How To Grow Strawberries Hydroponically

Introduction About Strawberry Plant

Hydroponically cultivated strawberry plants yield and produce well, and in many climates, the protected, heated environment of a greenhouse enables year-round or out-of-season production. Strawberry producers use greenhouse structures to either extend the cropping season or produce out-of-season fruit when returns are highest, or to avoid some of the production issues that soil-based systems face.

Strawberries are a crop that may be produced as an annual or long-term crop, making them ideal for hydroponic production. Strawberries are a small but extremely productive plant Many?growers?prefer?annual?cropping?systems?because?they?generate?their?best?yields?of?high-quality?fruit?in?the?first?season.?Crops?are?normally?grown?for?5?to?10?months?before?being?replaced.

Commercially there are two main groups of strawberry plants:

• Day Neutral Plants
• Short Day Plants

Day-neutral plants are induced to flower and fruit when temperatures are high enough to maintain growth irrespective of day length. With short-day varieties, floral initiation is triggered by short day lengths (less than 12 h) or by cool conditions. Refrigeration can be given to planting stock to provide the chilling period required for flowering.

Strawberry Propagation

strawberries are not raised from seed but vegetatively propagated from ‘runners’ which form on mature plants towards the end of the growing season. Runners from field-grown crops are harvested in autumn or winter and stored bare rooted before being used to establish new crops. These field-grown runners, once washed and given a fungicide application, can be used as planting stock for hydroponic crops; however, there is still a risk of the carryover of crown and root rot diseases using this method.

A preferable type of planting material is tip cuttings of strawberry runners which have been raised as plugs in soilless growing medium, thus have not been in contact with soil. Runner plants or runner tip cuttings used for strawberry crop establishment can be stored under refrigeration for an extended period of time, this process also providing the chilling period which is required for floral initiation.

Commercial growers prefer to use larger grade plug cell transplanting as planting stock as this ensures the crown has fully developed a new root system before transferring to the hydroponic system and has a good store of assimilate for new growth and early fruit development.

Production Systems For Strawberry

Hydroponic strawberries are grown in a diverse range of soilless systems, including solution culture methods such as NFT; however, substrate culture dominates commercial production as this allows support of the plant grown at the correct depth and control over root-zone moisture levels.

Strawberry plants are prone to infection by root and crown rot pathogens, particularly in the early establishment phase, and thus control over irrigation is vital for success of this crop. Commonly utilized substrates include rockwool (both slabs and granulated), coco fibre, peat, perlite, pumice, bark, LECA, untreated sawdust, rice hull and organic mixes.

For the production for strawberries systems include standard single-plane cropping, hanging gutters, vertical or ‘stacked’ pots, columns or staggered systems. Systems for growing strawberries that are vertical, hanging, in columns, or in stacked pots are designed to maximize greenhouse space by increasing the?plant density in comparison to single-plane cropping.

In this type of system has more plants and larger production potentials, plants on the lower levels are heavily shaded, making it best suited for cropping in high-light areas or in situations where supplemental lighting is possible. Single-level or staggered-level troughs are composed of one or more levels of troughs filled with substrate, supporting slabs, or growing medium like Rockwool or coconut fiber, allowing for optimal light absorption by all plants.

They?allow?for?air?movement?up?and?under?the?canopy?to?help?prevent?disease?and?are?positioned?at?a?comfortable?height?for plant?maintenance?and?harvesting.

The?rows?of?troughs?are?drip irrigated?with?the?nutrient?solution,?and?each?one?has?a?collection?channel?that?allows?it?to?drain. Plants are established into the tops or sides of troughs and after developing sufficient foliage, fruit trusses are trained over the edge of each trough so that they are held clear of the foliage and growing substrate.

Plant Density, Pruning, Pollination, and Fruit Growth of Strawberry

Plant Density

Plant density depends up on with the type of production system used and environmental conditions. Low?light?levels?can?negatively?impact?yields?and?berry?quality,?while?high?light?levels?can?stress?plants?and?interfere?with?their?ability?to?grow. In?single-level?or?staggered?trough-type?systems,?densities?of?12 – 24?plants/m2?are?typical;?this?is?rather?cultivar?dependent.

Pruning

For strawberry plants require little pruning; however, removal of the lower, older leaves as they age and senesce assists with good rates of air flow around the base of the plant for humidity removal and prevention of fruit and crop rot diseases.

Pollination

The floral development is often on strawberry plants which have insufficient leaf area to support fruit growth and the first few flowers are removed until the canopy is of sufficient size. Once flowers are fully open, greenhouse strawberry crops needs pollination assistance for large, high-quality berry production.

Pollen?formed?on?the?stamens?of?strawberry?flowers?is?dropped?onto?the?receptacle?during?flowering,?but?insects,?the?wind,?and?plant?movement?also?help?to?speed?up?the?process. Large air blowers that move down the rows and direct a blast of air over the blossoms in strawberry plants in a greenhouse help with pollination.

Commercial farmers can also employ portable beehives to pollinate greenhouse plants. On a smaller scale, brushing over the tops of the plants will also facilitate pollination. Pollination must be carried out daily as high rates of pollen transfer are required. Insufficient or uneven pollination will result in misshapen and undersized fruit.

