Strawberry

Application of Manures & Fertilizers

Strawberry (Fragaria sp.) is a native of temperate regions, but varieties are available which can be cultivated in subtropical climate. In India it is generally cultivated in the hills. Its main center of cultivation are Nainital (district) and Dehradun in Uttar Pradesh, Mahabaleshwar (Maharashtra), Kashmir Valley, Bangalore and Kalimpong (West Bengal). In recent years, strawberry is being cultivated successfully in plains of Maharashtra around Pune, Nashik and Sangali towns. The strawberry is the most widely adapted of the small fruits. Strawberries are grown throughout Europe, in every state of the United States, as well as in Canada and South America. The wide variation in climates within these regions and the wide adaptation of the strawberry plant permit harvesting and marketing, the fruit during greater part of the year.

Strawberry is a delicious fruit taken fresh in several ways. It also makes excellent ice cream and Jam on account of its rich aroma, and is also a good source of vitamin C. It is a soft and a highly perishable fruit, often shipped in frozen condition in Western countries.

Climate and Soil:

Strawberry thrives best in temperate climate. It is a short day plant, which requires exposure to about 10 days of less than 8 hours sunshine for initiation of flowering. In winter, the plants do not make any growth and remain dormant. The exposure to low temperature during this period helps in breaking dormancy of the plant. In spring when the days become longer and the temperature rises. The plants resume growth and begin flowering. The varieties grown in milder subtropical climate do not require chilling and continue to make some growth during winter.

From the standpoint of response to length of the light period, strawberries are placed in two groups: (1) varieties that develop flower buds during both long and short light periods, the overbearing varieties and (2) varieties that develop flower buds during the short light periods only, most commercial varieties.

Strawberry requires a well-drained medium loam soil, rich in organic matter. The soil should be slightly acidic with pH from 5.7 to 6.5. At higher pH root formation is poor. The presence of excessive calcium in the soil causes yellowing of the leaves. In light soils and in those rich in organic matter, runner formation is better. Strawberry should not be cultivated in the same land for a number of years. It is preferable to plant it in green manured field. Alkaline soils and soils infected with nematodes should be avoided.

A large number of varieties are available. For the hilly areas, varieties Royal Sovereign, Srinagar and Dilpasand are suitable. Some of the introductions from California, such as Torrey, Toiga and Solana may prove even more successful. The variety found successful in Bangalore has been named Bangalore and which has performed well at Mahabaleshwar also. For the north Indian plains, Pusa Early Dwarf which has dwarf plants, large firm wedge-shaped fruits, has been recommended. Another variety with rich aroma but softer fruits is Katrain Sweet. Some of the varieties found successful in warmer parts of the U.S.A. are: Premier Florida-90, Missionary, Blackmore, Klonmore & Klondike. Some of these may prove successful for cultivation in Indian plains.

Propagation is done by means of runners that are formed after the blooming season. The plants may be allowed to set as many runners as possible but not allowed to set any fruits. All the plants with good root system should be utilised to set a new plantation. Given the best attention and care, a single plant usually produces 12 to 18 runners.

The land for strawberry planting should be thoroughly prepared by deep ploughing followed by harrowing. Liberal quantities of organic manure should be incorporated in the soil before plating. Strawberry can be planted on flat beds, in the form of hill rows or matted rows, or it can be planted on raised beds. In irrigated areas, plantings on ridges is advised. In Mahabaleshwar, the usual practice is to plant on raised beds 4 x 3 meters or 4 x 4 meters. The planting distance should be 45 cm from plant to plant and 60 to 75 cm. from row to row. In the hills, Transplanting is done in March-April, September-October, but in the plains, the months of January-February may be utilised for this purpose. At Mahabaleshwar normally strawberry is planted during November-December.

The plants should be set in the soil with their roots going straight down. The soil around the plant should be firmly packed to exclude air. The growing point of the plant should be just above the soil surface. During planting, the plants should not be allowed to dry out and should be irrigated immediately after planting.

