Agriculture Reference
In-Depth Information
Table 4.8.
Aspects of leek cv. 'Splendid' as affected by planting date at
Wellesbourne, UK (from Salter
et al
., 1986).
Planting date
Aspect
10 April
3 July
Yield 168 days after planting (t/ha)
69
26
Day-degrees > 6°C from planting to harvest
1403
1203
Accumulated solar radiation (MJ/m
2
) from
2938
1733
planting to harvest
accumulated since planting, using a base temperature of 6°C and an f value
(Eqn 4.19) of 0.6 (see Fig. 4.51). Accumulated EDDs with these optimal
constants were a better predictor of diameter than accumulated day-degrees,
time since planting or radiation accumulated since planting.
Although bulbing is uncommon in leeks, 'bulbiness' can constitute a
quality defect. Strong bulbing, with the formation of bladeless inner scale
leaves, has been induced under 24 h photoperiods (Dragland, 1972). As with
most features of leeks, there is wide plant-to-plant variation in the extent of
bulbing in these conditions. Bulbs are also frequently seen at the base of the
flower stalk (van der Meer and Hanelt, 1990). Low soil temperatures also
favour bulbiness, possibly because of an accumulation of unused carbohydrate
at the base of the pseudostem (Dragland, 1972).
Fig. 4.51.
The relationship between leek sheath diameter and the accumulated
effective day-degrees from planting derived from seven experiments at
Wellesbourne and in Cornwall, UK. The best-fitting Effective Day Degree (EDD)
units were defined by: EDD
1
= DD
1
+ 0.6.R
1
, where DD are day-degrees with a
base of 6°C and R is the total solar radiation in MJ/m
2
for each day (from Wurr
et
al
., 1999. Courtesy of
Journal of Horticultural Science and Biotechnology
).
