Strawberries are adapted to many growing regions in India and commercial production is potentially profitable. Strawberries require a fairly long-term commitment. Commercial plantings are normally replaced at least every 4 years.
Strawberry is one of the important small fruit among the berries. Various strawberry species grow wild all over the world, but the cultivated strawberry is based upon two species Fragarin chiloensis and Fragarin verginiana. Hybrid between these two species was the ancestor of all the modern strawberry cultivar. Strawberry has great dietetic value and is one of the potential source of vitamin C and a good antioxidant source. Every 100 gm edible portion contains 89 gm water, 0.07 gm protein, 0.5gm fats, 8.4gm carbohydrates and 59mg ascorbic acid. The strawberry fruit is commercially consumed both in fresh form and can be preserved like Jams, Jellies, and squashes that can be used in off-season. The introduction of day neutral cultivars, fertigation, green house, standardization of agro techniques and improved storage techniques has revolutionized the strawberry industry.
Preparing the Plot, Soil & Climate Requirement
Strawberries perform best when grown in a sunny and sheltered part of the plot and the soil needs to be reasonably fertile and free-draining. To ensure the plants thrive, it’s important to prepare the ground about a month before planting. Start by ploughing and raking over the soil to remove any weeds or debris which could otherwise interfere with the growth of crop and can harbour pests and diseases, then incorporation of plenty of well-rotted compost into the earth. Finally, the surface should be raked-over several times to create a fine tilth and levelled land is ready for planting .Strawberries prefer soil reasonably rich in humus because of 70-90 % of its roots found in the top 15 cm of soil. It grows well on soil with pH 5.0-7.5. However, the plant thrives best in slightly acidic soil (pH 5.5-6.5). Soil should be fumigated before planting to control fungal diseases, particularly verticillium wilt. Soil fumigation with a mixture of methyl bromide and chloropicrin helps to increase root system, reduces N fertilizer requirement and control several weeds. The strawberry plants are strongly affected by the environmental parameters like temperature, photoperiod and light intensity. In cold climate, frost as well as winter injury seriously reduce yield of strawberry. Photoperiod has a marked effect on strawberry vegetative growth, plant morphology and yield.
Farmers should grow varieties which are resistant to pests and diseases, having adaptability for a desired climate, remain in production for a long period, high yielding and ability to retain size after the 3rd picking, good processing quality and have good runner producing capacity.
Fruit is of exceptionally high dessert quality with outstanding colour and flavour. It is very resistant to physical damages caused by rain. Plants are tolerant to viruses. Fruits are large, and the flesh and skin of the fruit is firm with excellent flavour. The fruit is suitable for the purpose of fresh marketing and processing. On an average, berry weights around 15-18 g. The fruits have good TSS value (12%), acidity (0.85%), vitamin C (55.5mg/100g) and sugar content (6.1%).
An early –maturing cultivar, it is tolerant to viruses. Fruits are large, and the flesh and skin of the fruit is firm, having good dessert and processing quality. The fruits have TSS 12.2%, acidity 0.98% and sugar 6.2%.Average berry weights about 9g.
Tolerant to viruses, it produces numerous runners. Fruits large, flesh and skin medium firm, dessert quality excellent, processing quality good, TSS 12.0%, acidity 0.97% and sugars 6.1%.Average berry weights 6.9g.
A day-neutral cultivar, it has the capacity to produce off-season fruits. It is different from day-neutral or ever bearing types. fruits large, flesh and skin firm, conic to blocky in shape, dessert quality good. It can be handled and shipped fairly well. Skin bright red, attractive, flesh red, internally somewhat hollow, light in colour at core, average berry weighs 15-18g, TSS 11.1%, acidity 1.0% and sugar 5.5%.
Fruits large, conical (necked fruit), skin bright red, flesh attractive red, somewhat firm, less hollow at core, high quality, sweet, slightly subacid, average berry weight 15 g, TSS 11.8%, acidity 0.98%, sugars 6%.Plant produces adequate runners.
It is a day-neutral, early-ripening and over-bearing cultivar. Fruits large, medium, conical, solid internally, slightly hollow, skin red, flesh red, firm, flavour excellent, suitable for fresh market and processing. It tastes sweet to slightly sub acid. Average berry weight 20-25g, TSS 11.2%, acidity 0.98% and sugars 6.1%.
