Crop Production in the East of Scotland - SASA

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