28/04/2022
Growing ๐๐๐๐๐๐๐ in aquaponics:
Plant spacing: 18โ30 cm (20โ25 heads/m2)
Germination time and temperature: 3โ7 days with temperature 13โ21 ยฐC
Growth time: 24โ32 days (longer for some varieties)
Temperature: 15โ22 ยฐC (flowering over 26 ยฐC)
Light exposure: full sun (light shading in warm temperatures)
Plant height and width: 20โ30 cm
Recommended aquaponic method: NFT and DWC
pH: 5.8โ6.2 for best results
๐๐ซ๐จ๐ฐ๐ข๐ง๐ ๐ฅ๐๐ญ๐ญ๐ฎ๐๐ ๐ข๐ง ๐๐ช๐ฎ๐๐ฉ๐จ๐ง๐ข๐ ๐ฎ๐ง๐ข๐ญ๐ฌ: Lettuce grows particularly well in aquaponics with 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 a tight head with crispy leaves, ideal for cooler conditions
- Butterhead lettuce, which grows leaves that are loosely piled and have no bitter taste
- Romaine lettuce, which has upright and tightly folded leaves that are slow to bolt and are sweet in taste
- Loose leaf lettuce, which comes out in a variety of colors and shapes with no head and can be harvested by picking single leaves without collecting the whole plant.
Lettuce is in high demand and has a high value in urban zones, which makes it a very suitable crop for large scale commercial production.
๐๐ซ๐จ๐ฐ๐ข๐ง๐ ๐๐จ๐ง๐๐ข๐ญ๐ข๐จ๐ง๐ฌ: Lettuce is a winter crop. For head growth, the night air temperature should be 3โ12 ยฐC, with a day temperature of 17โ28 ยฐC.
The generative growth is affected by photoperiod and temperature. Extended daylight and warm conditions (> 18 ยฐC) at night cause bolting.
Water temperature > 26 ยฐC may also favor bolting and leaf bitterness. The plant has rather low nutrient demand, but higher calcium concentrations in water help to prevent tip burn in summer crops.
The ideal pH is 5.8โ6.2, 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.
๐๐ซ๐จ๐ฐ๐ข๐ง๐ ๐ข๐ง๐ฌ๐ญ๐ซ๐ฎ๐๐ญ๐ข๐จ๐ง๐ฌ: Seedlings can be transplanted in aquaponic units at two weeks when plants have at least 2โ3 true leaves. Supplemental fertilization with phosphorus to the seedlings in the second week favors root growth and avoids plant stress at transplant.
Sowing lettuce into net pots right away further reduces transplanting stress. When transplanting lettuce in warm weather, place light shade nets over the plants for 2โ3 days to avoid 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.
๐๐๐ซ๐ฏ๐๐ฌ๐ญ๐ข๐ง๐ : 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 (250-400g). Harvest early in the morning when leaves are crisp, full of moisture and chill quickly.