Socioeconomic and agronomic drivers of soil fertility for sustainable soybean–maize rotations among smallholder farmers in Rwanda

Abstract Soil fertility decline and yield variability remain major challenges for smallholder farmers in Sub-Saharan Africa. Yet the influence of socioeconomic and agronomic drivers is not fully understood. This study investigated how farmers’ education, gender, fertilizer use, and cultivation duration affect soil fertility and soybean-maize rotation yields in Rwanda. A survey of 384 farmers was conducted in Nyagatare (Eastern Savanna) and Huye (Central Plateau) districts using a semi-structured questionnaire and field measurements. Data covered demographics, fertilizer application practices, cultivation duration, soil properties, and crop yields. Low adoption of fertilizer use was observed among the farmers, whereby less than 40% of farmers reported using inorganic fertilizer. In Nyagatare, female participation was positively associated with soil available phosphorus (+ 1.136 mg kg − 1 , 95% CI: 0.003–2.269). In Huye, extended cultivation (10–20 years) increased bulk density but reduced total nitrogen (-0.051-0.041%). Long-term cultivation (20–30 years) in Nyagatare increased soybean yields by 196.8-324.7 kg ha − 1 . Application of FYM consistently enhanced soybean and maize yields across both sites. These findings suggest that farmer characteristics and management practices shape soil fertility outcomes and crop performance in rotational systems. Strengthening education, promoting gender equity, and encouraging integrated nutrient management could support sustainable productivity gains among smallholder farmers in Rwanda.