Grain harvest has continued to string out, just as planting did, and many cotton growers have started to focus attention on the 2015 cotton harvest as well. In preparation for cotton harvest, the proper application of harvest aids is critical to help facilitate an efficient and timely harvest and to preserve fiber quality. Cotton being a perennial shrub, being grown as an annual crop will continue to grow as long as conditions are favorable. This is why harvest aids are needed to prepare the crop.
As the cotton plant reaches “cut-out”, the energy demand of the fruit exceeds that produced by the leaves of the plant. At this point, the growth of new leaves is temporarily halted. Once bolls mature and open, however, cotton plants may begin to resume vegetative growth, especially with additional rainfall and excessive soil nitrogen. Any vegetative regrowth before harvest can lead to significant problems due trash in the harvested cotton, lint staining and decreased color in picker-harvested cotton, and high moisture content.
Dr. Josh McGinty, Extension Agronomist in Corpus Christi and Dr. Gaylon Morgan, Extension Cotton Specialist, College Station recently released a few suggestions for consideration before applying harvest aids in the Texas row Crop Newsletter. What follows are a few of the key points growers should give thought to.
The proper timing of harvest aid applications can be thought of as a balance between allowing immature bolls to mature and preserving the lint quality of earlier maturing bolls. Applying harvest aids too soon may halt the development of green bolls that could contribute to yield, and may negatively affect fiber and seed quality. A few methods for determining the optimal timing for harvest aid applications include percent open boll, the sharp knife technique, and nodes above cracked boll.
Percent open boll is the most common method outlined on harvest aid product labels. This is simply the percentage of harvestable bolls on the plant that are open. Typically, product labels will recommend applications at 50 to 70% open boll. However, this is not the most accurate method as research has shown that optimal application timings may range from 42 to 81% open boll, depending on distribution of fruit on the plant.
The sharp knife technique is a determination of boll maturity that is made by cutting a cross section of the uppermost harvestable boll. A mature boll will be difficult to cut and will contain seed with dark seed coats and fully developed cotyledons. Very light colored seed coats and the presence of “jelly” inside the seed indicate an immature boll.
Nodes abovecracked boll (NACB) can also be used to time applications. From the uppermost first position cracked boll, count the main stem nodes from there up to the uppermost harvestable boll. Sufficient research has shown that harvest aids applied at three NACB will not result in any lint weight loss. If harvest aids are applied at NACB greater than four, yield loss can be expected.
The efficacy of harvest aid products is greatly affected by environmental conditions. In general, the most effective harvest aid applications are made under warm, sunny conditions, with low soil moisture (but sufficient to maintain active growth), without excessive soil nitrogen, to plants that have reached maturity and are not producing new leaves. Thorough spray coverage is critical when applying harvest aids. Choose a spray nozzle that will provide uniform coverage and small spray droplets. Total spray volume should be at least 15 GPA for ground applications and 5 GPA when aerially applied.
There are several good publications to help cotton growers make harvest aid decisions, such as the “High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide” which can be found at http://goo.gl/Yv9Tre. Because the efficacy of harvest aid products is greatly affected by environmental conditions, working with Claude Otahal Farm we will have several harvest aid treatments applied that growers can compare to one another. For more information please contact 361.767.5223.