Farmers who are forced to burn crop residue this spring should wait until environmental conditions are favourable.
“We urge them to choose a time when conditions will give good smoke dispersion,” says Zane Lewchuk, a soils and crops agrologist with Saskatchewan Agriculture.
“For example, burning should never take place at night. Knowing the current ventilation conditions can help minimize the risks inherent in agricultural burning. Noting the wind speed and direction is also critical for ensuring that fires can be controlled.”
The Ventilation Index is the best source of information about current ventilation conditions. It indicates how quickly and effectively smoke flushes from an area. The VI can be checked at Environment Canada’s National Air Quality Maps website available on the weather page at www.producer.com, or by phoning the nearest rural service centre.
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Nature also provides its own smoke-dispersal signals. For example, poor ventilation is indicated by stirred dust that tends to linger, or smoke from chimneys or small fires that tends to hang around the source or form a shallow trail that extends downward. Good ventilation is indicated by dust or smoke that does not remain in a column but is dispersed and carried off quickly.
Poor ventilation is also indicated by sounds that carry a long way, fog in low areas or an overcast day with low, smooth-textured clouds.
Cauliflower-shaped clouds and clouds high above the ground are signs of good ventilation.
More information on these indicators may be found at www.agr.
gov.sk.ca/cropresidue.
But Lewchuk said burning should be considered a last resort.
The best alternative is chopping the straw and spreading it uniformly on the soil. Wheat straw contains about 15 pounds of nitrogen, five lb. of phosphorus, 34 lb. of potassium and three lb. of sulfur.
“Nitrogen is the main nutrient lost with the smoke,” Lewchuk said.”Given today’s nitrogen prices, this loss is not insignificant. In addition to providing valuable nutrients, crop residues help build soil organic matter and help prevent soil erosion due to wind.”
