Top Dress Canola With Sulphur Deficiency
Some canola fields are showing signs of sulphur deficiency. In many cases, the fields have ample nitrogen, but are short on sulphur. Without enough sulphur, it doesn't matter how much of the other nutrients are available, the canola crop cannot produce top yields.
Post-emergence sulphur can be applied up to early flowering and still provide a yield benefit.
With sulphur deficiency, yellowing and leaf cupping tend to occur on new leaves first. Purpling of leaf edges can show up when deficiency is fairly severe. In fields short of sulphur, crops can usually find enough to get past the early rosette stage without visible symptoms. Deficiency symptoms often show up at flowering, which can be helped if detected early. Growers who suspect they may face a sulphur deficiency may want to take action now. (Click here and scroll down to the sulphur section for examples.)
Ammonium sulphate (dry) or ammonium thiosulphate (liquid) provides sulphur that is immediately available to the crop.
Purpling around leaf edges is one sign of possible sulphur deficiency.
Be skeptical of miracle cures. High yielding canola needs large amounts of N, P, K and S. Crop nutrition products that claim to meet canola's needs without supplying the pounds of nutrient required should be regarded with skepticism.
Fertilizers are registered through the Canadian Food Inspection Agency (CFIA), but not all crop nutrition products are registered. Controlled release coatings, urease inhibitors and inoculant extenders, for example, do not fall under the regulatory authority of the Fertilizers Act. When these are mixed with a fertilizer, the end product is regulated, unless the enhancers or extenders are put into a custom fertilizer blend (in which case registration is not required).
The CFIA's Crop Inputs Division "encourages" manufacturers of these products to seek a "Letter of No Objection" (LONO) from the CFIA to ensure that their use in fertilizers and supplements results in final products that meet safety, efficacy and labelling standards. This is something growers can request if they are looking for additional assurance related to claims made by providers of these products.
For more on top dressing, click here and here.
Source: Canola Council of Canada