Phosphorus allowances

Discussions concerning phosphorus allowances have ramped up in the last week. The source of these discussions? Merchants selling fertiliser asking farmers if they have a phosphorus (P) allowance to purchase compound fertiliser containing P.

This is raising alarm bells among farmers, with many describing it as new rules.

The rules concerning phosphorus allowances are not new and are part of the Nitrates regulations, but the introduction of the fertiliser register has put a greater focus on compliance.

A critical aspect to highlight is that in the absence of soil analysis, farms with a grassland stocking rate in excess of 130kg organic nitrogen (N)/ha in 2023 must assume index 4 for P and therefore have no allowance to purchase fertiliser containing P.

Farms with a grassland stocking rate of less than 130kg organic N/ha must assume index 3 for P in the absence of soil samples.

The table shows the permitted P allowance based on soil index and stocking rate. There is the possibility to increase above these levels where farmers adopt increased P build-up rates, but for the majority of farmers these are the relevant figures that count.

The higher allowances for low index soils reaffirm the value of having up-to-date soil analysis available.

Farmers also need to take account of the fact that in general, every tonne of concentrate feed purchased is deemed to supply 5kg P, and this must be deducted from the farm’s allowance.

A lower value can be used where there is evidence of a lower P level in the feed.

The Nitrates regulations state that an additional 15 kg of phosphorus per hectare may be applied on soils at phosphorus indices 1, 2, or 3 for each hectare of pasture establishment undertaken.

For farms with bovines, the previous year’s stocking rate can be accessed via

Sheep nutrient excretion figures are, unfortunately, not taken into account and need to be manually calculated. The nitrogen excretion rate for a lowland ewe and her lambs is 13kg, reducing to 7kg for a mountain ewe. Lowland hoggets have a nitrogen excretion rate of 6kg/annum and mountain hoggets 4kg.