Crop Scene Investigation - 28: The curious case of Quinn's corn
Monday, November 1, 2010
Why did the emergence get progressively worse as he moved from the first field planted to the later ones?
by BERNARD TOBIN
In spring 2009, many growers struggled to get their corn planted in rainy, wet conditions. In early June, after the crop was finally planted, Dekalb field agronomist Sean Cochrane got a call from Quinn, a Hastings County grower, asking if Cochrane could help him make sense of the erratic emergence that he had observed in his fields.
"Quinn planted a number of fields over a four-to-five-day period," recalls Cochrane, who headed out to take a look at the fields after receiving the call. "I started at the last field he had planted and then worked back through the first fields. I noticed a significant difference in the amount and type of emergence he was getting.
"The first field had emerged fairly well with the plants at the four-leaf stage. But it got progressively worse in the later fields. Things became quite variable as I worked my way to the final field he planted, where some of the corn was at four-leaf and some was just starting to break ground."
For Cochrane, the first potential explanation that came to mind was soil and planting conditions. Quinn said conditions were not ideal, but they really didn't change much over the planting period. Like so many other farmers in the area, he was battling excessive moisture and a planting window that was quickly closing.
Having worked with Quinn in the past, Cochrane knew the fields very well and promptly ruled out planting conditions as the source of the variability. "The soil was heavy, cloddy ground, but it had fairly high organic matter and good nutrient levels.
"When I looked at the soil conditions of the various fields, I didn't actually see a lot of variation from field to field in terms of cloddiness and the clay content. They all looked to be worked to the same extent with a similar amount of moisture."
Cochrane ruled out any herbicide or weed control issues – all fields were planted with Roundup Ready corn in conventionally tilled fields. But he did feel that fertilizer burn might have been a possibility. "Quinn was putting a small amount of dry fertilizer down with the planter. I looked at what had been applied and there wasn't enough nitrogen and potash, in particular, to cause any burn and we did not see any visual symptoms."
Cochrane's next step was to dig up some seed and see if the answer could be found underground. "When I saw that there was little seedbed variation among the different fields, I knew the answer had to be in the seed trench. Field conditions could not be the sole factor causing this much variation from field to field."
What he found beneath the soil was significant variation in the seed placement when he compared the fields. "In the later-planted fields, there was quite a bit of seed bounce where the seed was not directly in line with each other. Some seemed to be offset just slightly in the rows."
He also noted increased variation in the depth of planting. "Some seeds were an inch and three-quarters and some were pretty much on the surface. I knew then I had to take it in a different direction and start looking at the equipment side of things."
Cochrane then asked Quinn to show him his corn planter. With help from a tape measure and two pieces of paper, he solved the mystery in a matter of minutes.
Do you know what caused the variation in Quinn's corn fields? Send your solution to Better Farming at: rirwin@betterfarming.com 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