QUORUMAG

Quorum Ag · The wiki learn-wiki-sulfur.html

Minerals · protein’s partner

Sulfur

Works with nitrogen Episode 5 4 min read

The short version

Sulfur is built into protein alongside nitrogen, so a crop short of sulfur can’t finish the nitrogen it’s taken up. It’s also the bite in onions and garlic, and canola needs plenty of it. It doesn’t move much once it’s in the plant, so a shortage shows in the young leaves first.

Onions and garlic, canola and the other brassicas use the most sulfur. It’s the bite in an onion.

What it does

Sulfur is built into protein alongside nitrogen: two of the building blocks the plant strings together into protein carry sulfur. As a rough guide, a cereal takes up about one part sulfur for every ten to fifteen parts nitrogen. Canola takes up far more: nearer one part sulfur for every six parts nitrogen. Short of sulfur, the plant can’t finish the nitrogen it’s taken up. The nitrogen piles up unbuilt: the same backed-up assembly line Steve talks about with nitrogen.

Sulfur is also the bite in onions and garlic and the heat in mustard and the other brassicas, and canola needs plenty of it to set a full crop of seed.

Nitrogen, in a building block. Sulfur.

  • A young canola plant in early flower, its leaves an even blue-green.

    Enough sulfur

    the chain finished

    every link built, and the young leaves stay green

  • The same canola plant, its young upper leaves pale yellowy green all over.

    Short of sulfur

    the chain stops

    no sulfur for the next link: the nitrogen waits, and the young leaves go pale

Protein needs sulfur for some of its links. Short of it, the plant can’t finish its nitrogen, and the young leaves pale first. An illustration, simplified.

Young leaves first

Sulfur doesn’t move much once it’s in the plant, so a shortage usually shows first in the young leaves: pale, yellowy green, often all over, veins and all. In canola the young leaves can also cup, rolling inwards, and as the shortage deepens they can go pale between the veins. Young leaves first is the clue that sets it apart from nitrogen. Nitrogen moves, so its shortage yellows the old leaves first. A crop short of sulfur can look hungry for nitrogen even when it’s had plenty.

Sulfur, in the plant. Nitrogen, in the plant. Held: barely moves.

  • A flowering canola plant, its young upper leaves pale yellowy green all over.

    Short of sulfur

    canola

    the young leaves pale first: sulfur barely moves once it’s in the plant

  • The same canola plant, its big old lower leaves pale yellow all over and its young upper leaves green.

    Short of nitrogen

    the same canola

    the old leaves yellow first: nitrogen moves out of them to the new growth

Sulfur barely moves once it’s in the plant, so a shortage shows first in the young leaves. Nitrogen moves, out of the old leaves to the new growth, so its shortage yellows the old leaves first. Young leaves or old is the clue that tells them apart. An illustration, simplified.

In the soil

Most of a soil’s sulfur is held in its organic matter. The soil life releases it as sulphate when the soil is warm and moist, and sulphate washes through the soil easily. So crops run short in cold, wet springs, before the soil life gets going, and on sandy soils after heavy rain, even where there’s plenty in the ground.

Sulfur, as sulphate. The soil’s life. Blocked: stays locked up.

  • A young canola rosette, cut away below the ground: green leaves, a slender taproot, and dark crumbs of organic matter in the soil around it.

    Warm and moist

    young canola, in spring

    the soil’s life frees the sulfur, and the roots take it in

  • The same canola on a cold, wet day: puddles on the soil, and its young centre leaves pale yellowy green.

    Cold and wet

    the same canola, in a cold, wet spring

    the life is slow to wake, the sulfur stays locked up, and the crop runs short

Most of a soil’s sulfur is held in its organic matter. Its life frees it, as sulphate, when the soil is warm and moist. In a cold, wet spring it stays locked up, and the crop runs short with plenty in the ground. An illustration, simplified.

Sulphate or elemental

Sulfur goes on in two forms. Sulphate is the form the roots take up, so it works straight away. But it moves with the water, and on a sandy soil a heavy rain can wash it down past the roots.

Elemental sulfur, the yellow kind, can’t be taken up as it is. The soil’s life has to turn it into sulphate first, and that’s slow: faster in warm, moist soil, and when it’s ground fine. So it comes on slowly and lasts longer. And as it’s turned into sulphate, it makes the soil more acid: a help on alkaline ground, a cost on acid ground.

Sulfur, as sulphate. Elemental sulfur. The soil’s life. Rain.

  • A young canola rosette, cut away below the ground: green leaves, a slender taproot, and dark crumbs of organic matter in the soil around it.

    Sulphate

    young canola, sulphate on

    the roots take it up straight away, but a heavy rain can wash it down past them

  • The same young canola, cut away below the ground.

    Elemental

    the same canola, elemental sulfur on

    the soil’s life turns it into sulphate first, so it comes on slowly and lasts longer

Sulphate is the form the roots take up, so it works straight away, but it moves with the water, and a heavy rain can wash it past the roots. Elemental sulfur has to be turned into sulphate by the soil’s life first: it comes on slowly, lasts longer, and makes the soil more acid as it goes. An illustration, simplified.

When it matters most, crop by crop

The stages where sulfur is one of the minerals that matter most, in the program builder’s seasons. Each bar is a whole season, from sowing or planting to harvest, or a tree’s year. Build yours in the program builder.

  • Potatoes about 120 days

    Maturation

  • Beans about 70 days

    Maturity

  • Carrots about 120 days

    Bulking

  • Onions about 180 days

    Bulb filling and maturation

  • Sweet corn about 90 days

    Kernel fill

  • Cotton about 180 days

    Boll fill

  • Wheat about 170 days

    Grain fill

Where it fits in a program

  • Match it to the nitrogen. When you feed nitrogen, check that sulfur is keeping up.
  • Watch the big users: canola and the other brassicas, onions and garlic.
  • Plenty of common inputs carry sulfur as sulphate: gypsum, potassium sulphate, ammonium sulphate. Elemental sulfur is slower, because the soil life has to convert it first, and it makes the soil more acid as it does.
  • Keep calcium and sulphate out of the same tank. Together they can form gypsum, which drops out and blocks the lines.
  • Test the young leaves as well as the old.