Effect of Drying Parameters on Germination of Paddy Seeds in a Temperature-Controlled Solar Dryer

Post-harvest drying plays an important role in maintaining paddy seed quality. This study evaluated the effects of temperature-controlled solar drying on germination and seedling vigour of two paddy (Oryza sativa L.) varieties, TPS 5 and CO 51, compared with open-sun drying. Seeds with an initial moisture content of 20%-24% were dried at 40°C, 44°C and 48°C to final moisture contents of 12%, 14% and 16% (wet basis), with two replications per treatment. Germination was assessed on the seventh day using 50 seeds per replication. During sufficient solar radiation, chamber-air remained within approximately ±2°C of the set temperature. Solar-dried seeds showed higher mean germination (91.06 ± 5.92%) and vigour index (1536.67 ± 211.06) than sun-dried seeds (82.17 ± 3.86% and 1371.33 ± 228.11, respectively). Three-way ANOVA indicated significant effect of drying condition on germination (p < 0.001, η²p = 0.73), with significant drying condition and variety interaction (p = 0.003, η²p = 0.43). Root and shoot lengths were not significantly affected by drying conditions (p > 0.05). TPS 5 recorded the highest temperature-level mean germination at 44°C (96.33%). Overall, controlled solar drying at 40°C-44°C produced favourable germination and vigour responses, demonstrating its potential for maintaining paddy seed quality under the tested conditions.