Cotton (Gossypium hirsutum) response to imazaquin and imazethapyr soil residues

The effects of imazaquin and imazethapyr on cotton planted the year following application to soybean were studied on one silt loam and two clay soils in Arkansas from 1989 to 1991. Imazaquin was applied to soybean at 0.07 kg ai ha(-1) PPI and POST, 0.14 kg ha(-1) PPI, PRE, and POST, and sequentially PPI or PRE followed by POST at 0.14 kg ha(-1) per application. Imazethapyr was applied at 0.035 kg ha(-1) PPI and POST, 0.07 kg ha(-1) PPI, PRE, and POST, and sequentially PPI or PRE followed by POST at 0.07 kg ha(-1) per application. Soil residues of 0.07 kg ha(-1) imazaquin and imazethapyr did not injure cotton at any location. Residues of 0.14 kg ha(-1) imazaquin applied sequentially reduced cotton shoot dry weight for 6 wk after emergence on clay but not on silt loam soil. The PPI followed by POST sequential imazaquin treatment (0.28 kg ha(-1) total imazaquin) delayed initiation of fruiting and reduced yield and lint quality.