The capability of controlling plant growth without restricting yield continues to be of interest to plant scientists. Unfortunately, this restriction usually results in the reduction of yield, particularly in the case of indeterminate fruiting crops. A three year study, 1984-86, was initiated to determine how multiple applications of Pix would effect growth, yield, earliness and fiber quality.

McNair 220 and Coker 208 were selected to represent two distinct growth types. The Pix label recommendation of one pint per acre applied at early bloom was compared with multiple applications initiated at pinhead square and early bloom stages. The pinhead square treatment was 0.1 pint for three applications followed by four applications of 0.2 pint. All applications were made at weekly intervals.

There were no significant yield increases with any of the Pix treatments when compared to the untreated check nor was there a significant yield increase with multiple application treatments when compared to the single application at early bloom. The multiple application treatment at early bloom was the most consistent treatment in regards to yield increase. Cotton in all Pix treatments was significantly earlier than the untreated check and there was no difference in earliness between Pix treatments for the years 1984-85. Plant height was significantly reduced by all Pix treatments. There were differences among cultivars and treatments, but there were no cultivar x treatment interactions. Pix treated McNair 220 was shorter than Coker 208. The plots with multiple applications initiated at pinhead square were shorter in height than the plots with multiple applications initiated at early bloom, but were not different from the plots receiving the label recommendation nor was the multiple early bloom treatment different from the label recommendation. There were no consistent trends developed in fiber length, fiber strength, micronaire or boll size due to treatments.

These data indicate that cotton grown under good growing conditions will not show a significant yield response to single or multiple applications of Pix. However, there is a consistent nonsignificant yield response. The reduction in height has shown to reduce boll rot losses. This reduction in plant height could possibly have some positive effects in regards to harvesting efficiency and cotton grades, but these types of measurements were beyond the scope of this study. Cultivars responded similarly to Pix treatments and differences between cultivars are cultivar characteristics and not a result of treatments.