Generally, plants require about a tenth as much sulphur (S) as nitrogen (N), but sulphur deficiencies restrict plant growth as surely and severely as nitrogen deficiencies. Canola and alfalfa are examples of high sulphur-using crops (see Table 1).
Sulphur is not mobile in the plant, so a continuous supply of sulphur is needed from emergence to crop maturity. A deficiency of sulphur at any stage of growth can result in reduced yields.
For the first half century or more of cultivation, sulphur deficiency was not a concern on most of our soils because a large pool of organic sulphur was made available as organic matter mineralized. Over time, the pool of organic sulphur has declined significantly, mostly due to use by crops, particularly high sulphur-using crops such as canola and alfalfa (see Table 1).
Sulphur deficiencies occur throughout Saskatchewan, particularly:
- For high sulphur-using crops;
- On sandy soils;
- On gray soils in the northern grain belt; and
- On low organic matter soils