Crop Production News 2018 - Issue 2
By Ken Panchuk, PAg, Provincial Specialist Soils
It is widely known that sulphur is required for healthy stands and optimum yield of canola. However, sometimes sulphur application on canola is missed for one of many reasons, such as crop switching (a change in rotation at the last minute) during seeding. Post seeding application of sulphur is a viable option to correct sulphur deficiencies, but timing is important.
Sulphur is not mobile in plants, so a constant supply of sulphur is needed from shortly after emergence to the completion of seed filling. A shortage of sulphur at any stage of growth can result in reduced yield. When scouting fields, sulphur deficiency symptoms will appear in patches and seldom in the entire field. If symptoms appear in patches, take action by broadcasting some ammonium sulphate as soon as possible.
Sulphur deficiency symptoms on the first true leaves can be cupping upward of the leaves and/or yellow spotting. Other symptoms are:
- Cupping upward of the leaves with possible reddening of the underside of the leaf margins;
- Interveinal yellowing of the newest leaves;
- Spindly plants;
- Smaller pale yellow flowers; and
- Poor pod development with poor seed filling resulting in delayed maturity.
Research has shown that ammonium sulphate can be applied up to the early flower stage to rescue yield. However, the earlier the application is made, the better the chance of recovering full yield potential. For more information, see Sulphur Fertilization in Crop Production.