Cole Crops.pdf

ATTRA

Cole Crops and Other Brassicas:

Organic Production

A Publication of ATTRA - National Sustainable Agriculture Information Service • 1-800-346-9140 • www.attra.ncat.org

By Martin Guerena

NCAT Agriculture

Specialist

©NCAT 2006

Cole crops and other brassicas are grown throughout the U.S. These crops are an excellent choice for

many organic farmers because of the variety of crops in this family, their nutritional qualities, health

beneﬁts, compatibility in planting rotations, and pest-suppressive qualities. This publication covers

soils, fertility, planting, irrigation, pest management, harvesting and marketing.

Contents

to 65°F. (Maynard and Hochmuth, 1997)

An important fact to keep in mind is that

these plants are closely related and share

similar climatic requirements as well as pests

and diseases. However, though similar, they

are not identical. There may be larger dif-

ferences between varieties of broccoli than

between broccoli and cauliﬂower. Many

varieties from each group have been devel-

oped so that they vary in pest susceptibil-

ity, temperature tolerances, shape, color, and

length of growing season. Check with other

farmers in your area or your Extension agent

to see which varieties are adapted to your

local conditions.

The genus and species Brassica oleracea was

developed in western and central Europe

from wild species found in the Mediterranean

region. (Nieuwhof, 1969) Brassica rapa , a

similar species developed in Asia, consists of

turnips, Chinese cabbage, bok choi, rapini,

canola, and the mustards. Other plants in

Brassicaceae from other genera are: radishes

( Raphanus ), watercress ( Nasturtium ), and

horseradish ( Armoracia ). Nutritionally, bras-

sicas are high in carotenoids, vitamins C and

A, calcium, iron, magnesium, and dietary

ﬁber. Broccoli and broccoli-seed sprouts

in particular contain high levels of antioxi-

dant sulphoraphanes, which are anticarci-

nogenic compounds. The sulphoraphanes

are also thought to protect eyes from the

damage caused by UV light that can lead to

macular degeneration (Xiangqun and

Talalay, 2004) and to prevent high blood

pressure, heart disease, and stroke. (Lingyun

et al., 2004) Glucosinolates, chemical pre-

cursors to sulphoraphines, form isothio-

cyanates in the soil. Isothiocyanates are

Introduction .....................1

Organic Production .......2

Soil and Fertility ..............3

Planting and

Transplanting ...................3

Irrigation ............................4

Organic Integrated Pest

Management ...................5

Diseases ...........................11

Physiological

Disorders .........................13

Weeds ...............................14

Harvesting ......................14

Postharvest .....................15

Economics and

Marketing .......................16

References ......................18

Cauliﬂower. Photo courtesy of USDA.

B rassicaceae (the mustard family, pre-

viously Cruciferae or the crucifers)

include many food, forage, ornamen-

tal, and weed plants. The brassicas are clas-

siﬁed as “cool season,” meaning that they are

relatively resistant to frost and light freezes.

Throughout the U.S. they are grown in the

spring or fall, so that development takes place

when temperatures are cool. The northern

Midwest, Paciﬁc Northwest, and New Eng-

land produce brassicas in the summer, while

winter production takes place in the South-

west and other Sunbelt states. California

is able to produce brassicas year-round

because of the moderating effect of the cold

Paciﬁc current.

ATTRA — National Sustainable

Agriculture Information Service

is managed by the National Cen-

ter for Appropriate Technology

(NCAT) and is funded under a

grant from the United States

Department of Agriculture’s

Rural Business-Cooperative Ser-

vice. Visit the NCAT Web site

(www.ncat.org/agri.

html) for more informa-

tion on our sustainable

agriculture projects. ��

Cole crops are a group in Brassicaceae that

includes varieties of the species Brassica

oleracea such as broccoli, cabbage, cauli-

ﬂower, and Brussels sprouts. Optimal grow-

ing temperatures for most cole crops are 60

Introduction

Table 1: Brassicaceae Food Crops

Common

Name

Scientiﬁc Name Plant Part Eaten

biologically active compounds that are of

considerable interest to farmers because of

their ability to suppress some insects, dis-

eases, nematodes, and weeds in a process

known as biofumigation.

Horseradish Armoracia rustica

Root, leaf, sprouted seed

Upland cress Barbarea verna

Leaf

Ornamental crops in the mustard family

make up about 50 genera, including Ara-

bis , Erysimum (Cheiranthus), Hesperis , Iberis ,

Lobularia , Lunaria , and Matthiola . (Watson

and Dallwitz, 1992) The number of crops

in this family, their nutritional qualities,

health beneﬁts, compatibility in planting

rotations, and pest suppressive qualities

make these crops an excellent choice for

many organic farmers.

