Fine-earth translocation by tillage in stony soils in the Guadalentin, south-east Spain: an investigation using caesium-134 $ Timothy A. Quine a,* , Gerard Govers b , Jean Poesen b , Des Walling a , Bas van Wesemael c , Jose Martinez-Fernandez d a Department of Geography, University of Exeter, Amory Building, Rennes Drive, Exeter, Devon, EX4 4RJ, UK b Laboratory for Experimental Geomorphology, Catholic University of Leuven, Redingenstraat 16, 3000 Leuven Belgium; Fund for Scienti®c Research, Flanders, Belgium c Department of Geography, University of Middlesex, London, N17 8HR UK d Departamento de Geografa, University of Murcia, 3001 Murcia, Spain Abstract Tillage erosion is increasingly recognised as an important soil erosion process on agricultural land. In view of its potential signi®cance, there is a clear need to broaden the experimental database for the magnitude of tillage erosion to include a range of tillage implements and agricultural environments. The study discussed in this paper sought to address the need for such data by examining tillage erosion by a duckfoot chisel plough in stony soils on steep slopes in a semi-arid environment. Results of the investigation of coarse fraction (rock fragment) translocation by tillage in this environment have been presented elsewhere and the paper focuses on tillage translocation and erosion of the ®ne earth. Tillage translocation was measured at 10 sites, representing both upslope and downslope tillage by a duckfoot chisel plough on ®ve different slopes, with tangents ranging from 0.02 to 0.41. A ®ne-earth tracer, comprising ®ne earth labelled with 134 Cs, was introduced into the plough layer before tillage. After a single pass of the plough, incremental samples of plough soil were excavated and sieved to separate the ®ne earth from the rock fragments. Translocation of the ®ne-earth tracer was established by analysing the 134 Cs content of the samples of ®ne earth. These data were used to establish translocation distances for each combination of slope and tillage direction. Translocation distances of the ®ne earth were not signi®cantly different from translocation distances of the coarse fraction. For all sites, except uphill on the 0.41 slope, translocation distances were found to be linearly related to slope tangent. The soil ¯ux due to tillage for each site was calculated using the translocation distance and the mass per unit area of the plough layer. For slopes with tangents <0.25, the relationship between soil ¯ux and tangent was linear and the soil ¯ux coef®cient derived was 520±660 kg m 1 per pass. This is much larger than the coef®cients found in other studies and this high magnitude is attributed to the non-cohesive nature and high rock fragment content of the soil in this investigation. A second contrast with previous studies was found in non-linearity in the relationship between soil ¯ux and tangent when steeper slopes were included. This was a product of variation in plough depth between the steepest slopes and the remainder of the study area. On the basis of the study it is suggested that an improved understanding of tillage erosion may be obtained by considering the dual Soil & Tillage Research 51 (1999) 279±301 *Corresponding author. Tel.: +44-1392-263-352; fax: +44-1392-263-342 E-mail address: t.a.quine@exeter.ac.uk. (T.A. Quine) $ Paper presented at International Symposium on Tillage Translocation and Tillage Erosion held in conjunction with the 52nd Annual Conference of the Soil and Water Conservation Society, Toronto, Canada. 24±25 July, 1997. 0167-1987/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved. PII:S0167-1987(99)00043-4