Comparative analysis of monocropping and mixed cropping systems on selected soil properties, soil organic carbon stocks, and simulated maize yields in drought-hotspot regions of Rwanda

Rainfed agriculture which is the mainstay of the Rwandan economy has been severely affected by prolonged droughts and climate change impacts, resulting in severe food insecurity. In the Eastern Province, the adoption of monocropping (MnC) systems at dissent driven by the CIP may critically worsen the rain-fed agricultural gains against mixed cropping (MxC) systems in drought conditions. Therefore, this study aimed to analyze and compare soil organic carbon (SOC) stocks and simulated maize biomass and grain yields under MnC and MxC systems in Kayonza District, Rwanda. Soil samples (n = 96) were collected in 0–30 and 30–60 cm depths following the stratified simple random sampling technique. The SOC stocks were determined following the guidelines of the FAO of 2018. The biomass and grain yield for the past 20 years (2001–2021) was simulated using a calibrated and validated AquaCrop model (version 6.1) using daily climate data obtained from RMA, and maize crop, raw soil, and land management features collected at the field. The data were analyzed using IBM SPSS software (version 25). The results show that the SOC stocks of MxC soils were significantly (p < 0.001) higher (67.4 ± 1.8 tC ha(−1)) than that of the MnC soils (52.0 ± 3.8 tC ha(−1)). The depths avowed more highly significant (p < 0.001) SOC stocks in topsoils (0–30 cm depth) than that of the subsoils (30–60 cm depth) in the two cropping systems. This indicates that MxC sequesters more carbon and revamps soil C pools than the MnC system. The results also indicate that the simulated biomass and grain yields were highly significantly (p < 0.001) higher more and stable in MxC than in MnC fields for the entire past 20 years. Harnessing these findings, as C pools were monitored and analyzed in this study, N-bio-chemistry dynamics should also be conducted thereby comparing its environmental pools and impacts to both below and above-ground ecotones.