Soil-tool-residue interactions: measurements and modelling
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Date
2019-01-21
Authors
Zeng, Zhiwei
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Abstract
Soil-tool-residue interactions are at the centre of many agricultural field operations. The study of soil-tool-residue interactions is one of the fundamental aspects of soil dynamics in agricultural engineering. The aim of this study was to investigate dynamic behaviours of soil-tool-residue interactions including soil cutting forces, soil displacement, soil loosening and furrow profile, straw displacement, residue cover and incorporation. Experimental studies of soil-tool-residue interactions were conducted for various soil-engaging tools (fluted coulter, rippled disc, and compact disc harrow) working on several field conditions (corn stubble, wheat stubble, and bare soil) at different operational parameters (working speed and depth). Numerical models of the soil-tool-residue interactions were developed for a micropenetrometer, a subsoiler, and a sweep using the discrete element method (DEM). The models were calibrated and validated by comparing simulation results with experimental data from soil bin and field tests. Field testing results of vertical tillage tools demonstrated that fluted coulters left less surface residue, incorporated more residue into the soil, created a wider furrow, and disturbed a larger area than rippled discs. The effect of working speed was more dominant than the coulter geometry on the tillage performance of the fluted coulters. Soil bin tests of a compact disc harrow indicated that disc spacing and offset had significant effects on soil disturbance characteristics, and the effects varied with the tillage depth. The DEM simulation results showed that the soil-micropenetrometer model produced comparable results to the laboratory measurements, in terms of the variation of cone index over penetration depth. The soil-subsoiler model was capable of predicting soil cutting resistance and soil disturbance characteristics with relative errors ranging from 2.63 to 10.2%. The straw-sweep-soil model was able to simulate dynamic attributes of bulk materials and individual particles, such as straw movement, moving trajectories and velocity contours. This study embraced a broad topic of soil-tool-residue interactions. The results have advanced the science of soil dynamics and contributed to the engineering knowledge required for the development of high-performance agricultural machinery that consumes minimal tractor power and creates optimal field conditions for crop growth.
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Keywords
Soil dynamics, Agriculural machinery, Discrete element method, Numerical simulations, Conservation tillage, Soil bin tests