If implemented, changes to nitrogen excretion rates of farm animals as proposed by the agriculture water quality working group will assist farmers that exceed the 220kg N/ha derogation limit.

The proposals include the lowering of nitrogen excretion rates of dairy cows if low protein dairy nuts are fed and the reduction from 6kg to 1kg of organic nitrogen for calves in their first three months.

These proposals have been sent to the Minister for Agriculture and are expected to be included in the public consultation on the Nitrates Action Programme.

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The example below looks at the impact on a 40ha farm carrying 80 milking cows and 20 replacement heifers of each age group. The stocking rate is therefore one livestock unit per acre. Non-dairy replacement calves are sold at four weeks of age.

The impact on herds in both the middle and top bands are examined.

For the herd in the middle band, based on the current rules the average nitrogen excretion rate per hectare is 228kg N/ha. As this exceeds the limit by 8kg/ha the farmer would need to either acquire additional land, export slurry or sell stock.

If these changes are implemented and the farmer fed a low protein dairy nut for the summer, then the excretion rate falls to 217kg N/ha, below the limit of 220kg N/ha so this farm would be required to take no further action.

High band

For the farmer in the high band and based on the same size farm and number of stock, the excretion rate based on the current rules is 256kg N/ha, exceeding the limit by 36kg N/ha.

The farm still exceeds the 220kg N/ha limit even after the changes are made as the excretion rate is still 243kg N/ha.