Yield Potential And Management Of Late Planted Cotton

DR. TYSON RAPER

 JACKSON, TENNESSEE

In almost every cotton-related conversation I had during early May, the conversation quickly turned to our excellent early planting window- a window which opened earlier in 2024 than any of recent memory.  Since then, most have fought to find an opportunity to mud in any acres and many are now considering shifting some farms to soybeans.  In this blog, I attempt to cover yield potential of a late planted cotton crop and highlight several very important factors to consider when planting cotton at the end of our ‘normal’ planting window.

 Yield potential of late May/June cotton

 We have a narrow window this week before rain again pushes us out.  It is likely that a good portion of our acres will be plantedafter the 25^th of May- given next week finally breaks dry.  As we move later in the planting window, yield potentialtypically declines.  Dr. Shawn Butler and I generated a very large dataset evaluating planting date and population from many locations within Tennessee and several locations in both Missouri and Mississippi.  I still think this data is valuable, so I’ve included the response curve we generated below.  Keep in mind this data was generated with DP 1522 B2XF.  As you can see in the below figure, we captured approximately a 20% yield reduction when we delayed planting by 30 days, from early May to early June.  However, this was generated with DP 1522 B2XF several years ago- which brings me to my next point.

 Since 2022, Dr. Scott Stewart, the Director of the West Tennessee Research and Education Center, has allowed me to plant two locations of the Tennessee Official Cotton Variety Trial annually- one planted as close to the first of May as possible, and another planted as close to the first of June as possible.  Planting dates and average yields from those trials are included below.  From this table, you can clearly see a reduction in yield associated with a 30-day delay in planting, but you should also note that we are still averaging 90+% of the yield potential of May 1st cotton with a June 1st planting date.

This data is a little more favorable than the approximately 80% yield potential Dr. Butler noted with the single variety of DP 1522 B2XF.    More importantly, however- recall that the image above- freeze hit the area in early October of 2022 but we only observed an 8% reduction in yield associated with a June planting date!  So how do we make the best of a late planted crop?

 Managing late planted cotton

 Although management of the cotton planted May 20^th to the 25^th isn’t terribly different than cotton planted the 10^th through the 15^th, by the time we get to the 30^th through the 35^th of May, several management tactics should change.

 Plant population

 Properly select a target plant population.   I understand that no one wants to replant cotton which was initially planted on the 30^th of May, but dropping over 45,000 seeds per acre in late May will cost you from a maturity standpoint!  Thick stands result in plant-to-plant competition, which will result in etoliation (elongation of internodes to help compete for light), increased vegetative growth to attempt to ‘shade out’ the neighbor, and finally positioning of the first fruiting branch higher up the plant- later in the year.  Targeting 3 seed per foot on 38” rows (40,000 seed per acre) should result in approximately 2.75 plants per row foot which will be great middle ground- not too many plants to generate the plant-to-plant competition, but not too few as to delay maturity.

 Variety Selection

 Check our 2023 Tennessee Cotton Variety Trial Results for the late planted versus early planted Jackson locations.  The summary tables for these two locations are on pages 11 and 12.  Several of the highest yielding varieties in the early planted location were also the highest yielding varieties in the late planted location- those varieties would be great choices, as they have the yield potential to perform in a fuller season but will also deliver should heat units run short.  Many of the varieties you likely have in the shop are at the top of this list.

 Fertility

 Properly select nitrogen rate.  I have had several conversations lately with individuals considering a delayed application of N (all applied around first square) and/or a reduction in total N applied (target application rate of 60 lb N).  BOTH of these N management tactics are excellent for late planted cotton! A late planted cotton crop will mature more quickly if we delay the application until closer to when the plant needs it and limit the total amount of N that is applied.  Recall that as managers, we should be constantly considering the vegetative versus reproductive growth of the plant.  By selecting lower N rates and not applying N early in the plant’s life cycle, we are encouraging that plant to move into reproductive growth earlier.  In contrast, a plant which receives 120 lb of N at or immediately following planting will respond by growing a large amount of vegetative tissue and delay the development of the first fruiting position to higher up the plant- later in the year.  Again, these are critical management tactics for maximizing earliness!

 Sulfur should not be ignored- we need 8-12 lb- and potassium should be applied based on soil test applications.  Management of these nutrients does not change from a normal to a late planted crop, but I would encourage you to make sure K is available by the time the plant goes into reproductive growth.

 PGR

 I suggest you take a more aggressive approach to managing internode elongation in late planted cotton, as it is a great way to increase light penetration into the canopy and to increase retention of fruit lower in the canopy.  On aggressive varieties, this would mean an ounce per node at the 8-10 node stage, with plans to follow that application up with another ounce per node application within 7-14 days after the first, should internodes continue to elongate at an aggressive rate. Keep in mind many of these factors converge- management of plant growth will be easier if seeding rate and fertility has been properly managed.

 Insect Management

 Late planted cotton typically grows quickly enough to outpace thrips.  Unfortunately, it does often become very attractive to plant bugs and stink bugs later in the year.  We must aggressively manage plant bugs during the early flowering window to make sure we retain first position fruit low on the plant.  Furthermore, I would remain aggressive until the last effective flower has matured past a point in which these pests can do damage- possibly well into August.  This will likely be the only input, in my opinion, where late planted cotton will cost you more than early planted cotton.  However, this is an extremely necessary expense, as a ‘lax’ approach to insect management is typically the single most important differentiating factor between a profitable and unprofitable late planted crop.

 Closing thoughts

 The market and these rains have been tough on Tennessee’s planned cotton acreage and I understand the shift of acres.  I do not know what this year will hold and last year was clearly the best Tennessee cotton year ever.  The May 10th USDA Crop Production report gave an average of 1,250 lb lint per acre average cotton yield for Tennessee.  A look across the river helps put this in perspective- Missouri reported 1,361 lb and Arkansas had 1,295 lb in states which are overwhelmingly irrigated!  Last point- Tennessee’s average state cotton yield from 2015 to 2023 is 1,070 lb lint/acre (see table below).  The last year our average yield fell below 1,000 lb to the acre was 2014, and in that year, yields for the state averaged 878 lb of lint/acre.

DR. TYSON RAPER: University of Tennessee