Corn Watch 2006
Greg Stewart, OMAFRA
Corn Specialist
Keeping your eyes, ears and mind open can allow you to ask the right questions, test some new ideas and examine the way you are doing things.
 Figure 1. Weed control decision making: yield vs. profit |
1)
Replant Investigation The Ontario Corn Committee has a project underway to re-evaluate provincial recommendations on re-planting corn that has less than optimal stands. Funding for this project is being provided by the seed corn companies and by OCPA. Corn will be planted in trials at Ridgetown, Exeter and EIora on three planting dates (late April, early May and late May) with final populations set at 12,000, 18,000, 24,000 and 30,000 plants per acre. Eight representative hybrids will be tested at each location. This project will: (1) generate revised recommendations on the cost effectiveness of re-planting based on original planting date and plant population, (2) test whether or not a "one-size fits all" approach is appropriate for re-planting decisions or whether there are significant differences amongst hybrids (Le. flex versus fix). Result will be included in the OCC Report in December 2006 or can be viewed at www.gocorn.net. |
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2)
Light Interception When scouting fields some growers may be surprised at the low densities that exist in their fields (even the ones that they thought were pretty good) when they actually get out and do some plant stand counts. There are a number of questions to ask. Was it all the fault of the weather or in your early planted fields could you have increased seed drop, planted a bit shallower, done a better job of seed-bed preparation to improve emergence and hence final stand and light interception? |
 Figure 2. Walk your fields to evaluate late season plant health. |
3)
Late Season Plant Health
Of course, getting a solid corn canopy is one thing, keeping it there is another.
Here, your scouting really focuses on how well the canopy stays green and active
throughout the grain filling period. Scouting for plant health later into the
season may allow you to sort out some hybrids that have poorer leaf disease
resistance and/or allow you to look for nutrient deficiencies. From the nutrient
perspective, lower leaf firing can be a result of either nitrogen or potassium
deficiencies. Firing at the tip and then yellowing down the
leaf edges indicates a potash deficiency; firing at the tip and then yellowing
down the middle of the leaf indicates low nitrogen. Firing of the bottom leaves
is fairly common, and is often associated with dry weather, other soil problems
such as compaction or working the ground wet, and of course with eventual maturation
of the plant later in the season.
An Iowa study
indicated that if there was a check strip of relatively high N fertility in
the field, then leaf firing was a reliable indication of N status; without the
check strip, leaf firing was difficult to use as a specific indication of nitrogen
shortfall in the crop. However, if there is absolutely no firing, then, there
is a good chance that N rates were in excess of the most economic rate.
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4)
Peas as your N Supply |
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5)
N Calculator Validation
After years of gathering data and developing a new set of general nitrogen recommendations
for corn, 2006 is the first year where these new OMAFRA recommendations are
being put to the test in a wide array of field scale trials. Funding for these
field scale comparisons is being provided by OCPA, Agricorp, OMAFRA and the
Agricultural Adaptation Council (CORD IV). In 35 fields across the province,
growers are asked to follow the OMAFRA recommendations on the bulk of the field.
Several strips will also be imposed where the nitrogen rate is significantly
higher than the new recommendations and based on the growers past N use experience.
Assessments at the end of the season will evaluate the profitability behind
both N rates. This work will be of particular interest to growers in Eastern
Ontario where the research data supported nitrogen recommendations considerably
lower than traditional practices and lower than the rest of the province. Corn
stakeholders in the east who would like to stay abreast of the project can contact
Jonathaii. Klapwyk at Kemptville College - University of Guelph 613-258-8336
ext. 605
 Figure 3. Testing the value of fall seeded cover crops |
6)
Drying Costs versus Yield We recently have been analyzing the relationship between harvest moisture (drying costs) and yield from a wide range of hybrids planted at the OCC performance trials over the last several years. The results have lead me to suggest, that even with the relatively high costs of drying, that 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. I have been challenged that this conclusion only applies to early planted corn, I think that is correct! However, this is still an area with room for some more study, and 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 1987-2005 Corn Hybrid Selector you can find some spreadsheet tools to help you with these calculations. |
7)
Sulphur for Corn
Recent studies have shown response to sulphur that was not found in previous
studies. Sulphur deposition from acid rain and dry deposition, a result of air
pollution, has dropped dramatically as efforts to reduce sulphur emissions have
been implemented. For the first time in memory, winter canola fields in Grey
County in 2005 did not set seed, diagnosed to be a sulphur deficiency. Canola
is a very heavy user of sulphur, needing approximately 15 pounds/acre/year.
Wheat requires 12 pounds/acre/year, corn slightly less than this.
Studies by Dr.
Kurt Thelen, Michigan State University, found from 0 to 23 bu/ac yield increase
in corn yield in 2005, with an average increase of II bu/ac, from sulphur application.
The Middlesex Soil and Crop Improvement Association has a project underway this
year to compare dry starter fertilizer with and without sulphur. Stay tuned
8)
Weed Control Strategies
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? An Ontario field study (Hamill et ai, 2004)
demonstrated that weed control costs can be reduced by $45/ha when a profit
maximization approach to weed management was used. 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.
Since there are
a number of complex variables that must be considered before selecting a weed
control program that maximizes profit, computer based decision support programs
are required to consider all variables and synthesize them down to a strategy
that can be adopted.
A new project supported by OCPA and headed up by Mike Cowbrough (OMAFRA Weed
Specialist) will seek to improve the tools
that growers work with to make the best decision when it comes to weed contro\'
This project will: (1) develop, and deliver a "grower-friendly" computer
based decision support program for selection of profit maximizing weed control
strategies, and (2) incorporate and/or identify research that would improve
the decision support program. If you would like to participate in some aspect
of this project contact Mike at mike.cowbrough@omafra.gov.on.ca.
