A solar array on agricultural land and the classification

The published agricultural land classification map for most of England cannot tell you whether a field is best and most versatile land. The provisional maps drawn before 1988 do not separate Grade 3a from Grade 3b, and that single distinction decides whether a solar application is arguing about high quality land or about ordinary farmland.

What follows is an illustrative walkthrough of a ground-mounted array, assembled from the way these applications usually run. No areas, yields or costs are quoted, because they vary too much to state usefully.

The site and the proposed array

Two adjoining arable fields on a gently sloping plateau, in the ownership of a single farming family, with a distribution network connection available at an acceptable distance. The proposal was a ground-mounted photovoltaic array with an operational life of around 40 years, sheep grazing retained between the rows, and the existing hedgerows kept and reinforced.

No statutory landscape designation applied. The nearest listed building was a farmhouse some distance away with intervening woodland. There was no public right of way across the site, though one ran along a lane to the east.

On the face of it a straightforward case. The obstacle was the mapping.

Published land classification and its limits

The provisional agricultural land classification maps, produced at a coarse scale before the current criteria were published in 1988, show the whole area as Grade 3. That grade covers land of good to moderate quality and it was never subdivided on those maps.

Grades 1, 2 and 3a are best and most versatile land. Grade 3b is not. National policy expects poorer quality land to be preferred for this kind of development, and expects an applicant proposing to use higher quality land to explain why. Everything therefore turned on which half of Grade 3 the fields fell into, and the published map was incapable of answering.

Objectors had already written to the council quoting the map as evidence that the land was Grade 3. The parish council's letter described the fields as prime agricultural land. Neither statement was wrong on the published data, and neither was useful.

Post-1988 detailed classification exists for some areas and can be viewed through the national mapping services alongside other constraint layers. For this site there was none.

The site-specific soil survey

The only way to resolve it is a survey on the ground by a soil scientist.

The Agricultural Land Classification work followed the standard approach: auger borings on a grid across both fields, soil pits at representative points, and recording of texture, stoniness, depth, structure and signs of seasonal waterlogging. Those observations combine with climate data for the location, principally rainfall and accumulated temperature, and with gradient, to produce a grade for each part of the site.

Two factors usually decide whether Grade 3 land is 3a or 3b in lowland England. Wetness, expressed as a soil wetness class combined with the climate data, limits the range of crops and the number of workable days. And droughtiness, calculated from the available water the profile can hold against crop requirements, limits yield in dry years.

Councils usually expect a suitably qualified author for this work, and professional review is strongly advised. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.

Survey timing matters. Augering waterlogged ground gives unreliable readings, and a survey carried out in a saturated February can misrepresent the profile.

What the survey found and how it changed the case

The results split the site. The larger field, on deeper soils over a freely draining substrate, graded as subgrade 3a. The smaller field, shallower and stonier with a slowly permeable layer at depth, graded as subgrade 3b, with a band of Grade 4 along the steeper northern margin.

That changed the application in three ways.

The layout was revised to concentrate the array on the poorer land and to reduce the extent on the 3a field, accepting a smaller installed capacity. The planning statement could then describe a scheme that had actively minimised its use of best and most versatile land rather than one that asserted it.

The case on reversibility became central. Ground-mounted arrays on driven piles, with cable routes recorded and no concrete foundations, do not sterilise soil in the way a building does, and continued grazing keeps the land in agricultural use throughout.

And the objectors' strongest point lost its evidential base, because the survey was site-specific and their map was not.

Considering alternative sites

Alternatives are not generally a requirement in planning, but where higher quality land is proposed, policy expects an explanation of why poorer land was not used.

The submission covered four things. The grid connection constraint, which limits the search area far more than most objectors appreciate. Land availability and ownership within that area. Designations and constraints that ruled out otherwise suitable parcels. And the classification of the parcels that survived those filters.

Keep it short and factual. A long alternative sites study invites the objection that a better site exists, and the credible version of this section describes the filters rather than claiming an exhaustive search.

Landscape and glint assessment

The Landscape and Visual Impact Assessment followed the standard methodology, with viewpoints agreed with the case officer and the array modelled at panel height rather than at ground level.

Mitigation was conventional and effective: retaining and gapping up the hedgerows, additional native planting on the two open boundaries, and a set-back from the lane. Panels were specified with a low-reflectance finish.

Glint and glare was assessed because of a small airfield within the wider area. Aviation safeguarding has its own guidance and its own consultees, and the assessment has to address flight paths and control tower positions as well as road users. On this site the conclusion was that no unacceptable effect arose, though the assessment was the item the applicant had not budgeted for.

Biodiversity net gain was straightforward, because arable land carries a low baseline value and the grassland created beneath an array scores well. The Biodiversity Net Gain Assessment was completed by a competent person as the Environment Act 2021 regime requires.

The decision and the restoration condition

Permission was granted for a defined period, with the array to be removed and the land restored at the end of it.

The conditions that carried the agricultural case were these. A soil management plan governing stripping, storage and reinstatement during construction, following the national guidance on sustainable use of soils on construction sites. A requirement that the land beneath and between the arrays be kept in agricultural use. A decommissioning and restoration scheme, to be submitted before the array is removed, covering removal of piles and cabling and the reinstatement of soil structure. And a trigger requiring removal where the array ceases to generate for a continuous period.

The restoration condition is the one that persuades agricultural objectors, and it is worth drafting carefully rather than accepting the council's standard wording. A scheme that ends with compacted tracks and no subsoiling requirement does not restore anything.

A comparable rural case, turning on Green Belt rather than soil quality, is set out in the walkthrough of stables and a menage in the Green Belt.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it.

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