Crop Scene Investigation - 52: Why did Jeff's corn field lose 15 per cent?

Wednesday, November 5, 2014

by BERNARD TOBIN

When late May arrives and the plant population in your cornfield is less than expected, you may have a seed germination problem.

That's what Jeff was thinking as he walked his Chesley, Bruce County, corn field in late May 2013. "It was a cold, wet spring and a lot of corn fields were struggling," recalls Pride Seeds market agronomist Aaron Stevanus, who drove to the 30-acre field to investigate after talking with the grower.

"Jeff really thought it was a germination issue, but the hybrid has a reputation of doing well in tough conditions and we really wanted to take a closer look," recalls Stevanus. "It was cold and wet, so you can expect that five to 10 per cent of the seed won't germinate in those growing conditions, but this field had a stand reduction of about 15 per cent."

As he surveyed the two-leaf corn field, insect damage was one of the first things that Stevanus considered. "Millipedes are a pretty good bet. They're attracted to the CO2 that the seed releases during the germination process and they start feeding, but there was no evidence of millipedes or any other insect damage."

Stevanus noted that the field was corn-on-corn and had been conventionally tilled – plowed, disked and cultivated. "There was poor drainage in spots and it was borderline recreational tillage. It was worked to a fine powder and the tillage appeared to be uneven. In some areas, it was two inches deep, but four to six inches in other parts of the field."

Jeff told Stevanus that the target plant population was 32,000, which meant there should have been a seed about every 6.5 inches in the row. "We started digging wherever a plant was missing and, as expected, we did see some cold injury. In some cases, the seed had germinated and the cotyledon started going up, but when it hit the cool, wet conditions and temperature change, it got confused and started driving downward instead of upward."

But finding the seed wasn't always easy. Many of the unemerged seeds were 3.5 to four inches deep. That got Stevanus thinking. He asked the grower about his planter speed and tillage program. Jeff said he tilled and planted at a depth of two inches and his speed was "good."

But that just didn't add up. Stevanus then decided to dig what he calls a "side profile." He dug a trench along several rows of plants in the field to show how deep the seed was planted. "We started with several healthy picket fence plants that were all planted at two inches, then the seed would dive down to 3.5 inches and then come back up to two, maybe 1.5 inches. The side profile almost had a wave pattern."

As he surveyed the side profile of the row, Stevanus knew there could only be one thing causing the reduced emergence in the field. He asked the grower again about his planting speed. What was Jeff's definition of a "good" planting speed? He replied: "eight miles per hour."

Do you know what caused the poor emergence in Jeff's cornfield? Send your solution to Better Farming at: robertirwin@betterfarming.net or by fax to: 613-678-5993.    

Correct answers will be pooled and one winner will be drawn for a chance to win a Wireless Weather Station. The correct answer, along with the reasoning followed to reach it, will appear in the next issue of Better Farming. BF