Agronomy and Horticulture, Department of


Date of this Version



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agronomy, Under the Supervision of Professor Stephen C. Mason. Lincoln, NE: August, 2011

Copyright 2011 Mitchell J. Novacek


Maize (Zea mays L.) is widely grown for food, feed, and fuel, and optimal yield will be required to meet increasing demand due to world population growth and increased biofuel usage. This requires matching of the best maize hybrids with optimal plant population and spacing. Modern maize hybrids have increased “crowding stress” tolerance, and Bt (Bacillus thuringiensis) hybrids now resist European corn borer and corn rootworm which has created interest in altering row configuration and increasing plant population.

Three Bt hybrids were evaluated from 2009 to 2010 near Mead, NE at target populations from 69136 to 106173 plants ha-1 in 76 cm single rows and twin rows. Maximum yield occurred at the highest target population in 9 of 12 year, hybrid, and row configuration combinations although target population had a small effect on yield. Varying hybrid, plant population, and row configuration had small and inconsistent effects on grain yield, yield components, plant morphology and leaf area, interception of solar radiation, and stalk lodging. It appears that the major impacts of altering row configuration occur early in the growing season, and plant growth and other factors occurring later in the growing season have a greater impact on yield.

Two pairs of near isogenic Bt and non-Bt maize hybrids were evaluated under rainfed and irrigated conditions from 2008 to 2010 at target populations from 49383 to 111111 plants ha-1 near Mead, NE. For all hybrids and environments, yield increased linearly and the highest target population resulted in the greatest grain yield. Bt hybrids had 0.4 Mg ha-1 greater yield than non-Bt hybrids at all populations. Bt hybrids lodged less in three of five environments.

Results indicate that twin-row production has little influence on maize yield and growth in Nebraska. In general, maize yield increased linearly with increasing target population although the rate of yield increase varied across experiments, environments and hybrids. Farmers in East-Central Nebraska should consider increasing maize plant population and planting Bt hybrids to optimize maize grain yield.