Epsilon Archive for Student Projects

Abstract

Fish effluent from aquaculture is a valuable source of nutrients for plant growth, offering an alternative to the standard fertilizers commonly used in hydroponic systems. As it does not provide all the essential nutrients required for optimal plant growth, this study investigates the complementation with standard nutrient solution under different fertilization strategies, to assess the impact on the nutrition, growth, and development of tatsoi (Brassica rapa var. narinosa) in liquid and solid hydroponics.
Shoot biomass production, chlorophyll content, chlorophyll fluorescence, Normalized Difference Vegetation Index, Specific Leaf Area, and Specific Leaf Weight were evaluated as indicators of plant performance in the systems. Nutrient content in leaves, substrate and solutions was analyzed to identify potential deficiencies associated with increasing fish water percentages in the fertilization strategy. Five treatments were tested using combinations of fish wastewater (FW) from Tilapia (Oreochromis niloticus) cultivation and Hoagland nutrient solution (NS) as standard for hydroponics. The fertilization strategies applied were: 100% FW, 75% FW + 25% NS, 50% FW + 50% NS, 25% FW + 75% NS, and 100% NS. The pH levels were not significantly affected by the system or treatment; however, data indicated a trend toward alkalinization when using 100% fish water. Electrical conductivity (EC) and salinity were influenced by the treatments, showing a decrease with higher proportions of fish effluent. Nutrient availability varied depending on the system and fertilization strategy. In liquid hydroponics, calcium became more limiting with increasing percentages of fish effluent, whereas in solid hydroponics, it remained available due to peat's capacity to retain it. Leaf Ca concentrations were stable in both systems, except in treatments with 0% or 25% fish water in peat, where it was made unavailable through adsorption in the substrate. No iron deficiencies were noted, and potassium decreased with higher fish water percentages both in the solutions and leaves, while Magnesium decreased slightly with higher proportions of fish water in the solutions and leaves. Shoot biomass, chlorophyll content, and fluorescence were influenced by both system and fertilization strategy, but height, NDVI, SLA, and SLW were unaffected, indicating other factors at play. In liquid hydroponics, a 50/50 mixture of fish effluent and Hoagland's standard solution produced results comparable to the control. However, in solid hydroponic systems, yields were reduced due to nutrient adsorption by the substrate, which likely restricted nutrient uptake by tatsoi, thereby affecting plant growth. This method demonstrates the potential of fish effluent as a valuable resource for significantly reducing the reliance on chemical fertilizers in hydroponic systems, thereby minimizing environmental impacts and lowering overall costs. However, it also underscores the need for careful evaluation of fertilization strategies, including supplementation with Hoagland solution, particularly when substrates are involved, as they can influence nutrient availability, plant performance, and yield outcomes.
Shoot biomass production, chlorophyll content, chlorophyll fluorescence, Normalized Difference Vegetation Index, Specific Leaf Area, and Specific Leaf Weight were evaluated as indicators of plant performance in the systems. Nutrient content in leaves, substrate and solutions was analyzed to identify potential deficiencies associated with increasing fish water percentages in the fertilization strategy. Five treatments were tested using combinations of fish wastewater (FW) from Tilapia (Oreochromis niloticus) cultivation and Hoagland nutrient solution (NS) as standard for hydroponics. The fertilization strategies applied were: 100% FW, 75% FW + 25% NS, 50% FW + 50% NS, 25% FW + 75% NS, and 100% NS.

The pH levels were not significantly affected by the system or treatment; however, data indicated a trend toward alkalinization when using 100% fish water. Electrical conductivity (EC) and salinity were influenced by the treatments, showing a decrease with higher proportions of fish effluent. Nutrient availability varied depending on the system and fertilization strategy. In liquid hydroponics, calcium became more limiting with increasing percentages of fish effluent, whereas in solid hydroponics, it remained available due to peat's capacity to retain it. Leaf Ca concentrations were stable in both systems, except in treatments with 0% or 25% fish water in peat, where it was made unavailable through adsorption in the substrate. No iron deficiencies were noted, and potassium decreased with higher fish water percentages both in the solutions and leaves, while Magnesium decreased slightly with higher proportions of fish water in the solutions and leaves.

Shoot biomass, chlorophyll content, and fluorescence were influenced by both system and fertilization strategy, but height, NDVI, SLA, and SLW were unaffected, indicating other factors at play. In liquid hydroponics, a 50/50 mixture of fish effluent and Hoagland's standard solution produced results comparable to the control. However, in solid hydroponic systems, yields were reduced due to nutrient adsorption by the substrate, which likely restricted nutrient uptake by tatsoi, thereby affecting plant growth. This method demonstrates the potential of fish effluent as a valuable resource for significantly reducing the reliance on chemical fertilizers in hydroponic systems, thereby minimizing environmental impacts and lowering overall costs. However, it also underscores the need for careful evaluation of fertilization strategies, including supplementation with Hoagland solution, particularly when substrates are involved, as they can influence nutrient availability, plant performance, and yield outcomes.