A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Agricultural Systems and Engineering, School of Environment, Resources and Development

Thesis (Ph.D.) - Asian Institute of Technology, 2010

A study was conducted to evaluate the performance o f a powered disc compared to free rolling disc. This research was conducted in two steps. In the first part interaction between soil and powered disc was studied in the soil bin under controlled conditions for better understanding of its performance. A specially instrumented soil bin setup consisting of soil bin system and measurement system was fabricated. Double extended octagonal ring (DEOR) transducer and torque transducer with slip ring were used for forces and torque measurements. Performance of the three different types of tillage discs in powered and free rolling mode was evaluated in the sandy loam soil. Three different levels of the disc angle and three different levels of the rotational speed were considered for the powered discs, whereas three different levels of the disc angle we re considered for the free rolling disc. Soil bin studies revealed reduced draft requirement s when disc was changed from free rolling to the powered mode. Moreover it provided improved soil handling capabilities. Consequently powered disc was found advantageous over free rolling disc in terms of smooth soil displacement, easy soil volume handling , better inversion of the furrow slice, reduced soil reactions and improved energy utilization. On the other hand, soil bin results showed significantly lower draft for the spiral not ched tillage disc than standard and notched disc. Moreover spiral shaped cutting edge provided smooth cutting operation which identified as the shear cutting action, most useful in conservation tillage for cutting of the crop residues. Consequently spiral notched disc was selected for the development of the powered disc harrow. In the next part a powered disc harrow was developed based on the soil-disc interaction studies and subsequently evaluated for its field performance at different forward speeds. Performance of the powered disc harrow was compared with the unpowered disc harrow at similar operating conditions. Field evaluation studies showed similar trend of the results as the soil bin studies. It provided reduced draft, improved penetration and improved inversion than unpowered disc harrow. Operating gear 2L was appropriate for opera ting powered disc harrow. In short, powered disc harrow was advantageous for the conservation tillage practice in terms of the excellent penetration, smooth tillage operation, reduced draft requirements, improved cutting and mixing of the weeds, improved soil inversion and better energy utilization.