Nitrate Vulnerable Zones Action Programme review: consultation

5. Rates and limits on the field application of nitrogen fertilisers

5.1 Maximum application of nitrogen fertiliser

The NVZ Action Programme applies an Nmax limit to grassland, arable, and horticultural crops in Scotland to restrict the maximum application of nitrogen fertiliser based on published good farming practice. The Nmax limit is the maximum total nitrogen applied as manufactured fertiliser plus the crop available nitrogen supply from organic manure applications.

The current Action Programme requires a number of criteria to be taken into consideration when carrying out an Nmax calculation, including previous crop, planned crop, and soil type. An Nmax figure for each crop type, other than grassland, is derived from standard tables set out within the Action Programme, which can be adjusted to take account of higher than standard yields (for cereals and winter oilseed rape) and marketing requirements for specific cereal crops. For grassland the criteria used to derive the Nmax are rainfall, soil type and proposed management.

For any other crops that are not included in the standard nitrogen requirement tables within the Action Programme there is still a requirement to undertake an Nmax calculation following the nitrogen recommendations from the SRUC Technical Notes, below.

The standard nitrogen requirement reference tables in the Action Programme are also derived from the SRUC Technical Notes as follows:

• Technical Note (TN731): Nitrogen Recommendations for Cereals, Oilseed Rape and Potatoes
• Technical note (TN740): Fertiliser recommendations for soft fruit and rhubarb crops
• Technical note (TN734): Fertiliser recommendations for vegetables, minority arable crops and bulbs

These technical notes provide nitrogen recommendations to farmers to give the economic optimum yield and are updated following scientific research and evidence to ensure they provide up to date best practice guidance to farmers.

The Nmax calculations and associated standard nitrogen requirement reference tables in the Action Programme align with the most recent nitrogen recommendations in the SRUC Technical Notes, and we do not propose to change the maximum application of nitrogen fertiliser requirements outlined above.

Question 1

Do you agree with our review of the maximum application of nitrogen fertiliser requirements and our proposal that we do not change them at the current time? (Yes/No)

Where appropriate, please provide scientific research and evidence taking account of Scotland’s agricultural, soil and climatic conditions to support your view. (Text box)

5.2 Livestock manure Nitrogen (N) efficiency standard values

A key element of the Action Programme is the requirement for farmers to account for nitrogen (N) that will be available to crops following the application of livestock manure in their Nmax calculations. This requires farmers to use minimum nitrogen standard efficiency values set out in the Action Programme when calculating the amount of available nitrogen.

The nitrogen efficiency factors for cattle and pig slurry were increased following the 2013 review of the Action Programme. To support the review, ADAS was commissioned to conduct an assessment and update of manure N efficiency values on behalf of the UK administrations. The study^[3] supported the continuing use of current values used to calculate Nmax.

The Scottish Government is not aware of any scientific research that suggests that livestock manure nitrogen efficiency standard values require amending at the present time and do not propose to change them.

Question 2

Do you agree with our review of the livestock manure N efficiency standard values and our proposal that we do not change them at the current time? (Yes/No)

Where appropriate, please provide scientific research and evidence taking account of Scotland’s agricultural, soil and climatic conditions to support your view. (Text box)