Kohlrabi
Brassica oleracea (Gongylodes Group)
VARIETIES
(approximately 55-65 days).
Grand Duke,
Kolibri F1 (purple), White Vienna. For trial: Gigante, Granlibakken, Purple
Danube, Purple Vienna, Rapidstar, White Danube.
SEEDING
All kohlrabi
is direct-seeded. Kohlrabi seed numbers approximately 144,000 per pound.
Use hot-water and fungicide-treated seed to protect against several serious
seed-borne diseases. Hot water seed treatments are very specific (122
F exactly, for 25 to 30 minutes. Seed must then be quickly cooled and
dried). The seed treatments are best done by the seed company, and can
usually be provided upon request.
Use 1-2
lb seed/acre. Seed in early April to early May or July and August to avoid
harvest during the hottest part of the summer since hot weather may produce
inferior bulbs. Use only treated seed. Sow the seed 0.5 inches deep.
SPACING
Spacing
between rows should range from 12-20 inches. Thin plants to 3-4 inches
apart within the row.
FERTILIZER
It is recommended
to do a soil test for each field to be planted. The following rates are
only general recommendations. A more complete guide to fertilization and
lime requirements of kohlrabi and other cole crops may be found in Broccoli.
Nitrogen:
100-125 (N) lb/acre.
Phosphorus: 100-150 (P2O5) lb/acre, or more, depending on soil test.
Potassium: 100-125 (K2O) lb/acre, or more, depending on soil test.
Magnesium: 15-25 (MgO) lb/acre.
Sulfur: 30-50 lb/acre.
Copper, zinc and boron - as indicated by soil test.
IRRIGATION
Maintain
uniform soil moisture for highest quality product. A total of 8-12 inches
of water may be needed. Soil type does not affect the amount of total
water needed, but does dictate frequency of water application. Lighter
soils need more frequent water applications, but less water applied per
application.
HARVESTING, HANDLING, AND STORAGE
 Kohlrabi yield is approximately
120-160 cwt/acre. It is very important to harvest spring-sown kohlrabi when
they are small. They will get larger than tennis balls in fair soil, but
by this time they are of very poor quality. To get tender, sweet kohlrabi,
pick them when they are less than 2-2.5 inches in diameter. Fall-grown kohlrabi
is less likely to get woody and may remain at good quality until Christmas
when it is 4-5 inches in diameter.
STORAGE (quoted from
USDA Ag. Handbook #66):
Store kohlrabi at 32
F and 98 to 100 % relative humidity. Topped kohlrabi should keep for 2 to
3 months if stored under the recommended conditions. Some space between
containers for air circulation is desirable, and a high relative humidity
is recommended to prevent shriveling and toughening of texture. Packaging
in perforated film can be used to reduce moisture loss. Kohlrabi with leaves
has a storage life of only 2 weeks at 32 F.
Storage should be at
or near 32 F to prevent the development of diseases. Major storage diseases
are bacterial soft rot and black rot.
PACKAGING
Kohlrabi
is commonly packaged in 25-lb film bags; 50-lb film and mesh bags; or
24-lb cartons, holding 24 film bags, weighing 1 pound each.
PEST CONTROL FOR KOHLRABI
THE PESTICIDES
LISTED BELOW, TAKEN FROM THE PACIFIC NORTHWEST INSECT CONTROL HANDBOOK,
ARE FOR INFORMATION ONLY, AND ARE REVISED ONLY ANNUALLY. BECAUSE OF CONSTANTLY
CHANGING LABELS, LAWS, AND REGULATIONS, OREGON STATE UNIVERSITY CAN ASSUME
NO LIABILITY FOR THE CONSEQUENCES OF USE OF CHEMICALS SUGGESTED HERE.
IN ALL CASES, READ AND FOLLOW THE DIRECTIONS AND PRECAUTIONARY STATEMENTS
ON THE SPECIFIC PESTICIDE PRODUCT LABEL.
USE PESTICIDES SAFELY!
Wear protective clothing
and safety devices as recommended on the label. Bathe or shower after each
use.
Read the pesticide label--even
if you've used the pesticide before. Follow closely the instructions on
the label (and any other directions you have).
Be cautious when you
apply pesticides. Know your legal responsibility as a pesticide applicator.
You may be liable for injury or damage resulting from pesticide use.
WEED CONTROL
The Pacific Northwest
Weed Control Handbook has no control entries for this crop. Cultivate as
often as necessary when weeds are small. Proper cultivation, field selection
and rotations can reduce or eliminate the need for chemical weed control.
See the OSU
Weed Management Guide for an explanation of the stale seedbed technique.
Herbicides registered
for use on kohlrabi, but not evaluated by University personnel in the Pacific
Northwest, include DCPA, sethoxydim, and glyphosate (stale seedbed technique
only). Check herbicide labels for rates, restrictions, and weeds controlled.
INSECT CONTROL
Proper rotations
and field selection can minimize problems with insects.
THE PESTICIDES
LISTED BELOW ARE TAKEN FROM THE PACIFIC NORTHWEST INSECT CONTROL HANDBOOK,
AND ARE FOR INFORMATION ONLY. CONSULT PRODUCT LABELS FOR CURRENTLY LEGAL
REGISTRATIONS, RATES AND COMPLETE INSTRUCTIONS.
Insect and Description Control, Active Ingredient Per Acre
---------------------------------------------------------------------------
Aphids, including malathion - 1.25 lb
Cabbage aphid
Brevicoryne brassicae Lorsban 50W - 1 lb
Turnip aphid
Hyadaphis pseudobrassicae Pyrellin - 1 to 2 pt
Both species closely resemble Admire - see label
each other. Gray, mealy plant
lice that form colonies on foliage. Provado - 0.047 lb
M-Pede, 1-2% solution, see
label for rate per acre
Warrior - 0.02 to 0.03 lb
----------------------------------------------------------------------
Cabbage maggot Lorsban 4E - 0.05 to 0.086 lb
Delia brassicae ai per 1000 row ft.
Larvae are legless, white mag- Lorsban 15G - 0.045 to 0.009 lb
gots that feed on roots. ai per 1000 row ft.
----------------------------------------------------------------------
Cabbage flea beetle methoxychlor - 1.75 lb
Phyllotreta cruciferae
carbaryl - 1 lb
Small, shiny, steel-blue jumping
beetle. Frequently attacks young Lorsban 50W - 1 lb
plants; may require control measures.
Cryolite - see label
Warrior - 0.02 to 0.03 lb
----------------------------------------------------------------------
Wireworms Fumigants may be used prior to
Limonius spp. planting.
Brown, jointed larvae of click Telone II or C-17 - preplant
beetles. Kill young plants,
weaken older ones.
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DISEASE CONTROL
The Pacific Northwest Disease Control Handbook has no control entries for
this crop.
Proper rotations, field selection, sanitation, spacings, fertilizer and
irrigation practices can reduce the risk of many diseases. Fields can
be tested for presence of harmful nematodes. Using seed from reputable
sources reduces risk from "seed-borne" diseases.
Among fungicides registered, but not evaluated by University personnel in
the Pacific Northwest,
are Aliette, Maneb, and Telone. Check fungicide labels for rates, restrictions,
and diseases controlled.
For updates on above information and authors, please click on osu.orst.edu/Dept/NWREC/vegindex.html
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