Soil compactibility in relation to physical and organic properties at 156 sites in UK

The variation of soil compactibility and its relationship to plasticity, te xture, organic matter and particle density is considered for 156 sites and for one intensively sampled site. These sites were concentrated in east Sco tland and were the locations of Scottish Agricultural College (SAC) field e xperiments and surveys related to tillage and compaction. Compactibility wa s determined by a rammer method on sieved soil. The coefficient of variabil ity of compactibility (as maximum dry bulk density) was relatively low betw een sites (9.5%) and within site (4%). The soils covered a wide range of te xtures; sand contents ranged from 1.7 to 93.5 g 100 g(-1) and clay contents ranged from 2.5 to 49.1 g 100 g(-1) However, liquid limit was more importa nt than particle size fractions in the prediction of compactibility. Loss-o n-pretreatment prior to measurement of particle soil distribution was taken as a measure of readily oxidisable soil organic matter. This fraction was more variable and more relevant than total organic matter in determining me chanical behaviour. Compactibility was predicted adequately by a combinatio n of loss-on-pretreatment and liquid limit. Maximum dry bulk density and li quid limit were identified at important characteristics of the dataset and would be suitable parameters for measurement of soil physical/behavioural q uality. Although particle density was not particularly important in predict ing compactibility, it ranged from 2.36 to 2.87 Mg m(-3). Awareness of this variability is important for properties estimated by a calculation involvi ng particle density. (C) 2000 Elsevier Science B.V. All rights reserved.