OMAFRA Report: Why has corn take so long to emerge in 2020

A weekly report prepared by the staff of the Ministry of Agriculture, Food and Rural Affairs (OMAFRA).  If you require further information, call the Elora Resource Centre at 519-846-0941.  Office hours: 8:30 a.m. to 4:30 p.m. For technical information, call the Agricultural Information Contact Centre at 1-877-424-1300 or visit the OMAFRA website:

June 12, 2020

Some corn was planted around 10th of April. A much larger acreage got in between the 21st and 27th. The rest got in during the first part of May. Corn planted to date has gone in under very good soil conditions for the most part. The remainder of the corn will be likely planted after the 21st of May due to recent rains that will keep planters out of the fields.

Regardless of the planting date so far, little or none of that corn has emerged. Why? It’s primarily due to the overly cool conditions through April and the first part of May. While the seed has been taking many days to emerge, the seed remains in good condition. Planting was accomplished into very fit soils. While there was sufficient moisture for good seed-soil contact and initiating the germination sequence, the soils were not water saturated which is the biggest culprit to seed integrity in the soil. While the cool conditions have slowed emergence they have also reduced insect and disease pests from attacking the planted seed.

The Crop Heat Units (CHUs) system has two major uses in Ontario. Firstly, corn hybrids are selected for a farm based on the region of the province. The CHU’s have been determined for regions based on long term temperature averages experienced in different geographical areas of Ontario.

Secondly, CHUs are used to gauge the development of crops. So while CHUs are accumulated during warm days in April, their contribution to the seasonal totals tends to be small and quite varied from year to year. So, if in a given year, 150 CHUs were accumulated because of an “early spring,” they would start a corn seed on its growth journey.

Many farmers now have access to daily CHU data on their farm through their subscriptions with various crop consultants and service providers or have secured automated weather stations for their farms.

If you do not have this available, we have developed some tools to you to understand where things are in your region or you can track yourself:

Excel tool for you to keep track of your individual farm CHUs –

Current and historical daily weather data is available from:

Resources that describe corn development are available from: page16

The bottom line is that despite the long period from planting to emergence of some corn fields this spring, the seed is in good shape.

For entire article, please visit website –

Written by Ian McDonald, Crop Innovations Specialist, OMAFRA