Cultivation System Dominates Cucumber Performance and Root-Zone Microbiomes Across Biochar Particle Sizes

Area of Science:

• Horticultural science
• Microbiology
• Sustainable agriculture

Background:

• Hydroponic (HP) and aquaponic (AQ) systems are key in controlled environment agriculture.
• The interplay between nutrient delivery systems, substrate properties, and root-zone microbiomes is not fully understood.
• Substrate physical structure impacts water retention, aeration, plant growth, and microbial communities.

Purpose of the Study:

• To investigate the combined effects of nutrient delivery systems (HP vs. AQ) and substrate physical structure (biochar vs. coconut coir) on cucumber (Cucumis sativus L.).
• To analyze crop performance, yield, nutrient dynamics, physiological stress, and bacterial community composition.
• To determine the dominant factor influencing cucumber growth and root-zone bacteria.

Main Methods:

• Cucumber plants were grown in hydroponic and aquaponic systems using bamboo-derived biochar and coconut coir substrates.
• Evaluated vegetative growth, total yield, nutrient concentrations (nitrate), and physiological stress indicators.
• Analyzed bacterial community composition in the root zone.

Main Results:

• Aquaponic systems enhanced vegetative growth and total yield compared to hydroponic systems, with coarse biochar yielding the most (28.6 kg m⁻²).
• Aquaponics showed greater nutrient availability (up to 226 mg L⁻¹ nitrate) and reduced plant physiological stress, especially with biochar substrates.
• Cultivation system (AQ vs. HP) was the primary driver of bacterial community variation (19.3%), while substrate type had minimal impact.

Conclusions:

• Aquaponic systems, particularly with biochar substrates, offer superior cucumber growth, yield, and reduced plant stress compared to hydroponics.
• The cultivation system is the dominant factor influencing cucumber performance and root-zone bacterial communities.
• Bamboo biochar substrates show promise for enhancing crop production in aquaponic and hydroponic systems.