LED versus HPS Lighting: Effects on Water and Energy Consumption and Yield Quality in Lettuce Greenhouse Production

Dennis Dannehl,Daniel Veit,Uwe Schmidt,Thomas Schwend

doi:10.3390/su13158651

Dennis Dannehl, Daniel Veit + Show 2 more

Open Access

https://doi.org/10.3390/su13158651

Copy DOI

Abstract

High-pressure sodium (HPS) lighting is increasingly replaced by LED lighting in lettuce greenhouse cultivation. In contrast to HPS lighting, LEDs do not heat radiation. Therefore, the leaf temperature is significantly lower under LEDs. This raises the question of whether LED lighting has a positive impact on the reduction in water consumption during lettuce production. In this paper, we investigated this question and found that the water consumption of lettuce produced under LEDs was significantly lower (−15%) than under HPS without loss of yield. We also found that supplementary lighting increases the concentrations of caffeoylquinic acid, dicaffeoyltartaric acid, dicaffeoylquinic acid and that of the total phenolic compounds in lettuce leaves by 61%, 39%, 163% and 38%, respectively. Only the LED fixture was also efficient enough to increase the concentration of caffeoyltartaric acid (+24%). Most of the phenolic compounds showed a very strong positive correlation with the chlorophyll concentration in lettuce, which predominated in the leaves exposed to the LED lighting. Based on these facts, we conclude that by optimizing the light composition, more sustainable plant production, higher concentrations of chlorophyll and some phenolic compounds are possible.

Highlights

Lettuce plants are produced during winter seasons in greenhouses and in indoor farming without natural light all year round
Light emitting diodes (LEDs) have become more and more important in recent years, because they are more energy efficient and emit less heat radiation towards the plants, which means they can be brought closer to the plants compare to High-pressure sodium (HPS) lighting [3]
While HPS lighting primarily emits yellow and orange, but only a slightly bluish light (~5%) [4], light emitting diodes (LEDs) lighting can be constructed to match the photosynthesis action spectrum of a leaf [5], for instance the action spectrum of lettuce leaves according to McCree [6]

Summary

Introduction

Lettuce plants are produced during winter seasons in greenhouses and in indoor farming without natural light all year round. This is only possible through the use of supplementary light, where carbon arc lamps were one of the first assimilation lights developed and used at the end of the 19th century [1]. These have a bluish light spectrum and emit UV radiation.

Methods

Results

Conclusion