2008 Corn-on-Corn Considerations
By Greg Stewart, OMAFRA Corn Specialist

If a large percentage of your soybean ground got planted to winter wheat this fall and corn prices rise over the winter, some corn producers may consider planting plant corn on ground that grew grain corn in 2007. First, let’s consider some of the economics at play.

ECONOMICS
For many growers, arriving at accurate cost of production figures for your various cropping scenarios can be challenging and time consuming. However, without some good records, cropping choices will be difficult at best. To get you thinking we can examine some crop budget examples based principally on OMAFRA Crop Budgets for 2007. The starting point is listing the costs of production for both corn and soys in
traditional scenarios, put in some reasonable yield expectations and then factor how much additional cost you will experience if your rotation shifts to corn after corn instead of corn after soys. This is represented in Table 1 for three corn yield options while leaving soybeans constant at 41 bu/acre. You will notice that the additional costs for corn after corn are about $60 per acre. I arrived at this value from the following set of assumptions: additional tillage ($15) - compared to spring cultivation only on bean stubble, additional nitrogen ($11), genetic rootworm control ($5) - you could argue rootworm control could range anywhere from 2 to 22 dollars depending on your approach, and finally a corn-on-corn yield reduction of 5% ($25-33) depending on expected yield.

Table 1. might be so filled with values that you don’t agree with, or that are not applicable to your farm that you will need to start over. For example, there is a very real perception among some U.S. Corn Belt farmers and agronomists that there is no yield penalty for growing corn after corn compared to growing corn after soys. Research data from many universities still tends to show significant corn yield differences based on previous crop, but I would acknowledge the advances in genetics and agronomics have probably narrowed this gap. Ample supplies of manure might also shift the picture considerably.

If however Table 1. assumptions (including the prices) are reasonable enough for you, then you arrive at an observation; the possible success of growing corn after corn depends on the relationship between corn yields and soy yields on your farm. For example, if a producer is averaging 41 bushels soybeans and his corn yield over that same 5 year period is at 145 or less than prices are going to have to swing favourably towards corn to make corn-on-corn more profitable than planting soys on that same field. On the other hand, if you have been pulling off 170 bushel corn while your bean yields are still stuck at 41 bushels then corn-on-corn may be a very viable option.

If you do move towards some corn-oncorn then take the steps that will give you all the advantages possible. Here are some suggestions.

1. Order the hybrid
It is very difficult to think there is any thing more important than getting the right hybrid for corn-on-corn. Bt-rootworm protection, herbicide tolerant, Bt-corn borer protection, seed-applied insecticide, good stalk strength, and of course high yields are the traits you need to get. Wait to order this hybrid in March when the price of corn gets you salivating and you simply won’t be able to get it.

2. Identify potential fields with better drainage
Potential fields should be targeted where corn-on-corn has the greatest possibility for success. Ideally these may be some of your lighter textured soils or better drained fields where corn roots that are struggling with the stresses of corn-on-corn conditions are not frequently contending with wet soil conditions as well.

3. Identify potential fields where the 2007 corn crop was not herbicide tolerant
This will make controlling volunteer corn in 2008 with your herbicide tolerant hybrid a simple proposition.

4. Consider fall tillage options and improvements
There are some good examples in Ontario of reduced tillage systems working for corn-after-corn. However, my confidence in recommending them is limited. Until we have proven them out further, I recommend fairly aggressive tillage systems. Ensure that your fall tillage operation gets done for corn-oncorn under excellent soil fracturing conditions. Focus on uniformity, both of soil disturbance and residue management. Deep tillage that leaves the soil rough and the residue poorly distributed (i.e. a poorly set up chisel plow) will be tougher to deal with and give poorer results than a good job of discripping or mouldboard plowing.

5. Planter set-up to remove trash
Planter set-up should include precision depth control as in any previous crop scenario, but if corn residues are on the soil surface, it is critical to remove them with trash clearing devices from the row area ahead of the row unit openers.

6. Nitrogen At Planting
If you plan on sidedressing your nitrogen in June, be sure to meet the early N requirements at planting time. Normally we consider 30 lbs N/acre to be a good number for this early plant feeding. However, in a corn-on-corn scenario, where more of the soil nitrogen may be tied up in the decomposition of corn stover, it may be advisable to boost this number by 50% (i.e. 45 lbs N/acre).

7. Use the most economical N rate
Field parameters can be entered into the Ontario Corn N Calculator to help you ensure the most profitable nitrogen application rate for a corn-on-corn scenario. See calculator at www.gocorn.net

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