It is very successful under summer system. Plant tolerant to virus, Fruit has good dessert and processing quality. Fruit is quite susceptible to physical damage caused by rain. Fruits large flesh very firm, skin firm, red colour, average berry weighs 7.6g, TSS 12.2%, acidity 0.97% and sugars 5.5%.
Few more suitable varieties are Premier, Red Coat, Local, Jeolikot, Dilpasand, Bangalore, Florida 90, Katrain Sweet, Pusa Early Dwarf and Blakemore are also grown.
Strawberry is commercially propagated by runners, which is considered as natural vegetative propagation. Generally one plant produces 8-10 runners but under proper management, it can go up to 15 runners/plant, for greater survival and fast growth, the runners should be lifted in September and planted in poly bags using the potting media of 1 soil: 1 Sand: 2 FYM for one month. Propagation can also be done through crowns (3-5 plants/crown), but division of crowns of older plants is too time consuming and labour intensive. Runner formation can be stimulated with the application of IBA (100 ppm) 10 days before flowering, with Morphectin (50ppm) and by GA3 (50-100 ppm) spray. Propagation by seed is not suitable as the seedlings do not come true-to type.
Where there is incidence of viruses and nematodes, mainly in commercial plantation, the growth and production of plants may be reduced to half or even more. For this it is desirable to produce virus-free plants for commercial plantations. In addition, we can also control nematodes by raising them in fumigated soils. Virus and nematode-free planting material provides protection against serious diseases. For large scale propagation of virus-free plants, tissue culture is widely used. Under favourable conditions, one strawberry meristem can be multiplied to yield more than one million plants in a year. Plants can be regenerated from meristematic callus, anthers and immature embryos.
There are 4 training systems-matted row, spaced row, hill and plastic mulch. Mainly, matted row system is followed in our country.
This is the easiest and least expensive method. The runners are usually planted at 90 cm x 45 cm spacing. A spacing of 60 cm x 25 cm for Chandler is optimum. After the initial growth of the first year, runners are allowed to cover the vacant space all around the mother plants .ultimately covering the whole vacant space and giving the appearance of a mat. It is generally followed in heavy soils which are free from weeds. In this system, more number of plants can be accommodated/unit areas which give a higher yield under suitable conditions. The overcrowding may cause higher fruit rot. Therefore, care must be taken to maintain the optimum number of plants without overcrowding.
This system is suitable for cultivars which are average to weak in runner production. The daughter plants are spaced at definite distances by covering the selected tips of runners with soil which become plants. This is done till the desired numbers of daughter plants are obtained for each mother plant.
This system is for the cultivars developing a few runners. All runners are removed from the mother plants. The individual plants become large and bear more than those in matted row. The plants are planted 25-30 cm apart in twin rows 20-30 cm apart and 100-110 cm spacing between twin rows.
Black plastic film is used as mulch for the hill system to conserve moisture and control weeds. In this system, berries are kept clean and mould is reduced. The plants bloom earlier. They are less susceptible to damage by frost.
Manuring and fertilization
There are different recommendations for strawberry grown in different states in India. In Himachal Pradesh, applications of 50 tonnes farm yard manure along with 40 kg each of P2O5 and K2O/ha at the time of preparation of beds is recommended. The N (80kg) should be applied in 2 split doses; half in September or after the establishment of plants in September-October, and the remaining half before blooming.
For North hill conditions, apply farm yard manure (25-37.5 tonnes), N (75-100kg), P2O5 (80-120kg), K2O (50-80kg)/ha. The farmyard manure should be mixed in soil at the time of preparation of planting bed. Full dose of P2O5 and half of K2O are placed in the planting rows at 15-20 cm depth. Half N should be broadcast in inter-row spaces a month after planting and the remaining half N and K2O should be side dressed at the time of flowering. Foliar spraying of N (0.5%), P2O5 (0.2%) and K2O (0.5%), 4 times between August and February is also advised.
