Most common aquaponics plants

Vegetable production guidelines for common aquaponics plants

The information below provides technical advice on 12 of the most popular vegetables to grow in aquaponics. Information on optimal growing conditions, including specific growing instructions and harvesting techniques for each vegetable, is included. The guidelines below are based on the experience gathered from long-standing aquaponic farming, from horticulture manuals on soil/soil-less cropping, extension papers, and the professional experience of farmers and researchers. This list is by no means exhaustive. Rather, it should be used as an example of the types of information needed for any crop grown and help readers target their research when growing crops that are not listed here.

BASIL
pH: 5.5–6.5
Plant spacing: 15–25 cm (8–40 plants/m2)
Germination time and temperature: 6–7 days with temperatures at 20–25 °C
Growth time: 5–6 weeks (start harvesting when plant is 15 cm)
Temperature: 18–30 °C, optimal 20–25 °C
Light exposure: Sunny or slightly sheltered
Plant height and width: 30–70 cm; 30 cm
Recommended aquaponic method: media beds, NFT and DWC

Growing basil in aquaponic units: Basil is one of the most popular herbs to grow in aquaponic units, particularly in large-scale commercial monoculture units because of its high value and the high demand in urban or peri-urban zones. Many cultivars of basil have been tried and tested in aquaponic units including the Italian Genovese basil (sweet basil), lemon basil, and purple passion basil. Owing to the higher nitrogen uptake, basil is an ideal plant for aquaponics; however, care should be used to avoid excessive nutrient depletion of the water.
Growing conditions: Basil seeds need a reasonably high and stable temperature to initiate germination (20–25 °C). Once transplanted in the units, basil grows best in warm to very warm conditions and full exposure to sun. However, better quality leaves are obtained through slight shading. With daily temperatures higher than 27 °C plants should be ventilated or covered with shading nets (20 percent) during strong solar radiation seasons to prevent tip burn.
Growing instructions: Transplant new seedlings into the aquaponic unit when the
seedlings have 4–5 true leaves. Basil can be affected by various fungal diseases, including
Fusarium wilt, grey mould, and black spot, particularly under suboptimal temperatures
and high humidity conditions. Air ventilation and water temperatures higher than
21 °C, day and night, help to reduce plant stress and incidence of diseases.
Harvesting: The harvest of leaves starts when plants reach 15 cm in height and
continues for 30–50 days. Care should be used when handling leaves at harvest to
avoid leaf bruising and blackening. It is advisable to remove flowering tips during plant
growth to avoid bitter tastes in leaves and encourage branching. However, basil flowers
are attractive to pollinators and beneficial insects, so leaving a few flowering plants can
improve the overall garden and ensure a constant supply of basil seeds. Basil seeds are
a speciality product in some locations.

CAULIFLOWER
pH: 6.0–6.5
Plant spacing: 45–60 cm (3–5 plants/m2)
Germination time and temperature: 4–7 days with temperature 8–20 °C
Growth time: 2–3 months (spring crops), 3–4 months (autumn crops)
Temperature: 20–25 °C for initial vegetative growth, 10–15 °C for head setting
(autumn crop)
Light exposure: full sun
Plant height and width: 40–60 cm; 60–70 cm
Recommended aquaponic method: media beds

