Agronomy and Horticulture Department



Charles A. Shapiro

Date of this Version



Published in Agron. J. 93:404–407 (2001). Used by permission.


Glyphosate (N-(phosphonomethyl) glycine)-resistant (GR) soybean [Glycine max (L.) Merr.] technology is gaining acceptance in U.S. cropping systems, yet potential yield suppression from either cultivar genetic differentials, the GR gene/gene insertion process, or glyphosate is a concern. Other work shows that the GR gene/gene insertion process may suppress soybean yield. No one has reported the effects of glyphosate on a diverse group of commercially available GR soybean cultivars. In this study we evaluated one of the potential sources of GR yield suppression—the effect of glyphosate on yield, growth, and development of GR cultivars. Field experiments were conducted at four Nebraska locations with12 GR cultivars in 1998 and 13 GR cultivars in 1999. Soybean response to glyphosate, ammonium sulfate (AMS), and water application at 21 and 42 d after soybean emergence was compared with control plots treated with AMS and water in 1998. An additional control, water alone, was added in 1999. Grain yield among cultivars differed as expected with a range of 3.44 to 3.96 Mg ha-1 in the 2-yr averages. Glyphosate did not affect the majority of the soybean growth and development characteristics measured. Grain yield of GR soybean was not affected by glyphosate at any location or when averaged over locations. Two-year average grain yield of cultivars treated with glyphosate, AMS, and water was 3.74 Mg ha-1; this was not different from 3.79 Mg ha-1 with AMS and water treatment.