Nitrogen is one of the most important nutrients in crop production but is also widely recognised as a source of pollution to the environment, in particular watercourses.

As a result, Defra has established areas called Nitrogen Vulnerable Zones (NVZ) in which farmers and landowners have to adhere to set rules around the use of the nutrient.

Along with these rules, there is also a requirement to keep vast records to demonstrate compliance, which can be time-consuming and complex. 

Thankfully, however, there is a range of NVZ software tools and tips to help make the process, and compliance, easier.

In this article we will look at legislation for the UK, limits and restrictions on using nitrogen as a fertiliser, slurry spreading, record-keeping, useful software and the maps and areas designated as NVZs.

Nitrate Vulnerable Zones (NVZs) are areas deemed at risk from agricultural pollution caused by nitrate fertiliser or organic manure.

NVZs include about 55 per cent of land in England. Defra reviews them every four years to take into account any changes which may have occurred in nitrate levels.

If your farm or land comes under a designated NVZ zone there are rules you must follow which govern where and when inorganic nitrogen and organic manures and slurries can be applied and the records you have to keep.
  
The Environment Agency enforces NVZ rules and selects which farms to inspect. If you fail to comply with the NVZ rules, you could be prosecuted and fined.

The rules that govern the use of nitrate fertiliser and organic manures and slurries in NVZs include: 

According to the regulations, you must be able to store all pig and poultry manure and slurry in a yard or building between October 1 – April 1, and October 1 – March 1 inclusive for cattle, sheep, goats, deer and horses.

Bear in mind, you also have to provide storage for any slurry, rainfall, washings or other liquids entering the store during the storage period.

The compliance process requires you to make slurry storage records covering a number of points, including:

• Capacity of storage facilities on farm (update any changes to this within one week)
• Calculation of the volume of manure produced by the livestock you’ll keep in a building or hard standing during storage period
• Calculation showing amount of storage you need
• Changes in volume and storage capacity due to introducing livestock to farm for first time within a month
• Calculations to show how you’ve reduced volume by sending slurry off farm or spreading.

Assessing the risk of nitrogen getting into water courses must be done before any spreading of fertilisers or organic manures takes place, and weather conditions also need to be taken into account.

You cannot spread manufactured fertilisers or organic manures if a field is waterlogged, flooded or covered in snow, or if it has been frozen for more than 12 hours in the previous 24 hours.

Neither can you spread manufactured nitrogen fertiliser within two metres of surface water or organic manure within 50 metres of a spring, well or borehole, or within 10 metres of surface water.

If you have high readily available nitrogen manures there are times, depending upon soil type, when you can’t spread. These are closed periods, and the table below sets out the restrictions*:

	On Grassland	On Tillage land
Sandy or shallow soil	Sep 1 to Dec 31	Aug 1 to Dec 31
Other soils	Oct 15 to Jan 31	Oct 1 to Jan 31

Crop	Maximum amount of nitrogen you can spread within the closed period on each hectare
Winter oilseed rape	30kg (do not spread nitrogen after October 31)
Asparagus	50kg
Brassica	100kg (no more than 50kg can be applied every four weeks, up to the date you harvest the crop)
Grass	80kg (you can apply a maximum of 40kg at any one time, and must not spread after October 31)
Over-wintered salad onions	40kg
Parsley	40kg
Bulb Onions	40kg

Crop	N-Max Limit	Standard Crop Yield
Autumn or early winter-sown wheat	220	8
Spring-sown wheat	180	7
Winter Barley	180	6.5
Spring Barley	150	5.5
Winter oilseed rape	250	3.5
Sugar beet	120	-
Potatoes	170	-
Forage maize	150	-
Field Beans	0	-
Peas	0	-
Grass	300	-
Asparagus, carrots, radishes, swedes, individually or in any combination	180	-
Celery, courgettes, dwarf beans, lettuce, onions, parsnips, runner beans, sweetcorn, turnips individually or in any combination	280	-
Beetroot, brussels sprouts, cabbage, calabrese, cauliflower, leeks individually or in any combination	370	-

It’s separate from the field limit of 250kg per hectare from organic manures.

However, you cannot exceed 250kg of total nitrogen from all organic manures spread in any 12-month period on any single hectare of your land. This limit (the field limit) doesn’t include livestock manures deposited by grazing animals.

If you farm within an NVZ, it is vital to keep records of all fertiliser use for a minimum of five years. Records must also be updated on a regular basis. For example, you must update your field records within a week of sowing, spreading fertiliser or harvesting a crop.

Crop types, dates, and amount of fertiliser used must all be documented, and when using organic manures, the type of manure, method used for spreading, total nitrogen and crop-available nitrogen must all be recorded. 
Records must also include evidence of soil nitrogen supply and crop nitrogen requirements, how you calculated them and any written advice from a FACTS-qualified adviser.
 
Results from lab reports for sampling and analysis of nitrogen content in organic manure need to be recorded within one week of receiving the results.

Recording all that data may feel like a mountainous task, but thankfully there are software tools available to help farmers and land managers keep track of the information required. 

RHIZA’s Contour platform not only enables farmers to record all this information digitally, it includes data from Cranfield’s National Soil Map on all soil types in the UK, which can be used to carry out all NVZ calculations, including NMAX. 

By creating a visual representation of NVZs, farmers can better understand and plot their N applications more easily and accurately, and alerts users to non-compliant activities, so these can be corrected. 

 

*All dates and volumes are accurate at the time of writing.