Both by the calendar and what I am seeing in the field, cotton harvest aid considerations are coming to the forefront in another year. Harvest aid decisions truly do seem more art than science with so many variables affecting product performance and application timing. This time of year everyone in the industry pays extra attention to the weather forecasts and keeps an eye toward the cotton stage as we strive to take as much of the guess work out of harvest aids as we possibly can. Producers certainly do not want to miscarry a crop this late in the game. Consultants and advisors must be on their toes. Applying harvest aids too early can cause yield reduction, be harmful to fiber quality, and will damage seed weight and quality while applying too late exposes the precious fiber to the elements which can cause fiber degradation, and lint string and outright drop.
With that in mind, the 2013 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide is now available through http://lubbock.tamu.edu/. The Harvest-Aid Guide is stuffed with useful information updated annually for the purpose of helping producers and specialists make educated harvest aid decisions. Of particular interest to me are the latest Cotton Harvest-Aid Decision Tables. These tables contain the current list of locally tested and labeled harvest aid products complete with recommended rate ranges and surfactants. For a full overview of all cotton harvest- aid considerations, please reference the 2013 guide. There can seem to be endless factors effecting harvest aid decisions. Here, I would like to review the three main FIELD MEASURABLE factors influencing the basic ‘field ready’, or ‘field not yet’ question in cotton harvest-aid decisions.
If there is one factor that can be (or for some odd reason must be) used alone I would suggest evaluating the uppermost harvestable boll’s maturity. I prefer to utilize the old standard boll maturity rating system of 1 through 3. To evaluate the maturity of a cotton boll, use a sharp knife to cut into the boll somewhere between the upper half and upper third. If the boll is watery or jelly-like on the inside, then it is immature and needs more heat units. This boll can be rated as a maturity 1. If limited or no additional heat units are available from the environment, that boll can likely be considered as not harvestable, and another boll farther down the plant needs to be evaluated. If boll development is such that the knife cannot slice through the lint easily, then the boll is nearly mature. Close inspection of the seed will give further indication of boll maturity. If the seed coat is turning tan and the seed leaves (or cotyledons) are fully developed, the boll is nearing maturity. This boll could be rated as a maturity 3. In between these two ratings is a maturity 2. Fields that have an average boll maturity rating of 2.4 can be considered ready for harvest aids. We need only evaluate enough bolls to be confident in the average rating for that field that day.
A second factor is the NACB (nodes above cracked boll) stage of the field. For those who are accustomed to making in season NAWF (nodes above white flower) evaluations, this evaluation is very similar with one difference. In place of counting nodes from white flower to uppermost unfurled leaf, we count from uppermost cracked open boll to uppermost harvestable boll. When the cotton field averages 4 NACB, the field is likely ready for harvest aids.
The third factor is percent open boll. This is likely the easiest factor to understand, but requires the most effort to obtain. I prefer to measure 10 row feet from several locations within the field, counting the number of open bolls over the total number of bolls within all 10 foot areas to obtain an accurate percent open boll count for the field (percent open boll = # open bolls / # total bolls). Once a field reaches 60% open boll, then it can be considered ready for all harvest aids, except for pure desiccants which requires a 90% open boll count and is only really utilized in dry-land situations. Taking the percent open boll counts does take more effort but once we have taken the 10 row feet counts, other useful knowledge can be gleamed from the information such as yield estimates and field variability.
Ideally we should utilize and combine all three of these field measurable factors to help put as much science into our harvest aid art as possible. This data, gathered correctly, should then be considered along with many, many other factors, such as expected two week temperature, available sunshine, night time temperature, leaf drop, plant moisture content, expected freeze date,… just to name a few .
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