Long-term soybean–maize rotation experiments in cereal-based farming systems at Bako, Western Ethiopia

Maize monoculture is one of the major restrictions limiting maize productivity in Western Ethiopia. Although the inclusion of legumes in cropping systems is an essential approach for the sustainable management of farming systems and for reducing the nitrogen (N) fertilizer requirement for maize production in the long term, the effects of soybean on the sustainability of maize productivity and soil fertility are unclear in Ethiopia. Continuous cropping of maize has led to extensive degradation of soil and a decrease in crop productivity in Western Ethiopia. Thus, the study was conducted to compare the long-term impact of soybean on the sustainability of the production system in soybean–maize rotation and to monitor soil fertility dynamics in soybean–maize rotational systems. Nine different soybean–maize rotation treatments were laid out in Randomized Complete Block Design (RCBD) with three replications. The study results showed that soybean–maize rotation gave a relatively steady yield compared to the maize mono-cropping system. Soybean–maize rotation improves the productivity of component crops in cropping systems. The highest maize grain yield was recorded from soybean–maize rotation with fertilizer application for the two components (RS + M+) and soybean–maize rotation without fertilizer application for the soybean component (RS-M+), respectively. Soybean grain yield was significantly correlated with OC (%), OM (%), and TN (%), whereas maize yield was adversely correlated with soil parameters, except soil pH. Overall, the knowledge we can contribute to the readers from this study is that soybean–maize rotation plays an important role in achieving sustainable agriculture by increasing soil fertility and achieving stable soybean and maize yields and soybean should be inoculated with Rhizobium strain year after year continuously. Thus, it can be concluded that soybean–maize rotation with fertilizer applications (RS + M+) for two components can be used in maize belt areas of Western Ethiopia.