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Kohlrabi

Brassica oleracea (Gongylodes Group)

Last revised December 27, 2002

Fertilizer o Harvest, Handling, Storage o Disease and Weed Control o Insect Control


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 general recommendations only. 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 AND HANDLING

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 or modified from USDA Ag. Handbook 66 and other sources)

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.


WEED AND DISEASE CONTROL FOR KOHLRABI

THE PESTICIDES LISTED BELOW 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.

Note that Oregon law requires that agricultural pesticide use be reported to the Oregon Dept. of Agriculture under its on-line PURS system.

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 Pacific Northwest Weed Management Handbook for an explanation of the use of stale seedbeds for vegetable production.

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.

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.


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