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2017 Corn Seasonal Summary
The March 2017 planting intentions report by Statistics Canada estimated that Ontario farmers intended to plant 2.2 million acres of grain corn. This compares to a 5-year (2012-2016) average of 2.1 million acres of grain corn planted in the province (OMAFRA Crop Statistics).
While April was warmer than normal, some large rainfall events in the middle of the month limited very early planting. A warm, dry period during the last week of April allowed a small amount of corn to be planted early, generally limited to lighter soils of the deep southwest, and very well drained soils in other pockets of the province.
A few heavy rainfall events and cooler weather limited planting activity until the middle to end of the second week of May when field work resumed on lighter textured soils. By the start of the following week (May 14), corn planting was well underway across many parts of the province. A large majority of Ontario’s corn crop was planted during this week. Estimates in Southwestern and Eastern Ontario suggested 80-90% of intended acres were planted by the end of this week (May 20), while planting was reported to be slightly behind this pace in parts of Central Ontario. Some pockets of the province which had not yet been fit for planting or received heavy rainfall during this window were much further behind, particularly the Niagara region. Persistent rainfall resumed after this planting window in many areas, which pushed remaining corn planting to the end of May or beginning of June. Depending on region, some of these remaining acres were switched to shorter maturity corn while some were switched to soybeans.
Final grain corn planting estimates for the province were 2.12 million acres (OMAFRA Crop Statistics), down slightly from the 2.2 million acres estimated in the March Statistics Canada planting intentions report.
Early Season
Given that soil conditions remained relatively cool, many growers and agronomists noted that it took longer than normal for some of the earlier planted corn to emerge, 3 weeks or more in some cases. Slow emergence and wet soils also provided a greater feeding opportunity for below ground and early season pests which were more prevalent than normal. Most areas reported good stands at emergence, though a small amount of replanting was reported in some areas. One exception was a large amount of corn replanting in the Niagara and Haldimand regions where soil fitness was a challenge.
OMAFRA completed its annual Pre Sidedress Nitrate Test (PSNT) survey from June 5th to 6th, which coincides with the V3-V4 stages of corn. The survey measures relative background soil nitrogen supply by sampling fields which haven’t received any broadcast nitrogen just prior to sidedress time. The purpose of the survey is to gauge soil nitrate levels relative to previous years, and provide that information just prior to sidedress time. In 2017, the average PSNT value was 8.0 ppm, which is lower than the longterm (2011-2016) average of 11.0 ppm. This suggests natural soil nitrate supply in the 2017 survey was a little lower than what is typical. In general, each 5 ppm difference in PSNT generally changes an N recommendation by around 30 lb-N/ac, though the actual number depends on relative soil nitrate level and yield goal. See PSNT recommendation at The first half of June was generally co-operative for in-crop management practices such as sidedressing in Southern Ontario, while significant rain events presented a greater challenge for operations in areas of Central and Eastern Ontario.
With very active weather in 2017, there were a number of hail events throughout the province (Figure 1). Like most corn stresses, yield loss from defoliation is relatively minor during the early vegetative stages, gradually increasing and peaking at tassel and pollination time, and decreasing again through grain fill (Figure 2). Variability in plant recovery timing following a hail event may induce some plant-to-plant variability in crop staging, which may also result in some yield loss from “runt” plants which lag in recovery. In extreme wind/hail events with more advanced corn, plants may be broken off below the growing point which results in complete loss of those plants.
Pollination and Grain Fill
Given increasing feeding damage over the past couple of years, Western Bean Cutworm (WBC) activity was closely followed by many producers and agronomists. High trap counts were often noted by those who were monitoring WBC moth traps. While trap counts are useful from a monitoring and scouting-timing perspective (i.e. determining peak flight and egg laying), trap counts aren’t necessarily indicative of actual control requirements. Scouting fields for the 5% threshold of plants with egg masses or larvae was still recommended. More control was reported on corn acres in the vicinity of the traditional WBC range in 2017 (London region). More damage was reported in some areas which have not traditionally received significant WBC pressure, such as areas North and East of Toronto.
