Agriculture Reference
In-Depth Information
potentially suitable types can be quickly found as those that bulb at a similar
rate to existing, locally adapted cvs (Mettananda and Fordham, 1997).
Sowing dates and bulb development
Bulb onions are grown from two major seasons of sowing - autumn for
harvesting in the spring and early summer of the following year, and spring
sowing for harvesting in the late summer of the same year. Figure 4.31 shows
the seasonal pattern of leaf and bulb growth for typical spring- and autumn-
sown crops. In many countries - for example, Israel, New Zealand and the UK
- both autumn- and spring-sown crops are grown. In Israel sowings are made
in all months between mid-September and late March, and bulbs are harvested
between early March and late August. In this succession, cultivars with a
progressively increasing photoperiod requirement for bulbing are sown,
thereby ensuring there is always sufficient leaf growth before bulb initiation to
produce large bulbs (Corgan and Kedar, 1990).
Fig. 4.31.
The seasonal pattern of leaf and bulb growth of March-sown cv.
'Rijnsburger Bola' (a) and late August-sown cv. 'Senshyu Semi-globe Yellow' (b)
onion crops at Wellesbourne, UK.
