A1 Basingstoke and Deane Borough Local Plan Site 17
Total Page：16
File Type：pdf, Size：1020Kb
A1 BASINGSTOKE AND DEANE BOROUGH LOCAL PLAN SITE 17 : CHINEHAM LANE, BASINGSTOKE AGRICULTURAL LAND CLASSIFICATION ALC MAP & REPORT JUNE 1993 AGRICULTURAL LAND CLASSIFICATION BASINGSTOKE AND DEANE BOROUGH LOCAL PLAN SITE 17: CHINEHAM LANE, BASINGSTOKE 1. SUMMARY 1.1 ADAS was commissioned by MAFF's Land Use Planning Unit to provide information on land quality on 22 sites around Basingstoke in Hampshire. The work forms part of MAFF's input to the Basingstoke and Deane Borough Local Plan. 1.2 Site 17 comprises 2.6 hectares of land to the north-west of Basingstoke, Hampshire and was surveyed during April 1993. The survey was undertaken at a detailed level of approximately one boring per hectare. A total of 2 borings were described in accordance with MAFF's revised guidelines and criteria for grading the quality of agricultural land {MAFF, 1988), These guidelines provide a framework for classifying land according to the extent to which its physical or chemical characteristics impose long term limitations on its agricultural use. At the time of survey, the land was in permanent grassland. 1.3 The distribution of the grades and sub-grades is shown on the attached ALC map and the areas are given in the table below. The map has been drawn at a scale of 1:5000. It is accurate at this scale, but any enlargement may be misleading. Distribution of Grades and Sub-grades Area(ha) % total aqricultural land Grade 3a 1.0 50 3b 0.8 40 4 0.2 10 Total agricultural area 2.0 100 Non-agricultural 0.1 Urban 0.5 Total area of site 2.6 ha 1.4 Appendix 1 gives a general description of the grades and land use categories identified in this survey. 1.5 Good to poor quality land has been mapped at this site. Land assigned to grades 3a and 3b is limited by soil droughtiness arising from variable soil depth over chalk. The shallower the profiles the more severe the limitation. As a result very shallow profiles were assigned to grade 3b, whilst deeper soils are less droughty and grade 3a is appropriate. A small unit of grade 4 has been mapped where steep gradients of 13° were measured. - 1 - 2. CLIMATE 2.1 The climatic criteria are considered first when classifying land as climate can be overriding in the sense that severe limitations will restrict land to low grades irrespective of favourable site or soil conditions. 2.2 The main parameters used in the assessment of the overall climatic limitation are annual average rainfall, as a measure of overall wetness, and accumulated temperature, as a measure of the relative warmth of a locality. 2.3 A detailed assessment of the prevailing climate was made by interpolation from a Skm gridpoint dataset. (Met. Office, 1989). The details are given in the table below and these show that there is no overall climatic limitation affecting the site. 2.4 No local climatic factors such as exposure or frost risk affect the site. Climatic Interpolation Grid Reference SU 636 545 Altitude (m) 90 Accumulated Temperature Cdays Jan-June) 1430 Average Annual Rainfall (mm) 758 Field Capacity (days) 162 Moisture Deficit, Wheat (mm) 104 Moisture Deficit, Potatoes (mra) 95 Overall Climatic Grade 1 3. RELIEF 3.1 The site lies at an altitude of approximately 85-90m AOD sloping from the highest point in the north, southwards. To the east, surrounding an area of non-agricultural land a slope gradient of 9° limits land to subgrade 3B. To the west land falls away very steeply with a slope gradient of 13° limiting land to grade 4. Elsewhere relief is not a limitation to agricultural land quality. 4. GEOLOGY 4.1 The published geology map, sheet 284, Basingstoke (BGS, 1981) shows the underlying geology to be Cretaceous Upper Chalk. 4.2 The published soils map sheet 6 "Soils of South East England" (SSEW, 1983) shows the site to be mapped as Andover 1 Association - "Shallow well drained calcareous silty soils over chalk on slopes and crests. Deep calcareous and non-calcareous fine silty soils in valley bottoms". (SSEW, 1983). A detailed examination of soils on the site revealed the predominance of shallow soils over chalk on slopes. 