The flower stems should be removed as they appear on plants after planting. If not removed, flowers create a drain on the plants, reducing their vitality, number and size of daughter plants. This practice also helps establish the plants and aids in tolerating heat and drought. The removal of flower strains from cultivars which produce small number of daughter plants increases the number of runners and plant set. In Hill system, runners should be cut as and when they appear. With matted row system, surplus plants should be removed from outside the rows during late summer or autumn. The operation can be performed normally or with the help of cultivar and other specialized machinery.
Keep the crop weed-free during first season by cultivating, applying herbicides, or plastic mulch. The soil should be worked towards the plants. It should be ensured that soil remains around the crown without covering them. Cultivation should be restricted to only upper 2.54-5.08 cm of the soil. It should be continued till the straw mulch is applied (where it is used). Emergence of weeds during the fruiting season also affects pollination by honey bees, thereby reducing yields drastically.
Irrigation is a must and in humid regions, even short droughts reduce the yield, damaging the shallow root system. Since strawberry is a shallow-rooted plant, the plants require more frequent but less amount of water in each irrigation. Irrigation of newly-planted buds results in increased runner production and early rooting. Strawberry plants produce optimum growth when the soil moisture tension is maintained at less than 1.0 atmosphere. Excessive irrigation is, however, detrimental which encourages growth of leaves and stolons at the expense of fruits and flowers and also increases the incidence of Botrytis rot.
Irrigation should be applied in furrows between the rows. The alleys are usually cultivated after 2-3 days of irrigations. Care should be taken that water should not wet the leaves and fruits as it may increase the incidence of fungal infection. To obtain better fruit size and quality, it should be irrigated judiciously during harvesting. Nowadays trickle and sprinkler irrigation systems are becoming popular. In trickle irrigation, 30% water and energy are saved. Less disruption of picking schedules, better water supply during winter and less rotting of strawberries and saving in water are added advantages. Sprinkler irrigation is, however, valuable in areas where there may be heat stress (>85C temperature).
Harvesting and Post harvest Management
Strawberries are generally harvested when half to three-fourths of skin develops colour. For distant shipment green or white and still hard berries are harvested. Delaying in picking usually increases the proportion of overripe and rotten berries. The picking duration differs from cultivar-to-cultivar. It is 55, 35 and 32 days for Tioga; 55, 30 and 30 days for Torrey during first, second and third year respectively in Himachal Pradesh. For Haryana, U.P conditions, it is 53 days for Tioga and 43 days for Torrey. Depending upon the weather conditions, picked should be done every second or third day. Ripening is faster is hot weather. Do not leave any ripe or rotted berry in the field. Berries should be picked along with a small stem portion attached. Picking should be done in the morning. It facilitates better shelf-life. Thus a yield of 96.53, 47.52, 52.08, 47.83 and 44.24q/ha from cultivar Tioga, Torrey, Howard 17, Catskill and Blakemore respectively may be taken. However, with proper fertilizer management an average yield of 175-300q/ha may be taken.Some plant growth regulators like GA3 (50ppm) sprayed 4 days after flowering, and Maleic hydrazide (0.1-0.3%) sprayed after flowering increase yield up to 31-41% Morphectin (50ppm) improves the fruit size.
Strawberries are harvested in small trays or basket. They should be kept in a shady place to avoid damage due to excessive heat in the open field. For distant marketing; strawberries should be precooled at 4˚C within 2hr of harvesting and kept at the same temperature. After precooling, they are shipped in refrigerated vans. Strawberries can be stored in cold storage at 32˚C upto 10 days. Afterwards they lose their fresh bright colour, showing some shrivelling and deterioration in flavour. Strawberry fruit can be frozen for their processed product or as dessert. The strawberries having high flavour and a bright red colour. Olympus, Hood and Shuksan are quite suitable for ice-cream making, whereas those of Midway, Midland, Cardinal, Hood, Red chief and Beauty are ideal for processing.
Albinism is a physiological disorder in strawberry due to lack of fruit colour during ripening. Fruits remain irregularly pink or even totally white and sometimes swollen. They have acid taste and become less form. Albino fruits are often damage during harvesting and are susceptible to Botrytis infection and decay during storage. It is probably caused by certain climatic conditions and extremes in nutrition.
Harit Kumar, Dr. Anand Kumar Singh and B.V. Rajkumar
Department of Horticulture
Institute of Agricultural Sciences
Banaras Hindu University, Varanasi, Uttar Pradesh, India.