Corn School: Scouting yield potential improves crop management


With June arriving this week, corn is rushing ahead and growing rapidly.

Now’s the time for growers to get out and scout fields to identify planting issues, determine yield potential and start fine-tuning your management plan, says Kinburn, Ont., agronomist Paul Sullivan.

On this episode of RealAgriculture’s Corn School, Sullivan notes that stand assessment and plant counts are a critical measure for early-season corn.

To calculate plants stands, he counts the number of plants in 1/1,ooo of an acre (17.5 feet on 30-inch rows) in four different rows, then averages the counts and multiplies the average number of plants by 1,000 to obtain the plant population per acre.

“Count the number of plants, and look for uniformity of plant development and even emergence — you want them all at the same stage,” says Sullivan. It’s also important to assess the seedbed, noting soil conditions and look for any seed slot issues that may restrict early development of the root system and lead to less uniformity. If the stand has issues, it’s critical to determine if they are linked to soil conditions at planting, planter problems or other causes.

What does optimum emergence look like? Sullivan says if growers plant 35,000 seeds, a strong population would range from 33,500 to 34,000 evenly emerged plants at the same stage of development. He wants seeds to emerge within two to three days of each other. Later-emerging plants are typically one to two leaf collars behind and have significantly less yield potential.

“If we start to see 2,000 to 3,000 plants per acre (six to nine percent) that are behind by one leaf collars we will lose basically half the yield on those plants — cobs will be half the size,” says Sullivan. “If we’re two leaf collars behind we don’t have a cob at all.” (Story continues after the video.)

Sullivan notes that high yielding fields with even emergence will produce the equivalent of eight bushels per 1,000 plants. Fields with lower populations and/or late-emerging plants can easily reduce a field’s yield potential from 230 bu/ac to 200 bu/ac and lower.

There’s nothing growers can do to replace that lost yield. The focus then shifts to management decisions that optimize yield and profitability. In the video, Sullivan discusses how growers should use a yield potential assessment to best manage in-season inputs, including nitrogen rates and fungicide application.

It all starts with scouting, says Sullivan. “Get out and understand what you can control. If there’s weeds there right now, you have to get them out of there because they are going to take their toll.”

If growers know their yield potential, and the weather co-operates, they can make effective management decisions throughout the season. When it comes to nitrogen, for example, Sullivan says: “Once we get into side-dress timing, if it looks like we are short on nitrogen we may want to increase our rates.”

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