Growing Strawberries in Hydroponics
Strawberries are very well suited to hydroponic growing and the offer a quick return on capital outlays for the grower.They are grown widely as an NFT crop on a large scale; but are also well suited to a wide range of other hydroponic techniques, and are one of the most popular plants to be grown by hobbyists.
Strawberries require good drainage and aeration. They need reasonable ventilation (air movement) around foliage and fruit. A good quality water supply (with a low level of dissolved salts) is critical.
In summer, plantings require approximately 20 litres of water per square metre for good vegetative growth in sand culture. The Ideal temperature for good vegetative growth is 15°C to 18°C. Low temperatures over winter are required to break the dormancy which develops in autumn and higher temperatures are required for good crop development.
Strawberries require a pH of 6.0 (a high pH will cause iron deficiency). Sulphur, boron and magnesium are important minor nutrients. A lack of boron can result in poor pollination. Potassium or magnesium deficiencies can cause leaf burn. Potassium deficiency may also cause insipid and soft fruit. Keep the level of chlorine present to a minimum. Phosphorus level should be higher than in that used in the average nutrient mix.
Many commercial strawberry hydroponic systems are based on a trough system. Troughs, filled with gravel, perlite or granulated rockwool, are typically 10-15 cm x 15-20cm, with four or five troughs mounted vertically.
Strawberries can also be produced using the hanging bag system. In this system, a bag made of black irrigation fluming is hung from a frame. The a growth medium, and nutrients are fed in at the top and run to waste at the bottom. The strawberries are planted in holes in the side of the bag. Whilst this is an inexpensive system to set up, many growers do not fully understand the technique and fail to produce good crops.
Plants are spaced at 35-40 cm intervals.
Runners are removed from parent plants in mid to late summer and stored between 0°C and -2°C until ready for planting. Only use material which is free of virus. New varieties are propagated in tissue culture.
Put in any new plants in early autumn. Trim the roots to around 8 cm when planting. Runners which have been established in pots may also be used as planting material. Any flowers with runners are removed at planting time to prevent premature fruit formation.
Early plantings (late autumn) can give up to double the crop in their first season compared with late plantings (late winter).
Special cultural techniques
- Remove runners which develop on plants as they will detract from the quantity and quality of the crop (ie. only retain the main plant). Cut old leaves off at the end of each season’s harvest (late autumn), leaving only emerging new foliage.
- Replant every three to four years, (after that time, virus disease is highly likely to be affecting production, even if plants still look healthy).
- Some types of granulated media (eg. perlite and vermiculite) will adhere to the fruit. Laying a plastic mulch on the surface of such media will keep the fruit clean.
- Virus transmitted by aphids is a major problem.
- Snails, slugs, birds and various grubs will attack fruit at times.
- Fungal diseases such as botrytis can also affect fruit, particularly under humid conditions.
Harvest and post harvest
Harvest fruit as it changes to red on a daily basis. Strawberries are ready to pick when the colour has changed 60-70% pink, and the rest of the fruit is still white. Pick the fruit with the stalk still attached and place immediately in a cool place (10-15°C). Strawberries harvested at this stage and stored at 2°C will keep for up to 10 days.
Flavour is best on berries harvested when fully red, but the storage period is greatly reduced.
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