To feed the entire planet, rice, fish, and other crops must be multiplied. To meet the predicted demand for fish, aquaculture production will need to reach 140 million tonnes by 2050 59. Furthermore, rice paddy production must increase to around 1035 million tonnes by 2050 60. Further increases in fish and rice production, however, will encounter major environmental constraints due to competition for land, water, and other restricted resources caused by the combinations of direct and indirect climate change impacts 61. Aquaculture and agriculture must grow sustainably while considerably decreasing their environmental consequences in increasing food production 62.
The current study's goal is to create integrated horticulture-aquaculture production systems in greenhouse environments by combining hydroponic techniques (FRS and NFT) with IMTA and rice (IMTA-R-FRS and IMTA-R-NFT) compared to monoculture tilapia-rice systems (T-R-FRS and T-R-NFT). In terms of climate adaptation, the current experimental method attempts to improve the nutrient cycle generated by rearing aquatic animals (Nile tilapia, mullets, crayfish, freshwater mussels, and silver carp) while also optimizing WUE, NUE, and PUE efficiency. However, little is known about cultivating rice hydroponically using IMTA systems (IMTA-R-FRS, IMTA-R-NFT, T-R-FRS, and T-R-NFT). In such developed systems, information on the growth, yield, and productivity of rice and aquatic animals (vertebrates and invertebrates) is scarce. In the current investigation, the average water values of TP, TN, and TAN in IMTA treatments (IMTA-R-FRS and IMTA-R-NFT) were lower than those in monoculture tilapia treatments (T-R-FRS and T-R-NFT) may due the highest NUE and PUE in IMTA treatments (Nile tilapia, mullets, crayfish, freshwater mussels, and silver carp) compared to tilapia monoculture treatments.
Globally, three primary common hydroponics techniques were used, namely the nutrient film technique (NFT), floating raft system (FRS), and a gravel bed System (GBS) 63. In the current study, we used only two techniques, NFT and FRS (or deep water technique). Several studies have indicated that NFT is a well-liked and user-friendly hydroponic technique, however, its employment in commercial aquaponic systems is limited due to its lower efficacy in removing nutrients overall 63–65. A review conducted by Maucieri, et al. 66 reported that from 1997 to 2017, only 17% of research studies focused on the use of NFT in integrated aquaculture-hydroponics systems.
The current study indicated that the IMTA-R-FRS treatment produced significantly higher values for rice plant length, panicle length, effective panicles, and grain number per panicle than the other treatments (IMTA-R-NFT, T-R-FRS, and T-R-NFT). Furthermore, FRS treatments (IMTA-R-FRS and T-R-FRS) had the most significant thousand-grain weight, spikelet fertility, seed setting rate, and rice biomass (stem and leaf, root, kernel, and total rice biomass), FRS treatments had significantly higher (p ˂ 0.05) values than developed NFT treatments. These data indicate that the FRS treatments' (IMTA-R-FRS and T-R-FRS) production circumstances and parameters affect the characteristics of rice. Our findings contradict the findings of Frei and Becker 16, who found no significant (p ˂ 0.05) differences in rice characteristics (yield of grain, straw, stem, leaf, number of panicles, and seeds per panicle) grown in integration with tilapia and carp, or with carp only, compared to rice grown alone, due to differences in experimental designs, experimental conditions, and different aquatic abiotic factors. However, the current study's findings, which were consistent with previous studies that evaluated various types of hydroponic components together, indicated that NFT systems were less effective in terms of overall production, growth, and yields when compared to other aquaponic systems 40,63–65.
Concerning climate adaptation approaches, IMTA-rice aquaponic systems and tilapia-rice monoculture systems have both been demonstrated to reduce nutrient and water losses while increasing crop yields. They can also provide an extra source of income for farmers by selling both rice and aquatic animals to end customers. These methods, on the other hand, enable the optimal use of water and nutrients and are particularly promising approaches for optimizing WUE, NUE, and PUE efficiency 35.
Total N- and P-content reported in FRS treatments (IMTA-R-FRS and T-R-FRS) were considerably (p ˂ 0.05) higher than that reported in NFT treatments (IMTA-R-NFT and T-R-NFT), as shown in Table 3. N- and P-retention in rice kernel and total rice parts is also higher in FRS treatments than in NFT treatments (IMTA-R-NFT and T-R-NFT), as shown in Table 5. Several prior research studies have found that the NFT hydroponic approach is less effective in terms of nutrient removal and nitrogen removal efficiency when compared to other aquaponic systems. 40,63–65. The current results are in the same line with previous results reported by Li, et al. 20, who reported that the co-cultivating between rice-yellow catfish (Pelteobagrus fulvidraco), and rice-freshwater shrimp (Macrobrachium nipponense) in the same pond reduced the nutrients (TP, TN, TAN, and total potassium), reduced the proportions of respiration in water and sediment (by 64.4% and 38.7% in the rice-shrimp pond, respectively, and 66.1% and 31.7% in the rice-catfish pond, respectively). Additionally, it reduced the proportion of respiration between P. fulvidraco and M. nipponense and was considered an effective technique for reducing hypoxia in intensive culture ponds.
