Transport of imazaquin through undisturbed columns

The movement of imazaquin [2-(4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1 H-imidazol-2-yl)-3-quinoline-carboxylic acid] through large columns amended with wheat straw was studied.

A tractor-mounted hydraulic sampler extracted six large columns, which were mounted vertically in the laboratory. Wheat straw was applied at the rates of 0 and 4480 kg ha^-1. Imazaquin was applied at the recommended rate with pulse and duration times predicted by the FORTRAN program CXTFIT. Bromide was applied as the non-reactive tracer, and used to determine dispersion throughout the columns. This dispersion coefficient was used to determine the retardation factor for imazaquin. The bromide was measured by an ion specific electrode. The imazaquin in the leachate, soil and wheat straw was analyzed by HPLC.

The results showed that imazaquin in the soil and in the wheat straw was at or below detection limits. The imazaquin present in the leachate was in low concentrations over a period of 54 days. Mass balance calculations for the leachate accounted for 43% to 100% of the applied imazaquin. The retardation factor solved for by CXTFIT was higher than predicted using the current literature.

Preferential flow paths were qualitatively analyzed using Rhodamine B dye. The staining patterns were photographed. Preferential flow paths were evident to a depth of 30 - 40 cm.