|Authors: ||M.G. Blanchard, E.S. Runkle, J.M. Frantz|
|Keywords: ||annuals, bedding plants, energy consumption, flowering, greenhouse heating, Petunia ×hybrida, Tagetes patula|
The cost of fuel is an increasingly significant production expense for greenhouse growers in temperate climates.
High heating costs have motivated growers to improve the efficiency of crop production to minimize energy inputs.
We performed greenhouse experiments with Petunia ×hybrida ‘Dreams Neon Rose’ and Tagetes patula ‘Janie Flame’ to understand how mean daily temperature (MDT) and photosynthetic daily light integral (DLI) influence plant development.
This information was then used to determine how the production environment and crop timing influence greenhouse energy consumption for heating on a per-crop basis.
Seedlings of each species were grown in an environmental growth chamber at an MDT of 20.4°C with a DLI of 10 mol m-2 d-1 and under a 16-h photoperiod.
After 19 to 32 d from seed sow, seedlings were transplanted into 10-cm pots and grown in glass-glazed greenhouses at constant air temperature set points of 14, 17, 20, 23, or 26°C and under a 16-h photoperiod provided by high-pressure sodium (HPS) lamps.
At each temperature, plants were grown under two DLI treatments provided by the use of a shade curtain and different intensities of supplemental lighting from HPS lamps.
Time to flower in Petunia decreased from 43 to 17 d as MDT and DLI increased from 14°C and 4 mol m-2 d-1 to 26°C and 16 mol∙m-2 d-1. In Tagetes, time to flower ranged from 17 to 38 d.
A decision-support software (Virtual Grower) was used to estimate energy consumption at different locations in the United States based on the predicted crop production durations at different MDTs and DLIs.
For example, the predicted energy cost for greenhouse heating to produce a Petunia crop in Grand Rapids, Michigan, USA for a 1 April finish date was 8% lower when grown at an MDT of 20°C compared to that at 14°C. This information can be used by greenhouse growers to determine how to minimize heating input costs in the production of their crops.
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