Nitrate Vulnerable Zones Action Programme review: consultation

6. Nitrogen Fertiliser Applications – Closed spreading periods

6.1 Chemical Fertilisers

The NVZ Action Programme requires that manufactured nitrogen fertiliser must not be applied to crops and grassland during the periods identified in the table below. Previous trials work, funded by the Scottish Government, confirmed that there is no statistically significant response to autumn nitrogen applications on winter barley crops, even on sandy soils. Any manufactured nitrogen applied to winter barley and other winter sown cereals during this time will be poorly utilised by the crop. Any nitrogen that is not taken up by the crop poses a significant risk of being lost to the water environment.

There are 2 exceptions to this rule:

• Autumn nitrogen can be applied to winter oilseed rape in accordance with crop recommendations for nitrogen in the Action Programme
• Up to 100 kg/ha can be applied to other high N demanding field brassica crops.

We do not have any scientific evidence to support modifications to the closed periods for inorganic (i.e. manufactured) fertilisers and do not propose any changes.

Question 3

Do you agree with our review of chemical/ manufactured fertiliser closed period measures 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)

6.2 Organic Manures

The existing NVZ Action Programme prohibits the spreading, at certain times of the year, of organic manures that have a high readily available N content (defined as: more than 30% of the total N content is in a form that can be readily taken up by the crop) These manures include slurry, poultry manure and liquid digested sewage sludge.

Current organic manure closed periods for Scotland are:

* ^{Application permitted up to and including 15 September, if a cereal crop is sown before that date. Also permitted up to 30 September if the land is sown with oilseed rape, a catch crop, or a cover crop before that date.}

These periods are at times of the year when the risk of nitrate loss is high. Autumn and early winter are when leaching volumes are high, the ground is generally wet and weather conditions are not suited to crop growth, and therefore nitrogen uptake is low. The continued mineralisation of organic nitrogen in from previous applications organic manures in the spring and summer also provides nitrogen available to crops during the autumn and winter closed periods.

Manure and slurry are valuable assets to farmers and should be spread on land for agricultural benefit. They should therefore be applied at times when plants can utilise the nutrients, and when nutrient losses will be minimised. During the autumn and winter period plant root activity effectively ceases (or slows markedly), so any fertiliser or manure application during that period risks being leached away. Rain, at this time, heightens the risks of surface run-off directly to water courses or downward movement (leaching) to ground waters. By contrast, in the early spring the rise in temperature, together with significantly increased nutrient uptake by plant roots and lower rainfall, reduces the leaching risk.

The organic manure closed periods requirements aim to strike a balance between suitable and sufficient time for manure and slurry to be applied and the need to minimise nitrate losses. The goal is to encourage the most effective manure application in spring and summer to meet the period of high crop N requirement and to achieve a more integrated approach to minimise potential pollution.

We do not have any scientific evidence to support modifications to the closed periods for organic manures that have a high readily available N content and do not propose any changes.

Question 4

Do you agree with our review of organic manures that have a high readily available N content closed period measures 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)

6.3 Farmyard manures – Closed period

The Scottish Government has previously considered proposals to introduce a closed period for Farmyard Manure (FYM).

The risk of causing water pollution by spreading FYM is lower than for slurries. Surface run-off can still occur if heavy rain falls shortly after an application. As a guide, a standard application rate of 25-30 m³/ha is generally used, with crop nutrient requirements met through additional fertiliser applications. Lower rates should be used where soil and weather conditions are likely to increase the risks of pollution. Repeat applications should not be made for a period of at least 3 weeks so the crop can utilise the available nutrients.

The Scottish Government considers that due to the lower risk from FYM and the slower release of nitrogen from FYM the risk to groundwater from nitrogen leaching is minimal compared organic manures that have a high readily available N, such as slurries.

The risk from surface run off is also considered to be minimised by the 10m no spread buffer zone (measured from the top of the bank). Although buffer zones should be increased accordingly where the slope of the land increases to avoid the risk of run off reaching the water environment.

In consideration of the low risk to the water environment, the Scottish Government does not propose to introduce closed periods for farmyard manures.

Question 5

Do you agree with our proposal that we do not add a closed period for farmyard manure measure to the NVZ Action Programme? (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)