Agricultural Land Classification survey: grades and BMV

An Agricultural Land Classification survey exists to answer one question that the published maps cannot: whether your field is grade 3a or grade 3b. Grade 3a counts as best and most versatile land and attracts policy protection. Grade 3b does not. The provisional ALC maps published at national scale lump the two together as grade 3, so on any site where the loss of agricultural land is an issue, a site specific survey is the only way to settle it.

Why the split within grade 3 is the whole argument

The classification runs from grade 1, excellent quality, through grade 2, good quality, then grade 3 subdivided into 3a good to moderate and 3b moderate, to grade 4 poor and grade 5 very poor. Best and most versatile land means grades 1, 2 and 3a.

National policy expects poorer quality land to be used in preference to higher quality land where significant development of agricultural land is demonstrated to be necessary. The National Planning Policy Framework (August 2026 edition) carries that expectation, and the local plan usually repeats it with its own wording. Verify the current policy code on gov.uk before quoting it in a statement.

Because the national maps stop at grade 3, an objector can assert that a site is best and most versatile and an applicant can assert it is not, and neither has evidence. A survey converts the argument into a mapped finding. Where a proposal would lead to the loss of a substantial area of best and most versatile land, Natural England is consulted under the Development Management Procedure Order 2015, and the survey is what that consultation turns on.

What the survey involves on the ground

An ALC survey is a soil survey, carried out to the Ministry of Agriculture, Fisheries and Food guidelines published in 1988, which remain the standard method. It combines field observation with climate data and a set of limitation criteria.

The surveyor walks the site, records slope, microrelief and any flooding evidence, then takes auger borings on a grid. A detailed survey commonly uses a 100 m grid, giving roughly one boring per hectare, with the grid tightened where soils vary. Soil pits are dug at representative points to describe the profile properly, including structure, stoniness and depth to any impermeable layer.

Each boring record captures texture by hand assessment through the profile, colour and mottling that indicate waterlogging, stone content, depth of topsoil and the presence of gleying. Those observations feed the wetness and droughtiness calculations that usually decide the grade.

One point that surprises applicants: the surveyor is not looking for the best soil on the site. They are looking for the limiting factor, and a single shallow horizon of slowly permeable clay across half a field will set the grade for that half regardless of how good the topsoil looks.

Timing is flexible but not unlimited. Land can be surveyed through most of the year, though waterlogged or frozen ground makes augering unreliable, and a standing crop can restrict access. Booking the survey around the farming calendar avoids a return visit.

Climate, wetness and droughtiness limitations

Grading works by limitation. The surveyor assesses each factor and the most severe limitation sets the grade, so a site with excellent soils and a steep slope grades on the slope.

Wetness and droughtiness are described as interactive limitations because they depend on both soil and climate. That is why a soil profile identical to one graded 2 in a drier county can grade 3b in a wetter one, and why importing a grading from a neighbouring site is not evidence.

Reporting results as a mapped classification

The report should present a classification map at a scale that can be read against the application boundary, with the area of each grade in hectares, the boring locations plotted, and profile descriptions in an appendix.

It also needs to explain the reasoning. For each mapped unit, say which limitation set the grade and what the underlying values were. A report that gives conclusions without the wetness class or the calculated moisture balance is hard for Natural England or a case officer to test, and it invites a request for further information.

Illustrative example: a 12 ha field on the edge of a village is mapped as provisional grade 3. Survey shows slowly permeable subsoil with gleying at shallow depth across the northern 8 ha, giving a wetness class that limits it to 3b, while the free draining southern 4 ha grades 3a. The scheme is redrawn to take the northern land only. The figures here are illustrative.

How the finding feeds the planning balance

A finding of 3b removes a policy objection entirely. A finding of 3a does not defeat a scheme, but it puts weight on the other side of the balance, and it obliges the applicant to explain why the development is necessary and why lower quality land was not used.

That argument is made in the Planning Statement rather than in the survey. Set out the site selection process, any sequential consideration of alternatives, the area of best and most versatile land lost, and any mitigation such as soil handling and restoration for temporary uses. Solar and mineral schemes lean heavily on the reversibility point.

Objectors use the survey too, and they are entitled to. Where a parish council or a neighbouring farmer commissions their own grading and reaches a different answer, the case officer has two reports and no easy way to choose between them. That is another reason to publish the boring records and the calculations rather than the conclusions alone, because the report with the visible working usually prevails.

Soil handling deserves attention in its own right. Where land will be returned to agriculture, a soil resource plan describing stripping, storage and reinstatement is often conditioned, and it is easier to write while the survey team is still on site.

The classification also interacts with other evidence. Wet soils that limit the grade are usually the same soils that shape the drainage design, and our note on what goes in a Flood Risk Assessment and what goes in a Drainage Strategy explains how that evidence is split. Habitat survey work runs on a different calendar again, as our guide to reading the ecology scope sets out.

Who is competent to sign the survey

ALC grading is a soil science judgement. The surveyor needs practical experience of the 1988 guidelines, of hand texturing and of the wetness and droughtiness calculations, and councils will look at the author's background when the finding is contested.

PlanScope can draft the Agricultural Land Classification report structure around your site details and flag where field data is still needed, and it labels this report type as one where a suitably qualified author is expected. The field survey, the grading and the sign off belong to a soil scientist. For specialist technical reports, qualified professional input may be required.

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

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.