Organically‑grown greenhouse tomato under supplemental lighting – optimization of the light distribution

M. Dorais1, S. Pepin2, L. Gaudreau2, C. Ménard1, R. Bacon1 and M. Lemieux3


Organic cultivation has long been seen as key to improving the sustainability of
greenhouse tomato production systems. Yet, few organic systems have been established because of concerns about yield and fruit quality being lower in organic than in conventional productions.

As light is a key limiting factor related to plant productivity and fruit quality, supplemental lighting (SL) under organic farming could constitute a promising alternative to satisfy Canadian consumer demand for organic vegetables. Hence, the purpose of this study was to adapt an organic growing system to supplemental lighting.

A split-plot experiment was performed in a commercial greenhouse (Serres
Sagami, Chicoutimi, QC) to determine the effects of row spacing (main plots: 3 rows per bay vs. 4 rows) and growing system (sub-plots: conventional vs. organic) on tomato yield, plant growth parameters and fruit quality. A conventional system was used to establish a baseline for the productivity that can be reached with an organic crop under SL when nutrient availability may also be a limiting factor. Seedlings of Lycopersicon esculentum (cv Heritage grafted on Beaufort) were transplanted in 15-liters coco coir slabs vs. containers with organic soil and grown under supplementary lighting (HPS lamps) for six months. Plant density was similar between row spacing treatments and the irrigation management was based on soil matric potential measured at 15 cm depth using wireless tensiometers and an irrigation set point of –2.8 kPa.

Measurements of supplemental light at plant height (~1.7 m from HPS) and near the 5th leaf (~2.5 m from HPS) with a line Quantum showed no significant difference in PPFD (mean: 95 and 82 mmol m–2 s–1, respectively) between the two row spacings. There were no significant differences in measured plant growth parameters between the growing systems or the row spacing treatments. Tomato yield was similar between the organic and conventional crop system.

Our results will be discussed in term of light distribution and potential yield reached under a sustainable greenhouse tomato production.


Plant Canada Conference. Saint Mary's University, Halifax, NS. July 17-21, 2011

Author Locations and Affiliations

(1) Agriculture and Agri-Food Canada, Université Laval, Québec, QC,
Canada G1V 0A6
(2) Horticulture Research Centre, Department of Soil and Agri-Food
Engineering, Univ. Laval, Québec, QC, Canada G1V 0A6
(3) Serres Sagami, Chicoutimi, QC, Canada G7H 5B3

Posted May 2012