2005: Where Did all the Corn Come From?

Greg Stewart, OMAFRA Extension Specialist

If you have liquid manure, you probably like to get the most nutrient bang for your buck. Injecting the manure directly into the ground is an approach that may have a significant impact on the amount of nitrogen available for next year's corn crop. Consider an example of some of the decision making that is associated with manure application systems. At the time of writing this article I am not sure where the final provincial average corn yield will end up. However, it is very clear that we will set a new record. It may even end up close to 140 bu/ac! Last year we where surprised that an amazing end to the growing season allowed us to reach I3 I bu/ac as the provincial number. That was a record, with the highest average yield prior to 2004 being 129 bu/ac set in 1998.

Accompanying this issue of the Corn Producer magazine is the Ontario Corn Committee (OCC) Hybrid Performance Report; all 21 trials that were set out this year, survived the dry weather, and generated good data that are included in this year's version of the report. Incredibly, 14 of those 21 trials recorded average yields which were over 200 bu/ac. By comparison, 8 of last year's trials broke the 200 bu/ac mark. Besides the copy you received with the magazine, the OCC report can be found at www.gocorn.net or you can request additional copies from the OCPA office in Guelph.

So the question being asked at the coffee shops for weeks now is where did all this corn come from? This question is particularly poignant given the fact that on July 10 to the 15, most of us were wringing our hands and trying to decide how many bushels per day we were losing due to dry weather. We have some information that we are still gathering to explain the 2005 results but here is a summary of points to add to the discussion:

1. Early planting dates. Most of the corn this year was planted under good soil conditions and was in the ground prior to May 15. This promotes earlier canopy closure and captures more of the sun's energy centered around June 21. This energy cannot fall on bare
soil if you expect to break the 200 bu/ac mark!

2. Soggy Soils. Some of the research with nitrogen and tillage points to the stress the young corn plants experience when soils are frequently
saturated in May and June. While we had some corn that got damp and cold in late April and early May, the remainder of May and June were free from prolonged wet spells that saturate the ground and stress the corn plant, particularly at the ear initiation phase of development. The stage was set early for high yields in 2005 with good canopy growth and good downward root proliferation.

3. Timely Rainfall. Of course, dry soils, good root growth, and good soil structure eventually must give way to meeting the crop's water requirements; particularly the water requirements around the time of pollination. Rainfall that came over the period July 15-17 could not have come a day later in some parts of the province with out some yield depression. As it was, timely rainfall generated average to above average kernel set in most parts of the province.

4. Early pollination. The early planting dates and good growing conditions pushed most corn in the province to pollinate in the mid-July period. This allows grain filling to occur under much warmer conditions and during a time when sunlight intensity and day length keeps the photosynthetic engine running harder. In fact Dr. M. Tollenaar at the University of Guelph has measured actual photosynthetic rates during the grain-fill period on corn plants for years now. He has found that this maximum photosynthetic rate changes little from year to year with the exception, that is, of 2005 when photosynthetic rates were nearly 20% above average. The explanation for this is not clear.
Some of it may relate to the early silking dates and hence warmer temperatures and some of it may be related to increased sunlight intensity. Incoming sunlight (incident radiation) is measured at the Elora Research Station and the values for this year and the past few are presented in Table 1. Clearly sunlight intensity was about 10% higher for June and July but about average in August. The net result of excellent grain filling conditions was above average kernel density (test weight) and kernel size.

5. Cool nights. Research has suggested that photosynthetic activity and grain filling can be disrupted by cool nighttime temperatures; of course this is another reason why silking on July 18 is much better than silking on August 5th as it slides the grain filling period forward and away from the cool nights of September. So I checked the weather records to see if 2005 was any warmer on this front. We checked Kitchener data from August 10 to September 20'h for 2005 and for the past few years looking for the number of nights where the minimum temperature dropped below 10 C. Well, we certainly did not find any cold snaps but the number of nights when it dipped below 10 C was not much different in 2005 than in other recent years (back to 200l).

6. CHU. Adding together early planting, warm conditions through most of the growing season and the absence of September frost generated crop heat units that were well above average. The totals for each of the OCC sites are in the report and range from a low of 2946 at Alma, to a high of 3711 at Tilbury. CHUs do not make high yields in and of themselves but combined with some of the above mentioned factors, even the latest maturing hybrids had plenty of growing season to finish this year.

7. Genetics. It has been interesting to read some of the debate over the genetic contribution to recent high yields. I don't doubt for a minute that improved stress tolerance in our modern hybrids is responsible for some of the above average yields that we have in 2005. The contribution, however, to record high yields from specific traits that confer resistance to European Corn Borer or specific herbicides is marginal. Growing conditions, not GMO events, are at the heart of sorting out why fields that averaged 135 bu/ac did 180
this year.

2005 Hybrid Performance Data. A final word on using this year's data to select hybrids for 2006. Some have suggested that because this was such an abnormal year that the data is meaningless. I think that as you look over the 2005 data, and the 2004/2005 two year averages, that you will find the data to be very useful in most cases. If there is a word of caution it would be related to those hybrids that are new. A hybrid that has only this year's data available, which has very high yield index values, but also has above average harvest moistures in 2005 should be treated with some caution. If a hybrid couldn't come in this year with low harvest moistures what will happen to it in a more normal year? The drying costs might take a big stick to high yields. Perhaps buying two bags, not 20, is the prudent action.