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Lettuce 171 by 65AKdK


                                    Booklet No.171
                             Vegetable Production: VPS - 13
I.     Introduction
II.    Soil
III.   Climate
IV.    Varieties
V.     Seed and Sowing
VI.    Manures and Fertilizers
VII.   Irrigation
VIII. Interculture Operations
IX.    Insect Pests and Diseases
X.     Harvesting and Yield
XI.    Marketing and Storage
XII.   Seed Production
XIII. Uses and Composition
XIV. Economics of Cultivation


       Lettuce occupies the largest area among salad crops and thus it is the most important
salad crop of the world. Its tender leaves and heads are chopped and used as salad with salt
and vinegar. In this booklet cultivation practices of lettuce have been described in a simple and
easy language.

Dr. K. T. Chandy, Agricultural & Environmental Education

I. Introduction

        Lettuce (Lacllica sativa) belonging to the family Compositeae, is a herbaceous annual
which produces seeds freely in the plains. It is an annual for leaf or head and is a biennial for
seed. It is a self pollinated crop.

       Lettuce is probably the native of Europe and Asia Minor and has been in cultivation for
over 2,500 B.C. Now the crop is grown in a number of countries including India. It is more
popular in cities than in villages. Lettuce is mostly grown in kitchen gardens as a salad crop.

II. Soil

        The crop can be grown on many soils but sandy loams and silt loams well supplied with
organic manures are the best. Lettuce has a very shallow root system, therefore, the soil should
contain enough nutrition and moisture in its upper layers. Where early crop of the lettuce is
desired, sandy loam soil should be selected. But where earliness is not important, sill loam soil
is preferred. The optimum soil pH for lettuce is 5.0 to 6.6.

III. Climate
        Lettuce is a cool season crop and is usually grown at the time when cabbage and
cauliflower are grown. It thrives best in a relatively cool season with a monthly mean
temperature of 12 to 15.60 C. High temperature or warm season promotes bolting and causes a
bitter taste in the leaves and accelerates the development of lip burn. The seeds become
dormant and do not germinate properly when the soil temperature is above 22 to 300 C. Thus, a
long cool growing season is required for satisfactory growth and heading.

IV. Varieties

        There are four types of lettuce which are recognized as the sub- species of Lacllica
sativa. They are described below.

A. Head type
This type is again divided into two sub-types.

1. Butter head
       Butter head or bibb lettuce is a head type in which leaves are loosely folded. The inner
leaves are cream or yellow and outer leaves are green. Examples are white Boston, Bibb, etc.

2. Crisp head
        Crisp head is quite common lettuce in the U.S.A. and European countries. Leaves are
thin, crisp and frequently have curled and serrate edges. Heads are hard and durable.
Examples are Great Lakes, Crisp head and Imperial, etc.

B. Leaf type
       It is also called loose-leaf or loose-head lettuce. Plants do not form a head and leaves
may be serrate, deeply lobed and crinkled leaf colour varies from light green to red. Examples
are Chinese Yellow, Grand Rapids, Slobolt, etc.

C. Cos type
       Cos or Romain lettuce is an upright plant which grows about 25 cm high. The outer
leaves are smooth and green, the inner leaves are whitish green. The leaves are more crisped
than other types. Example, Dark Green, etc.

D. Stem type
       Stern type or asparagus can be used like celery and lettuce. The young leaves can be
used like lettuce. The plant produces an edible seed stalk which is eaten raw like celery or
cooked in Chinese dishes. For example, Celtuce.

       The following introduced varieties are recommended for cultivation in India.

1. Great Lakes
        The head is large, firm with green leaves and the outer leaves being blistered. It is fairly
resistant to tip burn but susceptible to powdery mildew.

2. Sioboit
        The leaf is broad, frilled, slight yellowish green. It is very late in bolting and is an ideal
variety for home gardens. It is a leafy type.

3. Chinese Yellow
      It is an early variety with light green, crisp and tender leaves. It is highly productive and
produces white seeds. It is a leafy type.

4. Imperial-859
       The head is medium large, solid and well covered by highly blistered outer leaves. It
stands well in summer weather.

5. White Boston
       It has soft solid heads, inner leaves have oily, soft and greasy texture.

6. Dark Green
       It is a cos type variety. It has narrow leaves with elongated upright heads.

V. Seed and Sowing

        The main sowings are done after the rains i.e. early October to November. Early sowing
will require to be harvested very early before they go to seed. Leaf types are sown either directly
on moist soil or started in a nursery and later transplanted. Since the seeds are tiny, the land is
prepared thoroughly and the seeds are sown in rows 15 to 25 cm apart. Seeds are dropped
very close together but later thinned to 3 cm and when they begin to crowd. Alternate plants can
be removed for use. About 2.5 to 3.5 kg seed will be required for one hectare field.

