The report from Indiana is that farmers are running out of time to plant corn and expect yields near yield trend lines, but date of planting is not the final determinant for corn yield.

“Planting date by itself does not guarantee or predict yield, but as we get this late now for the remaining planting, it certainly puts a higher risk of getting poor yields,” said Bob Nielsen, Purdue Extension crop production specialist during a Webinar May 27 in which several Extension specialists provided major considerations about planting corn in June.

June planting starts to increase the risk of lower and lower corn yields as every day passes going farther into June.

This year ranks among the slowest planted crops in the state of Indiana. Years of slowed planting in the state in the past 20 years were 1995, 1996, 2002 and 2009.

Delayed planting is not a predictor of yield disaster, just as early planting is not a predictor of higher yield. The 2010 corn planting was the earliest planted corn in the history of recent recordkeeping, but yield was lower than the trend line, noted Nielsen. Also 2009 was an example of a “very delayed planting season and yet because the rest of the summer was excellent weather, we ended up with statewide yields that were 8 percent higher than trend.”

When switching to an earlier hybrid, a main concern in late planting is selecting one with the best disease package, said Tony Vyn, Extension crop systems and tillage specialist. It can be a concern that not all maturity ratings are the same by each seed company. For example, a 105-maturity corn of one hybrid company compared to another one is not always equal.

Growers really might need help figuring out if they want to plant corn after June 20, which is a major date for when a grower needs to plant less than 100-day corn in Indiana. Also, most of the hybrids that short of season are not adapted well to Ohio and Indiana in general and might not be resistant to the disease spectrum of the states.

As every day passes, the risk of lower yield increases; therefore, it is important to not delay corn planting even a day. “The biggest opportunity we have to advance the seeding date on fields that are wet now is to consider doing shallow vertical tillage of undisturbed soil because vertical tillage brings along with it the opportunity to allow for successful planting using a so-called modified no-till system by as much as a day or two before a grower could achieve satisfactory planting in a pure no-till sense,” said Jim Camberato, Extension agronomist. “So, what we are recommending here is basically that there is some advantage to doing some disturbance of matted residue cover, especially following grain corn and especially in those situations where there is uneven residue distribution and where the rains have been such that they have caused a relatively compacted surface.”

Vyn said, “Plant populations target for optimum yield with late plantings is essentially the same as for early plantings. What may differ is the seeding rate to get those optimum plant populations because when we plant in June soils are warmer and you generally get faster germination and more successful emergence. Frankly, I think, if you want 30,000 final stand in June, you can probably seed just about 30,000, which might mean you could back off two or three thousand seed from early planting.”

The suggestion is that soil tests to determine nitrogen availability for the crop needs to be done again, even if it was done prior to fall or late winter fertilizer application. Camberato suggests both ammonium and nitrate analysis.

Both fall and spring applications of N could have been lost and another soil sampling needs to be taken at two depths—less than one foot and at 1 foot to 2 feet. “There is no way to guess how much N might have been lost from the soil from field to field,” Camberato said.

He also noted starter fertilizers usually hasten corn maturities slightly—20 to 40 pounds of N and 10 to 15 pounds of P2O5 is a logical combination.

Accessible N needs determined to calculate possible sidedress needs. Sidedress is the answer because delaying another day in planting to fertilizer is not appropriate.

If N-Serve and Instinct has been used for nitrogen application, there is a label restriction on crop rotation of one year, Camberato said. “If Instinct was used, the only harvestable crop that can be planted is corn. If N-Serve was used, planting can be wheat, sorghum or corn. Other harvested crops would have to be destroyed instead of used for animal or human consumption. It could also be delivered to an ethanol plant.”