PERFORMANCE EVALUATION OF 3 PRE-LIFT SOIL LOOSENING DEVICES FOR CASSAVA ROOT HARVESTING

Loosening the soil in the root zone before lifting the tubers out of t he soil is a function critical for efficient harvesting of cassava (Ma nihot esculenta, Crantz) both in terms of lifting force reduction and prevention of tuber damage. Therefore, three soil loosening devices we re modified for pre-lift soil loosening in cassava harvesting, and eva luated for performance in terms of soil disturbance and soil forces ac ting on them in a laboratory soil bin and in the held under similar so il characteristics. The devices include an L-tine, an A-blade, and a c ombination of a curved chisel tine working at a depth of 0.1 m ahead o f a L-tine. Results show that of the three devices, the A-blade had th e least soil forces and specific resistance followed by the L-tines. F urthermore, results indicate that the L-tines are most suitable for pr e-lift soil loosening in cassava harvesting due to their simplicity of fabrication, reduced damage to cassava roots and adjustable width. Th e results show that a harvester incorporating L-tines as the pre-lift soil loosening device (requiring draught farce of 18.6 kN/m) is techni cally feasible. (C) 1998 Elsevier Science B.V. All rights reserved.