Rice Yield and Plant Yield Variability Responses to Equidistant Spacing

Abstract

The effect of plant population density on rice (Oryza sativa L.) yields often is confounded experimentally by other effects such as mortality and spacing uniformity. Equidistantly spaced, transplanted rice was used in this study in an effort to obtain less equivocal information on the effects of spacing on plant yield variability. The objectives of this study were (i) to determine the effects of equidistant spacing and cultivar on rice grain yield and yield components and (ii) to determine variation in and relationships among the grain yields of individual plants in the rice crop community. Randomized complete block design experiments were conducted at Keiser, AR in 1984, 1985, and 1986. ‘Lebonnet’ and ‘Lemont’ were whole‐plot treatments and equidistant spacings (51, 76, and 102 mm) were the split‐plot treatments. Plant yield, crop yield, culms/plant, kernels/panicle, and kernel weight increased as spacing increased. Lemont had more culms/plant and greater kernel weight than Lebonnet whereas Lebonnet had more kernels/panicle. Optimum equidistant spacings for crop grain yields of transplanted rice were 53 to 71 mm. Plant yield coefficients of variation (CV) were greatest at the closest spacing. Increased plant yield CV at closer spacings is consistent with a large body of research which indicates plant communities become more hierarchical and variable as plant population densities increase. It is likely that efforts to account for individual plant yield variation must incorporate the control or measurement of relevant environmental variations.