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Ph.D. student, University of Manitoba

PINBOARD SUMMARY

In a field operation, tillage tools loosen soil for seedbed preparation and seed openers open soil for seed placement. A general term for these tillage tools and seeding openers is “soil engaging tool”. As agricultural fields retain more or less crop residue from previous crops, soil engaging tools interact with both soil and crop residue during field operations. Soil-tool-residue is a complex system, since soil consists of a matrix of discrete particles that are of random, heterogeneous nature, and exhibit sophisticated non-linear behaviors. Such a system cannot be modeled using traditional analytical or numerical methods. My proposed research will develop a universal model of soil-tool-residue interaction, which can address the complex nature of soil and existence of residue particles in agricultural fields. In the proposed research program, a new, innovative numerical method – discrete element method will be used to develop the universal soil-tool-residue interaction model. In the model, basic soil particles will be represented by spherical particles of various sizes. The particle constitutive laws will be defined in such a way that basic particles can form aggregates and have frictional, cohesive, viscous, and deformable behaviors like real agricultural soil. The cohesive behavior will be described using bonds between soil particles that are in contact. Bonds connect soil particles together, forming soil aggregates, and bonds are breakable under the impact of soil engaging tools. Calibration will be performed using fundamental soil mechanical tests so that the calibrated microproperties are universal, independent of soil engaging tool. In the model, a residue particle will be represented by a cluster of basic spherical particles arranged in a way that reflects the shapes of real crop residues. Models will be validated using laboratory and field data. Discrete element modeling of dynamic behaviors of agricultural soil is an emerging field. The universal soil-tool-residue model to be developed will mark a potential breakthrough in the area of soil dynamics, in that the model can be used to simulate the micro soil dynamics behaviors for any soil engaging tool, in any soil condition. The simulation results will lead to the emergence of new high-performance tillage and seeding tools that consume minimal tractor power and create optimal soil conditions for crop growth. The outcome will be also useful in crop residue management for sustainable agriculture.

4 ITEMS PINNED

Discrete element modelling of tillage forces and soil movement of a one-third scale mouldboard plough

Abstract: Publication date: March 2017 Source:Biosystems Engineering, Volume 155 Author(s): Mustafa Ucgul, Chris Saunders, John M. Fielke In Australia there is renewed interest in mouldboard ploughing to improve crop yields of non-wetting sandy soils. Burying the top layer of non-wetting soil and bringing to the surface soil that has better water holding capacity is beneficial for plant growth. To improve the effectiveness of the ploughing it is essential to: (1) optimise the tillage forces and (2) understand the soil inversion and burial process. Recent studies show that Discrete Element Modelling (DEM) has the potential to predict both tillage forces and soil movement of tillage implements. In this study a one-third scale mouldboard plough was constructed and tested in a soil bin where draught force, vertical force and soil movement were measured. A comparison of the measured and simulated draught and downward vertical forces showed a close agreement. A procedure was developed to compare soil movement, percentage burial of top soil and forward soil movement of the soil bin tests and the DEM simulations. The results showed similar trends and patterns for both the percentage of the top soil buried to various tillage depths and the forward soil movement. Due to the larger than actual spherical particles used in the simulation the forward soil movement was greater for DEM. The DEM showed some particles moving below the tillage depth. This shows that further model development is needed with work recommended to look at using both clump particle shapes and smaller particle sizes to improve soil movement predictions.

Pub.: 26 Dec '16, Pinned: 11 Jul '17

Discrete element simulations and experiments of soil disturbance as affected by the tine spacing of subsoiler

Abstract: Tine spacing is a key parameter for the design of a subsoiler and has a significant effect on soil disturbance, which is a critical performance indicator of subsoiling. In this study, a subsoiling model was developed using the discrete element method (DEM). A subsoiling experiment was also conducted in a field with a loamy clay soil to serve the model development and model validations. In both the simulation and experiment, two V-shaped subsoiling tines were investigated at five different tine spacings (300, 350, 400, 450, and 500 mm), a constant working speed (0.83 m s−1) and a constant working depth (300 mm). The results showed that the 400 mm tine spacing resulted in the highest particle forces in the middle and deep soil layers. The height of the unloosened soil between two adjacent subsoilers increased as tine spacing increased. When the tine spacing was varied from 300 to 500 mm, the undisturbed soil height was changed from 100 to 226 mm in the experiment, and from 79 to 170 mm in the modelling. When the tine spacing was 400 mm, the number of soil particles disturbed in the shallow soil layer accounted for 45.6% of the total soil particles disturbed, which was the least among all the tine spacings. Considering the characteristics of soil disturbance, the tine spacing of 400 mm appeared to outperform the other spacings.