Growing cauliflower in aquaponic units: Cauliflower is a high-value, nutritious winter crop that will grow and thrive in media bed units with adequate plant spacing. Cauliflower has a relatively high nutrient demand, and the plants react positively to high concentrations of nitrogen and phosphorus. Among other nutrients, potassium and calcium are important for the production of heads. The plant is particularly sensitive to climatic conditions, and the heads do not develop properly in hot, very cold or very dry conditions; therefore, selecting the suitable variety and the timing to transplant are crucial.
Growing conditions: Optimal air temperature for the initial vegetative growth of the
plant is 15–25 °C. For the formation of the heads, the plants require colder temperatures
of 10–15 °C (autumn crop) or 15–20 °C (spring crop) providing that a good percentage
of relative humidity and full sun conditions are met to develop good heads. Plants can
tolerate cold temperatures; however, heads can be damaged by frost. Light shade can
be beneficial in warmer temperatures (above 23 °C).
Growing instructions: Germinate seeds in propagation trays at 20–25 °C. Provide
direct sun from early seedling stages so plants do not become leggy. When plants are
3–5 weeks old and have 4–5 true leaves, begin transplanting into the aquaponic system
about 50 cm apart. To preserve the white colour of the heads, use string or rubber bands
to secure outside leaves over the head when it is about 6–10 cm in diameter. Once this
stage is reached, harvest may take less than a week in ideal temperatures or as long as a
month in cooler conditions. Too much sun, heat or nitrogen uptake can cause “ricey”
heads where the main flower separates into small, rice-like grains. Temperatures below
12 °C could instead produce “buttoning”. Cauliflower is susceptible to some pests
including cabbageworms, flea beetle, white maggots (larvae) and cabbage aphids, which
can be removed manually or by using other pest management techniques.
Harvesting: Harvest when the heads are compact, white and firm. Cut the heads off
the plant with a large knife, and remove the remaining plant and roots from the bed
pipe and place into a compost bin.

LETTUCE (MIXED SALAD LEAVES):
pH: 6.0–7.0
Plant spacing: 18–30 cm (20–25 heads/m2)
Germination time and temperature: 3–7 days; 13–21 °C
Growth time: 24–32 days (longer for some varieties)
Temperature: 15–22 °C (flowering over 24 °C)
Light exposure: full sun (light shading in warm temperatures)
Plant height and width: 20–30 cm; 25–35 cm
Recommended aquaponic method: media bed, NFT and DWC

Growing lettuce in aquaponic units: Lettuce grows particularly well in aquaponics
owing to the optimal nutrient concentrations in the water. Many varieties can be grown
in aquaponics, but four main types are included here: crisphead lettuce (iceberg), which
has tight head with crispy leaves, ideal for cooler conditions; butterhead lettuce, which
show leaves that are loosely piled one on another and have no bitter taste; Romaine
lettuce, which has upright and tightly folded leaves that are slow to bolt and are sweet
in taste; and loose leaf lettuce, which comes out in a variety of colors and shapes with
no head and can be directly sowed on media beds and harvested by picking single
leaves without collecting the whole plant. Lettuce is in high demand and has a high
value in urban and peri-urban zones, which makes it a very suitable crop for large-scale
commercial production.
Growing conditions: Lettuce is a winter crop. For head growth, the night air
temperature should be 3–12 °C, with a day temperature of 17–28 °C. The generative
growth is affected by photoperiod and temperature – extended daylight and warm
conditions (> 18 °C) at night cause bolting. Water temperature > 26 °C may also
favour bolting and leaf bitterness. The plant has low nutrient demand; however, higher
calcium concentrations in water help to prevent tip burn in leaf in summer crops. The
ideal pH is 5.8–6.2, but lettuce still grows well with a pH as high as 7, although some
iron deficiencies might appear owing to reduced bio-availability of this nutrient above
neutrality.
Growing instructions: Seedlings can be transplanted in aquaponic units at three weeks
when plants have at least 2–3 true leaves. Supplemental fertilization with phosphorus
to the seedlings in the second and third weeks favours root growth and avoids plant
stress at transplant. Moreover, plant hardening, through exposing of seedlings to
colder temperatures and direct sunlight, for 3–5 days before transplanting results in
higher survival rates. When transplanting lettuce in warm weather, place light sunshade over the plants for 2–3 days to avoid water stress. To achieve crisp, sweet lettuce,
grow plants at a fast pace by maintaining high nitrate levels in the unit. When air and
water temperatures increase during the season, use bolt-resistant (summer) varieties. If
growing in media beds, plant new lettuces where they will be partially shaded by taller
nearby plants.
Harvesting: Harvesting can begin as soon as heads or leaves are large enough to eat.
If selling to markets, remove the full plants and roots when harvesting as soon as
they reach market weight (250–400 g). Cut the roots out and place them in a compost
bin. Harvest early in the morning when leaves are crisp and full of moisture and chill
quickly.