Ontario Field Crop Report, Sept. 7
By Kate Ayers
Print & Online News Reporter
Producers aware of lower corn yield and overnight low temperatures did not find much relief in yesterday’s OMAFRA Field Crop Report.
Corn Frost Risk
The unseasonably cold weather of recent weeks has farmers concerned about frost risk and its implications on corn maturity. Especially those who may have planted late or have longer maturity hybrids. There are a few things that need to be considered when gauging crop stage and frost risk:
1.Crop Staging
As indicated in the twice-weekly report, the closer to maturity (black layer) corn is, the less impact a frost event will have on the crop. In review, corn growing stages are R1- R6. R6 or black layer stage marks physiological maturity.
The so-called black layer occurs when a small layer of cells at the base of the kernel near where the kernel connects to the cob die and turn black. This marks the end of the grain fill from the cob into the developing kernel.
The Field Crop Report described that at R6, maximum dry matter accumulation has occurred, so any frost or stress event after this stage will have little impact on yield unless harvestability is compromised.
2.Frost Severity
A light frost (i.e. 0oC) may damage or kill leaves, but may not be cold enough nor last long enough to kill the plant. If there is a living stem, translocation of dry matter to the developing grain can continue and provide some grain fill after a light frost event.
The report explains that in the event where temperatures are low enough (i.e. -2oC), or last long enough to penetrate the stem and kill the entire plant, the plant can no longer continue filling grain. Yield will be fixed.
The extent of damage a frost event will cause depends on which crop stage either type of frost hits the plant. The report points out, any frost event during the blister or milk stage would result in significant grain yield losses as much more grain fill is yet to occur at these stages. Also, a light frost at the beginning of dent stage may reduce yields by 25 per cent while a killing frost may reduce yields by 40 per cent.
3.Estimating Time to Maturity
The crop report illustrates that time to reach maturity can be estimated by knowing the approximate Crop Heat Units (CHU) required for each reproductive corn stage. It is also helpful to know the typical first killing frost dates for your area, based on a 30-year climate normal. With these, producers can determine how close to maturity the crop may be for the average expected first frost date.
For the full report, click here.