Many factors influence a producer’s approach to growing corn. Cost and convenience are often the dominant issues being considered. It’s not unlike your decisions surrounding having pizza for dinner. You balance making it yourself (with some associated savings) or order it delivered to the door and pay a bit
more. Cost and convenience arguments are at work when it comes to selecting N application systems as well. Cost is pretty straight forward and includes your N rate, product of choice and application costs. Convenience is more difficult to get a handle on as the issue is rarely about convenience, it’s about efficiency and how the N application system fits best into your operation.

Figure 1. Simon Farms of Rodney, Ontario have equipped their applicator such that sidedressing tall corn is not a problem.

Costs

Some possible N application scenarios and the costs associated with each are outlined in Table 1. One key factor in understanding this table is that we have
selected a pre-plant N requirement of 130 lbs N/acre, the N Calculator is then used to tell us how much this would be as a sidedress rate after putting down 30 lbs of N through the planter. The assumption is that this is a clay loam soil with a sidedress efficiency credit of 20%; hence the amount of N to be sidedressed is 80 lbs/acre not 100. On lighter textured soils this credit to the sidedress system is lower.

You will also notice that in the “weed and feed” approach, where UAN is applied with the pre-emerge herbicide, a cost of only $1.00 per acre was allocated to the N application. This assumes that the remainder of the cost is allocated to the herbicide application. This may be a fair assumption unless the producer has moved completely to post-emerge weed control and therefore this pre-plant application of UAN would have to be allocated the full cost of application, probably an additional $8.00-$9.00 per acre.

Of course many of you can’t access anhydrous ammonia and therefore that fact that this system comes out with the lowest cost is of no interest. Sidedressing UAN at a lower rate based on the N Calculator does provide some cost savings but they are not huge in the big picture.

One observation that most should make is that if nitrogen, say urea, in 2008 costs $0.56/lb of N then applying 30 lb per acre more than the crop needs costs you $16.80/acre and that cost easily overrides savings that you generate using any of the systems.

Convenience

Convenience may be measured by how N application interferes with other crucial farm operations. The sidedressers of the world like the fact that N application is one less thing to worry about in the hectic planting season. On the other hand, preplant applicators shudder to think about applying nitrogen in June when they are finishing beans, spraying herbicides or cutting hay. The other challenge with sidedressing has been the relatively narrow window in which to operate before the corn may get too high to sidedress, especially if rainfall in the first half of June reduces the number of suitable sidedress days.

Simon Farms of Rodney, Ontario have dealt a decisive blow to the narrow window problem. They have equipped their John Deere applicator with a Yetter high clearance tool bar that allows for application of sidedress UAN until the corn crop is 6’ tall. (see Figure 1). Steve Simon points to the increased opportunities to sidedress nitrogen under a wide range of circumstances, “Many times it is a planned approach - but often we are called in to situations where pre-plant applications have experienced problems and we can go in fix things up.” Besides applying nitrogen to all the corn in their family farm operation, Steve runs a custom application business and the toolbar significantly extends that season. When challenged about the crop running out of nitrogen before they get there the Simons are quick to point out that sufficient N is put down up front to carry it into later stages when the applicator arrives.

So, besides the wider window of application, do later applications of nitrogen make any gains in N efficiency or corn productivity? The work on this is inconclusive. Generally we found no indication within Ontario data that sidedress systems out yielded pre-plant corn. It may have taken less N to get there
with sidedress but the overall yields were the same. Some reports have indicated a boost to corn yields with very late applications of N, such as the Simons could perform, but nothing is very convincing to date. A project to work on in 2008!

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