Interaction of border and center rows of multiple row plots in watermelon yield trials

Abstract

Researchers interested in evaluating watermelon (Citrullus lanatus(Thunb.) Matsum. & Nakai) cultivars for yield often use multiple-row plots to simulate the monoculture system growers use or ingle-row plots to save on land, labor, and seeds. An important question is whether there is significant interaction of border rows with center rows when diverse cultivars are planted in adjacent rows. Based on recommendations from watermelon researchers in the U.S., ‘Charleston Gray’, ‘Crimson Sweet’, and ‘Sugar Baby’ were chosen to represent long, medium, and short-vined cultivars, respectively. Cultivars were planted in three-row plots with all nine combinations of the three represented in border and center rows. The experiment was a randomized complete block with the nine border by center plot combinations, two locations (Kinston, Clinton), and three replications at each location. Vine length was measured during the season, and fruit from four harvests were graded (marketable and cull), counted and weighed. Results showed that ‘Charleston Gray’ had the longest vines, followed by ‘Crimson Sweet’ and ‘SugarBaby’. In the analysis of variance, the largest effects (F ratio) on yield were from cultivar, location, and the interaction of the two. The smallest effects were border row and the interaction of center with border row. Center by border interactions were significant (5%level) in some cases, but were usually small and did not involve change in rank. Therefore, researchers interested in running trials with many cultivars and small seed quantities can obtain good data using single-row plots. However, there is a small (but significant) interaction of center with border rows in some cases, so testing at the final stage should be with trials having multiple-row plots or with cultivars grouped by vine length. Additional research is needed to determine the effect of cultivars having extreme plant types, for example dwarf cultivars in bordering rows with long-vined cultivars.