Heat has been in short supply this spring in most of the corn-growing region of Ontario, and cool conditions will impact the amount of nitrogen available to the corn crop in the early portion of the growing season.
When it comes to determining the rate of nitrogen growers should be applying at sidedress timing, Ontario Ministry of Agriculture, Food and Agribusiness soil fertility specialist Colin Elgie says it's important for growers to know how much nitrogen is actually coming from the soil.
"We know that all the nitrogen that goes into our corn crop doesn't just come from the fertilizer. A lot of that comes from that soil organic matter, things like crop residue, manure and cover crops — all that stuff that's mineralizing in the soil," says Elgie. "When we've had a cool spring like we've had this year, a lot of those microbes haven't been able to really get to work to mineralize that nitrogen, which means we've got a lower soil supply overall.
On this episode of the RealAgriculture Corn School, Elgie and host Bernard Tobin talk sidedress strategy at Ridgetown College where crops had received about 400 corn heat units as of May 31, about 50 CHU below the 10-year average. In these conditions, Elgie says growers can assume they have less nitrogen, but availability is highly variable and needs to be assessed on a field-by-field basis.
In the video, Elgie stresses the importance of pre-sidedress nitrate testing (PSNT) and shares tips on how to best collect soil samples for lab analysis. He adds that these recommendations are calibrated for fields with less than 30 pounds of nitrogen upfront, so it's important for growers to maintain a good database of past practices and fertility history that can be used to adjust nitrogen rates based on current test results.
Elgie also notes more growers are including nitrogen stabilizers in their sidedress strategies. He says the addition of nitrogen stabilizers depends on the risk of nitrogen loss. This year's cool conditions have reduced volatilization potential, but hot and dry conditions can increase the need for stabilizers.
Tap here for more on anticipated soil nitrogen supply for Ontario's 2025 corn crop.
See Related: Corn School: 4Rs drive side-dress nitrogen application
Tap here for more Corn School videos.
