A lack of response of irrigated soybean (Glycine max L. Merr.) in rotation with cotton (Gossypium hirsutum L.) in the Mississippi Delta, USA

The effects of cotton (Gossypium hirsutum L.): soybean [Glycine max (L.) Merr.] rotations on the respective crops are limited. This manuscript discusses the response of irrigated soybean in crop rotation with cotton. An irrigated soybean: cotton rotation experiment was conducted from the year 2012 through 2015 near Elizabeth, MS. The crop rotation sequences were included continuous soybean (SSSS), continuous cotton (CCCC), cotton followed by soybean (SCSC), soybean followed by cotton (CSCS), soybean followed by two year of cotton (SCCS), and cotton followed by two year of soybean (CSSC). The rotations were grown under two production systems conventional and transgenetic with respect to weed control. During this study, a weed control treatment of (pendimethalin pre-emergence vs. glyphosate post-emergence) as included on the soybean plots was used. The soybean yields across rotations within a year were not significantly different. The means yields differed among years (3655.1, 3023.6, 3500.6 and 2600.3 Kg ha-1 for the year 2012, 2013, 2014 and 2015, respectively) and appear related to difference in rainfall/irrigation amounts. The results revealed that the weights of 100 seed samples averaged 13.9g in the year 2015 which differed from the previous years (16.2, 15.6, and 16.2g; 2012, 2013 and 2014, respectively). Therefore, the rotations of cotton with soybean appear to have neither a beneficial or negative effect on soybean yield.