It was mid-June when Art, who farms 1,500 acres of canola, wheat, peas, oats and barley 10 miles east of Carrot River, Sask., noticed a problem developing in his oat crop.
Art had reason to be concerned. Areas of his field had deteriorated over a matter of days, and were showing patches of pale green leaves. “It looks like I turned the ammonia applicator on and off,” Art told me over the phone. “But that can’t be the case because the problem is showing in an irregular pattern.”
Art suggested that 3-1/2 inches of rainfall a few days before had caused the nitrogen to leach below the root zone.
Soon after his call, I headed out to Art’s field to see the crop for myself. Once there, I found his crop in exactly the condition he had described — irregular patches of light-green leaves were discolouring an otherwise healthy-looking crop.
On closer observation, however, I saw that only the newer leaves of many plants sported the pale green colour — the older leaves had maintained their natural healthy green hue. Generally, in the case of a rainfall heavy enough to cause nitrogen leaching, the whole plant is affected, not just the new growth — so a nitrogen deficiency couldn’t be causing the discolouration.
“What did you grow on this field before this crop?” I asked Art.
Art said he’d grown alfalfa for the local processor for three years prior to the oat crop. No fertilizer had been applied on the alfalfa field, although he had a fertility program in place for the oats, which included nitrogen.
“I think I know what’s troubling your oats, but we’ll have to do a tissue test just to make sure,” I told Art.
What’s caused the discolouration of Art’s oat crop? Send your diagnosis to Grainews, 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 a Grainews cap and a one-year subscription to the magazine. The answer, along with the reasoning which solved the mystery, will appear in the next Crop Advisor’s Solution File. †