Agriculture Reference
In-Depth Information
below and to the side of the cloves at planting. Nitrogen fertilizer applications
are usually split, typically 50% at planting, followed by a spring application to
the growing plants. The nitrogen in plant dry matter needed for maximum
yield declines from about 6% soon after emergence to 1.5% near to harvest
time. Like onion, garlic is a shallow-rooted crop. To attain maximum yields,
moisture in the top 30 cm of soil should be maintained close to field capacity
for most of the growing season. In California and in Israel it is recommended
that irrigation ceases when pseudostems soften and the foliage falls, which is
about 3 weeks before harvest. Irrigation later than this can result in rotting
and skin discoloration.
When ready for harvest the roots are severed with an undercutting knife. In
warm, dry climates the bulbs may then be left to dry in windrows in the field.
Bulbs should be protected from sun-scald by shading them with the remains of
the foliage. Dried tops and roots are then removed from the bulbs and they can be
stored in sacks or ventilated bins to a depth of 2 m (see Chapter 7). Where rain or
dew is heavy at the time of harvest, bulbs must be cured indoors. Modified potato
harvesting machines can be used to mechanize harvesting. Mechanical topping
and harvesting is satisfactory for garlic destined for processing.
Leek agronomy has been reviewed by de Clerq and van Bockstaele (2002). Leeks
must be grown to a certain size before they are marketable. The criteria for
marketability vary from outlet to outlet, and various specifications for marketable
size have been used in scientific studies on the crop. Currently, leeks of pseudostem
diameter greater than 20 mm and length greater than 150 mm, including a
50 mm 'flag' of green leaf at the top, meet UK supermarket specifications. Such
leeks should have an average fresh weight of about 160 g.
In some past studies, all leeks of diameter greater than 12.5 mm have been
classed as marketable, and in some more traditional markets large leeks,
greater than 40 mm diameter, are required. In fact, the leek is a variable crop
and some grading into different sizes is essential to satisfy the requirements for
uniformity demanded by most outlets. In Belgium, leeks are frequently
earthed-up as they grow to produce long, blanched, white pseudostems. In
common with other vegetables, a market for small 'baby' leeks has developed in
European supermarkets. Ninety per cent of leeks are sold for the fresh market in
Europe, 10% for processing.
Cultural systems aim to produce high yields of marketable specification at
the right harvest date. To achieve this, the grower has the choice of direct-drilled
or transplanted crops, they can vary planting or sowing date, transplant size,
plant density and cultivar and, for early production, they have the option of
using plastic crop covers to advance growth. The leek is a hardy crop and in the
cool, moist winters of western Europe, where temperatures rarely dip to -10°C,
