Abstract:
The study was carried out at The Open University of Sri Lanka to identify the suitable growth
media to combat temperature stress due to Global warming on growth and yield of Lettuce. Two
temperature conditions as temperature stress (T1), ambient temperature (T2) and five types of
growth medias as coir dust (M1), Coir dust: sand ( 1:1) (M2), coir dust : sand (1:2) (M3), Coir
dust : sand : cow manure (1:1:1) (M4) and top soil (M5) were tested in this study. All the treatments were arranged in a Completely Randomized Block Design (CRD) with three replicates.
Green leaf lettuce was the variety selected and growth parameters were measured at two weeks
interval. Yield parameters such as number of leaves, fresh biomass per plant and dry biomass
per plant were measured after harvest. Moisture (%) and porosity of the media were measured
to determine the water retention ability under the temperature stress condition. SAS Statistical
software (university version) was used for the statistical analysis and the data were statistically
analysed according to the General Linear Model (GLM) procedure and the mean separation
was done using the Least Significant Difference (LSD) at p = 0.05 level. The factors media,
temperature and their interaction effect were significantly influenced on the growth and yield
parameters. Treatment at temperature stress with coir dust: sand (1:2) (T1M3) and treatment at
ambient temperature with coir dust: sand (1:2) T2M3 were shown higher porosity and moisture
content. However, media which were shown higher porosity beyond the optimum level resulted
in lower moisture content due to high rate of drainage. Media of Coir dust: sand: cow manure
(1:1:1) (M4) was the only treatment which was positively affected on growth and yield of lettuce
under temperature stress condition. Therefore, media of Coir dust: sand: cow manure (1:1:1)
(M4) is the best suited growth media for Lettuce cultivation to combat temperature stress due
to global warming.