The seedling emergence from fluid-drilled germinating and natural onion seeds was compared at five sowing dates between 10 February and 18 May on irrigated and unirrigated plots in two experiments. In the second experiment fluid-drilled seeds selected for uniform germination were also included. There were few significant differences between the emergence of seedlings from germinating and natural seeds in the field sowings of Expt 1. However, a reduction in mean emergence time at the earliest sowing led to an increase in bulb weight while a reduction in the spread of emergence at sowing 3 led to a reduced coefficient of variation of bulb diameter at harvest. Under the less variable conditions on the irrigated plots of Expt 2 germinating seeds reduced mean emergence time and increased percentage emergence compared with natural seed at some sowings. Fluid-drilled selected germinated seeds, however, reduced mean emergence time and increased percentage emergence at every sowing and reduced the spread of emergence at all but the first sowing compared with natural seed.
Low soil moisture content made seedling emergence more unpredictable and reduced the benefits gained by sowing germinated seeds. The results presented suggest that techniques to increase the proportion of germinated seeds at the point of sowing and economical methods of applying water during periods of low soil moisture following sowing are needed if the full benefits of fluid drilling are to be realized.