M. Levy, H. Huppert
Onion seeds in Israel are produced in two irrigation regimes:
1. Without any irrigation-dry land.
2. Under full irrigation, when irrigation is applied, one of the important question is for how long to continue and at what stage should irrigation be stopped.
Different regimes of irrigation were tested in several studies in the field:
1. Irrigation was applied until onset of flowering.
2. End of flowering.
3. When the seeds reached the milk stage (70–80% moisture).
4. When the seeds were at was ripening state (40–60% moisture).
5. Full ripening (15–20% moisture)
During the entire experiments soil moisture was recorded.
It was found that in general the onion plant (including-bulb, stem and umbel) at the end of the umbel flowering has enough reserve nourishment to supply the requirement for seed maturation.
In the field when irrigation was discontinue from the stage of seed setting-milk ripening high yield and good quality of seeds was obtained. Hence this regime enables to use the irrigation system more efficiently, saving water and labour.
The yield of onion seed is affected by the irrigation regime. In Israel, onion for seed production is grow under two different regimes; (a) Dryland cultivation, whereby the onion plants grow, flower and produce seeds by utilizing only the water from the rainfall; and (b) Irrigation applied when necessary, usually one to three times after planting in October and before the rains start. In the spring-summer, an additional four to six irrigations are given from the last effective rain until the harvest.
In previous studies (Globerson, 1972; Globerson et al., 1972) we showed that in order to obtain a high yield of onion seed it is important to start irrigating directly after planting in October. However, there was no information on the response of the onion being grown for seed production to the time of irrigation cut-off. Therefore, the present investigation was designed to study the effect of different dates of cut off irrigation on seed development and quality.
