Hydroponic Lettuce Cultivation Using Organic Nutrient Solution from Aerobic Digested Aquacultural Sludge

Maha Ezziddine,Randi Seljåsen,Helge Liltved

doi:10.3390/agronomy11081484

Maha Ezziddine, Randi Seljåsen + Show 1 more

Open Access

https://doi.org/10.3390/agronomy11081484

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Abstract

The aim of this study was to demonstrate how aquacultural sludge can be processed and utilized as an organic nutrient solution (ONS) for hydroponic lettuce production. By using a previous developed method, approximately 80% of the processed sludge was reclaimed as a clear, nutrient-rich solution. The performance of the recovered nutrient solution on lettuce growth was assessed in a nutrient film hydroponic system. The results were compared to the results obtained using a conventional nutrient solution (CNS). Yield, fresh weight, water consumption, and nutrient and heavy metal content in leaf tissue were measured. In spite of a 16% lower average fresh weight obtained in ONS compared to the weight obtained in CNS, there was no statistical difference of the yield of lettuce among the two nutrient solutions. After the cultivation period, 90% of the lettuce heads grown in ONS exceeded the marked weight of 150 g. Foliar analysis revealed a similar or higher content of all nutrients, except of magnesium and molybdenum in the leaves of lettuce grown in the ONS compared to lettuce grown in the CNS. This study shows that nutrients recovered from aquacultural sludge can be utilized as fertilizer, thereby reducing the dependency on mineral fertilizer in hydroponic and aquaponic systems.

Highlights

IntroductionSoil supports plants’ roots and provides water, nutrients, and oxygen to these roots
In hydroponic systems, plants are grown without soil
total suspended solids (TSS), biological oxygen demand (BOD), chemical oxygen demand (COD) and nutrient content in aquacultural sludge can vary from one facility to another depending on several factors including fish species, fish density, fish age, fish feed, feeding management, flow regulation, and water treatment

Summary

Introduction

Soil supports plants’ roots and provides water, nutrients, and oxygen to these roots. In hydroponic systems, plant roots are supported by an inert medium in net pots while water and nutrients are delivered via nutrient solution [1]. Net pots are placed in a trough, channel, gully, or pipe with holes for the net pots. This provides physical support for the plants. Rectangular pipes with a width larger than their height allow for a much larger surface area of the nutrient solution, which increases nutrient uptake and plant growth [3]. Pumps are used to circulate the nutrient solution from the reservoir to the pipes which, preferably, should be positioned on a slope to facilitate nutrient solution flow along the pipe

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