       In nursery sowings, the transplanting is done when the plants are five weeks old and are
planted 20-25 cm apart in rows which are kept 30-40 cm apart. The heading varieties are
encouraged to form the heads by bringing the leaves together and tying them with strings. This,
however, may not normally be necessary.

VI. Manures and Fertilizers

       The common practice followed is the application of 15 -20 tonnes of farmyard manure,
50 to 86 kg of nitrogen, 50 kg of phosphorus and 50 kg of potash per hectare.

       The complete dose of farmyard manure may be applied to the soil at the time of field
preparation; and the entire doses of phosphorus and potash and half the dose of nitrogen may
be applied just before transplanting or sowing. The remaining half dose of nitrogen is applied as
top dressing one month after transplanting.

VII. Irrigation

       Watering should be copious. In the transplanted lettuce, the first watering should be
given immediately after transplanting. Afterwards watering should be done at 4-5 days interval.

VIII. Interculture Operations

       Weeds are removed by hand weeding. About 3 -4 weeding are required. Since it is a
shallow rooted crop, shallow cultivation is recommended.
IX. Insect Pests and Diseases

A. Pests
       The important insect pests of lettuce are described below:

1. Aphids
        Aphids are small green insects generally found in groups on tender shoots and leaves of
plants. They suck the cell sap and make them poor in growth. They cause considerable damage
to the lettuce crop.

        Aphids can be controlled by spraying commercial grade nicotine sulphate (4%) or
nicotine dust (3-4%): It should be applied when the temperature is about 10-210 C. Spray of
Malathion, parathion or Metacid has also been recommended.

B. Diseases
       Important diseases of lettuce are described below.

1. Downy mildew
        This disease is caused by the fungus Bremia lactzlceae. It is a widespread disease of
lettuce and occurs in all parts of the world where there is adequate moisture and medium to low
temperature. It is especially serious in temperate zones.

       Any part aboveground may be affected but the lesions are most common on older
leaves. Pale yellow areas appear on the upper side of the leaves and enlarge up to cm or more
in diameter. On the opposite sides of the spots, the fungus appears as the white downy growth.
Later on, these spots may coalesce and turn brown in colour.

       This disease can be controlled by spraying Dithane M -45 or Dithane Z- 78. Generally, 2
-3 sprays at 10 -15 days interval will be sufficient.

       Certain lettuce varieties like "Imperial-17" are resistant to this disease.

2. Slimy soft rot
        This is a bacterial disease caused by Ervinia sp. This is a sort of rot which first appears
as water soaked, greasy, soft lesions which spread rapidly and later turn dark brown and slimy.
This disease causes considerable damage in head lettuce.

       This disease can be controlled by the removal of heads and also by keeping the soil
surface relatively dry. Seriously affected plants should be removed from the field and destroyed.

3. Grey mold rot
        This disease can be a serious threat to lettuce where the fungus causing this disease
Botrytis cinerea is present on other crops like chick pea. It is an important transit disease.
However, young seedlings in seedbeds are most commonly damaged through damping off. In
the damping off phase, seedlings collapse and topple over. Soon the dead seedlings are
overrun by the grey moulds. On older plants in the field, spots appear on the older leaves as
large water soaked areas which turn yellow and gct covered by the grey fungal growth. Under
wet conditions, the entire leaf may be soon covered by this growth.
          The field control of grey mould depends on management of humidity in the crop. Only
light irrigation should be given and plants should be spaced to allow quick evaporation of water
from the leaf surface.

       Application of Brassicol to soil reduces soil-borne infcction. Application of Captor or
Ziram has given good results but these should not be used if the leaves are ready for marketing.

4. Lettuce yellows
        This is a viral disease and. known to occur on many other vegetables also. This may
cause considerable damage to lettuce in certain areas where the vector is present.

        On lettuce, the symptoms are expressed as dwarfing of the plant, chlorotic appearance,
failure of head formation and production of many upright secondary shoots. The latex from the
leaves clot on the margins and appeared as brown coloured pustules. Except vector control, no
other method is known against this disease.

5. Lettuce mosaic
        Lettuce is a widespread, seed-borne and aphid transmitted viral disease and causes
considerable damage. The plants give an unhealthy appearance. They are dwarfed and leaves
show green and yellow mottling. In head lettuce, there is failure of head formation. The mottling
is more pronounced in cool and cloudy weather.

       Use of disease free seed and control of aphids is suggested to check this disease.
Affected plants should be destroyed.

X. Harvesting and Yield

        The leafy varieties are harvested in 50 to 60 days when the leaves are still immature and
tender and large enough to use. In head varieties, it is harvested on attaining a good size and
the solid head, in about 60 -70 days. Cutting of leaves is preferably done in the morning and the
harvest is immediately sent to the market.

