John owns a mixed grain and cattle operation near Pincher Creek, Alta. On May 2, 2016, he approached me about one of his canola fields, which he thought wasn’t germinating properly.
“There are areas with no canola at all, just volunteer grain,” he said. “I think I have cutworm issues.”
I drove out to John’s farm to have a look for myself. Right away, I noticed a few things in the field that were of concern. As John suggested, the canola crop looked patchy. Some areas were coming up well, whereas others had only volunteer barley from the previous year — and no canola. In addition, there was substantial crop residue, which was unevenly distributed, throughout the field.
Upon closer examination, I found some of the canola plants looked unhealthy. The leaves of these plants, especially the younger ones, were chlorotic. These injured plants were distributed throughout the field. Specifically, the plants found in lower spots and areas in the field with heavy plant residue were chlorotic, whereas those located at higher elevations and areas with less plant residue were doing well. John’s other canola fields did not appear to be affected.
As a post-harvest burn-off the previous fall, John applied both glyphosate (Group 9) and a tank mix of glyphosate and florasulam (Groups 9 and 2) to his fields. He assured me only glyphosate was applied to the field in question, so I thought it unlikely herbicide carryover was a factor. However, there remained the possibility the sprayer tank wasn’t completely emptied or properly cleaned out before entering this field, resulting in residue contamination.
For two weeks after the crop was seeded, weather conditions were cool and dry, with temperatures dropping to a low of -2 C, briefly, one night at the end of April. John’s other canola fields didn’t appear to be affected by the cool weather, still, knowing every field is different, I wasn’t about to rule out weather issues just yet.
Other than the odd flea beetle bite, I didn’t find any signs of insect damage. In addition, no cutworms were present, and evidence of cutworms, such as cut stalks and freshly clipped leaves, was also absent. Thus, we ruled out pest pressure as the source of damage.
I had a strong hunch the heavy crop residue had something to do with the poor germination in this field. The areas with the heaviest crop residue also corresponded to the patches with no plants. Areas in which we found leaf yellowing also coincided with those of heavy crop residue. From this, I determined what had hindered germination and caused the plant damage.
Crop Advisor’s Solution: Successful seeding requires straw management
John and I monitored the crop closely for the following week to see if the damaged canola plants would recover, or if we had to consider reseeding. Fortunately, the crop survived the cold stress and produced a decent crop. However, there were some thin patches where yield was lost and the uneven plant population resulted in varied maturities, which provided a challenge when timing the swathing operation.
Residue management is often overlooked, and if not managed properly can lead to many problems the following season. Heavy residue can cause emerging crops to be stunted and, in severe cases, can stop plants from coming up altogether. Also, heavy residue levels on the field’s surface can prevent the soil from warming up in spring, and may increase frost damage risk.
In the fall, it is important to set the combine up properly, so that it chops the straw adequately and distributes it evenly across the field. In cases like this, where the straw is particularly heavy and is not evenly distributed, a grower may consider going over the field with a tillage implement to bury and/or spread some of the residue. For example, harrows will spread the straw.
Nathan Zilinski, CCA, AIT, works for Richardson Pioneer Ltd. in Magrath, Alta.