USING PLANT VOLUME TO QUANTIFY INTERFERENCE IN CORN (ZEA-MAYS) NEIGHBORHOODS

Measurements of above-ground plant volume were used to quantify corn i nterference with common cocklebur and velvetleaf, Separate experiments were carried out for each weed species in which neighborhoods with a radius of 50 cm were established around target plants of both species, selected from a range of corn plus cocklebur or velvetleaf densities, Height and canopy area of target plants and neighbor corn and weed po pulations were measured periodically during the growing season, Target plant (corn, cocklebur, or velvetleaf) size as well as corn and weed population size within each neighborhood were quantified as cylindrica l volumes, Regression analysis was used to quantify the relationship b etween target plant seed production and cylindrical volumes of the tar get and neighbor species, Both target and neighbor plant volumes were correlated with target plant seed production for all species, The rati o of target plant volume to total neighborhood plant volume (volume ra tio) was the independent variable that accounted for the most variatio n in target plant seed production, These volume-based variables may be used to develop competitive indices in physico-empirical based interf erence models.