Field trials were conducted in 1989 at the Tennessee Valley Substation, Belle Mina, AL and Prattville Experiment Field, Prattville, AL to investigate the interaction of row pattern, weed control level, and a plant growth regulator (PGR) on cotton. Row patterns were: solid 30 inch, solid 40 inch, skip 30 inch, and skip 40 inch. A 40 inch skip was used with pairs of 30 inch rows for the skip 30 pattern while a 62 inch skip was used with pairs of 40 inch rows for the skip 40 pattern. Two levels of weed control were used: a low level consisting of Treflan (0.5 lb ai/A) preplant incorporated and Cotoran (1.5 lb ai/A) preemergence, and a high level consisting of Treflan plus Zorial (0.75 lb ai/A) preplant incorporated and Cotoran (2.0 lb ai/A) plus Zorial (0.75 lb ai/A) preemergence. PGR treatments were either Pix (8 fl. oz/A) applied at pinhead square and again at first bloom, or no Pix. All combinations of row pattern, weed control level, and PGR treatment were applied to 4 row plots which were 40 ft. long. Treatments were replicated 3 times. DPL 50 cotton was grown at Belle Mina and DPL 90 at Prattville. Soil fertility, soil pH, and disease and insect control were maintained for optimum cotton production in both trials.

Solid 30 inch rows produced the numerically highest yield at both locations. Averaged over weed control and PGR treatments, seed cotton yields were 2516 lbs. and 2135 lbs. for Belle Mina and Prattville, respectively. Skip 40 inch rows produced the lowest yield with 2057 lbs. and 1730 lbs. for Belle Mina and Prattville, respectively. Yields for solid 40 inch and skip 30 inch patterns were intermediate between solid 30 inch and skip 40 inch patterns at both locations. No differences in yield were detected between weed control levels or PGR treatments when averaged over row patterns.