Crop Production in the East of Scotland - SASA

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Geology, Soils and Land Capabilityof till/drift over the lowlands of the East ofScotland. The origin of the till dependsupon the direction of movement of the icesheets and glaciers. In the South ofScotland, the direction of movement waspredominantly west to east, with the resultthat much of the till covering the Lothians,the Merse and the southern half of Fife isof Carboniferous origin. Further north, thedirection was more north to south, suchthat the till covering Tayside (Perth andAngus) is mainly of ORS origin, as shown bythe distinct red soils of the area. There arealso significant areas where the till iscomposed of igneous material of ORS age(e.g. N. Fife). The lowlands of Banff andAberdeenshire are covered with till fromDalradian and igneous rocks carriedeastwards. There are pronounced localdifferences; for example, the fourextensive soil associations of arableAberdeenshire are formed on tills ofcontrasting chemistry (Foudland: Dalradianschist; Insch: mixed till of gabbro andschist; Tarves: mixed till of acid and basicigneous rocks; Countesswells: granite till;Table 3.1), each relating to the “upstream”geology. Finally, the direction of flow in theMoray Firth area was south west to northeast, such that the till is made up ofMoinian schist and granite.Two other aspects of the glaciation of theEast of Scotland are important for soilformation. First, the mass of ice wasparticularly great on the Northern andEastern Highlands, with the result thatfluvioglacial processes, which washed outthe finer components of the till, were veryactive and prolonged during the period ofdeglaciation. Thus there are moreextensive areas of fluvioglacial sands andsandy loams in the northern half of thestudy area, and particularly in the Laich ofMoray (Corby/Boyndie Soil Association;Table 3.1), than in the southern half.Secondly, the weight of ice pressing onlodgement till, has tended to compress thematerial, with the result that most soils,even those with relatively coarse textures,have subsoils with lower hydraulicconductivities than would be predictedfrom their texture.SoilsThe soil types which have formed from thisvariety of parent materials over 10,000years depend upon the interactions ofseveral factors:• the texture of the parent material• its base status• its hydraulic conductivity• topography• annual precipitation• vegetation (mull or mor humus)which determine the degree and type ofleaching and/or waterlogging of the soilprofile. These processes have producedfour major arable soil types, to which mustbe added the more recent alluvial soils(Table 3.1; Figure 3.2):Brown Forest SoilKey factors lowering the rate of leaching,and preventing podzolisation orwaterlogging: high initial base status,particularly with igneous components;sandy loam to loam texture; free but notexcessive drainage; natural vegetationbroadleaf woodland with mull humus. Moreprevalent in the southern half of the studyarea. (Carpow/Panbridge; Darleith; Darvel;Hobkirk; Insch; Sourhope; Tarves)Brown Forest Soil with GleyingKey factors: high initial base status(particularly Carboniferous till); medium to25
Crop Production in the East of Scotland26fine tex tu re, possibly with co m p resse d( i n d u ra ted) subsoil, leading to imperfe c td rainage; low ra i nfall preve nting gleying ofupper horizions; natu ral ve g etation broa d l ea fwoodland with mull humus. Major soils ofthe Lothians and Fife: pote ntially the mostfe rtile so i l s, under low annual ra i nfall, ow i n gto high ba se sta tus and high wa te r- h o l d i n gca pa c i ty). (Ba l rownie; Kilmarnock; Mount b oy ;Wi nton; Wh i teso m e)Humus Iron PodzolKey factors: low initial base status(fluvioglacial deposits or coarseFigure 3.2 Schematic map of themajor soil types in the East of ScotlandKey:1. Humus Iron Podzols2. Brown Forest Soils,with Non-Calcareous Gleys3. Brown Forest Soils with Gleying4. Brown Forest Soils, and BrownForest Soils with Gleying(adapted from Coppock,1976)granite/schist till); sandy loam texturegiving very free drainage; high rainfall notnecessary; natural vegetation heath orconiferous woodland. Major soils of theNorth East but now effectivelyindistinguishable from Brown Forest Soilsowing to the mixing of horizons byploughing. (Corby/Boyndie; Countesswells;Forfar; Foudland).Non-Calcareous GleysSoils which we re wa terlogged until aro u n d1 ,000 yea rs ago or late r, now fre e l y- d ra i n i n g ,but natu ral so i l - forming pro cesses have beena r rested by cu l t i vation. (St i r l i n g ) .A set of representative soil profiles ispresented in Appendix 2.Land CapabilityIn the UK, information on climate, soil,topography and other physical propertiesare combined to give the Land Capability(formerly the land-use capability) of anArea (Bibby et al., 1991). Only the first fourof the seven classes are suited to arableagriculture:• Class 1: Land capable of producing avery wide range of crops. Cropping ishighly flexible and includes the moreexacting crops such as winter harvestedvegetables (cauliflowers, brusselssprouts, leeks). The level of yield isconsistently high. Soils are usually welldraineddeep loams, sandy loams, siltyloams, or their related humic variants,with good reserves of moisture. Sitesare level or gently sloping and theclimate is favourable. There are no orvery minor physical limitations affectingagricultural use.• Class 2: Land capable of producing awide range of crops. Cropping is veryflexible and a wide range of crops can begrown though some root and winter
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Crop Production in the East of Scotland - SASA

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