Cotton Re-Plant Decisions – Plant Populations

Several calls have come in this week regarding cotton re-plants.  Making a call on re-plants is one of the most difficult aspects of crop production.  However, several things should be considered when assessing a potential re-plant situation.  The number of healthy plants in the field should be considered first and foremost.  Based on research conducted by graduate students in my program at Mississippi State University, plant stands as low as 15,000 plants per acre will make acceptable cotton yields.  Keep in mind that this is assuming that all remaining plants are evenly spaced.  If a large number of 2-3 foot gaps exist in the plant stand, yield reductions will likely occur.  Below are the results from our work demonstrating the effect of plant population on cotton yield.

The calender date should also be given strong consideration when making re-plant decisions.  Given that today in May 16, we are already on the backside of what is considered the optimum time to plant cotton.  Although weather conditions during the fall in the past several years have been favorable, there is no guarantee that will be the case this year.  If you do decide to re-plant, you should consider planting a variety with the earliest maturity possible that has the potential to produce acceptable yields.  The 2014 Cotton Maturity Guide can be accessed using the link below if you have questions regarding maturity of a given variety.

2014 Cotton Maturity Guide

If re-plants are made over the next 2-3 weeks, it would be wise to manage for earliness.  Choosing an early maturing variety as mentioned above will be the first step in this process.  Other factors to consider include nitrogen application rates, plant growth regulator applications, and insect management.  If you have historically applied nitrogen at 120 lbs/ac on silt loam soils, consider scaling this rate back to 80 – 100 lbs/ac.  Excess nitrogen will promote a rank crop and delayed maturity.  The effect of plant growth regulators on earliness has been debated in scientific literature.  However, a shorter, more compact plant will be easier to defoliate and will allow for greater penetration of insecticides and herbicides.  Insects should be intensively managed in late planted cotton.  While cotton has a tremendous ability to compensate for early season fruit loss by setting fruit on upper and outer fruiting positions, these upper and outer fruiting positions are not a 1:1 replacement for lower and more inner fruit.  In addition, if we have an early fall, the plant may not have time to add fruit at upper at outer fruiting positions.

As a general rule, if you are agonizing over the decision to re-plant or not, I would be more apt to keep your existing crop.  This will become more and more true as we progress deeper into May.  If you have a healthy stand of 1 plant per foot of row, I would suggest keeping the crop as opposed to re-planting.  If populations are at or near the 1 plant per foot mark, you will need to take all available precautions to maintain your stand and protect those plants and the fruit they produce.