Is exporting slurry a viable option?

With the upper stocking rate limit for the majority of derogation farmers set to drop from 250kg N/ha to 220kg N/ha, affected farmers are scrambling for solutions.

One such option which has been mooted and which has been used in the past is to export slurry off the holding.

When it comes to exporting slurry, 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 has a stocking rate of 2.5 cows/ha and an organic nitrogen excretion rate of 230kg N/ha.

On the face of it, if this farm is in a 220kg area it 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.

It is currently assumed 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.

Now, the figure of 0.33m3 of slurry per week is subject to change based on the outcome of ongoing research by Teagasc, on behalf of the Department of Agriculture.

While that work is still ongoing, it is expected that the official figures for slurry production per week could increase by anything up to 20% to 30%. This would mean that slurry excretion rate per week would increase to 0.4m3 to 0.43m3 and have knock-on impacts for farmers in terms of slurry storage requirements.

It would also mean that the amount of slurry deemed to be available to export would increase.

So, theoretically, exporting 166m3 of slurry would be the equivalent slurry from 28 to 30 cows, rather than 36 as the current figures suggest.

Economic loss

Notwithstanding the economic and agronomic 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.

The next challenge is to ensure that the farm can import all of the phosphorus contained in the slurry

So, in this case, the farmer would need to find a farm or a number of farms that can import up to 160kg of nitrogen (only 40% available when importing) without exceeding 170kg N/ha of organic stocking rate and not exceed their nitrogen allowance in terms of meal fed in the previous year and chemical fertiliser used in the current year.

After that, the next challenge is to ensure that the farm 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. Only maize, beet or potatoes have a P allowance even at soil index four for phosphorus.

As there is 0.8kg of P per 1m3 of slurry, in this example the farm importing 166m3 is importing the equivalent of 133kg of phosphorus which is deemed to be 100% available.

The farm cannot accept this slurry if it can’t prove it has a requirement for that phosphorus and that it hasn’t already used up its allowance through buying fertiliser or meal.

For farmers in a derogation exporting slurry, the movement notification must be done online and the movement accepted online by the person taking in the slurry before 31 October each year.

For Irish farmers, there are a number of challenges with exporting slurry. For a start, the sheer volume of slurry to be exported in order to get a reduction in organic N/ha is massive.

In this example, about 36% of all slurry produced on the farm has to be exported in order to reduce nitrogen per hectare from 230kg to 220kg/ha. The practicalities and cost of moving this slurry are enormous.

Secondly, while slurry contains nitrogen, the main value in slurry is phosphorus and potash.

It’s important to note that approximately 42% of soils nationally are deficient in P and K.

Export

For farmers who decide to export slurry, they are exporting phosphorus and potash off the farm and either need to buy them back in chemical form though fertiliser (if they have a P allowance) or soil fertility will become depleted and grass growth suffers.

The nitrates derogation is being phased out in the Netherlands, meaning all farmers there will be farming at 170kg N/ha by 2026. The Irish Farmers Journal spoke to Dutch farmer Frans Van Kalmthout who has been operating at 170kg N/ha for the last four years.

With 340 cows on 125ha the overall farm stocking rate is 2.72 cows/ha.

Youngstock

There is a further 200 head of youngstock but these are being contract reared on a different farm so don’t count towards the farm’s nitrates figures.

With just 33ha around the home farm, the stocking rate on the grazing platform is extremely high at over 10 cows/ha. The cows have to graze for six hours per day for 120 days per year in order to get a top-up in milk price.

However, for 92% of the time, the cows are inside in the shed eating their TMR.

When in the shed all the slurry is gathered and stored and this is what differentiates the Dutch system with the Irish system.

Cows in Ireland are typically housed for three months of the year which is 25% of the time, compared to 92% in Holland.

There is vastly more slurry being produced in confinement systems compared to grazing systems and this is really a ‘get out of jail’ card for confinement systems when it comes to complying with the nitrates rules.

Last year, Frans exported over 5,000m3 of slurry off his farm to neighbouring tillage farmers which cost him over €50,000 in transport costs.

Despite exporting almost two-thirds of all the slurry produced on the farm, the Irish Farmers Journal expects that there is still sufficient slurry remaining on the farm to meet the nutrient requirements of the crops being grown by Frans.

However, if the farmer in the Irish case study was to get to 170kg N/ha, they would need to export 1,000m3 of slurry which is more than twice the total amount of slurry produced on a farm in a 14-week period.

This highlights that exporting slurry is not a viable option to reduce nitrate levels on Irish farms because the grass-based system doesn’t produce enough slurry to make exporting viable.

So while farmers like Frans and thousands of others in Holland can export their way out of the derogation, in the absence of more land, Irish farmers will have no choice but to cut cow numbers in order to comply with the cuts to the derogation.