Modelling tillage translocation using step, linear-plateau and exponentialfunctions

The distance over which soil is displaced and mixed during tillage has impo rtant implications for the understanding the dynamics of soil variability w ithin complex soil-landscapes. In two preceding studies of tillage transloc ation, tillage was observed to displace soil over a length of approximately 1 m following single passes of four tillage implements (chisel plough, mou ldboard plough, tandem disc and field cultivator), and over a length of app roximately 2 m per sequence of conventional tillage (one pass of mouldboard plough, two passes of tandem disc and one pass of field cultivator). Using data from these studies step, linear-plateau and exponential functions wer e assessed for their ability to estimate the magnitude of translocation and the redistribution pattern of soil within the till-layer, and to predict t he redistribution pattern of soil within the till-layer. On average, step, linear-plateau and exponential models estimated 100.0%, 100.2% and 102.5% o f the magnitude of translocation and 76%, 88% and 93% of the soil redistrib ution pattern, respectively. Based on these results, it was concluded that: linear-plateau and exponential functions are suitable models of tillage tra nslocation. The exponential model was superior to the step and linear-plate au models, and an improvement over the existing diffusion model. (C) 1999 E lsevier Science B.V. All rights reserved.