       The yield per hectare is 10,000 to 12,000 kg in the case of head lettuce. Open leaf types
generally give higher yield.

XI. Marketing and Storage

       After harvesting leaves are prepared into convenient size bunches and put into big
wooden baskets. While marketing care should be taken that no wrapper leaves are damaged in
head type lettuce.

        The fresh lettuce cannot be stored under ordinary conditions because they loose their
moisture very soon. However, the head lettuce can be stored for a few days under ordinary
conditions in a cool and well ventilated room. Under cold storage conditions, it can be kept at
0°C and 90-95 % relative humidity for about 2-3 weeks.

XII. Seed Production
        The early flowering varieties of lettuce produce good seeds in the northern plains. It is a
self-pollinated crop with cleistogamous flowers but some amount of cross pollination has also
been reported. It is suggested that two varieties should be kept 50 metres apart. The agronomic
practices followed are more or less the same as that of the crop to be raised for leaf or head
production purposes.

       Harvesting for seed should be taken up when a substantial number of heads have burst
and sown the pappus which is in the form of white hair or the seeds, and a good number of
heads, after opening, have turned brown or dark brown but have not shown out the pappus.

        White leaf type lettuce has no problem in producing flowering stalks. The outer leaves
should be turned open by hand and provide a slight cut in head type for facilitating the flowering
stalks to emerge easily.

       It produces an average of 595 kg per hectare of seeds in Chinese Yellow (leaf) and as
low as 30 kg per hectare in May King. Great Lakes (Crisp head) produces about 100 -125 kg
seeds per hectare.

XIII. Uses and Composition

         Lettuce is grown in many parts of India mainly as a salad crop. It is exceptionally rich in
iron, but in cell sap only a slight proportion of iron exists and this is all 1ost entirely precipitated
by boiling. Lettuce is reported to be anodyne, sedative, diuretic, and expectorant. Its seeds are
cooling, demulcent and refrigerant. India, lettuce is mainly a home gardern plant rather than a
field crop.

        The nutritive value of lettuce per 100 gm of fresh leaves is as follows: water 94.0 gm;
protein 1.3 g; fat 0.2 g; carbohydrates 2.0 g; fiber 0.6 g; vitamin A 540 I.U.; vitamin C 8 mg;
potassium 140 mg; calcium 22 mg; iron 0.5 mg; phosphorus 25 mg; sulphur 12 mg; and chlorine
50 mg.

XIV. Economics of Cultivation

        In India, lettuce crop is generally grown as a home garden crop. But gradually it is
getting very popular among the city dwellers as a salad crop and its large scale cultivation can
be profitably taken up near big cities and towns.

         Economics of cultivation of lettuce can be calculated with the help of the format given

A. Fixed cost
    1. Cost of the land Rs
    2. Cost of farm building and storage structurc, etc. Rs
    3. Cost fencing the field Rs
    4. Cost of clearing and levelling the land Rs
    5. Cost of farm implements Rs
    6. Cost of permanent or semi-permanent irrigation system Rs

B. Recurring cost
   1. Cost of land preparation Rs
   2. Cost of seed material Rs
   3.   Cost of manures and fertilizers Rs
   4.   Cost of insecticides and fungicides Rs
   5.   Cost of farm power Rs
   6.   Transportation charges on different articles Rs
   7.   Cost of farm labour (paid and unpaid)
           a. Field preparation Rs
           b. Seed Treatment Rs
           c. Seed sowing Rs
           d. Irrigation Rs
           e. Weeding and thinning Rs
           f. Application of manures and fertilizers Rs
           g. Application of insecticides and fungicides Rs
           h. Other intercultural operations such as roughing, removing disease affected
               plants, etc. Rs
           i. Supervision of the crop Rs
           j. Harvesting Rs
           k. Cleaning and grading Rs
           l. Packing Rs
           m. Marketing and storage Rs
           n. Any other labour involvement Rs
   8. Interest on fIXed cost (@.l0%) Rs
   9. Rent or revenue paid for land Rs
   10. Depreciation
           a. Farm structures Rs
           b. Farm implements Rs
   11.Repair and maintenance charges on different farm implements Rs
Total recurring cost Rs

C. Income
    1. Income from the heads as vegetables Rs
    2. Income from the leaves as vegetables Rs
    3. Income from the seed Rs
Total income Rs

Net profit = Total income -Total recurring cost

                        Purchase value -Junk value
Depreciation = ----------------------------------------
                        Life span
        Remark: Junk value is calculated only on those articles which can be resold after their
life span. Life span of building and machinery is 15 years and 10 years, respectively.


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