Mustards Brassica juncea

Leaf, stems and seeds

Rutabaga Brassica napus var. napobrassica Root, leaf

Rape Brassica napus var. napus Leaf, ﬂower stalk

Kale and collards Brassica oleracea var. acephala Leaf

Chinese kale or

Chinese broccoli

Brassica oleracea var.

alboglabra

Leaf, ﬂower stalk

Cauliﬂower Brassica oleracea var. botrytis Immature ﬂower stalk

Cabbage Brassica oleracea var. capitata Leaf

Portuguese

cabbage

Brassica oleracea var. costata

Leaf and

inﬂorescence

Table 1 includes the scientiﬁc and common

names of members of the mustard family and

lists the plant part eaten.

Brussels sprouts

Brassica oleracea var.

gemmifera

Axillary bud

Brassica oleracea var.

gongylodes

Kohlrabi

Enlarged stem

Organic Production

Organic production of brassica crops, or any

commodity, relies on management techniques

that replenish and maintain long-term soil

fertility by optimizing the soil’s biological

activity. This is achieved through crop rota-

tion, cover cropping, composting, and by

using organically accepted fertilizer products

that feed the soil while providing plants with

nutrients. Besides producing high quality

crops, a healthy, well-balanced soil can help

plants develop natural resistance to insect

pests and diseases. When pest controls are

needed, organic farmers manage insects,

diseases, weeds, and other pests with cul-

tural, mechanical, biological, and—as a last

resort—organically accepted biorational and

chemical controls.

Broccoli Brassica oleracea var. italica Immature ﬂower stalk

Savoy cabbage Brassica oleracea var. sabauda Leaf

Bok choi, Pak choi Brassica rapa var . chinensis Leaf

Mizuma Brassica rapa var . japonica Leaf

Kotasuma Brassica rapa var komatsuma Leaf

Rosette pak choi Brassica rapa var . narinosa Leaf

Choi sum, Mock

pak choi

Brassica rapa var . parachinensis Leaf

Chinese

cabbage, nappa

Brassica rapa var. pekinensis Leaf

Turnip

Brassica rapa var. rapa Enlarged root, leaf

Broccoli-raap Brassica rapa var. ruvo Leaf and young ﬂower

stalk

Arugula Eruca vesicaria Leaf

Garden cress Lepidium sativum Leaf

Watercress Nasturtium oﬃcinale Leaf

Radish

Raphanus sativus Radicula

group

Root

Daikon Raphanus sativus Daikon group Root

White mustard Sinapis alba Leaf and young ﬂower

stalk

Wasabi Wasabia japonica Rhizome, shoots

adapted from: Maynard and Hochmuth, 1997 and Larkcom, 1991.

In 2002, the USDA implemented the National

Organic Standards regulating organic produc-

tion nationwide. All farmers and ranchers

wishing to market their products as organic

must be certiﬁed. An exception to this

requirement is made for farmers who sell less

than $5,000 annually. For more information

on organic crop production and organic farm

certiﬁcation, see ATTRA’s Organic Crop Pro-

duction Overview and Organic Farm Certiﬁca-

tion and the National Organic Program .

Page 2 ATTRA

Cole Crops and Other Brassicas: Organic Production

Rapine,

Soil and Fertility

The brassicas are heavy feeders that can grow

on a variety of soils as long as the soils pro-

vide adequate nutrients and moisture and are

well drained. The soil is where plant health

begins and ends. A healthy soil will have a

greater capacity to moderate the uptake of

fertilizers and will allow a more balanced

uptake of nutrients, creating a healthy plant

that is less attractive to pests and more resis-

tant to pest damage.

succeeding crops may also need a nitrogen

boost. Organic sources of supplemental

nitrogen include guano, pelleted compost,

ﬁsh emulsion, blood meal, feather meal, cot-

tonseed meal, alfalfa meal, and kelp, and

they should be applied as soon as the plants

are strong enough (usually about 6 inches

tall) to withstand the side-dressing operation.

The mineralization of nitrogen and its avail-

ability to plants varies greatly, depending on

the nitrogen source, the temperature, humid-

ity, texture of the material, and microbial

activity. In a transitional or newly certiﬁed

operation, growers should keep records of

the materials they used and how the crops

responded to them. Once growers learn how

each material reacts to speciﬁc conditions,

and as the soil’s organic matter builds, fer-

tility management usually improves.

Composted manure and cover crop residues

usually provide enough phosphorus for bras-

sicas. If additional phosphorus is needed,

rock phosphate may be an option.

Soil components—minerals, air, water, and

organic matter—vary widely depending on

geography and climate. The challenge on

farmland is to maintain healthy soils with

adequate levels of organic matter. Healthy

soils will demonstrate the following charac-

teristics: good tilth, good habitat for numer-

ous and diverse microorganisms, absorption

and retention of water, the ability to buffer

salts and pH, an “earthy smell,” resistance

to erosion by either wind or water, and pro-

duction of healthy crops.

