MUTILLS - THE MELBOURNE UNIVERSITY TILLED SOIL MODEL

Abstract

ABSTRACT The Melbourne University Tilled Soil model (MUTillS) has been developed to simulate the effects of tillage and weathering on the tilled layer of a swelling clay soil. The model simulates the complex interactions between roughness and storage capacity of the soil surface, water content, moisture potential, bulk density, bulk shear strength, temperature, and macrostructure within the plowed layer and provides representative values for each of these variables. As developed, the model simulates the effects of a tined scarifier or cultivator, a blade plow, a rod weeder, and a grain drill on these soil properties. Simulation results of soil water content indicate that this parameter can be modelled with a standard error of estimate (SEE) of 2.7% and 3.5% (v/v), respectively, for conventional- and blade-plowed-based tillage systems. Results of individual tests of the other model components show that tilled layer bulk density can be predicted with a SEE less than 125 kg/m^, temperature at 50 mm depth with a SEE less than 2.4 C, surface roughness with a SEE less than 4.8 mm and surface storage capacity with a SEE of less than 4.8 mm. Simulated macrostructures are rated as similar or very similar to measured values in 17 of 19 tests, while only two cases are rated as slightly different or different. MUTillS also successfully simulates an envelope of maximum measured shear strength values.