Impact of Motorized Tea Harvesters on Tea Yield and Yield Determining Parameters

Motorized tea harvesters vary in shoot cutting & collecting mechanisms and reported considerable yield decline in Sri Lanka. In this study, three non-selective harvesters were used to evaluate the impacts of different cutting & collecting mechanisms on tea yield-determining parameters compared to manual harvesting (control). The machines used were battery-operated Forbes & Walker harvester with helically arranged picking arms (BatFW), battery-operated Kawasaki harvester with reciprocating blades (BatKW), and petrol-driven Kawasaki harvester with reciprocating blades (PetKW). Tea yield, coarse leaf content, operational time, shoot compositions, branch girthing, and root starch content were recorded for one year. The motorized harvesters reduced tea yield by nearly 50% compared to the control. The number of machines required (units/ha/day) were 6, 4 and 2 for BatFW, BatKW and PetKW, respectively, as compared to eight manual pluckers and the corresponding land extents covered were 0.17, 0.25 and 0.47 (ha/unit/day), as against 0.13 in manual. Manual harvesting and BatFW consumed comparable higher worker requirements than the others. The average shoot weight and shoot density were the least affected by BatFW. The highest immature (arimbu) shoot removal was by PetKW. The highest dormant shoot accumulation in the plucking table was by BatFW. Reciprocating blades harvested more productively (700 g/cm/day) than picking arms (500 g/cm/day). All machines affected branch girthing and root starch reserves compared to manual harvesting. The mechanical impacts on yield determining parameters viz., immature shoot removal, accumulated dormant shoots, affected yield components, poor branch development, and depleted root starch reserves collectively resulted the tea yield reduction.