Abstract
In the Mediterranean region, tomato plants are often cultivated in two short cycles per year to avoid the heat of summer and the low solar radiation of winter. Supplementary light (SL) makes it possible to cultivate during the dark season. In this experiment, a tomato F1 hybrid cultivar DRW7723 was cultivated in a greenhouse for a fall-winter cycle. After transplant, light emitting diode (LED) interlighting, with two light spectra (red + blue vs. red + blue + far-red) was applied as SL. Plant growth, yield, gas exchange, nutrient solution (NS) consumption, and fruit quality were analyzed. In general, the effects of adding far-red radiation were not visible on the parameters analyzed, although the yield was 27% higher in plants grown with SL than those grown without. Tomatoes had the same average fresh weight between SL treatments, but the plants grown with SL produced 16% more fruits than control. Fruit quality, gas exchange and NS uptake were not influenced by the addition of far-red light. Interlighting is, therefore, a valid technique to increase fruit production in winter but at our latitude the effects of adding far-red radiation are mitigated by available sunlight.
Highlights
Tomato (Solanum lycopersicum L.) is a short-lived perennial plant, generally cultivated under greenhouse conditions to obtain year-round production for fresh-market consumption, especially in soilless cultivation systems [1]
The findings of this study confirm that in the Mediterranean region, tomato production benefits when supplementary light is used in an autumn–winter cycle
The results demonstrate that a FR component added to the R + B spectrum did not improve the effects of light emitting diode (LED) interlighting, probably because the amount of FR supplied by sunlight is sufficient for plant growth and production
Summary
Tomato (Solanum lycopersicum L.) is a short-lived perennial plant, generally cultivated under greenhouse conditions to obtain year-round production for fresh-market consumption, especially in soilless cultivation systems [1]. Plants are usually transplanted in December and produce from March to November, while in areas with mild climate, such as the Mediterranean, growers prefer to transplant in late summer or autumn, producing tomatoes until late summer of the following year [1]. November and December, when the outside climate is rainy and cold and the daily light integral (DLI) is low, whereas in the Mediterranean region, the tomato plant cycle is stopped in early summer to avoid the need for greenhouse cooling [1]. In so-called “cold” (unheated) Mediterranean greenhouses, two short cycles are often completed per year (autumn and spring), leaving short production breaks when mid-summer (extremely hot) and mid-winter (low DLI and temperature) climate conditions are unfavorable [4].
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