Division of Information Technology, Engineering and the Environment
School of Advanced Manufacturing and Mechanical Engineering
School of Advanced Manufacturing and Mechanical Engineering
Thesis Abstract
Australian no-till farming often uses narrow point openers to open the soil and place seed and fertilizer in the furrow. They are generally used in conjunction with spraying of herbicide for weed control and press wheels to pack soil cover seeds. These openers can create soil throw which creates problems such as increasing depth of soil cover on the adjacent furrows, herbicide contamination above the seed area, increasing stimulation for weed seed germination and soil moisture loss. The factors identified that can reduce soil movement include: soil condition (texture, moisture and structure), tool settings (speed and depth) and geometry of opener. The objectives of this research are: 1) to quantify the effects of narrow point opener geometry on the processes of soil movement in a sandy loam soil, 2) to evaluate narrow bent leg opener designs as a strategy for controlling soil movement, focusing on the reduction of throwing soil tilth out of the furrow, 3) to model the mechanics and outcomes of soil movement with simple narrow point opener geometries using discrete element modelling.
In the first stage, the effect of rake angle values of 35o, 53o, 72o and 90o on the characteristics of soil movement by depth layers was investigated using a simple flat face narrow point opener. A low rake angle opener was seen to delve tracers placed deep in the soil up to the surface and was found to throw more soil and deeper soil out onto the furrow ridge while a larger rake angle opener gave more furrow backfill. Surface soil was thrown out of the furrow to the greatest extent for the 53° rake angle. In the second stage, bent leg design concepts was evaluated and optimised. They have the ability to loosen the soil in the furrow with minimal throw of soil out of the furrow. The results indicated that the three main key design parameters of bent leg opener to control soil movement are; 1) face chamfer, 2) shank offset and 3) foot height. Using opener face chamfer strongly reduces soil movement compare to blunt opener. The new bent leg design not only controls the movement of surface tracers (per-emergent herbicide) onto the adjacent furrow, but also increases the critical depth, a depth below which the soil is compressed sideways rather than being lifted upwards.
