WEST LAFAYETTE, Ind. — For Indiana farmers with a lot of acreage to plant, two Purdue Extension agronomists say it’s probably time to start planting corn while keeping in mind best agronomic practices.

Until recent days, cold temperatures and wet soils kept growers from field operations, including tillage, fertilizer applications and planting.

A few warm days had farmers out in full force, but with a cold extended forecast, many will have to decide whether to go ahead and plant corn or wait for higher temperatures.

Bob Nielsen said it depends in large part on the amount of acreage a farmer has to plant.

“If you farm small enough to where you have less than a week’s worth of planting, I’d wait another week and let the soils warm up,” he said. “But, clearly, if I had thousands of acres to plant, I’d go ahead this week if soils are fit. Some of these soils are drier than what we would expect, but it’s a field-by-field situation.”

The forecast for the next 10 days calls for below-normal temperatures with highs in the 50s and lows in the high 30s to low 40s.

“These temperatures are what we would have expected a couple of weeks ago, and that’s the time when farmers would have started planting in other years,” Nielsen said. “I think planting now is a moderate risk — nothing more than normal. If I had a lot of acres, I’d risk it.”

Part of the risk in planting when it’s cold is that corn might not emerge quickly enough, leaving it vulnerable to pests. The minimum temperature for corn development is 50 degrees.

According to the April 21 Indiana Crop Progress and Condition Report by the U.S. Department of Agriculture, only 1 percent of Indiana corn had been planted as of April 20, compared with a five-year average of 14 percent planted by the same date. Farmers in the state had only 3.7 days suitable for fieldwork in the two weeks prior to the report.

The optimum window for planting corn in Indiana typically is April 20 to May 10, with that window opening a week earlier in the far southern part of the state and a week later in the far north.

But while Nielsen urged farmers with a lot of acreage to go ahead and start planting, he and Purdue Extension agronomist Tony Vyn were quick to point out that farmers need to remember best agronomic practices — especially when it comes to planting quickly on the heels of anhydrous ammonia applications.

“Because weather delayed field operations, there’s now a small window between pre-plant anhydrous ammonia application and planting,” Vyn said. “A rush to plant corn soon after this typical pre-plant nitrogen application has an element of risk associated with it.”

The first roots of corn planted directly over the bands where a full rate of anhydrous ammonia was applied can suffer ammonia toxicity, especially in sandy and cool soils, areas where anhydrous was applied shallowly and when there has been little rainfall between the nitrogen application and seedling emergence.

Vyn encouraged growers to pay close attention to where they apply the fertilizer and to keep it away from the intended cornrows.

Real-time kinetic guidance systems can help farmers both apply fertilizer and plant more precisely, and this can be especially advantageous when there is less than 10 days between pre-plant anhydrous ammonia application and planting.

Another tip Vyn had for growers was to avoid doing unnecessary tillage just for the sake of being in the fields.

“There’s no sense in doing recreational tillage two weeks before planting,” he said. “The best time is a day before planting, so wait until you’re prepared to plant to do tillage. The only reason to do early tillage is if it’s your only weed control, but there are a lot of other weed-control measures.”