On the back of changes to Ireland's Nitrates Action Plan, the Department of Agriculture, requested Teagasc to undertake further analysis of some of its key new measures which are aiming to improve water quality.

Among the most significant changes is a stipulation that would reduce stocking rates on dairy farms (organic N/ha) under the Nitrates derogation from 250 to 220 should water quality in certain areas not improve.

In its detailed modelling, Teagasc found the proposal at a chemical N application of 250 kg N/ha, would reduce N leaching by 2.2 kg/ha (3.6%) respectively at one meter depth.

However, the move would reduce farm profitability by €374/ha. Teagasc said these reductions in profitability/ha highlight the importance of grass utilization in pasture based system.

Reducing organic N from 250kg/ha to 220kg/ha had three times greater impact in reducing profitability/ha than reducing chemical nitrogen by 10%.

A reduction in the use of chemical N on farms is a significant element of Ireland's Climate Action and Nitrates Action plans.

In its analysis, Teagasc found that reducing chemical N, at an organic N level of 250 kg of N/ha, from 250 kg/ha to 225 kg/ha, (10% reduction), 200 kg/ha (20% reduction) and 175 kg/ha (30% reduction) resulted in a reduction of N leaching to 1m by 1.3 kg/ha (2.1%), 2.7 kg/ha (4.4%) and 3.9 kg/ha (6.4%) respectively.

However, it also found that reducing chemical N application rates (kg N/ha) from 250 to 225, 200 and 175 reduced grass production (kg DM/ha) by 360, 736 and 1,133 kg, respectively. The corresponding reduction in profitability (€/ha) were €116, €224 and €322, respectively.

Teagasc did note that the impact of reduced chemical N application on grass production and profitability can be somewhat offset at farm level by greater use of low emission slurry spreading technology, increased soil fertility (including soil pH), greater precision in the use of chemical N application on grassland and incorporating white clover into swards.

Banding

The Department of Agriculture introduced three new livestock excretion banding rates related to milk yield/cow for dairy cows from 1st of January 2023 as part of the Nitrates Action Programme.

In the context of farms who are above the maximum 250 kg organic N/ha as a consequence of the introduction of banding, Teagasc found the least negative financial strategy at farm level to reduce organic N would be to contract rear or rear less replacement heifers or rent additional land.

Exporting slurry, it said is not practical given the quantities that are to be exported and its impact on soil fertility of the exporting farm as most grassland are close to farm P balance and therefore exporting will create a deficit across the overall farm.

Teagasc said reducing cow numbers from optimal levels has the most significant negative impact on farm profitability.

"It is therefore likely that farmers will attempt to exhaust other available options before a reduction in herd size is considered.

"While some dairy farms will find it very difficult to adjust their farming system to the new organic N excretion banding at a maximum organic N/ha 250, reducing the maximum organic N/ha to 220 would cause significantly greater difficulties for these farms.

"From the analysis and scenarios completed in this report the combined effect of banding and reducing from 250 to 220 could reduce profitability by 29% in the most extreme scenarios," it said.

In summation, Teagasc said reducing organic N/ha from 250 to 220 kg N/ha will only reduce N leaching by an additional 2.2 kg N/ha, but it will have a significant financial impact at farm level.

"Consequently, in order to optimise the cost : benefit ratio, a sequential approach to firstly allowing the impact of the 5 th NAP and the additional fertiliser reductions in the Food Vision Dairy Group Report to be assessed before introducing any reduction in organic N limits would be desirable," it said.