The roots of strawberry plants spread out close to the surface. Therefore, the soil should be well supplied with moisture, and hoeing should be done lightly and young plantation be kept weed free.

In cold climate the soil is covered with a mulch in winter to protect the roots from cold injury. The mulch keeps the fruits free from soil, reduces decay of fruits, conserves soil moisture, lowers soil temperature in hot weather, protects flowers from frost in mild climates and protects plants from freezing injury in cold climates. Several kinds of mulches are used, but the commonest one is straw mulch. The name strawberry has been derived from this fact. Black alkathine mulch is also used to cover the soil. It saves irrigation water, prevents the growth of weeds and keep the soil temperature high.

Since strawberry is relatively shallow-rooted, it is susceptible to conditions of drought. Planting early in autumn allows the plants to make good vegetative growth before the onset of winter. However, in this case it is necessary to ensure that newly planted runners are irrigated frequently after planting, otherwise the mortality of the plants becomes high. During September and October, irrigation should be given twice a week if there is no rain. It may be reduced to weekly intervals during November. In December and January, irrigation may be given once every fortnight. When fruiting starts, the irrigation frequency may should again be increased. At this stage frequent irrigation gives larger fruits.

Application of manures and fertilisers

Strawberry requires moderate amounts of nitrogen. Addition of organic matter to the soil, in the form of 50 tons of Farm Yard manure per hectare is highly desirable. It improves the water holding capacity of the soil and also gives better runner formation. Farm yard manure may be supplemented by chemical fertilizers to make up the total quantity of nitrogen from 84 to 112 kg per hectare, Phosphorus 56 to 84 kg per hectare, and Potash 56 to 112 kg per hectare. The Phosphatic fertilizer should be incorporated into the soil before plantings. The nitrogenous fertilizer be applied in Two doses (Three weeks after planting and again at the time of flowering) and potash at the time of flowering only. Application of adequate amounts of nitrogen gives higher yield of early berries.

Plant protection

Red spider mites and cutworms are important pests of strawberry. The mites can be controlled with 0.05 per cent Monocrotophos + 0.25 per cent wetable sulphur. The cut worms can be controlled by dusting the soil before planting with 5 per cent chloradane or Heptachlor dust at the rate of 50 kg per hectare and mixing it thoroughly in the soil by cultivator.

The two commonest diseases of strawberry are red stele, caused by the fungus Phytophthora fragariae and black root rot. The remedy for the former lies by growing resistant varieties like stelemaster and for the latter to maintain the vigour of the plants and rotate strawberry with other crops like legume vegetables (beans, peas etc). Strawberry also suffers from virus diseases known as yellow edge, crinkle and dwarf. Raising of strawberry nursery in the hills helps to check these. Strawberry also throws some chlorotic plants, which result from genetic segregation. These should not be confused with virus affected plants and should be rogued out.

Harvesting and yields

The fruit ripens during late February to April in the plains and during May and June at high elevations like Mahabaleshwar, Nainital and Kashmir. For local market the fruit should be harvested when fully ripe, but for transport to distant markets, it should be harvested when still firm and before colour has developed fully all over the fruit. Harvesting should be done preferably daily. Since fruit is highly perishable, it is packed in flat shallow containers of various types (cardboard, bamboo, paper trays etc.) with one or two layers of fruits. Harvesting should be done early in the morning in dry conditions. Washing the fruit bruises it and spoils its lustre.

The yield varies according to season and locality. A yield of 20 to 25 tons per hectare is excellent, though yields upto 50 tons per hectare have been reported under ideal conditions.

Post Harvest handling and Marketing

Strawberries are highly perishable and hence a great deal of care in harvesting and handling as well as its marketing also requires to be organised carefully. Usually the fruit is picked in the early morning and sent to the market in the afternoon of the same day or is picked in the late afternoon, stored overnight in a cool place, and sent to market the following morning.