Date of Award

5-1994

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Department of Agronomy

First Advisor

Charles Kennedy

Abstract

Mepiquat chloride, a plant growth regulator used in cotton (Gossvpium hirsutum L.) production, controls vegetative growth and improves boil set on lower fruiting branches. This response could either enhance or reduce problems associated with early square loss. The objective of this study was to determine the relationship between early square loss and mepiquat chloride on vegetative and reproductive growth of cotton. The cultivar, Deltapine 50, was planted at tvjo locations in 1992. Three levels of square removal (SR) (0%, 20%, or 40% of all squares 10-14 days after pin head square) and three rates of Mepiquat chloride (MC) {0, 4 applications of 12.25 g/ha a.i. weekly at match head square (4-12.25), and 2 applications of 24.5 g/ha a.i. biweekly at early bloom (2-24.5)) were arranged factorially in a RGB. Mepiquat chloride reduced plant height, while the 40% SR increased plant height at both locations. A significant (P<0.1) MC by SR interaction occurred for lint yield. Averaged across locations, the 4-12.25 rate of MC after 20% SR increased yield by 100 kg/ha compared to that rate at 0% SR. With the 2- 24.5 rate yields with 40% SR were 100 kg/ha more than no MC after 40% SR. Productivity of second node positions on lower fruiting branches tended to increase with increasing SR combined with increasing MC application as did the productivity of fruiting positions that developed later. These responses generally supported yield results. Earliness generally improved with MC, but not significantly. Micronaire was reduced below the premium range with the 4-12.25 MC applications but only at one location. The results of this study indicated that MC could contribute in improving yield potential after early season square loss, but the interaction between MC and SR and varying environmental conditions could complicate accurate recommendations.

Download

Share

COinS