2017 ASHS Annual Conference

Bell peppers bred for greenhouse production systems are often trellised in vertical growing systems to facilitate crop management and optimize space utilization. A protocol of one to four primary stems with pruned side shoots is often used to encourage reproductive growth and enhance productivity. Recommendations vary as to number of leaves to keep on the developing lateral side branches. A preliminary study suggested increased productivity when three leaves compared to one leaf were left on side branches in a two-stem trellising system. To further evaluate the importance of side shoot pruning, an experiment with the greenhouse bell pepper cultivars Fantasy (red), Paramo (orange), and Striker (yellow) was initiated. The study was completed in a greenhouse covered with the acrylic material DEGLAS®. Seeds were sown on Jan. 15 and the study conducted from Mar. 3 through Aug. 29. Supplemental lighting from high pressure sodium lamps was provided when outside ambient light dropped below 400 W·m^-2 between 6:00 AM to 10:00 PM. The plants were grown in a high-wire drip irrigation system using dutch (bato) buckets (17.7 L volume) filled with a 50/50 mixture of perlite and a peatlite medium (Pro-Mix BX). The plants were trellised into a “V” shaped system using two primary shoots off the main stem. The lateral side-stems developing on the two primary stems were trimmed over one or three leaves throughout the study. The pepper fruits were harvested mature with at least 90 percent color formation. Fantasy, Paramo and Striker produced significantly higher yields in the three-leaf pruning approach. During the production period from June through August, the highest yield was observed for the yellow pepper Striker at an average 4.3 ± 0.72 kg per plant in the three-leaf system. In comparison, the one-leaf system yielded 3.7 ± 0.67 kg for Striker. Fantasy and Paramo had similar yields at 3.8 ± 0.86 kg per plant with the three-leaf system and 3.4 ± 0.71 kg in the one-leaf pruning approach. Along with a larger yield, the three-leaf system also resulted in additional fruits per plant. Individual peppers were heavier in the one-leaf system for all cultivars but the size difference did not make up for the fewer peppers. The weight of individual peppers varied from 232.0 ± 14.76 grams for Striker (one-leaf system) to 190.3 ± 31.46 grams for Paramo in the three-leaf system.