Corn acreage has exploded from nearly nothing 50 years ago to 275,000 acres last year — and you only have to look at yields to see why.

Back in 1960, an average crop meant 25 bushels an acre. Today it’s 120, which also is why corn was in the spotlight at Ag Days.

Traditional thinking calls for corn to be seeded when the soil temperature hits 10 C, but Pam de Rocquigny, a provincial feed grains business development specialist, advised growers to get cracking and seed as soon as the ground can be worked in spring.

“Soil temperature doesn’t play as big of a role anymore,” de Rocquigny said in an Ag Days presentation.

“If you can get into your field in the end of April, guys will do that just to get their acres seeded.”

Along with advances in cold tolerance, new seed treatments mean the balance is shifted more towards calendar dates rather than soil temperature, and earlier planting gives a wider window for maturity and yield development before the first fall frost, which, it should be noted, arrived on Aug. 20 in 2004.

But Rob Park, owner of RJP Seed, still considers July 1 a critical milestone for corn development, much like his father did decades ago.

“It’s not scientific, but if your corn is knee-high by the first of July, it’s probably going to make it,” he said in a presentation on crop forensics.

This summer, with his corn developing well and drought south of the border boosting prices, he opted to push his management to a higher level in terms of fertility and pest management.

The result? A bin-busting 140 bushels per acre.

But in 2004, he recalled how his corn was knee-high to a grasshopper by July 8 and it was difficult to even see the rows. The cold and wet summer left it severely stunted and signs of nitrogen and phosphorus deficiencies were visible.

“We had a big decision. Do we put 100 pounds per acre of anhydrous up the rows?” he said. After seeing that his potential crop insurance payout would cover his losses, and discussing his options with various sources, he opted to give up on it.

“Farming to the end is not always the best decision,” said Park.

As for rotational considerations, de Rocquigny said following low-residue crops such as pulses or beans can give corn a boost in terms of warmer soil and residual nitrogen.

But as some growers in 2012 found out, seeding on canola stubble risks having a crop with purplish leaves, yield loss, and wetter grain at harvest due to phosphorus deficiency.

Canola’s lack of interaction with mycorrhizal soil fungi is to blame, and research shows that up to 80 per cent of corn’s early-season uptake of the immobile soil nutrient occurs via the symbiotic fungi.

High levels of starter phosphorus can compensate for this problem, she noted.

Herbicide-tolerant varieties make weed control simple, but letting weeds get higher than four inches can compromise yields, she added.

But while Manitoba farmers are falling in love with corn, growing it isn’t cheap. The provincial Agricultural Department’s 2013 cost-of-production guide for the western side of the province pegs seed at $76 per acre, fertilizer $89 per acre, and drying cost at $35 per acre.

But it pretty much pencils out even at the 10-year average yield of 81 bushels per acre (based on crop insurance data for risk area four) and a price of $5.02 per bushel.

Using the province’s total operating expenses budget of $295.82 per acre, average marginal returns on corn in the southwest stand at $110.80 per acre.

“To cover operating costs, you need 59 bushels per acre. To cover both operating and fixed costs, you need about 78 bushels per acre, and to cover total costs, you need 84 bushels per acre,” said de Rocquigny.