Adjusting Management Practices When Producing Glyphosate-resistant Soybean

The use of glyphosate resistant soybean (GRS) cultivars has increased rapidly from their introduction in 1996 to over 50% of Wisconsin soybean acres in 1999. While much research has been conducted using conventional cultivars to measure the influence of row spacing and seeding rates on soybean growth and yield, little has been done with new GRS cultivars. It may be necessary and/or more profitable to alter management practices with GRS cultivars. For example, does the increased seed costs of GRS cultivars justify decreased seeding rates? Greater seed costs at planting need to be offset by an optimized seeding rate, reduced herbicide costs, and/or increased yields to make GRS systems economically profitable to producers. Evaluating GRS versus conventional soybeans at several row widths and seeding rates will allow for the comparison of these variables measured by their effect on yield, leaf area index, plant height, lodging, disease incidence, and gross margin.