Abstract:
The increasing adoption of LED grow lighting has created new opportunities to optimize plant
growth through precise manipulation of light spectrum and intensity. Stage-specific spectral
management has gained considerable attention as an effective strategy for improving crop growth,
productivity, and resource-use efficiency. The present study was conducted to evaluate the effect of
dynamic red and blue LED spectral treatments on the growth performance of red amaranthus
(Amaranthus tricolor L., cv. Vyga) under an indoor cultivation system.
A dual-rack LED lighting system was developed using Arduino Uno, PWM-based intensity
control, MOSFET driver circuits, potentiometers, and a 16×2 I²C LCD display for real-time monitoring
and regulation of light intensity. The photosynthetic photon flux density (PPFD) was calculated and
maintained according to the crop growth stages. Two dynamic spectral treatments were evaluated:
Treatment 1 (T1) with a Blue to Red spectral progression and Treatment 2 (T2) with a Red to Blue
spectral progression, while maintaining stage-specific PPFD requirements during germination,
seedling, and vegetative growth.
Biometric observations, including plant height, stem girth, number of leaves, and leaf area,
were recorded at seven-day intervals to assess plant growth under both treatments. The experimental
data were analysed using two-way Analysis of Variance (ANOVA) to determine the effects of LED
treatment, growth period, and their interaction on plant growth.
The results showed that all biometric parameters increased progressively with crop age under
both treatments. However, Treatment 1 (Blue to Red progression) consistently outperformed Treatment
2 (Red to Blue progression) by recording greater plant height, higher stem girth, increased number of
leaves, and larger leaf area. The two-way ANOVA further confirmed that both LED treatment and
growth stage had significant effects on plant growth, demonstrating the importance of stage-specific
spectral management.
Overall, Treatment 1 (Blue to Red progression) was found to be the most effective lighting
strategy for promoting the growth and development of red amaranthus under controlled indoor
conditions. The developed Arduino-based LED lighting system provides an efficient, economical, and
adaptable approach for indoor farming and vertical farming, with potential for application in the
cultivation of other leafy vegetable crops