The current findings are consistent with previous findings reported by Li, et al. 20, who found that co-cultivating rice-yellow catfish (Pelteobagrus fulvidraco) and rice-freshwater shrimp (Macrobrachium nipponense) in the same pond reduced nutrients (TP, TN, TAN, and total potassium), and reduced the proportions of respiration in water and sediment (by 64.4% and 38.7% in the rice-shrimp pond, respectively, and 66.1% and 31.7% in the rice-catfish pond, respectively). Additionally, it reduced the proportion of respiration between P. fulvidraco and M. nipponense and was considered an efficient approach for minimizing hypoxia in intensive culture ponds. Frei and Becker 16 observed similar trend results in an integrated greenhouse study (group1- rice-tilapia/carp cultivation, group2- rice-carp culture, group3- rice only). The rice and fish groups (Groups 1 and 2) received supplemental feeds, whereas the rice group received only mineral fertilizer. The rice-carp culture increased rice yields, however, the carp/tilapia culture decreased rice yields when compared to rice alone. Li, et al. 23 compared the efficiency of nutrient removal and water stability of integrated co-culture between rice and two shrimp species, whiteleg shrimp L. vannamei and freshwater shrimp M. rosenbergii, using paddy fields and two freshwater water ponds and two brackish water ponds. The results showed that the TN, TAN, TP, and chemical oxygen demand in shrimp-rice integrated ponds were substantially lower than in shrimp monoculture ponds, indicating that shrimp-rice integrated pond cultivation is a successful way to improve nutrient utilization efficiency.
The results of the present study concluded that the highest significant rice yield was reported by IMTA-R-FRS (8801.8 kg ha− 1) compared to other experimental treatments T-R-FRS (5837.5 kg ha− 1), IMTA-R-NFT (4870.3 kg ha− 1), and T-R-NFT (2527.5 kg ha− 1). The final yield of rice and fish mainly depends on the co-culture system, co-culture conditions, and aquatic animal species compositions. This finding was previously supported by several studies 17–19,21,26,67. In India, Mohanty, et al. 19 reported that when co-cultured with different aquatic animals of major South Asian carp, C. catla, common carp, C. carpio, rohu, L. rohita, mrigal carp, C. mrigala, and freshwater shrimp M. rosenbergii, the total yield of rice ranged from 3 to 3.6 tonne ha− 1 with a total final yield of aquatic animals ranged from 906 to 1282 kg ha− 1. In another socio-economic study conducted in Bangladesh, Gupta, et al. 18 demonstrated that when rice was co-cultured with fish (O. niloticus, C. carpio, Java barb, and B. gonionotus), the overall production of rice ranged from 3.8 to 5 tonnes ha− 1 and 118 to 616 kg ha− 1 aquatic animals production. Purba 67 reported in another study in Indonesia that the overall yield of rice and fish (O. niloticus and C. carpio) in the integrated co-culture system was 7.8 tonnes ha− 1 for rice and ranged from 0.8 to 625 kg ha− 1 for fish. Another benefit of employing IMTA-developed treatments (IMTA-R-FRS and IMTA-R-NFT) over tilapia-developed treatments (T-R-FRS and T-R-NFT) is enhanced aquatic animal biomass gain and profitability, which is one of the targets to attain for climate adaptation and mitigation. The total weight gain of aquatic animals increased in the current study compared to the monoculture system. Besides the rise in aquatic animals gains, the rice final yields of the developed systems IMTA-R-FRS, T-R-FRS, IMTA-R-NFT, and T-R-NFT were 8.8, 5.8, 4.9, and 2.5 tonne ha− 1, respectively, as compared to the traditional rice cultivation in Egypt, ranged from 6 to 8 tonne ha− 1 68.
Another promising finding of this study is that the apparent FCR values in the IMTA system (0.73) are much better than those in the monoculture system (1.58). This means that current IMTA-developed methods allow farmers to profitably produce a variety of aquatic creatures such as mullets, crayfish, freshwater mussels, and silver carp without the usage of costly extra feed.
As presented in Table 6, using IMTA treatments, the gain of N-retention in aquatic animals (86.05%) and rice (10.82%) was a total of 96.88%, compared to a total of 69.81% in tilapia treatments (68.07% by tilapia and 1.74% by rice). One of the study's interesting results is that using IMTA-developed treatments (IMTA-R-FRS and IMTA-R-NFT) has an N- and P-retention advantage to tilapia-rice monoculture (T-R-FRS and T-R-NFT). As demonstrated in Table 5, N-retention in IMTA-Rice increased from (86.07%) to 95.64% and 87.32%, respectively, using IMTA-R-FRS and IMTA-R-NFT treatments, compared to 70.32% and 68.28% in tilapia-rice monoculture (T-R-FRS and T-R-NFT, respectively). P-retention in aquatic animals increased from 55.12–60.47% and 55.83% using IMTA-R-FRS and IMTA-R-NFT treatments, respectively, compared to 19.86% and 18.74% in tilapia-rice monoculture (T-R-FRS and T-R-NFT, respectively). These data revealed that the developed IMTA treatments (IMTA-R-FRS and IMTA-R-NFT) are more efficient in nutrient removal efficiency than tilapia monoculture treatments (T-R-FRS and T-R-NFT). This outcome can be attributed to the synergistic power of different feeding habits of aquatic animals in the IMTA system (mullet, crayfish, mussels, and silver carp), which significantly boosted the nutrient removal utilization efficiency. Tarigan, et al. 21 investigated various rice-fish integrated aquaponics systems in freshwater and brackish water. The results of this study revealed increases in water use efficiency (31%), P (18%), and N (10%) in a freshwater treatment.