This classic research paper provides the foundation for determining copper deficiency in western Canadian soils. Results from more than 1,000 soil samples indicated that copper deficiency is of greatest risk in certain grey wooded soils of the northern prairies. Field trials then determined the response potential to copper fertilizer relative to soil test levels using a DTPA extraction. Combined with growth chamber studies, it was determined that the critical soil test level was 0.4 ppm DTPA extractable copper. In these conditions a copper fertilizer response was often more than 20 percent in tested wheat, barley, and canola. However, it was also determined that copper is highly variable on even fields with uniform topography, so a single composite sample from any field may not be adequate to assess the potential for copper deficiency. In transect measurements of a cultivated soil and adjacent native prairie, the level of copper varied by over 30 percent on 50 meter transects. It is therefore advisable to use the soil test critical level of 0.4 ppm as a guide, but to confirm potential response with strips of fertilizer application.
Below are a couple of examples of copper deficiency in wheat crops:
Sources:
G. A. Kruger, R. E. Karamanos, and J. P. Singh. Can. J. Soil Sci. 65: 89-99.
