Abstract:
High temperature and water scarcity in the dry zone of Sri Lanka reduce coconut
production by affecting pollen quality, leading to reduced fruit set, size, and quality.
The girdle micro-sprinkler system (GMIS), which uses water efficiently, can lower
canopy temperature by spraying water as a fine mist when positioned near the canopy.
This study assessed the impact of GMIS on pollen viability, pollen germination, fruit
set, and soil properties of coconut in the dry zone of Sri Lanka. Tree-by-tree variation
was evaluated under two treatments: with GMIS and without GMIS (control), each
with ten replicates. Canopy and floral temperature, as well as relative humidity, were
measured weekly. The number of bunches, nuts, fallen button nuts, and unopened
inflorescences per tree were counted biweekly. Pollen viability and germination were
assessed at four temperatures (26°C, 28°C, 30°C, and 32°C). Data were analyzed
using the mixed effect model in R Studio. Canopy temperature, floral temperature,
and relative humidity showed no significant differences between treatments, possibly
due to rain interruptions during the research period. There were no significant
differences in the number of bunches, nuts, or unopened inflorescences between
treatments, yet they were slightly high in coconut with GMIS. Pollen germination
was significantly reduced under non-irrigated conditions, likely due to inadequate
sugar accumulation at high temperatures. These findings confirm that the GMIS
improves pollen quality that enhance germination. The optimal pollen germination
occurred at 32°C for both treatments. Soil pH and EC were 8.1 and 142 µS cm-1 in
the irrigated treatment, compared to 7.9 and 128 µS cm-1 in the non-irrigated
treatment. Rainfall during the experiment alleviated drought conditions, potentially
influencing the results. Thus, repeating the study under more severe drought
conditions is recommended to obtain more reliable findings.