Given the moderate temperatures and reasonable soil moisture in most parts of the province, conditions for pollination were generally good. Most concerns at that time were more related to fields where crop maturity was later than preferred, with tassel emergence and pollination not occurring until the last week of July or even into the very beginning of August in some areas. Crop maturity concerns continued through to the end of August, especially in shorter growing season areas where Crop Heat Units were behind normal.
By the first week of September, many fields still ranged from mid to late dough to early dent stage in later planted and shorter season areas, and very late dough to dent in others. This suggested black layer, or physiological maturity, could still be as much as 3-4 weeks away for some fields. This continued concerns about crop yield and quality. In general, a corn crop should get to at least the early dent stage before a light frost to still achieve manageable yield and quality (Table 1). A light frost (generally considered temperatures below 0°C but above -2°C) may kill leaves and significantly reduce photosynthetic activity, but still leave the stem alive for translocation of existing plant resources for grain fill.
Table 1. Estimated risks to grain corn yield and quality from late-season frost damage (Pub 811, Agronomy Guide for Field Crops).
Crop Growth StageFrost DamageEstimated Grain Yield LossGrain Quality Concerns
Mid-doughcomplete plant40%severe
leaves only25%severe
Early dentcomplete plant25%moderate
leaves only15%moderate
Half milk linecomplete plant10%minor
leaves only0-5%none
This table is meant as a guide. Differences among hybrids, overall plant vigour at time of frost and subsequent temperatures will all affect final grain yield and quality.
Temperatures that remained well above seasonal throughout most of September were well received, and provided the opportunity to push a majority of the corn crop to maturity prior to a significant frost,  or where the crop was further behind, far enough along that yield and quality were still manageable.
Corn silage harvest started later than normal for many livestock producers, with earlier harvested fields generally coming off the second half of September, and harvest continuing on through to the middle of October in some areas. Many growers reported good silage yields.
The annual Ontario ear mould and vomitoxin survey was completed from October 7th to 19th. The purpose of the survey is to measure the relative levels of vomitoxin in the grain corn crop just prior to harvest to gauge grower and industry risk. A total of 179 samples were collected from across the province. Visual mould symptoms and vomitoxin levels were much lower than the 2016 survey, and 86% of samples tested below the 2.00 ppm threshold. This compared well to the long-term (2011-2016) average of 88%. While some fields may have elevated risks, results suggest that most corn should move through the system efficiently in 2017. While Western Bean Cutworm feeding was still evident, feeding appeared less severe than samples collected in previous surveys. The final report is available at
Some of the earlier grain corn harvest, including high moisture corn, started during the last two weeks of October as growers finished soybeans. Harvest was getting underway in many parts of the province by the beginning of November. While harvest was going in earnest by the middle of November, some growers were still waiting for better soil conditions or lower grain moistures. Where not already complete, harvest was generally wrapping up by the first of December. While relatively minor in overall acres, some very late planted corn was still in the field in some regional pockets of the province.
Despite growing season challenges, and with exception to a few pockets of the province where dry weather prevailed for the latter half of the summer, many growers reported yields above expectations or farm averages. In some shorter season areas where reaching full crop maturity may have been a challenge, and parts of Central and Eastern Ontario that experienced well above average rainfall, many still reported yields close to average. Good quality and test weight were reported in longer season areas, while lighter test weights were reported in some shorter season areas.
As of December 20, Agricorp reported that 86% of Agricorp insured acres had been reported with an average yield of 185 bu/ac. This compares to a 10 year average yield of 170 bu/ac for these same growers. The current 10 year average grain corn yield for Ontario as a whole (2007-2016) is 155 bu/ac (OMAFRA Crop Statistics).
Final Ontario Corn Committee corn hybrid trial results are posted, and available at the homepage of
Despite planting dates that were later than many would have liked, yield outcomes were still very good in many regions. Ontario planting date trials would support that there is an extended window where yield potential for a hybrid with a maturity adapted for that region remains high. Based on Ontario planting date trials conducted from 2006-2009, yield potential is still roughly 95% on May 20 at Elora, May 25 at Exeter and June 1 at Ridgetown (Figure 3).
Source : field crop news