Experiments were conducted in 1989-90 to determine the response of weed free cotton to trifluralin (1.0 lb ai/A) applied preplant incorporated (PPI) followed by (Fb) preemergence (PRE) application of clomazone (1.0 lb ai/A), trifluralin (1.0 lb ai/A) PPI Fb clomazone + fluometuron (1.0 + 1.5 lb ai/A) PRE, and clomazone + fluometuron (1.0 + 1.5 lb ai/A) PRE without trifluralin. Disulfoton, fenamiphos, PCNB, phorate, or aldicarb (1.0 lb ai/A) were used as in-furrow granules with the above herbicide treatments.

The studies were conducted on a Leeper silty clay loam soil in 1989 and on a Leeper silt loam in 1990. 'Des-119' cotton cultivar with a seeding rate of 70,000 seed/A was planted in 38-inch rows on a prepared seedbed 5/16/90 and 5/01/90. All herbicides were applied broadcast with a boom sprayer with 8003-VS fan nozzles spaced 20 inches apart and a boom pressure of 25 pound pressure per square inch. The application volume was 20 gallon/A with water as the carrier.

Trifluralin Fb clomazone + fluometuron and clomazone + fluometuron applied alone or Fb either aldicarb or fenamiphos caused 50% or more chlorosis to cotton seedlings reduced plant populations by 80% or more, and seed-cotton yield by about 20 to 60% in both 1989 and 1990. Clomazone + fluometuron Fb PCNB in-furrow granules caused 36% chlorosis in 1990 but none in 1989. This treatment reduced plant population by 34% only in 1989 but had no effect on yield both years. Clomazone + fluometuron Fb either phorate, disulfoton, or disulfoton + PCNB, and trifluralin PPI Fb clomazone or clomazone + fluometuron with phorate in-furrow granules caused 20% or less cotton seedling chlorosis, in both 1989 and 1990. These treatments had no effect on plant populations (50,000/A in 1989 and 36,000/A in 1990) and seed-cotton yield average of 1030 lb/A in 1989 and 2538 lb/A in 1990.