Premium
Degradation of the sulfonylurea herbicides chlorsulfuron and triasulfuron in a high‐organic‐matter volcanic soil
Author(s) -
T.K. James,
Patrick T. Holland,
A. Rahman,
Yanyan Lu
Publication year - 1999
Publication title -
weed research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.693
H-Index - 74
eISSN - 1365-3180
pISSN - 0043-1737
DOI - 10.1046/j.1365-3180.1999.00131.x
Subject(s) - sulfonylurea , sorghum , loam , chemistry , organic matter , agronomy , phytotoxicity , environmental chemistry , soil water , environmental science , biology , soil science , organic chemistry , insulin , endocrinology
The degradation rates of two sulfonylurea herbicides, chlorsulfuron and triasulfuron, were determined at two application rates, 15 and 30 g a.i. ha –1 , in a sandy loam soil of volcanic origin under controlled environment and field conditions. Residues were measured using a modified gas chromatographic (gc) determination method. Both herbicides degraded rapidly in the acidic soil (pH 5.7) with high organic matter levels (7.3% o.m.), generally according to first‐order rate kinetics. The respective half‐lives ranged from 22 to 38 d for chlorsulfuron and from 31 to 44 d for triasulfuron under five controlled temperature/soil moisture regimens, ranging from 10 to 30 °C and between 40% and 80% maximum water‐holding capacity. Half‐lives in the field were considerably shorter (13 d for chlorsulfuron and 12–13 d for triasulfuron). The degradation rates of the herbicides were influenced more by soil temperature than by soil moisture content. Bioassays using white mustard ( Sinapis alba L.) and forage sorghum [ Sorghum bicolor (L.) Moench] were also used to determine the persistence of phytotoxic residues of both herbicides in the field, and the results showed that the effects of chlorsulfuron disappeared within 8 weeks. Triasulfuron residues disappeared within 9 and 14 weeks for the 15 and 30 g a.i. ha –1 rates respectively.