The concept of ‘Nutrient Neutrality’ (NN) has prompted interest within the Island’s farming community but, the implications and opportunities are somewhat opaque. This note attempts to describe the subject in general term but is not a definitive guide.
Background
In 2018, the condition of internationally important wildlife sites in the Solent covering estuaries, mudflats, sandflats, and sandbanks, were assessed by Natural England. In their terms they were found to be in an ‘Unfavourable’ condition. The cause of the problem was water quality within the Solent. High levels of nitrogen and phosphorus were causing eutrophication, effectively fertilising the wildlife sites causing adverse changes to the vegetation in the form of dense mats of green algae. These nutrients are believed to come from agriculture or wastewater from housing and other developments
Future Development
Any future development upon land that drains to the Solent would risk adding to the problem of water quality. A temporary block on new developments, necessary to protect the wildlife sites, was eventually resolved via the mechanism of NN. The intention was to ensure development would not add to the existing nutrient problem. But how would NN work in practice?
NN in practice
Developers are required to calculate how much nitrate would be produced by their new housing and meet that sum by offsetting nitrate entering the Solent from other sources. Part of that calculation would take into account the efficiency of sewage treatment works and water quality conditions set by the Environment Agency.
Agriculture, rightly or wrongly is regarded, as a key source of nitrate entering the Solent. A developer could therefore balance out his additional nitrate loading by reducing an equivalent amount that would otherwise be applied to farmland. As can be imagined it is not easy to know with any degree of certainty how much nitrate fertiliser applied to an Island field near the coast, or river draining to the Solent, would enter the sea. Even if it were possible to truly reach NN the problem level of nitrate in the Solent would of course remain the same, it just does not get any worse! NN does not appear to address the problem originally identified.
To be certain that the NN calculation is sound many factors must be considered. In terms of a farm looking to engage with NN the two obvious questions are how much N does the land receive (and over what timescale) and does the farmland obviously drain to the coast or river catchment?
Natural England suggest ‘mitigation land (i.e., where NN fields are proposed) should be appropriately secured to ensure that at the time of appropriate assessment it is certain that the benefits will be delivered in the long term. Natural England advises that this can be achieved through an appropriate change of ownership to a local planning authority or non-government organisation. However, it is recognised that there may be other legal mechanisms available to the competent authority to ensure deliverability and enforceability of a mitigation proposal. These can be considered on a case-by-case basis. They also wish that NN land is within the same catchment as the development location.
The alternative to changing the ownership off NN land from a local planning authority or non-government organisation isto acquire, or support others in acquiring agricultural land elsewhere within the river catchment. Changing the land use in perpetuity such as to woodland, heathland, saltmarsh, wetland, or conservation grassland is suggested to reduce the nitrogen loss that would otherwise result from the farming operation.
Woodland planting
Planting trees on grazed/cultivated fields would secure a permanent land use change without the land needing to change hands. But how many trees would need to be planted? Natural England suggest that to achieve NN, 20% canopy cover at maturity would be required. This would be approximately 100 trees/ha and preferably be native broadleaves species. The nitrogen leaching rate from woodland planting is believed to be 5 kg/ha/yr.
For NN, as applied to small scale developments, might include pond creation, wetlands, local nature reserves, community orchards (without nitrogen inputs), and small-scale tree planting. Small strips of ‘greenspace’ could be established alongside footpaths perhaps hedged either side to provide access and a wildlife habitat.
NN land on the Island
The map below shows the catchment where there is potential for NN particularly for development on the Island. However, Natural England have a preference for land ‘within the lower fluvial catchment and in close proximity to water courses that drain into the Solent estuaries and harbours. Sites that are located on tertiary geology or clay are preferred or sites that are located on the break of slope onto chalk bedrock. These sites reduce the time lag between the nutrient benefits of changes to land use within the catchment and the benefits to the designated sites’
NN Brokering
Defra are setting up a Nitrate trading platform but the Hampshire & Isle of Wight Wildlife Trust are already brokering NN contracts. From their website…
Once we have secured mitigation sites and agreed the capacity of the site with Natural England the Trust will be able to finalise the cost per kg of nitrogen offset.
In addition to the cost per kg, which we currently estimate will be in the region of £2,500 – £3,000 per kg, excluding VAT, an administration fee of £1,000 will be applied for each transaction (not each kg of nitrogen) plus legal fees.
We will aim to keep legal fees as low as possible. Nitrate credits will be sold to developers either through a conditional contract for larger developments contingent on the granting of planning permission, with payment due shortly after planning permission has been granted or by a simple sale for smaller developments, usually those below 5kg.
There are already areas of farmland on the Island where NN is to be applied such as Little Duxmore Farm and new sites are being considered. Apparently large payments can be offered but what is the true financial reward when land use might be heavily constrained over an extended timescale, perhaps 80- 125 years? An example on the Townsend Chartered Surveyors webs site describes a payment of £138,840/ha over 80 years, equivalent to an annual payment of £1,735.50/ha.
An Alternative Approach
There is another approach to improve water quality within the Solent harbours caused by both nitrogen and phosphorus in the Medina catchment! Defra’s Catchment Sensitive Farming programme, managed by the Island’s Area of Outstanding Natural Beauty (AONB), works with our farms to reduce diffuse sources of pollution such as fertiliser and slurry run-off. It delivers environmental benefits from reducing diffuse water pollution and provides practical solutions and targeted support. This enables Island farmers and land managers to take voluntary action to reduce diffuse water pollution and protect and the environment.