Evaluation of the Impacts of Mechanical Harvesting on Tea Yield (Cultivar TRI 2027) in the Low Country of Sri Lanka

Due to worker shortage in the plantation sector of Sri Lanka, timely maintenance of plucking rounds has become a difficult task for the tea growers. As a result, the abandonment of tea fields has become a common practice in the estate sector. Harvesting, the most labour intensive field operation in tea cultivation has adversely affected under worker scarce situations. Although, motorized harvesting is the apparent alternative to manual harvesting when the labour supply is limited, the drastic yield and quality reductions and deterioration of health of tea bushes limit the use of machines for harvesting. Such downsides are reported to be resulted from three basic impacts, viz. removal of arimbu (immature) shoots, higher severity of harvesting and removal of maintenance foliage. Hence, a detailed study was carried out to quantify the contribution of each impact for yield reduction under mechanical harvesting.
Results showed that the greatest impact in the yield reduction was exerted by removal of arimbu shoots (55%) followed by higher severity of harvesting (15%) and removal of maintenance foliage (12%). The removal of arimbu shoots and maintenance foliage adversely affect the sink: source relationship of the bush and thus, photosynthesis. This reduces available carbohydrates for growth and affects branch (vascular system) development and thus, the translocation capacity of the bush. Insufficient carbohydrates and poor translocation capacity result in low shoot density and shoot weight, higher dormancy, reduced root starch reserves and consequently reduction in yield. Use of machines only during cropping months, avoiding a deep cut into the plucking table and good agronomic practices minimizing environmental stresses were identified as remedial measures arresting yield losses.