Experiments were conducted in 2004 and 2005 at the West Florida Research and Education Center near Jay, FL to determine the feasibility of twin-row cotton production. Deltapine 555 Bollguard/Roundup Ready was planted in a twin-row (19 cm apart) and single-row planting pattern spaced 76 cm apart with a final plant populations of 1, 2, and 4 plants foot-1. Three herbicide application timings (1, 2, and 3 applications) were investigated with the following treatments: 1) glyphosate (1 kg ha-1) plus S-metolachlor (1.12 kg ha-1) postemergence over-the-top (POT) to 4-leaf cotton; 2) 4-leaf POT followed by glyphosate (1 kg ha-1) early postemergence-directed (EPDS) to 6 to 8-leaf cotton; 3) 4-leaf POT followed by 6 to 8-leaf EPDS followed by MSMA (2.24 kg ha-1) plus prometryn (1.34 kg ha-1) late postemergence-directed (LPDS). Visual weed control ratings recorded 20 weeks after planting (WAP), photosynthetically active radiation (PAR) 8 and 10 WAP, date of canopy closure, and seed cotton yield are presented. Data indicates that at least two herbicide applications are needed for greater than 90% control of sicklepod, yellow nutsedge, smallflower morningglory, and tropical spiderwort regardless of planting pattern and plant population. Furthermore, twin-row planting pattern captured more PAR than single-row cotton 8 WAP, however this advantage was overcome 10 WAP by increased plant populations. No differences in seed cotton yield was observed between twin and single-row cotton planting pattern, indicating that cotton can be planted in twin-rows without a detrimental effect on yield.
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