Pub.: 11 Apr '17, Pinned: 11 Jul '17

Simulation of seed motion in seed feeding device with DEM-CFD coupling approach for rapeseed and wheat

Abstract: A numerical study of gas-solid flow in seed feeding device of air-assisted centralized metering system was carried out by means of Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD) coupling approach. In this model, discrete particles phase was applied by EDEM software and continuum gas phase was described by ANSYS Fluent software. Effects of throat’s area, throat length, airflow inlet velocity and seed feed rate were studied and analyzed in terms of gas field and seed movement. Simulation results showed that, throat’s area and airflow inlet velocity mainly affected airflow outlet velocity and seed velocity of airflow direction which resulted from drag force, while seed movement was affected by throat length and seed feed rate slightly. The increase of throat area resulted in the decrease of seed velocity and pressure loss in a certain range. Seeds moved slowly and generated the phenomenon of bounce and concentration for low airflow inlet velocities. With the airflow inlet velocity increased, resultant force and seed velocity developed. The proper airflow inlet velocity was 16–20 m/s and 20–24 m/s for rapeseed and wheat, respectively. It showed that DEM-CFD coupling approach is reliable as a tool for understanding the physical phenomenon of seed movement in airflow field. Numerical simulation of seed motion based on DEM-CFD coupling approach can provide theoretical basis for developing operating performance of seed feeding device.

Pub.: 18 Nov '16, Pinned: 11 Jul '17

Soil structure changes induced by tillage systems

Abstract: Publication date: January 2017 Source:Soil and Tillage Research, Volume 165 Author(s): Luiz F. Pires, Jaqueline A.R. Borges, Jadir A. Rosa, Miguel Cooper, Richard J. Heck, Sabrina Passoni, Waldir L. Roque Structure represents one of the main soil physical attributes indicators. The soil porous system (SPS) is directly linked to the soil structure. Water retention, movement, root development, gas diffusion and the conditions for all soil biota are related to the SPS. Studies about the influence of tillage systems in the soil structure are important to evaluate their impact in the soil quality. This paper deals with a detailed analysis of changes in the soil structure induced by conventional (CT) and no-tillage (NT) systems. Three different soil depths were studied (0–10, 10–20 and 20–30cm). Data of the soil water retention curve (SWRC), micromorphologic (impregnated blocks) (2D) and microtomographic (μCT) (3D) analyses were utilized to characterize the SPS. Such analyses enabled the investigation of porous system attributes such as: porosity, pore number and shape, pore size distribution, tortuosity and connectivity. Results from this study show a tri-modal pore size distribution (PSD) at depths 0–10 and 10–20cm for the soil under CT and a bi-modal PSD for the lower layer (20–30cm). Regarding the soil under NT, tri-modal PSDs were found at the three depths analyzed. Results based on the micromorphologic analysis (2D) showed that the greatest contribution to areal porosity (AP) is given by pores of round (R) shape for CT (52%: 0–10cm; 50%: 10–20cm; 67%: 20–30cm). Contrary to the results observed for CT, the soil under NT system gave the greatest contribution to AP, for the upper (0–10cm) and intermediate (10–20cm) layers, due to the large complex (C) pore types. For the μCT analysis, several types of pores were identified for each soil tillage system. Small differences in the macroporosity (MAP) were observed for the 0–10 and 20–30cm between CT and NT. A better pore connectivity was found for the 0–10cm layer under NT.

Pub.: 09 Aug '16, Pinned: 11 Jul '17