Production Environment for Strawberry

Strawberries have a reasonably high light requirement for good yields and high quality fruit. According to Miyazawa et al. (2009) during the vegetative stage,?optimum DLI was 29.3 mol/m2 per day?for strawberry growth at a?temperature of 25°C.

For the greenhouse strawberry production temperature range of?16–25°C?are suitable. Slow the emergence of new leaves and extend the fruit development phase, due to low temperature.

High temperatures above 30°C both in the root zone and aerial environment tend to inhibit strawberry growth and fruit

production severely.

Fruit quality also suffers with a loss in flavour and an increase in softness combined with rapid ripening under warmer conditions. It is possible to manipulate plant growth and fruit development by chilling the root zone to 10°C (Sakamoto et al., 2016) under warm and tropical growing conditions.

Strawberry crops respond to the use of CO2 enrichment which gives increases in yields and lessens the time to harvest. Enrichment to levels of?700–900 ppm?CO2 has been found to give an increase in total plant yield of 50–70% (Itani et al., 1999).

Strawberry Crop Nutrition

To maintain good fruit quality for the strawberries requires high levels of potassium during the fruiting phase. During the establishment and early vegetative stage a formulation which provides an?N:K ratio of 1:1?may be applied until the time of fruit set on the first inflorescence, with the level of potassium gradually increased as fruit load increases on the crop.

According to Morgan, 2006?N:K ratios for strawberries typically fall within the range 1.0:1.7 to 1.0:2.0?during the fruiting phase.

Under low temperature conditions plants are prone to iron deficiency due to reduced levels of iron uptake. Depends up on the environmental conditions, stage of growth and system of production EC levels for strawberry production vary. Minimum?EC of 1.6 mS/cm?is required during the harvest period to maintain good fruit quality from all systems.

In Winter Low-light conditions, EC levels are run higher at 2.2–3.0 mS/cm to maintain fruit quality with lower levels run in summer and under higher-light conditions to prevent excessive plant stress and assist with water and calcium uptake.

Strawberry Pests, Diseases and Disorders

Common pests include?greenhouse whitefly?(T. vaporariorum),?tobacco whitefly?(B. tabaci),?greenhouse thrips?(H. haemorrhoidalis),?two-spotted mite?(T. urticae),?aphids?and?caterpillar larvae.

Under warm, dry growing conditions, mites can be a particularly damaging and difficult-to-control pest on strawberries with early control required because crops can be destroyed by this persistent pest. Outdoor hydroponic systems require bird netting for protection.

Diseases of strawberries are often connected to poor environmental control, particularly overirrigation of the root zone, predisposing the plants to root and crown rot pathogens and high air humidity which is a risk factor for foliar diseases. Wherever possible, cultivars with some resistance to common root rot pathogens like red stele root rot or red core (Phytophthora fragariae) should be chosen.

Other root rot pathogens include?Pythium,?Rhizoctonia,?Fusarium?and?Verticillium?which may spread through a crop from the initial source of infection

Fruit rots are common where fruit is in contact with damp substrates or when air flow is restricted and humidity levels high.?Botrytis (grey mould)?of fruit can occur under greenhouse conditions, particularly under cooler temperatures, and?leather rot (Phytophthora cactorum)?may also infect ripening fruit.

Malformed berries are commonly caused by poor pollination or damage to the achenes (small seed-like structures) on the surface of the fruit. Temperatures which are too high or too low also contribute to malformed fruit and undersized berries.

Overly soft fruit texture is often a problem where crops have been grown under temperatures that are higher than optimal but can also be due to incorrect plant nutrition and low EC levels.

Deficiencies in potassium during fruiting is another common cause of soft fruit which does not store well, as is low levels of calcium or restrictions in calcium uptake by the plant.

Harvesting

Strawberries require daily harvesting as they must be removed from the plant at the correct stage of maturity when at least

three-quarters ripe rather than when over-mature and starting to soften, which reduces shelf-life.

Allowing fruit to fully ripen on the plant results in a greater flavour and sugar levels than those harvested at the first signs of coloration. Fruit harvesting should occur in the morning when temperatures are still cool and the plants turgid.

Once harvested berries require cooling to?below 5°C?as rapidly as possible to prolong shelf-life and fruit quality.

Reference

1. A Practical Gide ” Hydroponics and Protected Cultivation By Lynette Morgan
2. https://strawberryplants.org/
3. https://extension.umn.edu/strawberry-farming/day-neutral-strawberries#:~:text=Day%2Dneutral%20strawberries%20have%20a,high%20tunnels%20or%20tabletop%20systems
4. .https://cipotato.org/riskatlasforafrica/trialeurodes-vaporariorum/
5. https://irac-online.org/pests/bemisia-tabaci/
6. https://entnemdept.ufl.edu/creatures/orn/thrips/greenhouse_thrips.htm
7. https://entnemdept.ufl.edu/creatures/orn/twospotted_mite.htm
8. https://www.ontario.ca/page/strawberry-aphids-and-their-management-strawberry-farms#:~:text=The%20strawberry%20aphid%20(Chaetospihon%20fragaefolii,one%20strawberry%20plant%20to%20another.
9. Leafroller caterpillar on a green leaf. Photo credit: Shutterstock/Garmasheva Natalia
10. https://bonnieplants.com/blogs/garden-fundamentals/strawberry-leafrollers#:~:text=Leafroller%20caterpillars%20are%20common%20pests,silk%20webbing%20on%20strawberry%20leaves.