Organic matter is the soil component pri-

marily responsible for these traits. Organic

matter is broken down by soil organisms,

creating humus. Humus in turn provides

nutrients to crop plants. Sustainable soil

management maintains soil health and pro-

ductivity by taking care of and increasing

the soil’s organic matter. Cultural practices,

such as the application of manures and com-

post, using cover crops, and rotating crops

are methods to achieve this. Healthy soil

can be considered a living organism that

must be nurtured in order to sustain its life

and productivity.

Throughout their life cycles, brassica crops

require particular nutrients in varying quan-

tities to support optimal growth and repro-

duction. Nitrogen is the nutritional element

that most cultivated crops need in the great-

est amounts. Plants use it to form proteins,

chlorophyll, protoplasm, and enzymes. In

cole crops, it’s most important for overall

growth, and adequate amounts are neces-

sary for best yields. Usually the initial nitro-

gen available from green manure or com-

post is enough, but as the plant develops it

may need supplemental nitrogen, and

soil manage-

ment main-

tains soil health

and productivity by

taking care of and

increasing the soil’s

organic matter.

Potassium (potash) requirements for cole

crops are high. Composted manures, com-

posted straw and hay (especially animal bed-

ding), granite dust, material derived from

langbeinite, kelp meal, and wood ash (if not

contaminated with colored paper, plastic, or

other synthetic substances) are acceptable

sources of potash.

The macronutrients calcium and micronutri-

ents boron, manganese, molybdenum, and

iron are important for cole crop develop-

ment. Biologically active soils with adequate

organic matter usually supply enough of these

nutrients. Compost and seaweed products

are sources of supplemental micronutrients.

For more information on soils and fertiliz-

ers see the ATTRA publications Sustainable

Soil Management , Alternative Soil Amend-

ments , and Sources of Organic Fertilizers

and Amendments .

Planting and Transplanting

Most brassicas are direct-seeded into pre-

pared seedbeds. The optimal time to plant

is when soil temperatures are between

65 and 75°F, though some varieties can

germinate in soils with temperatures as low

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Page 3

S ustainable

as 45°F and as high as 85°F. (Lorenz and

Maynard, 1980) The seedbed should be

pre-irrigated or solarized to reduce potential

weed problems. Seeding machines such as

the ICS vegetable precision planter, Earthway

planter, Planet Junior, and Stanhay planters

are suitable for both small and larger scale

operations and can place seed at any desired

space. If the bed is seeded too closely, thin-

ning is necessary to achieve proper spacing.

Good quality seed with a high germination

percentage is important when establishing a

direct-seeded stand.

Some crops that have high seed costs,

long growing seasons, and special growing

requirements, such as cauliﬂower and Brus-

sels sprouts, are usually transplanted from

greenhouses to the ﬁeld. Crops like cabbage

and broccoli can either be direct-seeded or

transplanted, depending on conditions such

as season and costs. Direct-seeding broc-

coli during mid-summer for a fall crop is less

expensive than using transplants. During late

winter, using transplanted broccoli may open

a marketing window for spring production

that could be economically advantageous.

Transplanting can overcome some problems,

such as soil crusting and high or low soil

temperatures, that can cause uneven seed-

ling emergence. Factors like these should be

taken into consideration when choosing the

type of plant establishment.

Growing transplants requires great expe-

rience and skill. Transplants can be

purchased commercially and must be certi-

ﬁed organic if they are used in a certiﬁed

organic operation. For more information on

transplant production, see the ATTRA pub-

lication Plug and Transplant Production for

Organic Systems .

Advantages in using transplants are uni-

form stand and quality, efﬁcient use of

seed, season extension, reduced weeding

costs, reduced irrigation, shortened crop-

ping period in the ﬁeld, and less exposure

to pests. Transplants should be free of pests,

weather hardened, and not be long or leggy.

Hardening is the process of gradually accli-

mating young greenhouse plants to the

outside environment. Most transplants are

hardened two weeks before planting in the ﬁeld.

Transplants should also be well irrigated

prior to planting, so that the plants can sur-

vive until they are irrigated in the ﬁeld. Also,

transplanting should be done during cool

weather and with minimal root disturbance to

reduce transplant shock. Transplant shock is

the stress every transplant experiences while

adjusting to its new environment.

