Corn Watch 2008

Greg Stewart, OMAFRA Corn Specialist

Some things to think over, read about, watch for or try out in this upcoming growing season.

Fungicides on Corn

There has been lots of discussion this winter on the yield boosting potential of fungicides on corn. The odds of getting enough yield from a single application at tassel emergence to cover the cost of product and application seems to range anywhere from 35 to 80 %. University of Guelph work in 2007 did show some real yield boost even in the face of low leaf disease pressure. The challenge in 2008 is to define the fields where the odds of getting a real return on investment are better than 50 %. This is where the science is weaker than we would like it. Some suggestions for fields to target
fungicide applications include: evidence of leaf diseases, higher levels of crop residue, corn after corn, hybrids that have poorer disease ratings or hybrids that have higher yield potential. OCPA is supporting work in 2008 to try and sort out why some hybrids seem to respond much more to applications of the fungicide Headline than do others.

Rescuing Weedy Corn

Lots of weed research over the years has indicated the significant yield hit you may take if weed control is delayed to say, the 7 leaf stage compared to the yield potential if the crop had been sprayed at the 4 leaf stage. Some research work from Wisconsin has outlined that this delay in weed control will
also decrease the nitrogen use efficiency in your corn crop and indicated that significantly high N rates were required because of delayed weed control. So the point is still to control weeds on time to increase yields and to save nitrogen. However, if for some reason you did find yourself in a delayed weed control situation then an additional application of N may in fact help to restore some of that lost yield. This is an idea that will be examined in plots this year but it could make for an interesting on-farm trial. For example, you spray glyphosate at the 8 leaf stage to cleanup the mess and then
consider sidedressing an additional 50 lbs of N per acre in a strip to see if yields can be boosted.

Maximizing Planter Potential

This past winter there has been more discussion on maximizing yields and yield contests than in quite a while. Is there a single thing you could do to your planting operation to boost yields? The question can be answered in one word: uniformity. Do what it takes to get all corn plants emerging together and growing at the same rate such that inter-plant competition remains very uniform. Try some improved field cultivation techniques to get a more uniform seedbed, plant at 2.5 mph instead of 6 mph and then compare yield and uniformity of cob size. And remember that at the end of the day
uniformity is not so much measured by the space between plants but by the uniformity in plant size.

Drying Costs versus Yield

For several years now we have been analyzing the relationship between harvest moisture (drying costs) and yield from a wide range of hybrids planted at the OCC performance trials. The results suggest that even with the relatively high costs of drying, selecting full season hybrids with higher yields and higher drying costs was a more profitable option than shorter season hybrids with lower yields and lower drying costs. Of course early planting will be critical in making this relationship work on your farm. Since hybrid selection and drying costs can vary tremendously from one farmer to another it is the kind of number crunching the individual growers should be doing on their own. For example, on your operation how many additional bushels of yield does it take to cover off the costs of an additional point of moisture? If you go to www.gocorn. net and click on 1987-2007 Corn Hybrid Selector you can find some spreadsheet tools to help you with these calculations.

Seed Cost Cutting

Some growers in Ontario have now fully adopted site specific seeding GPS driven seeding rates. The real win seems to be on fields with areas where low water holding capacity seriously restricts yield potential in most years. On these droughty areas cutting seeding rates from 32,000 to 22,000 seeds
per acre can represent a savings of $25/acre and in most years is not associated with any yield loss.

Further developments in the precision planting area now include individual row unit shut-off mechanisms that can be GPS (RTK) controlled. Air clutches can be installed on each row unit and as the planter approaches the headland row, units are automatically shut off. Pay back is undoubtedly much greater on irregular shape fields but some researchers are claiming cost benefits that rival any obtained from reduced spraying overlap using the same
type of technology.

WeedPro75

Do you select your weed control program based on yield maximization or profit maximization? Is it a Cadillac or Firefly when it’s time to buy herbicides? A profit maximization strategy for weed control considers herbicide costs, efficacy, crop staging, environmental conditions, weed emergence relative to the crop and most importantly competitiveness of the weed species present in the field.

A project supported by OCPA and headed up by Mike Cowbrough (OMAFRA Weed Specialist) has come to fruition. The result is a web-based tool called WeedPro75 that is now available to help you make herbicide decisions. Try out this new tool by visiting www.weedpro75.com.