Part of the market development agronomist job for Cargill is to sort through the information in the marketplace and to use our own experience to simplify your decisions on the farm. One of the most challenging spaces for competing information is the fertilizer market, and sulphur (S) products in particular.
Recently, a new slow-release sulphur product has hit the western Canadian market. It’s a compost product containing S particles and promising release of S over five years. Theoretically you apply it and you don’t need to add S for the next five years. However, there is not enough data to back up this theory.
With new products like this coming to market promising a variety of benefits, it’s time to break it down to four key considerations to separate the good from the questionable:
Because elemental S is not available to plants and must be broken down to become available to the crop, many growers apply it as ammonium sulphate so it’s available in the current crop year. When applying elemental S, it must be done one to two years ahead of the crop it’s intended to feed. Some of the S in a slow-release product application will be available, but just how much is too difficult to predict.
Particle size matters.
The more finely ground the S particle, the more available it will be to the plant because each particle must be broken down by a microbial process involving water and oxygen. Products containing S particles of widely varying sizes will be less predictable in terms of when the crop will be able to use it. Products like MicroEssentials® S15™ and MicroEssentials SZ™ contain 15% and 10% S respectively, applied to fertilizer granules as a micronized coating. The S itself is a combination of elemental S and sulphate, meaning most of it breaks down in year one, leaving a small amount for the second year.
In the new slow release products, the S particles vary widely and as a result it’s difficult to predict just how long it will take them to break down into the plant-available form. Think inches versus micrograms. It’s an important consideration, because you need S for your canola crop when you need it, not at some point over a five-year span.
Soil pH affects performance.
Over time, elemental S increases acidity in the soil, and nutrient availability changes with acidity (pH of 6-8 range is good). Lower pH is when you see levels close to 6 (breaching to 5.7). If your soil pH is high (7.5-8) you could look at using a high organic matter, slow release product to bring it down. Ask yourself how many pounds you would need to apply to make this happen. 1,000 lb/ac? 10,000 lb/ac? What other issues might you cause because of these high rates?
Beware of other risks.
Always look critically at products that don’t have performance data to back them. Some products are made of composted material, but what’s in the load you receive? If you use it, you run the risk of also importing pests, pathogens or heavy metals. You need to ensure the compost is disease-free because you don’t want to introduce pathogens to your farm.
If you have questions about this or any other fertilizer product, or you’d like to look at your fertility plan with an expert, call your nearest Cargill location.
MicroEssentials is a registered trademark of The Mosaic Company. S15 and SZ are trademarks of The Mosaic Company.