January 2009
Summaries of Presentations Given
at the 2008 Cotton Field Day
Fertilizer Alternatives
Dr. Carl Crozier, Soil Science, Vernon James Research and Extension Center
Carl Crozier
With the cost of conventional fertilizers rising with petroleum costs, cotton growers are among those looking for cheaper alternatives that can deliver the same nutrient benefits to their crops.
Carl Crozier is exploring the use of poultry litter and composted poultry manure as possible nutrient alternatives. At the Upper Coastal Plain Research Station, he is engaged in a 3-year study to explore the impact of different poultry waste options in both conventional and no-till cotton production. The types of waste used include fresh manure from layer operations, composted layer manure and broiler litter (which include both manure and organic matter such as wood shavings). In addition to examining the nitrogen and phosphorus soil content with these amendments, Crozier is also exploring crop yields, nutrient uptake by cotton plants and soil nutrient stratification. Crozier says it is important for growers to understand that they must have any fertilizer alternative tested for nutrient content in order to properly apply it to fields. In the first year, results have shown that broiler litter and composted layer manure can be economical alternatives to the use of inorganic fertilizers in cotton.
Soil Compaction
Dr. Alan Meijer, Soil Science
Alan Meijer
Any grower knows that running equipment through a field can compact soil where crops grow. Alan Meijer has used GPS monitors attached to field equipment to show that 65-85 percent of the land area in a cotton field will experience at least one equipment pass during a production season. This is significant, considering that up to 90 percent of soil compaction occurs during the first equipment pass. Soil compaction varies depending on soil type, and clay soil layers are most prone to compaction, Meijer says. His research has show that plant roots growing into compacted soil will be more stunted that roots growing in soil that is not compacted. In addition, water flows into compacted soils much more slowly than into non-compacted soils, a factor that can be significant during drought, when limited rainwater is more likely to run off in compacted soils. Meijer advises growers to limit equipment traffic to a limited set of field rows.
Variety Tests
Dr. Daryl Bowman, Crop Science
Daryl Bowman
Bowman conducts official variety tests in cotton at five research stations. Based on information gathered at these locations, he reports on the earliness or lateness of maturity and yield. In addition, Bowman reports on factors like variety storm hardiness. Such information helps growers determine which varieties are the best value for their planting needs. Due to the phasing out of Bollgard cottons to Widestrike and Bollgard II cottons, the mix of varieties in the OVT has changed dramatically. This is the biggest change since the advent of Roundup Ready and Bollgard cottons and will require growers to start choosing new varieties that may have very little data. It is critical that they look at unbiased data like the information published in the OVT books.
At-Bloom Fungicides
Dr. Steve Koenning, Plant Pathology
Steve Koenning
Some years back, Florida researchers reported that five applications of fungicides to cotton resulted in higher yields. Steve Koenning is among the researchers who have tried to duplicate those study results. The tests of fungicide sprays were done at first bloom, full bloom and two weeks past bloom. Though he has not determined if there are yield differences, Koenning has seen that there are no disease differences in cotton plots receiving up to five fungicide applications. Part of the reason, he believes, is that North Carolina sees little foliar disease in cotton to begin with. Current problems with leaf spot are largely a result of three factors: potassium deficiency as a result of low soil moisture, sun scald and early or normal cut-out.
Insect Management
Dr. Jack Bacheler, Entomology
Jack Bacheler
Thrips and stink bugs remain two of the biggest insect problems facing North Carolina Bt cotton growers. Thrips are tiny insects that are difficult to count and identify, but they cause tremendous damage to cotton seedlings, especially crops planted in mid- to late-April. Jack Bacheler recommends that growers plant cotton in the window of May 5-12 when possible to minimize thrips damage as a result of better grow-off conditions. Stink bugs remain another mid- to late-season problem in North Carolina, though their abundance and damage to bolls varies from year to year and from field to field. The stink bugs, it appears, do not cause as much boll damage per boll as bollworms, but significant yield and quality losses can result from these pests. Tests have shown that the optimal timing for spraying to reduce stink bug damage is during weeks 3 to 5 or 6 of the bloom period, and routine scouting of quarter-sized bolls and the use of the new “dynamic” thresholds best defines the precise time when applications, if any, are needed.
Weed Management
Dr. Alan York, Crop Science
Alan York
Roundup Ready cotton fields have been hit by a number of glyphosate-resistant weeds in recent years, including a resistant horseweed and Palmer amaranth, a pigweed species. Horseweed seeds have been found at altitudes far from the ground, so seeds can travel a great distance by air. With easy dispersal, once the resistant biotype is present, growers can expect the problem to continue to increase. York suggests that growers assume all horseweed present is glyphosate-resistant and plan burn-down programs accordingly. To control glyphosate-resistant horseweed, he recommends Clarity plus Valor plus glyphosate or 2,4-D plus Valor plus glyphosate. Palmer amaranth is a very aggressive weed that produces lots of seeds and can quickly become the dominant weed in a field. Once glyphosate resistance is selected for, the weed is nearly impossible to control post-emergence with currently available products. Growers must depend upon aggressive pre-emergent treatments, which can be expensive. York emphasizes that “salvage control” is not an option. York doesn’t see many new herbicide options on the horizon, but he said cotton with multiple herbicide resistance traits is in active development, which will offer additional tools to deal with problem weeds.
Defoliation
Dr. Keith Edmisten and Guy Collins
Keith Edmisten
Defoliation is the final step in preparation for harvest. Edmisten and Collins recommend that growers not defoliate too early, to prevent damage to bolls and foliage regrowth prior to harvest. Growers should look for at least four nodes above the crack (or open) boll before harvesting. In 2008, Edmisten reported seeing greater regrowth on plants than in previous years.
Seth Hall
Petiole testing for nitrogen and potassium
NC State senior Seth Hall reported on how to use petiole testing to establish data. Hall instructed growers to find the tallest plant in a row or plot, remove the petiole from the leaf and send it North Carolina Department of Agriculture and Consumer Services test labs. Though leaf tests show nutrient uptake for 10-14 days, petiole tests show growers exactly what is happening on the day of sampling.
- Natalie Hampton
