To Evaluate Adjustments For Late Corn Planting

On June 03, 2019

To Evaluate Adjustments For Late Corn Planting

While we’re moving beyond the ‘ideal’ planning dates for many portions of the state, there are still many factors to consider when making planting decisions. Extension Agronomist Zach Larson points out in many years, planting into good conditions may trump planting at the ideal time. 

The past 30 days brought above average precipitation to most of the state, and with many places receiving over 2 inches of rain in the past week, late planting will be reality for many.  This week’s USDA Crop Progress and Condition Report estimates that 26% of the state’s corn crop was planted as of May 12th, compared to the 5-year average of 38%, with tillage operations slightly ahead of the average.  While late planting often brings concerns of reduced yields and switching hybrids there are many pieces to the puzzle that ultimately affect the number of bushels in the bin come fall.

The first thing to consider is the planting date.  Planting date does influence corn yield, with optimum planting dates ranging from April 15th to May 1st in the southeastern corner of the state to May 15th to 25th in the northern tier and Laurel Highlands.  However, those differences are relative differences, assuming all other growing conditions being equal.  When looking at the entire growing season, we have many factors to consider and planting date likely means little when it comes to understanding the total amount of yield variability form year to year.  A look at planting date data from Ohio  delayed planting date data from Ohio (“historical”-perspective) helps to demonstrate this point showing years of late planting where average corn yields were both higher and lower than historical averages.

A 30-day (approx.) window exists where corn can achieve 95% or more of maximum yield potential.  Once the planting date is about two weeks beyond the ideal date the amount of potential yield loss per day begins to increase. 

At this point there is still adequate time for full-season hybrids to reach physiological maturity by typical first frost dates.  And while the differences in yield between full-season and short-season hybrids have been blurred in some cases, full-season hybrids may still out yield their short-season counterparts.  What makes this possible is the ability for full-season hybrids to “adapt” to the shorter season by requiring fewer growing degree days to mature than what they’re rated for.  Research from Ohio and Indiana show that a hybrid planted 30 days late can reduce the necessary growing degree days to reach black layer by 6.8 degrees per day of late planting.  This suggests that a hybrid that takes 2600 growing degree days (GDDs) to mature can do so with 200 fewer GDDs when planted 30 days late. 

However, a tradeoff still exists, with full-season hybrids potentially taking longer to dry down than their shorter season counterparts.  This could be entirely dependent on fall conditions though, with a warm and dry fall favoring smaller differences in drydown between full and short season crops.

While one can stress over potential yield impacts from late planting, the impact from poor corn emergence is more concrete.  The yield penalty from inconsistent emergence is widely documented in many studies, a summary of which can be found here: . The risks of sidewall compaction, poor seed placement and improper seed trench closing should be considered before putting the planter in the ground.  Therefore, it is still best to wait for good planting conditions and stay the course with good practices.  Particular attention should be paid to downpressure settings, soil buildup on gauge wheels and closing wheel adjustment.  Shortcuts such as planting at a shallower depth should be avoided as it can result in more variable emergence.

While we’re wetter and a bit behind we would like to be, by no means is it time to panic, as there are many things that will determine the success of our 2019 corn crop.  At this time one can take solace knowing that we’re not that far from historical trends, and a decent period of good weather may quickly change our outlook.

To Protect Your Flowering Wheat From Infection And Toxin Contamination 

Wheat across southern PA is heading now, while risk for scab infection is increasing.  Extension Plant Pathologist Alyssa Collins tells us to be sure to keep an eye on the Fusarium Head Blight (FHB) Risk Assessment Tool as it will become critical for those farmers who are trying to make the decision to spray small grains or not.  This forecasting site is an online model that helps us predict infection risk levels everywhere in the state. It works best in the Mozilla Firefox browser and updates each day around 10am.  Visit it at your convenience or sign up to have updates e-mailed or texted directly to you. I will add commentary about disease risk in our area to give some human perspective, and you can have this commentary sent to your e-mail or phone by signing up.

Sprays prior to heading do not suppress scab, but one labeled fungicide, Miravis Ace may be applied at 50% heading.  The best control with all fungicides will result from spraying at the first sign of anthers.  Caramba and Prosaro (Group 3) or Miravis Ace (Group 3 + 7), give good control of scab as well as most leaf and head diseases. All three products provide similar disease suppression. They do not need to be tank mixed with another product to control these diseases.  Spray nozzles should be angled at 30° down from horizontal, toward the grain heads, using forward- and backward mounted nozzles or nozzles with a two directional spray, such as Twinjet nozzles.  These sprays become rainfast quickly, and so an application followed by rain should not be cause for alarm.

Once your crop begins heading, there is approximately a 5 to 6 day window to apply a fungicide. The labels state the last stage of application is mid-flower and there is a 30 days to harvest restriction.  Do not use any of the strobilurins (Quadris, Headline), or strobilurin/triazole (Twinline, Quilt, Stratego) combination products at flowering or later. There is evidence that they may cause an increase in mycotoxin production. 

At this point in the season, the only way to reduce the scab problem is to spray. But in general, do not rely solely on fungicides, as they will provide at most a 50–60% reduction in scab severity and vomitoxin. The best long-term management strategy starts with selecting resistant varieties, and then time sprays properly to achieve greater control.

Quote Of The Week: “Do not laugh to much or too loud in public.” Rule number 24 from George Washington’s Rules of Civility And Decent Behavior in Company and Conversation