In California most cole crops are grown on

raised beds, making cultivation and irrigation

easier. Broccoli and cabbage are planted in

2 rows per 40-inch bed. Broccoli is spaced

at 8 inches and cabbage at 12 inches apart

within the row. Cauliﬂower is usually grown

on a single, narrower row (36 to 38 inches),

off center along one side. As irrigation water

evaporates, salts accumulate on the ridge of

the mounded row. The seedlings are planted

below the ridge to avoid salt accumulation

in the root zone. Depending on the variety,

cauliﬂower can also be grown on 2 rows per

40-inch bed, 12 to 14 inches apart.

Irrigation

Soil texture, environmental conditions, and

crop age are factors to consider when irri-

gating any crop. Cole crops are generally

shallow-rooted, with roots ranging from 18

to 24 inches long. Some exceptions to this

are mustard, rutabaga, and turnips, whose

roots range from 36 to 48 inches. (Doneen

and MacGillivray, 1943) Chinese cabbage

and pak choi have shallow root systems that

respond well to light, frequent irrigations.

(Larkcom, 1991) Essentially, the art of

irrigation is applying the right amount of

Linear or lateral move irrigation system in broccoli.

NCAT photo by Martin Guerena.

Page 4 ATTRA

Cole Crops and Other Brassicas: Organic Production

water to the plants so that they produce an

economically viable crop. Too much water

is wasteful and can cause problems with dis-

eases and weeds. Too little water causes

plants to slow their development, eventually

causing stress, pest susceptibility, and lower

yields. So, how much is enough?

A rule of thumb is that vegetables will need

about 1 inch of water per week from rain

or supplemental irrigation in order to grow

vigorously. In arid regions about 2 inches

are required. (Lorenz and Maynard, 1980)

Sprinkler irrigation should be used for ger-

minating seeds and establishing transplants.

Once the plants are established, furrow or

drip irrigation is recommended.

healthy plants that are more productive and

resistant to pests.

Larry Phelan and his colleagues from Ohio

State University found that fewer corn borer

eggs were laid on corn grown in organic

soil. The researchers took soil from an

organic farm and from a conventional farm

and repeated the experiment in a green-

house. They treated each soil with organic

or chemical fertilizers to determine whether

the results were due to short-term nutrient

uptake. Again, corn grown in organic soil

had fewer eggs on it, regardless of the fertil-

izer that was applied. Modern agricultural

methods are not conducive to maintaining

ecological equilibrium because of constant

tilling and synthetic inputs to the soil. Dur-

ing their evolution, plants obtained nutrients

solely from the soil food web. According to

Phelan, it is the slow release of nitrogen in

this system that ultimately causes the corn

borer to lay fewer eggs. The plants in the

conventional system were nutritionally out-of-

balance, receiving too much nitrogen. The

extra nitrogen formed free amino acids that

were not tied up in proteins, stimulating the

insects to feed and deposit eggs.

Another plant protection phenomena attrib-

uted to soil microbial activity is induced and

acquired systemic resistance, in which the

plant’s immune system is stimulated to resist

pest attack. In one study, the soil fungus

Trichoderma hamatum induced systemic

resistance in cucumber against Phytophthora

crown rot and leaf blight. (Khan et al., 2004)

The concept of healthy soils being respon-

sible for plant health has long been known

to organic farmers, and scientists are just

starting to document it.

IPM is based on the following components:

pest identiﬁcation, monitoring, mechani-

cal and physical controls, cultural con-

trols, biological controls, and chemical

controls. For a detailed description of inte-

grated pest management concepts, see the

ATTRA publication Biointensive Integrated

Pest Management .

T he biological

Organic Integrated

Pest Management

Integrated Pest Management (IPM) is a broad

ecological approach to pest management

using a variety of pest control techniques

that target the entire pest complex of a crop

ecosystem. Integrated management of pests

ensures high-quality agricultural production

in a sustainable, environmentally safe, and

economically sound manner. (Bajwa and

Kogan, 2002.)

and cultural

insect con-

trols for cole crops

involve understand-

ing the ecology of

agricultural

systems.

Soil health is based on soil biology, which

is responsible for the cycling of nutrients.

The complex interactions of this biological

community are known as the soil food web.

The soil ecosystem is composed of bacteria,

fungi, protozoa, nematodes, algae, arthro-

pods (insects and mites), and large soil-

dwelling mammals like moles, ground squir-

rels, and gophers. The photosynthesizers

or primary producers in this system use the

sun’s energy to convert atmospheric carbon

into sugars. Other organisms feed off these

primary producers. Dead organisms and

their byproducts decompose, becoming the

soil’s organic matter that stores nutrients

and energy. Plants use these nutrients, pre-

venting them from accumulating in soil and

water. The life cycle of all these organisms

improves the condition of soils by enhancing

structure, water-inﬁltration and water-hold-

ing capacity, and aeration. This results in

The biological and cultural insect controls

for cole crops involve understanding the ecol-

ogy of agricultural systems. We invite pest

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