Large greenhouse experiments are often required to generate the necessary statistical power to adequately test scientific hypotheses. The results of these experiments can be confounded by variation in greenhouse light levels, temperature, and humidity, among other variables. For example, structural members, installed equipment, and tall vegetation adjacent to greenhouse walls can reduce solar radiation by up to 50% (Wang and Boulard, 2000) and produce variation sufficient to influence treatment responses (Guertal and Elkins, 1996). To address this issue, randomization and frequent rotation of pots within greenhouse experiments is necessary. Depending on the size of the experiment, however, a manual rotation process can be labor-intensive, cumbersome, and potentially damaging to the plants. Mechanized rotation systems have the potential to facilitate pot rotation (Kacira and Ling, 2001; Lazarovitch et al., 2006). The objective of this article is to describe an inexpensive, easily fabricated rotation system constructed from 24-inch (61 cm) skate wheel conveyor and wire pallet decking that can substantially reduce the time required for pot rotations. For example, in a recent experiment involving two greenhouse bays (three 1.4 m by 9.4-m benches per bay) and 1200 pots, a full manual rotation took 10 h of labor. This time was reduced to 40 min using the skate wheel conveyor system described here.
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