Dissipation of imazapyr, flumetsulam and thifensulfuron in soil

Abstract

The degradation of imazapyr, fiumetsulam and thifensulfuron applied at 500, 40 and . M) g active ingredient (a.i,) ha"', respectively, to si!t loam soil was sttidied under laboratory and field conditions. Herbicide residues were analysed by a lentil {Lem culinaris L.) bioassay. Results showed ihat temperature had a significant effect on herbicide degradation. Vk'hereas the impact of soil organic matter ami pH were less well defined. Half-lives for iniazapyr, flumetsulam and thifensulfuron in soil samples from the 0-5 cm layer (64% organic carbon) at 15 "C were 125, 88 and 5-4 days, respectively, and 69, 30 and .^-9 days at 30 °C. ]n soil sampled from the 15-20 cm layer (3-5% organic carbon) half-lives were 155, 70 and 6-4 days, respectively, at 15 "C and 77, 24 and 4-8 days at 30 °C. A field experiment investigated the degradation and teaching of each herbicide under two precipitation regimes (natural precipitation (208 mm), and nattjral precipitation pJus 75 mm irrigation (283 mm)] over 4 months to a soil depth of 25 cm. Thifensiitfuron degraded rapidiy, whereas residues of flumetsulam and imazapyr leached below 25 cm in both the low-and highprecipitasion treatments after 4 months. Significant itnai^apyr residues were still present in the soil to 25 cm depth after 3 months. A miilt:component model for herbicide dissipation was developed and evaluated using data from the laboratory and fieid experiments. lntrottuction

Toxicidade da mistura formulada de imazethapyr e imazapic sobre o azevém em função do teor de umidade do solo

“…No entanto, outro aspecto importante a ser considerado é que, em solo arenoso e com invernos chuvosos, pode haver maior lixiviação dos herbicidas, levando assim a resultados diferentes do encontrado neste experimento, podendo os herbicidas ser transportados para profundidades maiores no solo, ficando fora da região de absorção das plantas (McDowell et al, 1997;Jourdan et al, 1998).…”

Persistência dos herbicidas imazethapyr e imazapic em solo de várzea sob diferentes sistemas de manejo

“…Concordando com isso, McDowell et al (1997) eHJourdan et al (1998 -1 ), semeada após um ano da última aplicação dos herbicidas, num sistema com dois anos de uso dos herbicidas, em cinco épocas de avaliação e nove preparos de solo: PD = plantio direto; PDA = plantio direto mais azevém; 1PSA = um preparo de solo (PS), em abril; 1PSAA = um PS em abril mais azevém; 1PSO = um PS, em outubro; 2PSMO = dois PS, em maio e outubro; 2PS = dois PS, em abril e outubro; 3PS = três PS, em abril, maio e outubro; 4PS = quatro PS, em abril, maio, agosto e outubro. Santa Maria-RS, 2006/07.…”

Determination of imazethapyr residues in soil and grains after its application to soybeans

“…10,11) Organic matter and pH significantly affect imazethapyr behavior in soil. 8,12) However, imazethapyr does not readily leach under field conditions, 13) even though some authors have reported leaching of imazethapyr below 25 cm in soil during four months. 8,14) As a result of leaching and runoff, imazethapyr residues were reported in streams and rivers in the Midwestern USA at concentrations above the maximum residue limits in 71% of samples.…”