Crops: Crop Scene Investigation - 14: Why is corn breaking down in Chuck's 'best dirt?'

Monday, December 1, 2008

by DAVID TOWNSEND

I was sure that it was serious when I got a call from a corn grower who said that stalks were mysteriously breaking down in his 'best dirt.' Growers know their fields. They know that, when a particular piece of ground delivers year after year, there is cause for concern when things don't look right.

Chuck, a grower from Simcoe County, called from his field just before harvest. "My stalks are breaking down in my best dirt, but they're standing up in the poor dirt. What's happening?" he asked.

I knew the field Chuck was talking about. It has a gravel knoll up near the barn and the opposite, lower end is where he's harvested some of his best yields. What he described was definitely backwards.

I wondered if he had treated the two parts any differently this year. I knew there weren't any varietal differences in the field. Perhaps it was two different crops last year, which could affect available nutrients. "We've been cropping it for 15 years and it's always been one rotation," said Chuck.

I asked if it was possible that he had only manured the knoll. Wrong again. Chuck also shared some soil test results to prove it wasn't a fertilizer issue.

As we walked the field, I could see why he was alarmed. The corn at the lower end had really small ears and was shorter than normal. The plants were stressed, which caused stalk rot, and they were breaking down as a result. Herbicide carryover and insect damage came to mind, but I quickly ruled out both.

Strangely, the crop got progressively better as we walked higher up the knoll. The plants were upright, with better ears and more yield potential.

Chuck and I recalled the season's weather. It had been a wet spring, followed by a dry summer. "That low end is always a better producer than the knoll in dry years," said Chuck. "It usually holds the moisture while the knoll quickly dries out."

Maybe it was a case of inconsistent planting depth? But that wasn't the issue either. What I found when I put my shovel in the ground at the low end unlocked the clue to this mystery. The soil was compressed in layers of flat, thin horizontal plates. The root system was so poor that I was surprised stalks and ears had formed at all. The roots had grown down the seed slot instead of out into the surrounding soil.

I asked Chuck what the conditions were like when he planted. "Well, it was probably wetter than it should have been in this low end," he admitted. I explained what had happened – Chuck was paying now for a decision he had made in April.

Can you positively identify what happened with Chuck's corn? 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

David Townsend, CCA, is Technical Information Manager for NK® Brand, Syngenta Seeds. He is based near Clinton.