Mid-May last year, I got a call from a farmer who had healthy green fields of barley one week, and yellowing stands of stunted, dying plants the next. I had scouted the fields only the week before — and everything looked fine. Edward, who farms 14,000 acres of wheat, canola, barley and yellow peas east of Vulcan, Alta., told me almost every plant in the field was turning yellow. He thought he might have an issue with herbicide carryover.
At the field, straight away I noticed his barley, at the three-to four-leaf stage, was stressed. The plants were yellowing, stunted in their growth and the lower leaves were turning brown from the tips inward. The history of Edward’s field seemed normal: he had applied fertilizer to the field the previous fall in the form of anhydrous ammonia, the field had been sown to barley on canola stubble and had been planted north to south. No in-crop herbicide had been applied that spring. What did not appear normal was a distinct striping pattern running northeast to southwest in which healthy plants were present in distinct rows at an angle to the seed row.
Together, Edward and I considered the possible sources of the deterioration of his barley plants. We ruled out environmental factors such as frost and heavy precipitation because no frost had been reported and an adjacent field of wheat showed no symptoms of stress due to rain or frost. We contacted Edward’s neighbours and determined drift was not an issue because the surrounding fields had not been sprayed in the past two weeks. There was evidence of herbicide carryover from 2009 but because no barley plants showed symptoms of carryover, such as purpling, marker weeds appeared healthy and another field of barley Edward had planted was showing exactly the same stress symptoms yet different herbicides had been applied to this field in 2009, we concluded carryover could not be damaging Edward’s barley plants.
I took some tissue tests which confirmed my suspicion — the yellowing plants were deficient in nitrogen and the samples taken from the healthy plants in Edward’s field had sufficient levels. Thus, some areas of Edward’s field were nitrogen deficient. This result surprised Edward because in the fall of 2009 he had applied nitrogen to his field in the same way — in the form of anhydrous ammonia — that had generated successful results for him for many years.
Edward had applied 80 pounds of nitrogen, but the dry soil conditions the previous fall combined with the heavy rainfall (eight inches) right after seeding of the barley, made the nitrogen inaccessible to the plants, with the exception of the plants growing in the areas of concentrated anhydrous ammonia — the drill rows. These areas, forming bands in the fields where water did not leach nitrogen deep down into the soil profile, provided enough nitrogen to allow normal growth and development of the plants.
Good management practices include applying fertilizer in the correct amounts, at the proper place and time and in an appropriate form. Applying fertilizer in the fall means higher risk of nitrogen losses and a strong possibility of a deficiency. If applying nitrogen in the fall, it is important to remember the soil temperature should be below 5 C. This will ensure that the applied fertilizer remains in a form that is less susceptible to losses. Another option is to apply 30 to 50 per cent of the total nitrogen requirement as slow-release nitrogen in the spring with the seed, enhancing nitrogen availability throughout the entire growing season.
To Edward, I recommended a foliar application of nitrogen for his barley crop. Within a few days the crop was already showing signs of growth and recovery. In the end, Edward was happy — the fields yielded around 70 bushels per acre.