Corn yields are generally not maximized when the crop is planted so late.
But with little precedent for the current situation, especially with uncertainties over the US-China trade war, it is unclear just how much the final output may be reduced.
Late on Monday, the US Department of Agriculture placed US corn planting progress at 49pc as of Sunday, well off the five-year average of 80pc.
This was 1 point below trade expectations and up 19 points from the previous week.
Prior to Sunday, the slowest US corn planting pace for the date was 50pc in 1995, and the slowest within the last 20 years was 68pc in 2009.
The central United States has been historically wet ever since last fall, and the frequent rainfall on top of already-waterlogged soils has worsened the delay.
Even when the rains break, a farmer may have to wait longer than usual to begin field work because the ground is so saturated.
When planting falls so critically behind normal pace, the market looks for a huge catch-up week, but the weather has not allowed for one yet this year.
The biggest corn planting week on record was the one ended May 19, 2013, when US farmers seeded more than 40 million acres or 43pc of intentions. Last week's 19-point progress would imply that about 17.6 million acres of corn got planted.
It is starting to get late in the game as final corn planting dates for full crop insurance coverage are fast approaching.
Those range from May 25 in the Dakotas to June 5 in the Eastern Corn Belt states.
But producers may be willing to push beyond those dates given that the economics of planting corn are now strongly in favor of the yellow grain versus soybeans.
The new-crop futures ratio of CBOT soybeans to corn favors the latter to the strongest degree during May since 2011.
On Tuesday, July futures were flirting with $4 per bushel, a level that has been elusive for the most-active contract since May 29, 2018, the day it was all but confirmed that a trade war would break out between the United States and China.
December corn reached $4.13 per bushel, its highest level since early August.
The ongoing trade war further complicated the US corn and soybean growing season on Tuesday as Bloomberg reported that the Trump administration was considering payments of $2 per bushel for soybeans and 4 cents per bushel for corn to offset farmers' losses.
That is up from last year's payments of $1.65 per bushel for soybeans and 1 cent per bushel for corn.
As of Tuesday, it was not yet clear whether the new payments would be based on this year's crop or an average production history, details that could reduce pressure on farmers to get the corn in and encourage more bean acres.
However, a USDA spokeswoman said on Tuesday that the aid is being designed to avoid skewing planting decisions and that farmers should make those decisions on current market signals, not expected trade aid.
LOWER YIELDS?
With current progress the slowest on record, there are not many analog cases available for comparison.
Additionally, there have been very few disastrous corn yields in recent years, regardless of the planting pace.
In the last 30 years, May 19 planting progress stood below 75pc only seven times before.
Three of those were in the 1990s.
Three more years, 2002, 2011, and 2013, all had poor weather conditions during the growing season. Yields were below the long-term trend in all six of those years.
The seventh year is 2009, the only year of the group where yields ended up above trend.
Summer weather was favorably cool and wet, whereas most of the other years were either hot, dry, or a combination of both.
Seasonal forecasts published last week by the US government suggest that June through August is likely to be favorably cool and wet across the majority of the Corn Belt.
July and August are the most critical months for corn yield development, and as of now, most US producers have plentiful soil moisture.
One caveat to the favorability of this forecast is the delayed crop development.
As of Sunday, only 19pc of US corn had emerged compared with a five-year average of 49pc.
Current forecasts show May finishing on the warm side in the Eastern Belt but cooler in the Western areas, particularly farther north.
A little bit of heat early in the growing season can be good for corn as it helps with emergence and establishment.
Slow planting plus prolonged cool weather could pose yield risks if development is delayed too much by July and August. Late emergence by itself is not enough to lower yields, though.
Recently, it has been rare for corn yield to fall further than 3pc below the long-term trend.
In the last 20 years, only three years have featured final corn yields below that mark: 2002, 2011, and 2012.
The deviations were about 3pc below trend in both 2010, and 2013.
Assuming the 2019 trend yield is 176 bushels per acre, losing 3pc would result in 170.7 bpa.
If USDA's harvested area peg of 85.4 million acres is not reduced, the lower yield alone would result in a crop 450 million bushels lighter than the current forecast of 15 billion bushels.
If harvested acres were reduced by 3 million, a yield of 170.7 bpa slashes almost 1 billion bushels off the current harvest prediction.
That would make for some interesting conversations around 2019-20 ending stocks, currently predicted by USDA at 2.485 billion bushels.