Crops: Crop Scene Investigation - 7: Tracking down suspects in Alistair's alfalfa

Wednesday, December 19, 2007

by DAVID TOWNSEND

I love my job because it keeps me on my toes. Every now and then I get a call from a grower with a problem that really challenges my agronomic knowledge. That's one of the reasons I enjoy the agriculture industry - there's always something new to learn.

I got a call in the spring from Alistair in Wellington County with a situation that really had me stumped. He was discouraged by the emergence of his newly seeded alfalfa crop. "It's coming up in strips throughout the field," he said. "Do you think the rest will fill in?"

Not having the benefit of seeing the field, I needed Alistair to paint me a picture. "Does it look good anywhere?" I asked.

"The headlands are okay and so are the strips I mentioned, but the parts in between have as few as two plants per square foot," he said.

This was far from the target of 20 plus plants per square foot we try to achieve in the seeding year. Because you leave alfalfa down over a two-to four-year period, and it thins as the years pass, you need strong establishment in the first year.

I wondered if Alistair's equipment was the culprit. He had direct seeded three weeks prior using a no-till drill at a rate of 18 pounds per acre, well within our recommendations. "Have you changed your equipment in any way?" I asked. "No, I've been doing this for a number of years and I've always had good results," he said.
Weather had to be at play here - alfalfa emergence requires moisture and
I thought perhaps it was too dry. But Alistair dashed that theory. "We had a really nice rainfall after it established."

Soil condition, type and fertility were the next suspects to investigate. "We started planting early in the morning and the soil condition seemed to be fine," said Alistair. "Have you ever had to lime the field?" I asked, wondering about the fertility of the clay soil. "No, we had a soil test and the pH was 7.5."

Herbicides can sometimes interfere with crop emergence. Alistair said the field was coming out of soybeans treated with Pursuit the year before. There's no carryover concern here as Pursuitis registered on alfalfa.

On the drive to Alistair's field, I pondered another puzzling piece of evidence - the crop had slightly better emergence in the section of the field planted later in the day. I could see this for myself as I walked the field. I also noted my boots were sinking deeper than expected into the soil. I asked Alistair to describe his seedbed preparation and planting process. "We used a coulter cart to loosen the ground," he said. "Next, we ran a no-till drill with the seed openers and scattered the seed through the forage box onto the soil's surface. Then we went around the field once more with a packer."

Alistair wasn't kidding about the strips - there was perfectly emerged alfalfa in the tractor tracks up anddown the field. This was all the evidence I needed to close this case.

Can you positively identify the problem with Alistair's alfalfa? 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.

Have you solved the mystery of the wilted soybeans featured our November investigation? For the first time since this series began we seem to have stumped our readers. Keep trying! BF

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