Consider Elemental S For The Long Term

If the sheer volume of product running through the seeder is bogging you down, it might be time to give an old product a fresh look. Elemental sulphur (S) is bulky, sure, but when put down in sufficient quantities it can provide enough S for three or four growing seasons. The key element to making this fertilizer form work is time.

Elston Solberg, senior agricoach and president of Agri-Trend Agrology, completed his master’s thesis on elemental S in 1986. “We figured out then how to make elemental S work, and here we are in 2010 still rehashing all the arguments of sulphate forms versus elemental S,” he says. It doesn’t need to be as complicated as many make it out to be, he says.

“The primary factors to consider are particle size and the degree of particle dispersion in or on the soil,” he says. If you can wrap your head around what has to happen and the factors that affect the microbial conversion of elemental S into the plant available sulfaphe form you can make elemental S work on your farm.

ALLOW FOR BRIDGE YEAR

Solberg says that the finer the original particle size of the elemental S, the faster the conversion to sulphate form. Plants can only take up sulphur in the sulphate form, so it’s essential that enough of the elemental form converts each year in order to feed the crop. It’s possible to achieve a 50 to 60 per cent conversion in the first year if the particle size is fine and the product is exposed on the soil surface to allow for weathering. Where farmers often make a mistake is by putting the product down in a band or with the seed. “Not enough breakdown happens, maybe 20 per cent per year, in the seed row,” Solberg says.

Farmers considering using elemental S need to account for what Solberg calls the bridging year. “It’s critical that the elemental S go down with enough sulphate to provide for the current year’s crop, especially if you’re putting it on in the spring,” Solberg says. “Putting down both will hedge your bets in the first year.” He recommends a spring application of elemental S go down with a low-demand crop such as a cereal, allowing enough time to pass before a high-demand crop, such as canola, starts drawing on the converted S.

“A more common strategy is to surface-broadcast say 200 pounds of elemental S which should provide enough S for three or four crops,” he says. Some farmers with a lot of sulphur-loving canola in rotation may go as high as 300 pounds or more in the fall.

A good portion (as high as 60 per cent) of fall-applied elemental S should be available for the following crop, if put down in sufficient quantities. Broadcast application works just fine for elemental S, as there’s no need to fear the same volume of losses that fall-applied nitrogen is subject to. Sulphur can leach through the soil profile but only the portion that has been oxidized, to the sulfate form.

SLOW-RELEASE PRODUCT

There are two major advantages to elemental S: a one-in-three (for canola heavy rotations) or one-in-four- year application frees up tank space at seeding; and, it’s a natural slow-release product. The advantage of shifting bulk out of the seeder is an easy one to accept, but a year like 2010 really drives home the benefit of a slow-release product in the soil.

“This growing season, the fields that had elemental S put on last fall or even before that had significantly higher S levels in tissue samples than those that had had sulphate forms of S put down in the spring,” Solberg says. That’s the beauty of a slow-release product. While yes, some leaching occurred with all the moisture this year, the elemental S continued to weather and release S as the season continued. For many canola fields especially, elemental S meant the difference between adequate S and a deficiency regardless of what was applied in the spring.

But it’s this slow release that can trip up farmers. “The most common pitfalls when making the switch is under applying S in the first year or applying elemental S inappropriately, such as in the seed row, which only results in about 20 per cent availability,” Solberg says.

What’s more, a mature elemental S production system has no need for the high seed-placed S rates that can cause seed toxicity concerns. It means not worrying about including sulphur in any of your fertilizer blends.

Incidentally, this strategy will work in the fall, early spring or even after seeding

ACIDITY CONCERNS

There are those who say they won’t use elemental S because of its acidifying nature. Solberg says that yes, as elemental S converts to sulphate forms, the immediate area around the particles will acidify to a degree, but he likens it to the difference between an ember and a bomb. “Elemental S breaks down slowly, causing a slow and steady heat versus ammonium sulfate which explodes like a bomb in the soil,” he says. However, that discussion is somewhat misplaced, as he says that if your soil is so acidic you’re worried about this low level of acidifying then you’ve likely got bigger issues that need addressing.

The long and the short of it is, the amount of acidifying that occurs when using any S form is minimal and of little consequence in most soils and shouldn’t be a reason to skip applying S. “All fertilizers (including nitrogen) have some acidity associated with their application,” Solberg says. In some cases, such as those with alkaline soils, the acidifying nature can work in your favour.

While sulphur is always a focus of canola production discussions, the nutrient is important to all crops, Solberg says. “Every crop has an ideal nitrogen to sulphur ratio. When sulphur is lacking, even for cereals, yield potential and quality can suffer,” he says.

The only way to ensure proper levels of both nutrients is through soil and tissue samples, and the ideal ratio varies by crop. “For canola, we like to see a five-or six-to-one nitrogen- to-sulphur ratio. For cereals, that ratio is more like 10-to-one,” Solberg says. To put that in perspective, a 50-bushel canola crop that needs 165 pounds of nitrogen also needs about 30 pounds of actual S to avoid a deficiency. Of course, that’s actual pounds of nutrients, not pounds of product required to meet that need, and that’s after you’ve accounted for average losses to leaching, which, this year at least, no one could have accurately predicted.

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