Edward farms 14,000 acres of wheat, canola, barley and yellow peas east of Vulcan, Alta. I was surprised to hear from Edward a week after I had visited his farm — his crops looked great at the time. He said he was very concerned about his barley field. In the past week, almost every plant in the field was turning yellow. “You need to take a look at my field, I think I’ve got an herbicide carryover issue,” he told me. When I scouted that field the week before the plants had looked green and healthy.
When I arrived at the field I noticed right away the barley was in a state of stress. The plants, at the three-to four-leaf stage, were yellowing and somewhat stunted in their growth. The lower leaves were yellow and turning brown from the tips inward. In some areas of the field, certain weeds, such as stinkweed, were purpling. But there appeared to be no correlation between the location of purpling weeds and yellowing barley to each other or position in the field.
Edward had applied fertilizer to the field in the fall of 2009 in the form of anhydrous ammonia. The field had been sown to barley on canola stubble, and had been planted north to south, but I observed a distinct striping pattern running northeast to southwest. Here, healthy plants were present in distinct rows at an angle to the seed row. We headed to Edward’s other barley field a mile down the road only to discover that field showed exactly the same symptoms!
As I looked at Edward’s yellowing stand of plants, I considered the possible sources of its quick deterioration. Could the problem be environmental — we’d had a lot of rain already that spring — or maybe frost caused the damage? Perhaps herbicide application, drift or carryover was responsible? When we checked weather records, we discovered no frost had been reported in the area, also the adjacent field of wheat showed no signs of damage due to frost or heavy precipitation.
In 2010, no in-crop herbicide had been applied to this field, and after consulting Edward’s neighbours, we determined drift was not an issue because no fields had been sprayed during the past two weeks. There was evidence of herbicide carryover from 2009 but because the barley plants did not show any signs of purpling (a symptom of carryover from that particular type of herbicide), marker weeds that are known to be susceptible to the herbicide were healthy and Edward’s other barley field showed exactly the same symptoms of stress yet different herbicides had been applied to this field in 2009, I concluded carryover was not causing the damage to the crop.
Tissue tests taken from the lower leaves of healthy and unhealthy plants confirmed what I thought might be causing the problem in Edward’s barley field.
What is causing Edward’s barley plants to turn yellow? Send your diagnosis toGrainews,Box 9800, Winnipeg, MB, R3C 3K7; email [email protected] or fax 204-944-5416 c/o Crop Advisor’s Casebook. Best suggestions will be pooled and one winner will be drawn for a chance to win aGrainewscap and a one-year subscription to the magazine. The best answer, along with the reasoning which solved the mystery, will appear in the next Crop Advisor’s Solution File.