EFFECTS OF PHOTOPERIODS ON GREENHOUSE TOMATO AND PEPPER PRODUCTION

Abstract

Most works on artificial lighting of winter greenhouse vegetable crops studied the effects of photosynthetic photon flux but rarely photoperiod. Over the last three years, we conducted experiments to find out the best photoperiods for production of greenhouse tomato and pepper. We found that extending photoperiod up to 20 hrs increased productivity of pepper plants while continuous light (24 hrs) decreased yields. For tomato plants, productivity reached a maximum under a 14-hr photoperiod while longer photoperiods (16 to 24 hrs) did not increase yields. For both pepper and tomato plants, optimal growth (shoot fresh and dry weights) was obtained under the same photoperiods that gave the best productivities. We also observed leaf chloroses on tomato plants after 6 weeks under photoperiods of 20 and 24 hrs and leaf deformations (wrinkles) on pepper plants exposed to continuous lighting. We also observed that plants under continuous light grew better and flowered earlier during the first 5 to 7 weeks of treatments. So, tomato and pepper plants can use advantageously continuous supplemental lighting for a short period of time but are negatively affected on a long term basis. Future works should look at varying photoperiods to optimize yields.