The effect of sowing pre-germinated seeds of lettuce (Lactuca sativa) on seedling emergence

Glasshouse and field experiments were conducted to investigate the effects of sowing both untreated and pre-germinated seeds, with or without a gel carrier, and also pelleted seeds into soils of different moisture contents and at different temperatures on seedling emergence of lettuce cvs Cobham Green and Avondefiance. Pre-germinated seeds with radicles 1–2 mm long gave, on average, 15 and 4% higher final percentage emergence than untreated and pelleted seeds respectively. Sowing pre-germinated seeds having radicles longer than 2 mm gave more variable levels of emergence and often reduced emergence, particularly when they were sown into dry or drying seedbeds. Increasing the rate of gel carrier from 0 to 30 ml m^_1 of row reduced emergence progressively from 67 to 30%. Pre-germinated seeds emerged 2–5 and 3-0 days earlier than untreated and pelleted seeds, respectively, at a soil temperature of 10 ^oC; at 15 ^oC the corresponding figures were 0–5 and 3–5 days. Sowing pre-germinated seeds reduced the spread (i.e. variability) of emergence by an average of 37 and 47% compared with untreated and pelleted seeds, respectively.