Corn growers may want to wait on nitrogen application, particularly in a wet year.
A nitrogen application at the end of June or early July will help limit nitrogen loss and better time it to when the plant is actually looking for the nutrient, speakers said during a recent field day at the Canada-Manitoba Crop Diversification Centre near Carberry.
The corn plant is taking in nitrogen at a prodigious rate between mid-June and mid-August, field tour attendees heard. As of mid-July, more of that nitrogen starts to go to the ear, cob and grain, and grain quickly claims most of that uptake.
“Because corn is such a long-season crop, it takes up the majority of its nitrogen in the second half of the growing stage, once it begins the reproductive phases, so if you can delay your application until the V4 to V8 stage, then you can eliminate about a month or more that the nitrogen sitting in the soil not being used, which eliminates the time in which it can be lost,” said University of Manitoba master’s student Lanny Gardiner.
He hopes to hone in on the finer points of corn nitrogen management, such as placement, source and timing in Manitoba conditions. Most knowledge currently comes from outside the province, he noted.
Manitoba Agriculture looked at split nitrogen rates at 10 sites in Manitoba in 2016 and 2017. Trials simulated different split rates at the V6 stage in 2016 and V8 stage the following year. John Heard, the lead of the project, noted yield response at six of those 10 sites. “Effective in-season decision tools could have eliminated need for additional (nitrogen) application,” at the unresponsive sites, he noted.
For sites that did respond, split application yielded similarly to when an equal rate was applied all at once at seeding.
Heard estimates that about 15-20 per cent of nitrogen is currently applied after seeding. More recently, some producers may have embraced dribbling nitrogen between the rows when corn is more advanced, similar to Gardiner’s research, Heard said.
“We’ve tended to have some dry years in recent years, so there hasn’t been any advantage to doing it. Any perceived advantage would be because there’s been nitrogen losses.”
Excess water in May and June often contributes to nitrogen loss in corn, something growers haven’t had to deal with in recent years.
The in-crop application would be a challenge for newer corn growers who may not have row-crop equipment, Gardiner acknowledged.