Behavior of pre-mix formulation of imazethapyr and imazamox herbicides in two different soils.

Imidazolinone group herbicides are known for longer persistence in soil. Therefore, a laboratory study was performed to evaluate the persistence of pre-mix formulation of two imidazolinone herbicides-imazethapyr and imazamox in clay and sandy loam soils. Herbicide formulation was applied at 70 and 140 g a.i. ha equivalent to recommended doses in legumes. For achieving efficient sample preparation, three methods namely ultrasonic-assisted extraction (UAE), matrix solid phase dispersion (MSPD), and solid phase extraction (SPE) were optimized. MSPD gave better recoveries (85.22 to 96.00%) over SPE (80.10 to 84.78%) and UAE (56.44 to 66.20%). Residues were estimated using gas chromatography tandem mass spectrometry (GC-MS/MS) which is previously not reported in open literature. Dissipation followed first-order kinetics and half-life period of 23.5 to 43.3 days in clay loam and 19.6 to 39.8 days in sandy loam soil. The results revealed the persistent nature of pre-mix formulation of both herbicides as only 64.2 to 86.6% residues dissipated after 90 days of application in both soils.