I used to use ASN, which is 14%S, so all the sulphur for the year was applied in one spreading. This was very convenient, but I started hearing about research showing early embryonic deaths in dairy herds after high applications. The first of the sulphur needs to go on in April/May, just at the start of the breeding season.

Despite so many continuing to use ASN at that time, I considered it too much of a risk.

I have been using three bags per year of 26%N with 5%S as soon as finished with urea. This is basically a blend of CAN and ASN. Different companies use different rates – the higher the sulphur, the lower the nitrogen. Usually it will be the same price per tonne as straight 27% CAN.

Protected urea with sulphur product

I had heard of a protected urea with sulphur product. The initial Teagasc trials on cereals were showing no performance difference between it and CAN so I decided to try it. The version sourced by my co-op has 38%N with 7.6% sulphur. Two bags per acre will give the same coverage as the three bags of CAN-based fertiliser.

There is a link between fertiliser and various emissions. Urea is best on climate emissions over CAN. CAN is better than urea on ammonia emissions because of volatilisation. That is the urea N reacting with the air in warm dry conditions. The urease inhibitor used in the protected urea products prevent this reaction. I expect research to intensify due to the increased pressure because of climate change and air quality issues.

From a farmer’s point of view, of course, I need to know it will give value for money. I bought the first of the sulphur in May. The CAN/sulphur product available was 24%N 6%S, costing 59c per unit of N and included 0.25 units sulphur per unit of N. The equivalent protected urea cost 56c per unit of N but with a smaller 0.2 units S. Not much of a price difference.

Move on to present day prices and the story has changed with a 27%N 5%S CAN product, and CAN falling in price faster than urea. The comparison is now 46c with 0.19 units S versus 48c with 0.2 units S. Well worth buying as needed instead of bulk this year.

The straight nitrogen fertiliser comparison is 27% CAN at 52c per unit of N, 46% protected urea at 44c and straight 46% urea 37c. Worth checking out depending on soil moisture.

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