5. AGRICULTURAL LAND CLASSIFICATION 5.1 Paragraph 3.1 and the table below provides the details of the area measurements for each grade and the distribution of each grade is shown on the attached ALC map. - 2 - 5.2 The location of the soil observation points is shown on the attached Auger Sample Point map. Subqrade 3A 5.3 With inference from detailed information gained on land of similar altitude and relief immediately to the west, land was classified as subgrade 3A. The presence, too, of a long since disused chalk pit on site revealed shallow soils over chalk. This softer, more easily rootable chalk similar to that found at Pit 1 site 18 was found to be penetrated by roots to a depth of approximately 45 cm (into the chalk). Profiles are well drained but suffer from moderate droughtiness due to the proximity of chalk to the surface. Consequently land is classified as subgrade 3A. Within this map unit land of better quality was found but due to it's limited extent was not mapped separately. Subqrade 3B 5.4 Land of this quality is found to the east of the site. Profiles typically comprise topsoils of calcareous medium silty clay loam containing 2% flints by volume. This was underlain by harder, less weathered, and less easily rootable chalk of which pits 2 and 3, site 18 immediately to the west are typical. From pit observations roots were found to penetrate the chalk to a depth of 20 cm. Consequently, although well drained, land suffers from significant droughtiness imperfections and is classified as subgrade 3B. In addition slope gradient limits land to this subgrade. Using an optical reading clinometer a slope angle of 9° was recorded. Grade ^ 5.5 Poor quality land is mapped at the location of a disused chalk pit mentioned previously. Again using an optical reading clinometer a slope gradient of 13" was recorded limiting land to this grade. 5.6 The area mapped as urban includes a house and garden with built-up or hard uses within. 5.7 The area mapped as non-agricultural marks the site of another chalk pit which is heavily overgrown with bushes. Resource Planning Team ADAS Ref: 1501/32/93 Guildford Statutory Group MAFF Ref: EL 15/144 ADAS Reading - 3 - Sources of Reference BRITISH GEOLOGICAL SURVEY, 1981. 1:50,000 scale Solid and Drift edition geology map, sheet 284, Basingstoke. MAFF, 1988. Agricultural Land Classification of England and Wales. Revised guidelines and criteria for grading the quality of agricultural land. (Alnwick). METEOROLOGICAL OFFICE, 1989. Climatological datasets for agricultural land classification. SOIL SURVEY OF ENGLAND AND WALES, 1983. 1:250,000 scale soils map, sheet 6. "Soils of South East England" and accompanying legend. - 4 - APPENDIX 1 DESCRIPTION OF THE GRADES AND SUBGRADES The ALC grades and subgrades are described below in terms of the types of limitation which can occur, typical cropping range and the expected level and consistency of yield. In practice,, the grades are defined by reference to physical characteristics and the grading guidance and cut-offs for limitation factors in Section 3 enable land to be ranked in accordance with these general descriptions. The most productive and flexible land falls into Grades 1 and 2 and Subgrade 3a and collectively comprises about one-third of the agricultural land in England and Wales. About half the land is of moderate quality in Subgrade 3b or poor quality in Grade 4. Although less significant on a national scale such land can be locally valuable to agriculture and the mral economy where poorer farmland predominates. The remainder is very poor quality land in Grade 5, which mostly occurs in the uplands. Descriptions are also given of other land categories which may be used on ALC maps. Grade 1 - excellent quality agricultural land Land with no or very minor limitations to agricultural use. A very wide range of agricultural and horticultural crops can be grown and commonly includes top fmit, soft fmit, salad crops and winter harvested vegetables. Yields are high and less variable than on land of lower quality. Grade 2 - very good quality agricuUural land Land with minor limitations which aflfect crop yield, cultivations or harvesting. A wide range of agricuiturai and horticultural crops can usually be grown but on some land in the grade there may be reduced flexibility due to difficulties with the production ofthe more demanding crops such as winter harvested vegetables and arable root crops. The level of yield is generally high but may be lower or more variable than Grade 1. Grade 3 - good to moderate quality agricultural land Land with moderate limitations which aflfect the choice of crops, timing and type of cultivation, harvesting or the level of yield. Where more demanding crops are grown yields are generally lower or more variable than on land in Grades 1 and 2. Subgrade 3a - good quality agricultural land Land capable of consistently producing moderate to high yields ofa narrow range of arable crops, especially cereais, or moderate yields of a wide range of crops including cereals, grass, oilseed rape, potatoes, sugar beet and the less demanding horticultural crops. Subgrade 3b - moderate quality agricultural land Land capable of producing moderate yields ofa narrow range of crops, principally cereals and grass or lower yields ofa wider range of crops or high yields ofgrass which can be grazed or harvested over most ofthe year.