AGRONOMIC UPDATE: September 19, 2025….Harvest fast approaching….

   

Topics:

  • GDU/Weather Update
  • Corn – Soybean condition
  • What to look for heading into harvest….

TEMPERATURES & GDU ACCUMULATION:

As of September 18th, we have accumulated approximately the following for Growing Degree Units in 2025:

Planting Date     GDD’s2025          Average GDD         Departure from average

April 17                  2756                           2621                              +135 (+8 days)

April 24                 2704                           2575                              +129 (+8 days)

May 1                     2658                           2528                              +130 (+8 days)

Corn – Soybean Conditions…

  • From the above numbers, we see that GDU accumulation has gained a few days since the last update on the 9th. We are at now reaching GDU numbers that get us close to black layer.  The early and mid-maturity hybrids planted in April are basically at black layer, with the fuller season hybrids at 7/8 milk line or beginning black layer, which is matching the GDU numbers above.  The end-of-April and first-part-of-May planting dates still need some time yet, as they are 2/3-3/4 milk line, another 7-10 days yet. Any delay in emergence at planting will delay maturity by a few days compared to the above numbers. Temperatures for September have been average to slightly above normal.  This allowed the crop to gain some ground.  Current long-term forecasts are predicting average temperatures through September with above-normal for October into November. Last year at this time, we saw warmer temperatures, dry conditions and very low humidity throughout harvest….it appears that the 2025 harvest will not see these conditions to the near the extent seen in 2024.  Considering the growing season, we can be glad much of our crop got planted by first week of May….
  • Corn fields in the area are starting to lose their color.  This is happening earlier than past years. This is due to, one, natural senescence as the plants reach maturity, and two, from disease and stress from growing season, with this having the biggest impact. Plant staygreen will vary from field-to-field, and from hybrid-to-hybrid (even within a hybrid family itself), as the next weeks progress. Monitor plant staygreen over the next few weeks.  Monitor those fields that lose color the quickest over next few weeks (a few area fields are already there) as they will be the first ones to go after for harvest.  Due to the increased stress the crop experienced this year, we expect stalk quality to be poor come mid-to-late October (in some cases in next couple of weeks)….rapid color loss is still the key indicator for potential problems with stalks, etc., and they should be at the top of your harvest priority.  Monitor those fields that lose color the quickest over next few weeks as they will be the first ones to go after for harvest. Late leaf disease pressure and overall stress, will lead to potential harvestability issues even on those fields where a fungicide was applied….timing of application and what product used will play a much bigger role this year than past years for staygreen and late-season standability….
  • Disease and Harvest: Leaf disease has been heavier than normal once again this year. Southern Rust was heavy throughout the area and is impacting plant health.  However, disease from Tar Spot is having the biggest impact on late plant health over the last two weeks.  Impact on plant health from Tar Spot has increased greatly since the first of the month, mostly seen in loss of plant staygreen…some area fields have really ‘turned’ over the past 7-10 days.  We do see separation on Tar Spot tolerance across seed companies versus Pioneer. As observed in the past few years in the eastern states, Pioneer has shown increased tolerance to Tar Spot versus many competitors….see photos below:
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  • These photos show difference in P1413AM versus 113 day competitor.  Middle photo is from satellite imagery taken on September 13th. Photos of the plants and from  drone were taken September 18th.  All from same field.  Video link is from this field:  P1413AM vs 113 day Competitor – late-season health
  • The above phots were taken in a plot on September 12th.  P13777 family has shown good tolerance to Tar Spot so far this season.
  • Below are a couple more photos showing late-season plant health and impact of Tar Spot.  Both photos taken September 18th.  First photo is a field completely dead, with tops breaking out, and hand shelled @ 20% (not a Pioneer hybrid).
  • Late-season plant observations:
  • P13777PCUE plant health
  • P14830AML plant health
  • Please keep in mind that these are local, field specific, observations and not indictive of the area as a whole.  However, they do show trends for plant health and potential stalk issues as the season progresses.  Bottomline, have harvest equipment ready to go now and be flexible to move from field-to-field depending upon late-season health, etc.  2025 harvest looks to be one to get done quicker than past years. There is increased potential to have some corn fields needing to be harvested before soybean harvest is completed….
  • Ear Molds: Wet and damp conditions of the past few weeks has led to ear molds starting in most corn fields. As to what level of molds we will see, and to what impact they will have on yield and harvest, remains to be seen; however, potential is significant to see higher ear molds than past few years. We need dry, low humidity, and breezy conditions (also needed for crop drydown) over next few weeks to slow the progression of these molds; however, once they are present, they will remain on the ear, even with drier conditions….any new spell of moisture will allow them to increase again.  Those hybrids which keep a closed husk into harvest will be the most prone for increased ear molds….as well as those fields shutdown early due to disease or stress….
  • There is some very good corn in many area irrigated fields, as kernel depth and color looks good as we move into the later half of September.  We still expect to see more variability in irrigated yields overall this year versus past few years, mainly from the growing season we had, especially in the sand versus heavier soils.  One potential on yield for 2025 will be ‘can we get it our before it wants to fall apart?’  As mentioned above, we expect to have more standability issues this year than we have seen over the past number of years.
  • Grain moisture drydown is dependent upon temperature and ear husk structure.  Starting to see some husks begin to open in fields now.  On average, it takes 15-20 GDU’s to lower grain moisture each point from 30% down to 25%, 20-25 GDU’s per point of moisture from 25% to 22% and 25-30 GDU’s per point from 22% to 20%.  A high of 75 degrees and a low of 55 degrees equate to 15 GDU’s, which should roughly take a point of moisture out per day when grain moisture’s are 25%+.  So temps in the mid-70’s for highs and mid-50’s for lows should take corn from 30% to 25% in a week’s time.  Forecasted temperatures for the next 7-10 days will give us 12-16 GDU’s/day….drydown will be on the slow side for the rest of September by the looks of it.
  • Soybean harvest moisture: There is an average yield reduction of 7-8% when going from 13% moisture to 8% moisture soybeans.  This means an average loss of 6 bushels/acre (using an 80 bu yield) just in moisture, along with potential reduction from header loss, etc.   The below chart shows the average yield lost from lower harvest moisture and delayed harvest over five year on-farm study from Pioneer.
  • Weather conditions as of late, along with future forecasts, is leading to a slower development of soybeans getting ready to harvest….as well as a delay in harvest overall.  Forecasts do not look to be conducive for much harvest in September….
  • All for now.  As harvest progresses, we will text out plot info and updates.  Have a safe and successful harvest!!

Starman Seed & Supply, Inc.

 

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