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Inter-row Competitive Effects among Four Cotton Cultivars¹

Inter-row competition among cotton (Gossypium hisutum L.) genotypes may cause major biases in the estimation of cultivar performance. The objective of the present study was to evaluate the nature and importance of such effects among four cotton cultivars and relate the results to field evaluation techniques.

Four cultivars, representing the extremes of vegetative growth habit among the strains currently being tested in North Carolina, were grown. Inter-row competition was measured using each cultivar as a test cultivar subjected to all possible pair wise combinations of the same four entries as competitors. Thus, there were 10 competitor combinations for each test cnltivar, for a total of 40 treatments. A randomized block design of six replicates was grown at each of three locations in North Carolina. Six traits were measured including seed cotton yield, lint yield, lint percent, boll weight, plant height, and plant width.

The four cultivars differed significantly in competitive ability. Although effects on all traits were noted, fiber and seed cotton were the only traits which were modified sufficiently to be of major concern in an evaluation program. Both additive (average) and specific inter-row competitive effects were observed for yield. Mean squares for average effects were consistently larger than those for specific effects. Averaged over the three locations, biases expected from the use of nonbordered single-row plots ranged up to 13.2% for lint yield. Competition effects of this magnitude suggest the need to use bordered plots for measuring yield, at least in advanced trials.

Key Words: Gossypium hirsulum L. • Cultivar testing techniques

² Formerly graduate student (present address, Univ. National Agraria, La Molina, Lima, Peru) and professor of crop science, N. C. State Univ., Raleigh, NC 27607.

Received for publication November 4, 1974.