With confirmation last week that the new upper stocking rate limit for farmers in a derogation will be 220kg N/ha in 2024, farmers stocked above this are left wondering what to do.

Essentially, they have four options. They can reduce cow numbers to get back under the 220kg limit, increase land area to dilute their nitrates over a larger area, export slurry to reduce their nitrates or do a combination of the above.

In terms of exporting slurry, there are a couple of things farmers should keep in mind if planning this option.

The first thing to say is that a lot more slurry needs to be exported now in order to make a substantial impact on reducing nitrates than before. This is because the amount of nitrogen contained in 1t of slurry has reduced from 5kg to 2.4kg.

Take a 40ha farm with 100 cows, which is a stocking rate of 2.5 cows/ha and an organic nitrogen excretion rate of 230kg N/ha.

On the face of it, this farm exceeds the limit by 10kg N/ha or 400kg of N across the whole farm. As there is deemed to be 2.4kg N in every 1t, 1m3 or 1,000l of slurry the farm would have to export 166t, 166m3 or 166,000l of slurry to get back under 220kg N/ha.

Presumed

It is currently presumed that each cow produces 0.33m3 of slurry per week. So if a cow is housed for say 14 weeks in the winter, she produces 4.62m3 of slurry over the winter.

Therefore, exporting 166m3 is the equivalent of exporting all the slurry produced by 36 cows on the farm.

Notwithstanding the financial loss of these nutrients from the farm (most of the value of slurry is in P and K), the next problem is finding a farm that can take all of this slurry.

Farmers cannot import slurry if they are stocked greater than 170kg N/ha. So, in this case, the farmer would need to find a farm that can import 400kg of nitrogen without exceeding 170kg N/ha. A farm can export slurry to multiple farmers.

After that, the next challenge is to find a farm that can import all of the phosphorus contained in the slurry.

As of this year, all farms importing slurry and stocked greater than 130kg N/ha or all tillage farmers importing slurry must provide soil samples or else it is presumed that the farm is at index four for P which means slurry cannot be imported on to the farm as it has no P allowance.

Exporting

OK, so let’s presume that the farmer exporting the slurry identified a grassland farmer with 40 hectares and a stocking rate of 140kg N/ha.

In this case, they have ample capacity in terms of nitrogen for importing slurry. Even after importing 166m3 of slurry, their organic nitrogen figure will still be 150kg N/ha, so a good bit lower than the 170kg limit.

Let’s also presume that this farmer importing the slurry has soil samples showing that the farm is at index two for phosphorus, which at that stocking rate is an allowance of 23kg P/ha.

In this case, the farm would have sufficient allowance to import slurry, but would need to ensure they remain within the P allowance when chemical P is used also.

There is 0.8kg of P per 1m3 of slurry, so as this farm is importing 166m3, it is importing 133kg of phosphorus.

The next step is to record the movement of slurry and this has to be carried out online before 31 October. Both parties - the one exporting the slurry and the one importing the slurry - must log on to Agfood to register the movement.

The two biggest obstacles to exporting slurry is overcoming the loss of nutrients from the farm that is doing the exporting.

In this example, about 30% of all the slurry produced on the holding needed to be exported in order to get under 220kg N/ha, even though the farm started out at 230kg N/ha.

The next obstacle is finding a farmer that has capacity to import the slurry in terms of being under 170kg N/ha and has soil samples.