Crop Scene Investigation - 31: Why was excess residue accumulating in Richard's fields?

Sunday, February 6, 2011

by BERNARD TOBIN

How growers manage crop harvest residues in their fields can have a huge impact on the performance of the crops that follow.

For the past two years, Brian Hall, an Ontario Ministry of Agriculture, Food and Rural Affairs edible beans and canola specialist, has been working with Richard, a Wellington county grower, to help him manage the high levels of residue remaining in his canola fields after harvest.

"Richard had been no-tilling his winter wheat after canola for a couple of years and he was having a lot of trouble with 'hair-pinning' (residue pushed in but not cut) and seed placement," explains Hall. "Excessive residue was reducing drill penetration at planting, and we were also seeing chaff being forced into the furrow. As a result, he was getting poor seed-to-soil contact, poor establishment and winter kill in his winter wheat crop."

Hall's prescription for the problem was better residue management, which led to Richard deciding to purchase a residue management tillage tool that allowed him to break up and partially incorporate the canola residue before planting his winter wheat.

"Last October, I went out to one of his fields to see whether his solution was working," recalls Hall. "Richard had told me his wheat had good establishment and he was really pleased how things had worked out." Hall noted the field's improved establishment and excellent plant distribution and population, but he also noticed an odd pattern emerging across the wheat field, which was at the three- to four-leaf stage.

"Richard hadn't really noticed it, but I pointed out these narrow strips, probably three or four rows wide, across the field," says Hall. "The plants were a shade lighter in colour – a yellowish, pale green – and a little smaller and slower to develop."

Richard had applied 100 pounds per acre of monoammonium phosphate (MAP) with the seed at planting and also broadcast 200 pounds per acre of 6-24-24, so there should have been enough nitrogen available to the crop at this stage of growth. Prior to the three to four-leaf stage, wheat seedlings live off the food reserves in the seed.

Hall says Richard was puzzled because he felt he did everything right. The grower made special note of the job his residue manager did in incorporating the large amounts of residue produced by a tremendous canola crop that yielded 3,500 pounds per acre. "When I finished with the residue manager, the field was black, everything was incorporated," Richard told Hall.

When Hall started digging up the discoloured plants, the puzzle started to fit together. About three inches down in the yellow areas, he consistently found a one-inch thick mat of canola residue. He also noted that the yellow stripes could be found about every 25 feet across the field.

Do you know what caused the discoloured narrow strips in Richard's winter wheat? Send your solution to Better Farming at: rirwin@betterfarming.com or by fax to: 613-678-5993. Be sure to include your complete contact information with your answer.

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