Protected cultivation of strawberry

A. Environment

• Strawberry grows well under temperate climate
• The main challenge in cultivating strawberries in temperature control and by means of a cooling system, the temperature in the greenhouse is never allowed to exceed 30 degrees Celcius.
• Some cultivars can be grown in sub-tropical climate.
• Maximum growth rate observed at 22-25C day and 7- 13C night temperature.
• Photoperiod is effective for vegetative growth, plant morphology and yield.
• Daylight period of 12 hrs. or less and moderate temperature are important for flower-bud formation.
• Each cultivar has a different day length and temperature requirement

B. Media:

• Sandy loam to loamy soil with pH 5.7-6.5 is ideal for cultivation.
• Soil fumigation with a mixture of methyl bromide and chloropicrin helps to increase root system, reduce fertilizer requirement and control the weeds.
• Soil: Sand: FYM in the ratio of 1:1:2 is considered as best potting media.

C. Varieties Cultivated:

• Important strawberry varieties cultivated are Chandler, Tioga, Torrey, Selva, Belrubi, Fern and Pajaro.
• Other varieties include Premier, Red cost, Local Jeolikot, Dilpasand, Bangalore, Florida 90, Katrain Sweet, Pusa Early Dwarf and Blakemore.
• But Japanese strawberries are sweeter than the local variety and fetch a much higher price

D. Planting Material:

• Strawberry is commercially propagated by runner plants.
• Runners are uprooted from nursery, made into bundles and planted in the field.
• These can be kept in cold storage before transplanting.
• It can also be propagated through crowns (3-5 plants/crown), but division of crown of older plants is too tedious and expensive for cultivars producing runner plants readily.
• For large scale propagation of virus free plants, tissue culture is widely used because under favourable conditions, one strawberry meristem can be multiplied to yield more than one million plants in a year
• In Nepal, mostly imported from Europe and America

E. Planting Season:

• The ideal time of planting runners or crowns September-October.
• If the planting is done to early, plants hack vigour and result in low yield and quality of fruits.
• If planted very late, runners develop in March and crops are light.
• Spacing: Hill row system either in single or double rows on 15-20 cm raised beds with plant to plant and row to row distance of 30 x 30-45 cm and 90-120 cm is kept between twin rows.

F. Nutrition and irrigation

a. Nutrition : A fertilizer dose of 25-50 tonnes farmyard manure, 75-100 kg N, 40-120 kg P2O5, 40- 80 kg K2O/ha. May be applied according to soil type and variety planted.

b. Irrigation:

• Strawberry being a shallow-rooted plant requires more frequent but less amount of water in each irrigation.
• Excessive irrigation results in growth of leaves and stolens at the expense of fruits and flowers and also increases the incidence of Botrytis rot.
• Trickle and sprinkler irrigation systems are becoming popular nowadays. In case of trickle irrigation, 30 % water and energy are saved

G. Cultural Operations: Mulching, Training, Bud and Shoot thinning/ Deshooting/ Debudding

a. Mulching: Mulching in Strawberry minimizes the freezing injury, suppresses weed growth and more importantly reduces the chances of softening of fruits.

• The commonly used mulching materials include clean, black and double coloured polythene.
• Mulching with black or double colour polythene material gives good weed control, advances early cropping and increases total yield.

b. Training: Four different types of training systems viz. matterd row, spaced row, hill and plastic mulch are used to train the strawberry plants.

c. Bud and Shoot thinning: Removal of 1-2 buds/plant improves fruit yield and quality.

d. Deblossoming : Removal of the flower truss to prevent fruiting and increased the yield of early saleable runner.

e. Control of Runner : Runners should be allowed to be allowed to root along the rows until sufficient crown are formed.

f. Excess runners are not required and should be removed from the rows.

H. Use of Growth Regulators

• Application of GA3 (50 ppm.) sprayed four days after flowering and maleic hydrazide (0.1-0.3 %) sprayed after flowering increases the yield by 31-41 %.
• Morphactin (@ 50 ppm.) improves the fruit size.

I. Harvesting: Maturity index-when half to three quarter of the skin develops colour. For distant market harvested at berries are green/white and still hard. Picking on alternate days and pick the berries by nipping off stalk and not holding the fruit.

J. Yield: 500 g/plant 22 tons/15000 plants

K. Insect Pests:

• White grubs, cutworms and hairy caterpillars attack the crop. Areas where strawberries are to be planted should be free from white grubs and cutworms.
• Application of malathion (0.05%) on appearance of caterpillars has been found to be effective in most cases.

L. Diseases:

• Albinism (lack of fruit colour during ripening) is a physiological disorder in strawberry.
• It is probably caused by certain climatic conditions and extremes in nutrition.
• Fruits remains irregularly pink or even totally white and sometimes swollen.
• They have acid taste and become less firm.
• Albino fruits are often damaged during harvesting and are susceptible to Botrytis infection and decay during storage