Derris microphylla: A Potential Alternative High Shade Tree Species for Albizia moluccana (AKA: Falcataria moluccana) in Low Grown Tea Fields in Sri Lanka

Shade harmonizes micro-climatic environmental factors favorable for tea. Presently, growers use Albizia for this purpose in low and mid elevations. However, its fast growth and large size have caused difficulties in shade management. This observation led the Tea Research Institute of Sri Lanka (TRISL) to identify an alternative tree species to Albizia. Hence, the main objective of this study was to test the growth performances of alternative high shade tree species and study their effect on the growth and yield of tea. The experiment was established in Houpe Estate, Kahawatte with two new high shade tree species viz., Derris microphylla and Cassia nodosa planted at 3 planting distances (6x6 m, 9x9 m and 6x9 m). The control treatment was Albizia moluccana planted at 6x6 m. Treatments were arranged in Randomized Complete Block Design (RCBD) with 3 replicates. The growth of shade and tea, tea yield and soil parameters were recorded over a period of four years. Height of C. nodosa was found to be inadequate, as a high shade tree in tea. Its trunk was thinner than A. moluccana but, profuse branching necessitated more frequent lopping. Other unfavorable characteristics of C. nodosa included high mortality rates, spiky trunk, and defoliation during dry weather, where tea requires shade the most. D. microphylla exhibited smaller girth and height than A. moluccana, resulting in a more manageable stature for routine maintenance. Other growth characteristics of D. microphylla and its influence on tea yield were comparable to those of A. moluccana (control) and showed no pest or disease infestations. Soil parameters under A. moluccana and D. microphylla were also comparable. Therefore, D. microphylla could be considered as a potential alternative to A. moluccana in the establishment and management of high shade in tea at low elevation.