Al-Kaisi, M. M., Archontoulis, S., & Kwaw-Mensah, D. (2016). Soybean spatiotemporal yield and economic variability as affected by tillage and crop rotation. Agronomy Journal, 108 (3), 1267-1280.
To investigate how soybean yields and economics vary across sites, tillage systems and cropping systems, and which factor contributes the most to the year-to-year variability.
In collaboration with Dr. Mahdi Al-Kaisi group we statistically analyzed a comprehensive long term soybean dataset (2003–2014) that included the effects of 7 sites (Sutherland, Kanawha, Nashua, Ames, Lewis, McNay and Crawfordsville) x 5 tillage systems (no-tillage, strip-tillage, chisel plow, deep rip, and moldboard plow) x 2 cropping systems (corn-soybean and corn-corn-soybean) on soybean yields and economics in Iowa. The experiments were replicated (n=4) and are still on-going and maintained by Dr. Mahdi Al-Kaisi.
Soybean yields varied from 22 to 75 bu/ac and the coefficient of variation varied from 15 to 25% across years and sites (Fig. 1). Crop rotation had a greater influence on soybean yields and economics than tillage systems. The corn-corn-soybean system resulted in 9% greater soybean yields and 11% greater economic returns than corn-soybean rotation in five out of seven locations (Fig. 2). The tillage effect on soybean yield was not significant. The economic return with no-tillage exceeded that with conventional tillage due to lower input cost for the no-tillage system. A systems analysis of combined soybean (this study) and corn data (Al-kaisi et al., 2015) across years and sites showed that the economic return was higher in corn-soybean rotation, followed by corn-corn-soybean and then by the continuous corn system (Fig. 3). Read more here.