Effect of Weather Conditions on Cotton Growth

Several questions have come in this week regarding the effect of cold weather and moisture on cotton growth.  Cotton is sensitive to cold temperatures as well as excessive soil moisture.  Generally speaking, having one of these situations is made worse by having the other as well.  In other words, cold temperatures are problematic; however, problems usually worsen when cold temperatures occur in conjunction with excessive soil moisture.  This is most true for cotton that has just been planted.  Cotton seed that imbibes cold water during the hours after planting is most likely to incur damage.  Cotton seeds that have germinated and are subjected to temperatures of 50°F can suffer from root abortion and/or death.  Cotton that was planted prior to or during cold temperatures that occurred early this week has been slow to germinate and develop.

Rainfall received late last week was needed in many areas; however, excessive moisture can lead to problems.  Heavy rainfall can result in soil crusting as well as increased damage from seedling disease (as above, this situation is compounded by the occurrence of low temperature).  As a result, rotary hoes have been running in some fields where crusting is an issue.  If a given field became waterlogged following excessive rainfall, problems can occur depending on the length of time soil remained waterlogged.  Fields that remained waterlogged for 24 to 36 hours may have increased incidence of seedling death.  Saturated conditions prevent oxygen from reaching cotton roots which can ultimately result in seedling death.  Roots generally become discolored which is accompanied by a reduction or stoppage of growth.

Cotton does not grow when temperatures fall below 60°F.  A large portion of our cotton crop was planted last weed and as a result, cotton in many fields has emerged but has been very slow to develop.  Compounding this problem is the level of thrips that many are experiencing.  Dr. Angus Catchot has provided a post in regard to this situation on this blog. 

Cotton that has been impacted by environmental conditions has left some weighing replant options.  As we all know, the decision to replant can be one of the most difficult decisions to make, especially considering the calendar date.  Factors to consider when making replant decisions are stand uniformity and health of existing stand.  Generally speaking, cotton planted after May 15^th will not yield as well as cotton planted prior to that date.  This is a general rule based on past research; however, given the weather conditions so far this year, that date may not apply.  As indicated above, some cotton has struggled due to environmental conditions.  If you have a uniform population that appears to be healthy you have no major cause for concern as of now.  However, if you have stands that have frequent skips larger than 2 – 3 feet, yield reductions will likely occur.  Research has indicated that uniform stands in the 15,000 – 20,000 plant per acre range can provide optimum yields.  If you have recently planted seedlings that are unhealthy, not growing properly, and may ultimately result in poor stands, replanting may be the best option.  Cotton re-planted during optimum conditions will likely germinate and develop quicker than cotton suffering from non-uniform stands, damaged root systems, etc.