Interplot Competition in Sweetpotato [Ipomoea batatas (L.) Lam.] Variety Trials

Fifty-four varieties of sweetpotato [Ipomoea batatas (L.) Lam.] were evaluated over three dry and two wet seasons from 2010 to 2013 in two-row and four-row plots to detect the presence of interplot competition, or competition between two neighboring varieties, in sweetpotato variety trials. The performance of each variety when bordered by another variety on one side (unbordered treatment) and when bordered by itself (bordered treatment) was compared in two ways: 1) comparison of yields from two-row plots (unbordered) and from the two inner rows (bordered) of four-row plots and 2) comparison of yields from the two outer rows (unbordered) and from the two inner rows. No significant differences were observed between the two treatments in either method of comparison in all trials conducted, indicating that interplot competition did not exist in the experiments conducted. The significant Spearman's rank correlation coefficients for varieties between treatments in all tests supported the conclusion. Sweetpotato variety trials can therefore be conducted using only two-row plots, that is, plots with no extra or guard rows.