That said, in hydroponic systems, a plant’s nutrient levels can be enhanced simply by adding nutrients to the solution. These nutrients could include calcium and magnesium, or microelements such as zinc or iron. Conversely, soil-based systems are relatively inefficient because of nutrient leaching and evaporation, thereby requiring more inputs than hydroponic systems, which can more precisely control the crops’ growing environments. As a result, hydroponic systems lead to greater yields, reduced water and nutrient losses, and a greater uniformity of produce. Different Types of Produce Many high-input and short-duration crops are grown in hydroponic systems (Wootton-Beard 2019). In principle, it is possible to grow any crop using hydroponics, provided the plant can access enough water and nutrients to support its growth. Hydroponic systems grow many high-input crops such as peppers, tomatoes, strawberries, and cucumbers (Wootton-Beard 2019). The use of hydroponics to grow flowers and other nonvegetable, high-value crops has increased in recent years (Jones 2016). Short-duration crops, which are crops that reach maturity in a short period of time but are sensitive to changes in environmental conditions, are well-suited for hydroponics. These crops include leafy greens, annual herbs, and salad leaves (Wootton-Beard 2019). Short-duration crops require protection from pests and disease and carefully controlled irrigation to maintain leaf quality. Hydroponic systems do this and, in the case of leafy crops, keep them free from soil contaminants (Wootton-Beard 2019). Table 5.1 presents a list of examples of crops grown in hydroponic systems. All these crops tend to be profitable enough to justify a hydroponic operation (Jensen 1999). TABLE 5.1 Examples of Human Food or Animal Feed from Hydroponic Crops Vegetables
Fruits
Herbs
Grains/ animal fodder
Flowers
Leafy greens, radishes, celery, cucumbers, potatoes, yams, peppers, wheatgrass, onions, leeks, carrots, parsnips, squash, zucchini, corn, bok choy, kale, Swiss chard, arugula, watercress, chives, broccoli, beans, squash, peas, cauliflower, cabbage, carrots, onions, radishes, beets, microgreens, melon
Tomatoes, watermelon, cantaloupe, strawberries, blackberries, raspberries, blueberries, grapes, dwarf citrus trees (lemons, limes, oranges), dwarf pomegranate tree, bananas
Chives, oregano, mint, basil, sage, rosemary
Barley, oats, wheat, sorghum, alfalfa, cowpea, maize, rice
Roses, peace lilies, hoya, snapdragons, dahlias, carnations, orchids, petunias
Source: Original table for this publication.
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Insect and Hydroponic Farming in Africa