-Yellow Ultisol）中磺酰三唑酮（sulfentrazone）淋溶与持效性的影响。供试土壤装填于直径10 cm、长50 cm的聚氯乙烯（PVC）柱体中。试验处理设置如下：磺酰三唑酮与6种助剂（Adesil®、Break-Thru®、Assist®、Hoefix®、Fera®及Nortox®植物油）混配处理、仅施用磺酰三唑酮无助剂处理，以及不施除草剂的空白处理。在含磺酰三唑酮的处理组中，除草剂以1.0 kg·ha⁻¹的剂量施于柱体顶部，施药12小时后对柱体进行60 mm的模拟降雨处理。为验证磺酰三唑酮的淋溶情况，从每根柱体中按每5 cm一层采集土壤样品至50 cm深度，将样品转移至300 cm³的盆栽容器中，采用高粱（Sorghum bicolor）进行生物测定。在高粱出苗后21天（Days After Emergence，DAE）时，进行中毒症状视觉评分，并测定地上部干物质占比。为探究助剂对土壤中磺酰三唑酮持效性的影响，待首次种植的高粱植株收获后，立即补种新的高粱种子，并于出苗后21天进行药害评分与地上部干物质测定。该操作重复进行至施药后173天，此时植株已无可见中毒症状。助剂Break-Thru®可有效降低磺酰三唑酮的淋溶风险。与磺酰三唑酮混施的助剂对供试土壤中除草剂的持效性无显著影响。磺酰三唑酮在供试土壤中的持效时长为143天。