2007: The Season That Could Have Been

Greg Stewart, OMAFRA Corn Specialist

Planting and early growth

Excellent, dry spring weather and good soil conditions resulted in an early start for most corn planting. The majority of the corn crop was planted April 25 to May 10 in seedbed conditions that were better than expected given the wet harvest and wheeltracked fields from the fall of 2006. Uniform plant stands and good early growth were the norm in most of Ontario’s corn fields on June 1, 2007. By mid-June the crop looked good but dry soils started to highlight some nutrient deficiencies (Magnesium, Zinc, etc.) on lighter textured soils and/or where pH was out of balance.

Weed control from pre-emerge and postemerge applications was generally good across the province. In situations where weed control did fail to control weeds during the critical period (3-8 leaf stage) the crop suffered very significantly as the dry weather progressed on into July.

Growing Season

Precipitation was extremely spotty, but generally well below average in most regions. The exceptions being notably the areas east of Kingston, and parts of Oxford and Perth counties. From May 1st to August 31st an average of 73% normal rainfall was recorded, compared to the 30 year average. Some areas received less than 25 mm in the period from May 1 to July 31! In many fields, the dry conditions seemed poised to wipe out pollination. Interestingly, even in some of these very dry areas, the crop hung on well and plants that failed to at least set a reasonable ear (1/2 to 2/3 grain) were quite rare. The corn crop did benefit from a lack of extreme heat in July, for example London only recorded three days over 30°C. Wilting of the crop certainly occurred during the day, but the lack of high heat stress did allow most fields to recover overnight. The exception to this was on the sands and heavy clays where available water simply could not keep up with the crop’s demands and resulted in significantly reduced yields.

From May 1st to August 31st the average, across 15 Ontario weather stations, was 2570 Crop Heat Units in 2007. This compares to a 30 year average of 2544 CHU’s. September and October added significantly to CHU totals in some areas and caused rapid lowering of both whole plant silage moistures and grain corn moistures. In some cases grain moistures fell 6 points in a single week. At the Ridgetown OCC Performance Trial site the week ending the day after Thanksgiving
resulted in an accumulation of nearly 200 CHUs, a total usually reserved for the hottest week in July! For the most part, harvest moistures across the province were below normal and resulted in significantly lowered drying costs.

OCC performance trials and grower experience in 2007 generally showed significant yield advantages for longer season hybrids. Advantages that outstripped any increase in drying costs as a result of higher harvest moistures.

Harvest Index

Of course for some corn producers, 2007 was the real deal with yields that rivaled and in some cases eclipsed 2006 levels. In some areas it was challenging to understand where all the corn came from given adequate, but modest amounts of rainfall. At some of these areas, we carefully divided and weighed plant components at harvest (see Table 1 for results). The most striking observation was that the Harvest Index shot up to as high as 63%. Traditionally corn physiologists have suggested that Harvest Index has been quite stable over the past several decades (at about 50%) that is, the grain is equal in weight to
the total of the rest of the above ground parts (stalks, leaves and cob). From the limited trials we examined this year, higher harvest index seems to be a significant factor in higher yields.

Corn Pest Problems

Corn was free from any widespread significant insect and disease pressure in 2007. The lack of rainfall generally meant low leaf disease pressure in most areas. And although the province was not free of ear moulds and the associated vomitoxins in the grain, instances were quite sporadic and modest in nature. This came as welcome relief in light of the 2006 situation.

Concerns were expressed in September that stressed plants trying to fill ears might have cannibalized stalk tissue and be prone to stalks rots and lodging. This did not occur and aided by generally favourable weather conditions in September and October, the crop stood quite well through to harvest.