Agronomy and Horticulture Department


Date of this Version



Published in Ecological Applicalions. 4(3), 1994, pp. 5 18-524 Copyright 1994 by the Ecological Society of America. Used by permission.


Two greenhouse experiments were conducted to evaluate the performance of individual oat (Avena sativa) target plants as influenced by neighbor oat plants with different spatial arrangements. Crop spatial arrangement was separated into three com- ponents: (I) population density, (2) distance between plants (distance dispersion, DD), and (3) angular arrangement of plants about one another (angular dispersion, AD). Distance dispersion was quantified using a weighted mean distance from a target individual to its neighbors. Angular dispersion of neighbors around the target was quantified using a measure of circular variance. DD and AD were combined to create a dispersion index (DI). At constant density, distance dispersion treatments were combined with angular dispersion treatments in a randomized-block factorial design. Target plant biomass production was predicted using a rectangular hyperbola equation including population density, DD, AD, and DI as independent variables. Fifty-five and 44% of the residual variation (the variation not accounted for by density alone) in individual plant yield was accounted for when spatial arrangement (DI) was added to the regression. The approach can be used to compare the intensity of competition among different crop planting patterns.