Between bags/acre, units/acre and kg/ha the whole thing gets confusing. At this time of year, you should be spreading between 23 and 46 units/acre of nitrogen on grassland that has not received any slurry yet.

To convert this to kg/ha you multiply units/acre by 1.25. To convert kg/ha to units/acre you multiply by 0.8. Working out how many tonnes of fertiliser you need to buy depends on the product you are using. Urea is the product of choice in spring, because it is more stable in the soil. Every bag of urea is 46% nitrogen, while every bag of CAN is 27% nitrogen. So you need to spread less urea to do the same job – and because it is cheaper you get more bang for your buck.

However, urea has a lower bulk density than CAN, which is why it is harder to spread at large widths. There is 1.5t on a pallet of urea and 2t on a pallet of CAN. Table 1 gives a breakdown of fertiliser rates and how much product you need to spread at the desired rate.

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Special focus: fertilisers 2017

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