Management of Ultra Narrow Row Cotton
Type of DegreeDissertation
Agronomy and Soils
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Ultra Narrow Row cotton (Gossypium hirsutum L.) production systems may have the potential to increase lint yields, decrease risks to losses from water stress, and allow the use of conservation systems which could contribute to long-term soil productivity. Recent technological developments have improved the feasibility of production of Ultra Narrow Row (UNR) cotton, defined as cotton grown with row spacing of 25-cm or less, but management techniques are poorly defined. We conducted three coordinated field research trials in central and south Alabama from 1998 through 2001 to investigate planting dates and plant populations for UNR (20-cm) cotton, methods to control plant height for efficient harvesting, and cropping systems that utilize cover crops and conservation tillage with UNR cotton production. In the first experiment, planting dates of May, June and July, were tested with 198 000, 296 000, 395 000, and 494 000 plants ha-1. May plantings generally yielded > June > July, although with a dry spring June yielded > July > May. Yields from May plantings tended to increase with plant populations below 494 000 plants ha-1, while June planted yields tended to decrease with increasing populations, with little effect in July. In the second trial, mepiquat chloride (MC) growth regulator was applied to UNR cotton using seven decision methods, either preplanned (0, 0.0493 or 0.0984 kg a.i. ha-1 total) or in response to plant growth (2.5- and 5.1-cm internode length, Pix STIK, or Deltapine Cotton Growth Regulator Guide [Deltapine CGRG]). Height was adequately controlled (less than 81-cm) by all decision methods recommending > 0.0493 kg a.i. ha-1 of MC, in the one year (1999) with excessive height. The 5.1-cm internode method resulted in the best combination of plant height control while minimizing MC applications. Lint yields were increased in only one year with MC application. In the third trial, legumes (white lupin [Lupinus albus L.] + crimson clover [Trifolium incarnatum L.]) were compared to rye (Secale cereale L.) as a cover crop for UNR and wide rows, with no-till and conventional tillage systems on a drought prone soil. Conventional tillage systems yielded greater than no-till in two of three years, on this drought prone soil. Cover crop type had little effect on yield where adequate plant stands were obtained. UNR cotton yielded over 50% more than wide rows in one year, over 15% more in another year, and the same in another, with never a relative yield decrease. These results indicate that UNR cotton production could be a more profitable system for cotton producers in the southeast United States.