Division of Information Technology, Engineering and the Environment
School of Advanced Manufacturing and Mechanical Engineering
School of Advanced Manufacturing and Mechanical Engineering
Thesis Abstract
The development of power tiller operated seeders (PTOS) is in progress in Bangladesh and other developing countries. Much of the design and development work follows adaptive field research based on trial and error and focussing mainly on the cropping and economic performances rather than considering the fundamental agronomic seed furrow parameters required for the targeted crops. Example furrow quality parameters include considerations of depth, width, and shape of furrow, extent of backfill, soil tilth, and sidewall smearing. A furrow of uniform width and depth, well backfilled (implying minimum soil throw out of the furrow) with suitable tilth (e.g. clod size distribution suited to seed size) is desired. It is also expected that the furrow sidewalls and bottom surface should be free from high levels of compaction which can retard plant growth and inhibit water and oxygen movement. A sound understanding of the influence of blade design and operation on such furrow parameters can aid in designing better performing technologies and achieve a superior crop performance.
An experimental single row rotor unit was developed to enable the testing of three blade geometries at four rotary speeds in laboratory soil bin environment. A novel method of measurement of furrow backfill and sidewall strength was developed and evaluated. The blade geometry and rotary speed was found to significantly alter most of the furrow parameters and there is a great potential to improve the existing blade design. For example, the combined effect of blade geometry and rotary speed could vary furrow backfill levels between 35 and 98%, and soil tilth fineness indicator between 42 and 93%. The conventional blade resulted in poor furrow backfill, achieving only 52% on an average, but improved to an average 82% with a modified blade design.
From the study to date, it can be summarised that the horizontal width portion of the blade is responsible for soil throwing. A more uniform furrow shape and more complete furrow backfill can be achieved by omitting the horizontal width portion of the blade at no loss of soil tilth fineness. Such a blade can also reduce the risk of any adverse increase in furrow sidewall strength when compared with the conventional blade. Although, the furrow backfill can reduce with increasing rotary speed, a high rotary speed (375-500 rpm) may be preferable for other desired furrow properties. This study will also investigate how the new blade design performs across various field and operating conditions, as well as crop performance results when associated with a planter unit. The findings of this study will help design better performing strip-till drills for small scale farmers in the developing world.
