As high temperatures continue and rainfall remains scarce, many Illinois producers are getting concerned about prospects for the 2024 crops.
While it is not very productive to ask ourselves if we should have managed tillage and planting differently, remembering how this year’s crop is faring might inform some of our decisions in the future.
After a planting season that stretched from late March to mid-June and included a substantial amount of replanting, Illinois corn and soybeans are almost completely planted. Stands are generally good, in some cases after replanting.
Crop condition has dropped some but is much higher than it was at this time in 2023 before rains turned things around and yields ended up high.
With high temperatures, almost 400 growing degree days have accumulated over 16 days. The corn has accumulated almost 1,100 GDD since planting, which should have it at about V15.
That’s it’s only at V11 means that stems have elongated more slowly than normal, probably due to less available water.
Rainfall will quickly restore rapid stem elongation in such fields, but plants may end up shorter than normal.
The rate of GDD accumulation over the past 10 days has been unusually high. As an example, 92 GDD accumulated at Champaign over June 17-19. This does not come from high daytime temperatures — which have been in the 90s — because the high temperature cutoff is 86 degrees, meaning that any temperature above 86 is treated as 86 to calculate GDD.
Getting to 30 GDD for a day with high temperatures above 86 means the lowest night temperature was 74 — (86+74)/2 – 50 = 30.
The accumulation of 200 GDD in a week is occasionally seen in July but seldom in June. It is commonly thought that high night temperatures lower crop growth rates. That may be the case, but we do not think that would be enough to lower corn yield potential at this point in the season.
The soybean crop has reached stage V8-R2, with eight expanded trifoliolate leaves and flowers at most developed nodes. These plants have a little less leaf area than if they had had a more plentiful water supply, but there is no indication that node and pod numbers have been compromised.
While the development of drought-stress symptoms during the day is not welcome, it has rarely translated into serious yield loss, providing that rain returns before growth (height increase) appears to stop.
Having good leaf color in the morning indicates that plants have root systems established well enough to take up N and also that the plant has moved a fair amount of water out of the soil into the air. More transpiration means more photosynthesis.
Unlike corn, soybeans showed little effect of dryness in late afternoon on June 20. We know from experience, including in 2023, that node number and leaf area can increase very rapidly once rain falls.
Late-planted crops
The photo above shows soybean and corn in a field on South Farm in which wet soils delayed planting until June 4. Soil moisture was good at planting, and about an inch of rain fell within a week of planting. It has been dry since then.
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