What is An Acceptable Final Plant Population in Cotton?

This planting season has been challenging for a number of reasons.  Cool, wet weather in early May gave way to very dry weather for several weeks thereafter in many areas of the state.  Emergence problems have been observed in several areas and has many asking what is an acceptable plant population in cotton?  There are several things that should be considered when determining what is acceptable in terms of final plant populations.  Research conducted at Mississippi State suggests that a minimum of 15,000 plants per acre is needed to maintain yield potential.  However, there are several things to consider when determining your final plant population.  First and foremost, you must determine the number of live, healthy plants you have in a given field.  When you are determining how many plants you have, make a mental (or otherwise) note of how many 2-3 foot skips are present in the area you are examining.  If you have a solid stand of cotton for several feet and then large gaps but the plant population averages out to 15,000 or greater plants per acre for the area you are in, you will likely see yield reductions.  If the field you are examining has a minimum of 15,000 healthy plants per are and minimal 2-3 foot skips, you still have good yield potential (see graph below highlighting data generated at Mississippi State).

Several management decisions should be considered if you are dealing with a field with low plant populations.  I would protect fruit that forms on the remaining plants to the greatest extent possible.  Given that you have less plants per acre, it will become necessary to maximize production of the remaining plants in order to maintain your yield goals.  I would not change my nitrogen application rate.  The seeds in cotton bolls are the primary sink for nitrogen in the cotton plant, if your yield goal has not changed then your nitrogen application rate should not change.  Let the plant dictate your plant growth regulator application strategy.  In areas with low plant populations, cotton will fill in these gaps (if they are less than 2-3 feet).  This outward growth may somewhat limit vertical growth compared to what you may see in fields with normal plant populations.  However, if you see internode length (check internode length between the fourth and fifth node down from the top of the plant) exceeding 2.5″, a PGR application is needed.  Keep in mind that not all varieties and fields are created equal.  If you have an aggressive variety and very good growing conditions, a heavier application rate is needed compared to a passive variety growing under more challenging conditions.

While no one likes to see poor emergence and low plant populations, cotton is very resilient and can withstand low populations and still make a tremendous crop.  Given that we are into the first week of June, re-planting at this point is not feasible.  If you have plants that are relatively evenly spaced and have a minimum of 15,000 plants per acre, manage your crop for maximum yield as you would in a normal plant population scenario.