Sulphur

  • Top-dressing at early flower

    Sulphur

    Pale flower colour can hint at sulphur deficiency. This photo shows sulphur deficient flowers on the right, normal on the left.

    The ideal time for a sulphur top up is any time before flowering, but a top up at early flowering may pay off if plants are showing signs of sulphur deficiency.

    The ideal time for a nitrogen top up is before the 5-leaf stage of canola, but AAFC research out of Indian Head, Saskatchewan, shows that nitrogen top dress as late as 5-10% flower can still provide a yield benefit.

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  • Top dress: Identify N and S deficiency

    Sulphur

    Sulphur deficiency symptoms include cupping and purpling of leaves, but soil tests and a knowledge of cropping history will help to confirm.

    Growers who used elemental sulphur as their only sulphur source may see deficiencies in this year’s crop. Elemental sulphur will not be available when the crop needs it. In following the 4-Rs of fertilizer, elemental sulphur applied at seeding is not the “right source” or the “right time.” Sulphur deficiency symptoms (see the photos) that appear at the bud to bolt stages can be fixed with a top-dress of ammonium sulphate, a highly available source of sulphur.

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  • When does top-dress fertilizer make sense?

    Sulphur

    Click here for more information on products, rates and timing for best results from a fertilizer top-dress. This article has just been updated.

    If you’re on the fence about a top-dress application, consider applying a rate high enough to make a difference — such as 30 pounds of nitrogen or 20 pound of sulphur — to part of a field. Mark the location and compare yields for treated and untreated areas. Increasing greening does not necessarily translate into increased yield, so a simple observation of crop colour is not enough to determine the value of the top dress. If you do see a yield difference, the best solution may be to increase fertilizer rates at seeding.

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  • N does bad things when S is missing

    Sulphur

    When fields are sulphur deficient, canola that receives only nitrogen fertilizer (front left in photo) can yield less than canola that receives no fertilizer at all (right in photo). Canola plants need sulphur to produce three key amino acids: methionine, cysteine and cystine. Without the S to build these amino acids, N creates toxic amides in the plant that greatly inhibit seed set.

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  • How much fertilizer does canola need?

    Sulphur

    When setting fertilizer rates, it helps to know your target yield and how much fertilizer canola needs per bushel of yield. Some of that will come from soil reserves and from organic matter. The rest has to be applied as fertilizer.

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