Timely Cotton Harvest

  • Delaying harvest to wait for the last few bolls to open can compromise the potential yield of a cotton crop.
     
     
  • Harvest delays can subject a cotton crop to weather-related quality issues.
     
     
  • Timely harvest aid applications and harvest can help maximize the potential for cotton yield, fiber quality, and overall net return.
     
     
  • Implementing practices to keep moisture away from the cotton after harvest can help maintain fiber quality until it is delivered to the gin.
     

  
Figure 1. A timely cotton harvest aid application can help maximize cotton yield potential and fiber quality.

Harvest Aid Application Decisions

Deciding when to make harvest aid applications can be difficult. Without implementing practices to protect quality and yield losses from poor weather conditions, the value of the crop can be quickly reduced. Timely harvest aid applications can promote an earlier harvest and help preserve fiber quality. Any delays in harvest, even with timely harvest aid applications, can have an adverse effect on both the yield and quality of lint.1

Applying Harvest Aids

Cotton leaves naturally defoliate at physiological maturity. Defoliation may also occur if cotton plants are stressed by disease, nutrient deficiency, drought, or frost. Chemical defoliants are used as a cotton harvest aid to help accomplish the following:
 
 
 
  • Cotton leaf removal.
     
  • Lint quality improvement by minimizing lint staining and trash quantity.
     
  • Reduced the incidence of boll rot.
     
  • Increase harvest speed and efficiency.
     
  • Earlier harvest timing within the day and during the season.
     

Type of Defoliant

There are two types of defoliants available to use as harvest aids. The first type has herbicidal activity, which works by causing injury to the plants, resulting in the production of ethylene. Ethylene production triggers leaves to drop. If the herbicidal defoliant is applied at rates too high, the leaves may die too quickly, bypassing ethylene production and causing the leaves to remain on the plant (leaf stick).The second type of defoliant has hormonal activity, which promotes ethylene production in the plant, leading to leaf drop. Hormonal defoliants can be less susceptible to leaf stick than herbicidal defoliants.2

Application Timing

It is important to carefully time defoliant applications to achieve the highest yield potential and quality because once a cotton crop has been defoliated, little to no boll maturation occurs. There are several methods that can be used to determine application timing. Traditionally, the firmness of the bolls (uppermost harvestable boll is difficult to cut with a knife), the color of seed coats (thin, brown), and the percent of open bolls (50-60%) in the field can help determine when to apply a defoliant. Growers can also apply defoliants based on plant growth, which can be a more accurate way to determine when to apply. A defoliant application is recommended after an accumulation of 850 heat units (DD60s) after cutout. Additionally, cotton plants are unable to effectively load more bolls after reaching 4 to 5 nodes above white flower (NAWF); therefore, an application after this maturity is recommended. Regardless of the method or combination of methods used, fields should be visually inspected prior to harvest aid application.2,3
 
 
 
 
 
Apply defoliants 10 to 14 days before desired harvest date. An application should occur either early in the morning or late in the afternoon when humidity is the highest and with little to no wind. It is best to stagger defoliation to help manage harvest timing and reduce potential yield and quality loss from defoliated cotton weathering in the field. Four days after application, leaves should begin to drop and complete defoliation should occur around ten days post application.2

Crop condition.

Drought-stressed cotton may have thick leaf cuticles which can reduce the efficacy of harvest aids, and the addition of a surfactant may be necessary. Cotton that has rank growth can require two defoliant applications due to the thick canopy preventing complete coverage. Increasing the application rate is not effective because a higher rate is just as unable to penetrate the canopy as a normal rate.2  Selecting flat-fan or hollow-cone nozzles coupled with a carrier volume of 15 gallons per acre can help maximize canopy coverage.3

Weather During Harvest

Harvest aids work best when average temperatures remain above 60° F. Lower temperatures can slow leaf drop and boll opening. Fall harvest aid applications made in the cooler temperatures of late fall can reduce the defoliant efficacy and increase the potential for quality losses due to cool, wet, late-season weather. Delays in defoliation can push back harvest dates and result in significant yield and quality reductions from delayed harvest timing. Fiber length, strength, and color can be affected, resulting in lower lint loan values and net returns per acre. Timely harvest also allows more time for cotton plant residue/stalk destruction. Plant decomposition is an essential part of insect and disease management.

Post Harvest Storage

After harvest, the seed cotton must be protected from the elements until it is ginned. To help protect cotton during storage, cover rectangular modules with a high-quality tarp. Tarps should be checked for any tears or pin holes before use. Round bales should be wrapped with plastic that covers the cotton that is most exposed to the weather (Figure 2). A later harvest may result in excess moisture content that can cause condensation; therefore, modules and bales should be monitored.When elevated moisture content levels occur, temperatures can increase within the module potentially reducing lint grade and seed germination. Extreme cases may result in spontaneous combustion. Ideally, cotton harvested at correct moisture content levels should only increase 10 to 15° F in the first 5 to 7 days of module storage, then level off or decrease in temperature. A 15 to 20° F temperature increase during the first 5 to 7 days indicates a high moisture content problem and the module should be ginned as soon as possible.3 After the initial daily temperature check, modules should continue to be checked every 3 to 4 days. If at any time during storage a module reaches a temperature of 120° F, the cotton should be ginned immediately.

Cotton Picker Fire Safety Tips

Cotton pickers are very large, complex, and expensive pieces of equipment. Heat from the unit combined with dry debris and lint can easily cause a fire within the unit and in the field. These simple tips can prevent or help in the event of a fire:

  • Do not park an idling picker with the exhaust facing a module or bale 
     
  • Be sure the area behind the cab, near the transmission, kept free of debris. High temperatures can easily cause a fire to ignite.
     
  • Keep two functional ABC fire extinguishers available, one in the cotton picker cab and one within reach from the ground.
     
  • Never enter a basket or chamber if a fire is suspected.
     
  • Always keep a cell phone or farm radio nearby to alert others in a fire occurs.
     
 

  
Figure 2. Round cotton bales protect the areas of the bale most exposed to weather.
 

 
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