Growth of Basil (Ocimum basilicum) in DRF, Raft, and Grow Pipes with Effluents of African Catfish (Clarias gariepinus) in Decoupled Aquaponics

Abstract

Basil (Ocimum basilicum) was cultivated in Rostock, Northern Germany, in a decoupled aquaponic system with African catfish (Clarias gariepinus) under intensive rearing conditions by using three hydroponic components, the dynamic root floating technique (DRF), the raft technique, and grow pipes. A 25% of the recommended feed input still allowed African catfish growth and provided adequate nitrogen and calcium levels in the process water. After 36 days, the plants were examined with respect to 16 different growth parameters. DRF performed significantly better than raft and/or grow pipes in 11 parameters. Total weight of basil was significantly higher in DRF (107.70 ± 34.03 g) compared with raft (82.02 ± 22.74 g) and grow pipes (77.86 ± 23.93 g). The economically important leaf biomass was significantly higher in wet and dry weight under DRF cultivation (45.36 ± 13.53 g; 4.96 ± 1.57 g) compared with raft (34.94 ± 9.44 g; 3.74 ± 1.04 g) and grow pipes (32.74 ± 9.84 g; 3.75 ± 1.22 g). Two main factors limited plant growth: an unbalanced nutrient concentration ratio and high water temperatures with an average of 28 °C (max 34.4 °C), which resulted in reduced root activity in raft and grow pipes. DRF was able to maintain root activity through the 5 cm air space between the shoots and the nutrient solution and thus produced significantly more biomass. This suggests DRF to be used for basil aquaponics under glass house conditions with high-temperature scenarios. Future studies are needed to optimize nutrient loads and examine systems with the plant roots exposed to air (Aeroponics).

A Comparative Evaluation of Aquaponic and Soil Systems on Yield and Antioxidant Levels in Basil, an Important Food Plant in Lamiaceae

“…Inevitably, the demand for basil is considerably high among both hydroponics and aquaponics producers. Studies indicate that owing to its characteristics, basil is the most used herb for different hydroponics and aquaponics experiments [18]. Basil produces 1.8 kg per meter square under aquaponic production, and only 0.6 kg per meter square in soil cultivation [19].…”

“…Previous studies showed that basil has a lot of characteristics and properties that make it one of the most common herbs used extensively in the kitchen as well as in several other business sectors [15,18,20]. Nevertheless, while previous researchers found that basil production and yield is higher in the case of aquaponic systems than in soil systems, no information is available on the level of antioxidants present in basil grown in both systems.…”

Economic Analysis and Improvement Opportunities of African Catfish (Clarias gariepinus) Aquaculture in Northern Germany

“…Option 2 integrates a highly productive 10,000 m 2 basil greenhouse with artificial lighting for year-round production. Basil has already achieved promising results in aquaponics [24]; only small amounts of additional fertilisation, especially with potassium and iron, would be necessary [25,26]. The greenhouse (returns 248,502 EUR/year; ROI 6.93%) together with aquaculture would result in returns of 284,502 EUR/year and an ROI of 6.26%.…”

“…This is nowadays recognised also on German markets, seeking new investments into African catfish RAS and further increasing production capacity. In addition, several studies demonstrated that African catfish effluents can be used in aquaponics to produce valuable plant products such as basil (Ocimum basilicum) [24][25][26], mint (Mentha spicata) [27] and pumpkin (Telfairia occidentalis) [28]. However, the development of African catfish farms in Germany were primarily promoted by the European Maritime and Fishery Fund (EMFF) [29] in the form of investment subsidies of up to 49%, but were also supported by the Renewable Energy Law (EEG), where the use of warm water from biogas production inside the RAS was compensated with an additional subsidy (Combined Heat and Power bonus-CHP) [30,31].…”

Spearmint (Mentha spicata) Cultivation in Decoupled Aquaponics with Three Hydro-Components (Grow Pipes, Raft, Gravel) and African Catfish (Clarias gariepinus) Production in Northern Germany

“…Fruiting crops, such as tomatoes (Solanum lycopersicum) or cucumbers (Cucumis sativus), are often cultivated in nutrient-film-technique (NFT) systems [4,5]. Basil (Ocimum basilicum) grew best in an ebb-and-flood gravel substrate system compared to grow pipes (similar to NFT) and raft; [6]) and showed good growth performance with the dynamic root floating technique (DRF; [7]) and in aeroponics [8]. An international study in 2015 showed an earlier preference for raft and media bed components for aquaponic crops [9].…”