ACCUMULATED THERMAL TIME AFFECTS GROWTH, YIELD AND PHENOLOGICAL DEVELOPMENT OF SESAME (Sesamum indicum L.) IN THE DRY ZONE OF SRI LANKA

Abstract

The present experiment was conducted to determine the impact of accumulated thermal time on the growth, yield and phenology of Sesame (Sesamum indicum L.) in the dry zone of Sri Lanka. Uma, Malee and MI-3 varieties were selected and the seeds were sown on three different dates in the 2016 Yala and 2016/2017 Maha seasons. The experiment was set up according to a two-factor factorial randomized completely block design with three replicates. Accumulated thermal time was calculated as growing degree days at the vegetative stage, flowering initiation, 50% of flowering, 100% of flowering and physiological maturity using minimum and maximum daily temperature. Then the plant height and the number of leaves per plant were plotted against the accumulated thermal time using the sigmoid growth model. The seed dry weight and dry weight of 1000 seeds were recorded at maturity. The relationship of plant height and the number of leaves per plant with accumulated growing degree days (AGDD) was significant for all varieties at different sowing dates in both seasons. The flowering of sesame initiated at 741 and 713.1 of AGDD in Yala and Maha seasons, respectively. The AGDD needed for 50 % flowering in the Yala is greater than the Maha season. Full flowering occurred in Maha earlier than the Yala season. Plants reached physiological maturity early in the Maha season. Seed weight per 15 plants and seed weight per plot were significantly affected by the interaction between variety and the sowing date in Maha and Yala seasons, respectively. The highest seed weight per 15 plants was recorded in var. Uma and var. Malee in Yala season while the highest seed weight per plot was also recorded by var. Uma. Furthermore, 1000 seed weight was greater in var. Uma than other varieties in both seasons. Sowing seeds early in the season increased seed weight per 15 plants in Yala while seeds per plot and 1000 seed weight in Maha season. According to the results of the present study, var. Uma could be considered as an efficient sesame variety that performed better when sown early in the season. Therefore, cultivating var. Uma, early in the seasons might be beneficial in terms of growth and yield in the dry zone of Sri Lanka. However, further field studies are needed to give a solid recommendation.