NVZ Guidance Note: Closed Period Application of Inorganic Nitrogen
SEERAD area offices have received several notifications of applications during the closed period where the agronomic justification has not been acceptable. This note has been prepared to provide guidance on the type of justification that is acceptable. Producers should be aware that failure to adhere to this guidance will be regarded as a breach of the NVZ rules. From 2005 such breaches may lead to deductions from your single farm payment.
Autumn fertiliser nitrogen is NOT generally recommended for winter sown cereal crops as profitable responses are not normally attained and the practice could increase N losses to watercourses. The reason for the lack of profitable response to autumn fertiliser N is believed to be due to the presence of available 'mineralised' N in the soil after the previous harvest. There will also be further production of 'mineralised' N when soil temperatures remain above about 5 degrees Celsius. MAFF Fertiliser Recommendations (RB209) state that "soil mineral N within rooting depth is usually used efficiently, approaching 100%. This is because it is evenly distributed within the soil and readily accessible for root uptake. Fertiliser nitrogen is used less efficiently than soil mineral N. This is probably because fertiliser nitrogen is less well distributed within the soil. For crops suffering from disease, soil, drought or other growing problems, nitrogen uptake efficiency may be much lower"
There are some specific examples where autumn fertiliser Nitrogen may be justified for winter cereals. Responses to autumn Nitrogen have been recorded on sites with sandy soils of high pH and low manganese content. In these cases it appears that the acidifying effect of ammonium containing fertilisers is more important than the presence of extra N. Autumn fertiliser Nitrogen may also be required in the following situations, in some years:
· Sandy/ free draining soils with low organic matter
· Crops established by direct drilling or minimum tillage
· Crops established in fields where straw has not been properly ploughed in or poorly chopped prior to ploughing.
The preferred course of action in these situations is to take a 'wait and see' approach. If the crop starts to show obvious symptoms of nitrogen deficiency a top dressing equivalent to 50 kg/ha of 34.5:0:0 would be an acceptable application, provided that mild growing conditions are likely to persist
However if your agronomist recommends autumn nitrogen under other circumstances you should ensure that they provide you with a field specific justification which should include details of soil types, previous cropping and any other factors that are seen as relevant in making that recommendation. Alternatively, a lack of available nitrogen may be demonstrated by soil mineral N analysis. In these circumstances additional nitrogen can be justified where this shows levels, prior to sowing, of below 40 kg/ha for winter wheat and 50 kg/ha for winter barley. This assessment must be made regularly and 'insurance' applications of 5:24:24 and similar products are not permitted.
Any applications of nitrogen during the closed period must be notified to your SEERAD area office within 3 days of the application being made. This notification must include:
· The date of the application
· The quantity and type of fertiliser applied
· The agronomic justification for the application
Note that you may also notify your SEERAD Area Office in advance of applying autumn N.