Sowing and harvesting dates as well as storage periods have considerable
influence on rice seed quality as measured by seed viability, seedling vigour, 100-
seed dry weight, dehydrogenase activity, electrical conductivity, seed moisture
content and field emergence. Two experiments were conducted at EI-Sirw
Experimental Station, Agriculture Research Center during 2002 and 2003 seasons.
The main results could be summarized as follows:
Sowing rice seed in early date 25 th April reduced seed viability, seedling
vigour and field emergence, while electrical conductivity and seed moisture content
were increased. In contrast, sowing date 15 th May improved seed viability, seedlings
vigour, 100-seed dry weight, dehydrogenase activity, field emergence and it reduced
electrical conductivity and seed moisture content. Harvesting rice plant at the early
date 23 day after heading reduced seed viability, seedlings vigour and field
emergence but it increased electrical conductivity and seed moisture content.
Harvesting date 37 day after heading improved seed viability and seedlings vigour.
Increasing storage period decreased seed viability, seedlings vigour, 100-seed
weight, dehydrogenase activity, seed moisture content, field emergence and
increasing electrical conductivity. Positively significant correlations were found for the
most studied traits and sowing dates except for negatively significant correlation with
seed moisture content. Furthermore, significantly positive correlations were obtained
for all the studied traits with harvesting dates. On the other hand, significantly negative
correlations for seed moisture content and electrical conductivity with delaying
harvesting dates. Storage periods had significantly negative correlation with the most
studied traits excepting electrical conductivity while significant positive correlation was
found. Meanwhile germination percentage had insignificant negative correlation. The
study suggested, sowing rice (c.v. Giza 178) from (5:15 May) and harvesting 30:37
days after heading and storage until 8 months to obtain high seed viability and
seedling vigour.