Bad weather for an extended period can drastically delay planting. So, what’s a farmer to do once the optimal date for planting corn has passed? And just what does ‘optimal’ mean anyway?

Essentially, the optimal planting date is one that has been adapted by analyzing many years of data. It factors in average planting dates, harvest moistures (crop maturity) and grading factors that would define good test weight.  

However, more than planting date, the growing season ahead is what truly defines the crop. A late start to 2017 in Southwestern Ontario tested growers’ patience and the average planting date was May 20. But, thanks to a great September and open fall, the crop was one of the largest ever, and was of very good quality.  

The reality of later planting is that germination and emergence happen much more uniformly, and typically a hybrid requires ~10chu/day less to reach maturity as we get later into planting.  

The above chart demonstrates average planting date and final provincial yield. Where yields have been maintained regardless of early seeding, there is not a strong correlation to planting date and final yield.  

We must also consider factors such as, when will the earlier hybrid flower, and what adaptability it has to a farmer’s region. If the earlier hybrid is not adapted and cannot perform within 10% of the selected hybrid, growers are at greater risk of giving up $/acre returns.   

OMAFRA pub811 recommends the following dates of when to consider the ‘switch’ based on maturity region: 

And, when planters do roll, remember that early hybrids may have limited testing and may be less adapted to particular areas, which means it’s important to maintain seeding rates. Uniformity and rate of germination should be better once optimal conditions arrive. It is crucial to maintain seeding depth at no less than 1.75” and most importantly to plant ½” into moisture.      

Here are some additional resources that support the need to maintain hybrid selection until closer to the end of May in order to maximize growing season and yield potential: 

• THE PLANTING DATE THE PLANTING DATE CONUNDRUM FOR CORN 
• TO SWITCH OR NOT TO SWITCH OR NOT TO SWITCH HYBRIDS
• HYBRIDS ADJUST TO HYBRIDS ADJUST TO DELAYED PLANTING DATES
• SHOULD I SWITCHSHOULD I SWITCH TO AN EARLIER MATURITY?
• CORN YIELD'S CORN YIELD'S RESPONSE TO PLANTING DATE