Three rates of Pix (mepiquat chloride) were applied at early bloom to Stoneville 825 cotton conventionally planted and no-tilled into crop stubble in rows 76 cm and 102 cm apart during 1987 and 1988. A Memphis silt loam soil at Jackson, Tennessee was used for these experiments. A randomized split-split-plot design was used each year. Main plots were cotton planted in a Conventionally prepared seedbed or no tilled into old crop residue. Sub-plots were rows spaced 76 cm and 102 cm apart. Sub-sub-plots were treated with Pix at 50 gms ai/ha, 25 gms ai/ha, 0 gms, and a check. Each Pix treatment was followed by Prep (ethephon) at 1.12 ai kg/ha. Neither Pix nor Prep was applied to the check.

Conventionally-planted cotton yielded significantly more and matured earlier than cotton no-tilled into soybean stubble in 1987 and cotton stubble in 1938. Cotton planted in rows 76 cm apart yielded significantly more lint in 1988 and 64 kg more lint per ha in 1987 than cotton planted in rows 102 cm acart. Plots treated with Pix yielded significantly more and matured earlier than untreated check plots. However, a significant chemical by tillage interaction occurred in 1987 because Pix did not improve lint yields of no-tillage cotton grown in rows 102 cm apart. No interactions were detected in 1988 data. Highest yields were obtained from plots receiving 25 gms ai/ha Pix, but plots receiving 50 gms ai/ha matured earlier in 1988.

Plots treated with Prep were earlier maturing as expected, Prep treated plots yielded slightly more lint than plots receiving a standard defoliation treatment.

Conventionally-planted cotton was 9.2 cm taller than cotton no-tilled into stubble. Stoneville 825 grown in rows 76 cm apart averaged 5.1 cm taller than when grown in rows 102 cm apart. Lint quality differences were small and inconsistent in these experiments.