Corn Yield Response of Bt and Near-Isolines to Plant Density

Abstract

Optimum plant densities for Bacillus thuringiensis (Bt) corn (Zea mays L.) should be higher than non-transgenic corn subjected to European corn borer (ECB; Ostrinia nubilalis Hubner) damage because of the reduced potential for stalk lodging. The objectives of this research were to determine if yield differences occurred in Bt compared to near-isoline hybrids and to determine if different optimum densities exist for Bt and near-isolines. Bt hybrids were compared at target densities ranging from 20000 to 36000 plants per acre at different midAtlantic locations in 2000 and 2001. Yield increases ranged from 5 to 8% in 2000 at all locations. In contrast, Bt corn performed better than near-isolines at only one of three locations in 2001, with a 10% yield advantage. Relationships between yield of near-isolines and ECB damage were weak. Plant density affected yield at all locations in both years. Regression analysis of grain yield on plant density did not reveal a consistent hybrid response, although some evidence exists that suggests Bt hybrids are more efficient than near-isolines at producing yield as plant density increases. The inability to identify different optimum densities for Bt and near-isolines may have been due to low stalk lodging, plant density treatments that did not maximize yield in most instances, or the absence of different optimum densities.