COMPARATIVE ANALYSIS OF SOIL ORGANIC CARBON STOCKS, SIMULATED MAIZE BIOMASS AND FARMERS’ PERCEPTIONS ON MONO-CROPPING AND MIXED CROPPING SYSTEMS KAYONZA DISTRICT, RWANDA

Abstract

Rain-fed agrarian reported as the backbone of the Rwandan economy has been severely affected by prolonged droughts and climate change impacts, resulting in severe food insecurity. In the Eastern Province, adoption of mono-cropping (MnC) system at dissent driven by the CIP may critically worsen the rain-fed agricultural gains against of mixed cropping (MxC) systems in drought conditions. Therefore, this study aimed to analyze and compare SOC stocks, simulated maize biomass and grain yields and farmers’ perceptions of 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 yields for past 20 years (2001-2021) were 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 calibration and validation were performed using measured and observed maize grain yields for past 20 years (2001‒2021) obtain from RAB and NISR respectively, and raw soil data collected through the soil profile study in the study area. The farmers’ perceptions were assessed using both Likert-scale questionnaires, focus group discussions (FGDs), and in-depth group interviews (IDGIs). The mixture of purposive and multi-stage random sampling technique was used for selecting sample households (n=196). The data were analyzed using IBM SPSS software (version 20). Thematic content analysis method and Pearson correlations were used for analysis of farmers’ thoughts. Binomial logit model was used to determine the effect of the selected determinants on the adoption of MxC, and otherwise, MnC systems. The results of soil properties 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 highly significant (p<0.001) SOC stocks in topsoil (0-30cm depth) than that of the subsoil (30-60 cm depth) in the two cropping systems. This indicates that MxC sequesters more carbon and revamp soil C pools than MnC system. The results also indicate that the simulated biomass and grain yields were highly significantly (p<0.001) higher and stable in MxC than in MnC fields for the entire past 20 years. The results also show that the majority of the respondents were more involved in MxC during the agricultural season B than in MnC. Further, the results show that the household head’s sex, distance to the market, and access to climate and weather information were positively significantly (p<0.05) linked to the farmers’ adoption of MxC in spite of MnC. Hence, this study’s findings indicated that MxC were more socio-economically and ecologically beneficial to farmers than MnC under drought conditions as they were majorly chosen and adopted while having substantial C sequestration potentials. Harnessing this, the indigenous MxC system should modernized and altered into intercropping systems for better aesthetics and nutrient use efficiency while meeting the wants of smallholders, planners and policy-makers.