Going Hydroponic Bananas
With banana plantations around the world under attack by a soil-borne pathogen creating uncertainty for the popular Cavendish cultivar, many are realizing hydroponic bananas have some major advantages.
Worldwide, banana production is facing a major crisis. The industry, which is heavily reliant on a single, vegetatively propagated cultivar (Cavendish) is under attack by deadly fungal pathogens. Black Sigatoka and Panama disease (Fusarium) wipe out banana plantations, contaminate soil, and spread rapidly though and between production areas. This is not a new phenomenon with banana cultivation. In the 1950s the monoculture of one of the first widely grown commercial cultivars, Gros Michel, was wiped out by banana pathogens leading to the development of the then Fusarium-resistant Cavendish variety. However, as we all know, pathogens have an incredible ability to evolve and mutate, new strains of Fusarium developed and are threatening the banana industry once again. Ninety-five percent of the bananas consumed in North America are the Cavendish cultivar and thus susceptible to the new strains of Fusarium, and with bananas being the fourth-most consumed food crop and a major staple for millions of people in the tropics, finding ways to overcome these disease threats is of global importance. While plant breeding of cultivars with resistance to both these pathogens may hold promise, the ongoing development of new disease strains is a continuing possibility.
With Fusarium being a soil-borne pathogen, soilless production of bananas has come of increasing interest in both traditional and non-traditional banana production areas. Bananas have been grown in greenhouses for decades, however, production has been limited to subtropical areas with sizable plantations set up in plastic houses in the Canary Islands and Morocco. These are largely soil grown, using greenhouses to modify the environment with a higher daytime temperature, protection from sunburn, wind, and hail, giving increased yields. More recently, hydroponic greenhouse bananas have been successfully grown in the Netherlands using coco peat and stonewool substrates to avoid the risk of aggressive fungal pathogens.
Advantages of Soilless Bananas
Hydroponic production of bananas, particularly in greenhouses, could have some major advantages — the main objective is prevention of plant losses and the heavy use of agrochemicals to control fungal pathogens. Yields are increased within a protected climate and with optimal application of water and nutrients. While production costs are higher than traditional outdoor plantations, consumers may be willing to pay for spray- free, locally produced fruit that has not been shipped large distances to markets. There are also several other sweet-fruited banana cultivars that may appeal to local markets and result in less reliance on the Cavendish variety.
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Growing Hydroponic Bananas
One of the main concerns with hydroponic banana production is the size of the mature plants. Cavendish is a tall variety and can grow in excess of 15-20 feet in height with a spread of eight feet, however, a greenhouse banana industry would be better focused on growing the dwarf, smaller-fruited varieties such as Dwarf Cavendish, Grande Naine, Lady Finger, Orito, Williams, Poyo, Dwarf Red, or Dwarf Apple — many of these grow to between six to 10 feet tall. Grande Naine and Dwarf Cavendish are the most widely planted cultivars under greenhouse production and perform well in hydroponics as well as in soil-based systems.
Hydroponic systems for bananas need to account for the heavy demand for both water and nutrients. Drip irrigation is most commonly used with daily water consumption of 2.6 gallons per plant in winter and 5.3 gallons per plant in summer being reported for greenhouse grown crops. Large tubs/pots with at least 24 inches depth or deep beds of a suitable growing substrate are recommended, both to provide sufficient volume for the large and extensive root system which develops, but to also provide plant stability as top-heavy plants can topple over when carrying a heavy fruit load. While dwarf cultivars are somewhat more compact than taller types, some form of staking or plant support may be required. Suitable substrates include coconut fiber, stonewool, perlite, and combinations of these.
The growing environment for bananas requires warm, humid conditions. The plants are frost sensitive and while cooler nights may not be too damaging, daytime temperatures should not fall below 61°F. Optimal temperatures are between 77-90°F, however, warmer conditions are tolerated provided sufficient water is supplied.
Bananas are largely propagated from offshoots/suckers/pups, however, tissue cultured plantlets are another method that prevents disease carryover from one crop to the next. Banana plants are not trees, but are a tall, herbaceous, short-lived perennial monocot. The leaves are large and overlap which forms a type of thick trunk. Rhizomes form around the base of the plant from which suckers develop, these are cut and used for production of the next crop. Commercial varieties of banana develop fruit without needing to be pollinated, the fruit clusters or bunches contain “hands” of fruit consisting of several individual “fingers.” Many cultivars produce at least 60 fruit from one flowering. Fruit production takes approximately 16-18 months from planting to harvest, after which time the main stem of the plant dies back and is removed, being replanted with new suckers. Bananas are not day-length responsive and a plantation that is successively planted over many months could produce fruit year-round, providing sufficient warmth is provided.
Bananas don’t require a lot of maintenance during the production phase — removal of any extra suckers that form around the base of the plant helps to direct nutrients and assimilates into flowering/fruit development. Some flower/bunch pruning may be carried out depending on cultivar — this includes removal of the oversized secondary flowering at the base of the bunch as well as some fruitlet removal to encourage a greater fruit size in the remaining hands.
Nutrition in Hydroponic Hydroponics
Banana plants are heavy feeders with a particularly high requirement for potassium during the fruit development stages. Uptake of macro nutrients is in the following order: Potassium (K) > Nitrogen (N) > Calcium (Ca) > Magnesium (Mg) > Phosphorus (P). For micro elements the uptake order is: Manganese (Mn) > Iron (Fe) > Boron (B) > Zinc (Zn) > Copper (Cu). Bananas under optimal growing conditions can be produced with a nutrient EC in the range of 1.6-1.8 and a pH of 5.5-5.8. Nutrient formulations for banana crops are somewhat different than many other plants — the requirement for potassium is high throughout the production cycle and commercial plantations should use customized recipes for optimal plant growth and fruit quality. A typical banana formulation would contain the following levels of elements (at EC 1.6): N = 148ppm, P = 20ppm, K = 454 ppm, Mg = 48ppm, Ca = 70ppm, Fe = 5ppm, Mn = 3ppm, Zn = 0.60ppm, B = 0.70ppm, Cu = 0.10ppm, Mo = 0.10ppm.
Recommended leaf nutrient levels in banana plants can be used to diagnose any deficiency symptoms and act as a guide to hydroponic nutrient formulations for this crop. Although foliar levels are useful to determine nutrient requirements, in heavily fruiting crops such as bananas, a significant amount of the potassium take up is incorporated into fruit tissue and this should be accounted for during the fruit development stage.
The recommended foliar nutrient levels for bananas are:
- N: 2.4–3.0 percent
- P: 0.25–0.24 percent
- K: 2.7–3.5 percent
- Ca: 0.4—1.0 percent
- Mg: 0.20—0.36 percent
- Fe: 60 - 80 ppm
- Mn: 25 -150ppm
- Zn: 15 -18ppm
- Cu 5 - 9ppm
- B: 11 ppm
Bananas, particularly the dwarf varieties, are a promising commercial crop for hydroponic and greenhouse production, however, the most compact types also make excellent house plants and indoor garden specimens. Ease of propagation, attractive tropical looking foliage, and possibility of fresh banana fruit are just an additional bonus.