Agronomics of Cotton Grown on a 38-cm Row Spacing in North Carolina

Abstract

Abstract HAMM, GARY STEPHEN. Agronomics of Cotton Grown on a 38-cm Row Spacing in North Carolina (Under the direction of Dr. Keith Edmisten).

Cotton (Gossypium hirsutum) planted in a 38-cm row configuration is an innovative idea that has come about in the past few years. There has been some interest in narrow-row cotton due to the availability of a new harvester capable of harvesting cotton on 38-cm rows. Producers have raised questions regarding changing their cotton production strategies in order to maximize yield potential for cotton grown on 38-cm rows. Agronomic practices that allow for maximum yield potential have yet to be determined for narrow-row cotton. Four separate field experiments were conducted in 2005, 2006 and 2007 at Upper Coastal Plains Research Station, near Rocky Mount, NC, Central Crops Research Station, Clayton, NC, and Duplin County, NC in order to define these agronomic practices. Cotton was planted on 38-cm row spacings using a vacuum planter. One experiment was conducted to observe the effects of seven nitrogen rates ranging from 0-196 kg N ha-1 on yield potential, plant uptake of nitrogen, growth habits, fiber quality, and economic returns of narrow-row cotton. The second experiment was conducted to look at the effects of fourteen different application methods on plant height control, yield, and fiber quality. The strategies consisted of making applications to narrow-row cotton at certain growth stages with different rates of mepiquat pentaborate. The third experiment consisted of making a herbicidal defoliation application to narrow-cotton at six different percent open boll stages ranging from 0-100 % open bolls to determine yield and fiber quality parameters. The fourth experiment was conducted to determine if narrow-row cotton could be planted in a double crop situation with wheat which is an uncommon practice in NC. For this experiment, narrow-row cotton was planted in comparison with wide-row cotton for yield and economic potential at five different planting dates ranging from May to July. The last two planting dates ranging from mid June to July were conducted so that cotton could be planted in harvested wheat stubble for economic evaluation of wheat yield plus cotton yield for profit potential. The nitrogen experiment determined that yields and economic returns declined at nitrogen rates higher than 67 kg N ha-1 although plant uptake of nitrogen rose as nitrogen rate was increased. There were negative affects observed in plant height and node numbers from increases in nitrogen rate. The second experiment determined that plant growth regulators being applied at the 8-leaf stage, regardless rate or application strategy, gave the most adequate height control of all methods. There were no benefits seen with applications being made earlier than the 6-leaf stage. Yield data suggested that current recommendations for plant growth regulators can be used for 38-cm cotton along with earlier application timings without affecting yields. The defoliation study showed that as defoliation was delayed until later timings there was a trend for increase in yields. Data suggested that prolonging defoliation yielded less than desirable fiber quality. Defoliation efficacy improved as timings were delayed. Yield data from the double crop study suggested as planting date was delayed yield declines were observed in both wide and narrow-rows. Data also suggested that optimal yields can be obtained from 38-cm row cotton in a double crop situation with wheat in NC if a late frost occurs. Growing cotton in a double crop situation in areas with longer growing seasons would be economical and be viable in replacing soybeans as a double cropping option. Cotton grown on a 38-cm row pattern showed higher yields and returns than cotton grown on 96-cm row pattern making it a better option in a double crop situation.