Crop Scene Investigation - 27: What happened to Larry's wheat?
Wednesday, October 6, 2010
by BERNARD TOBIN
Agronomist and certified crop advisor Paul Sullivan spends a lot of time walking fields. In late June, you can find him out in wheat fields trying to determine the best application timing for fungicides. He knows what he's looking for – a field that has even heading with 75 per cent of the heads on the main stem fully emerged.
But that's not what he always finds. Last June, while evaluating a field for Larry, one of his grower clients, Sullivan spotted a curious looking area in the middle of the field. "There was this block that was not as advanced as the rest of the field," recalls Sullivan. "It almost looked like a different variety. The plants were shorter and the heads were not out as complete as the rest of the field."
After consulting with Larry, Sullivan found that the entire field had been planted with the same variety on May 5. The spring wheat was no-tilled into soybean stubble, which had produced IP soybeans the previous year. There was some perennial weed pressure at planting, which required a burndown.
"Initially, I thought a part of the field might have emerged before the burndown was applied. That could have explained the delayed development. But the application timing ruled out that theory," says Sullivan.
"When the burndown was done, the field was a bit sticky, so I could see the sprayer tracks and it was obvious that the spray application did not line up with the damaged area."
As he surveyed the field, he noted that the block began just off the headland of the field, at a point where the drill would enter the field for another run. That raised the question of seeding depth, but further investigation revealed there was no difference in the affected area compared to the rest of the field.
Still, Sullivan was convinced the slow-developing plants were linked to Larry's new drill, which he had purchased just two years ago.
"The problem with the block looked like something related to the planting operation, so I decided to focus on fertilizer. Larry was applying it in-furrow through the drill. It was 9-43-10 at 75 pounds per acre. After planting, he then broadcast urea with Agrotain on it at 175 pounds per acre.
"There should have been no nutrient issues, but I decided to compare the fertility for the affected area and the rest of the field. We had had poor growing conditions in May and June and, in a no-till field, the effect of the starter fertilizer was going to be more dramatic than in other years."
When Sullivan reviewed the results, he was surprised that the phosphorus levels in the poor-performing block were quite low. It didn't make sense.
"I asked Larry if he had changed anything on the drill while he was in the field. He thought about it and told me that he did increase the seeding rate on the planter before finishing up the field – specifically, the area that made up the block. It was late in the planting season, and he explained that he was getting into a new batch of seed and wanted to make sure he had a good plant population, so he adjusted the rate before finishing off the field.
"With this revelation, I walked into the field and did several plant counts in the block and the normal areas of the field. When I compared the results, there was no difference in the plants per acre."
There could be only one answer to this riddle.
Do you know what happened in Larry's wheat field? 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