Solute Transport During Chemigation of a Level Basin

Chemigation can be an efficient means of applying agricultural chemicals, however little research has been done to assess leaching of chemicals applied with chemigation. This study compared the leaching behavior of two conservative mobile tracers, one (Br) applied in the irrigation water and a second (o-TFMBA) sprayed onto the soil surface immediately before irrigation. Sixteen days after irrigation, sixty-six, 42-mm diameter soil cores were taken to a depth of 2 m from within the sprayed plots. The soil cores were sectioned into eight 0.25-m long cores from which Br and o-TFMBA were extracted. Tracer distributions exhibited considerable variability across the basin, with the o-TFMBA tracer generally exhibiting less erratic behavior than the Br. Only Br, which was applied with the irrigation water, showed significant trends between mass recovered and position within the basin. The o-TFMBA exhibited less leaching with the mean depth of tracer penetration being 0.42 m. Bromide showed significantly (P = 0.05) deeper penetration of the soil profile with a mean depth of leaching for the recovered Br being 0.69-m, or about 60% deeper than the o-TFMBA. Results indicate that chemigation may actually increase rather than decrease deep leaching of agricultural chemicals.