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Conservation agriculture (CA), combining reduced or no tillage, permanent soil cover, and improved rotations, is often promoted as a climate-smart practice. However, our understanding of the impact of CA and its respective three principles on top- and subsoil organic carbon stocks in the low-input cropping systems of sub-Saharan Africa is rather limited. This study was conducted at two long-term experimental sites established in Zimbabwe in 2013. The soil types were abruptic Lixisols at Domboshava Training Centre (DTC) and xanthic Ferralsol at the University of Zimbabwe farm (UZF). The following six treatments, which were replicated four times, were investigated: conventional tillage (CT), conventional tillage with rotation (CTR), no tillage (NT), no tillage with mulch (NTM), no tillage with rotation (NTR), and no tillage with mulch and rotation (NTMR). Maize (Zea mays L.) was the main crop, and treatments with rotation included cowpea (Vigna unguiculata L. Walp.). The soil organic carbon (SOC) concentration and soil bulk density were determined for samples taken from depths of 0–5, 5–10, 10–15, 15–20, 20–30, 30–40, 40–50, 50–75 and 75–100 cm. Cumulative organic inputs to the soil were also estimated for all treatments. SOC stocks at equivalent soil mass were significantly (p<0.05) higher in the NTM, NTR and NTMR treatments compared with the NT and CT treatments in the top 5 cm and top 10 cm layers at UZF, while SOC stocks were only significantly higher in the NTM and NTMR treatments compared with the NT and CT treatments in the top 5 cm at DTC. NT alone had a slightly negative impact on the top SOC stocks. Cumulative SOC stocks were not significantly different between treatments when considering the whole 100 cm soil profile. Our results show the overarching role of crop residue mulching in CA cropping systems with respect to enhancing SOC stocks but also that this effect is limited to the topsoil. The highest cumulative organic carbon inputs to the soil were obser

The biogeochemical effects of conservation agriculture (CA), such as soil organic carbon storage and greenhouse gas emissions, have been extensively studied. However, recent research has shown that management practices also have biogeophysical effects on both local and global climates by altering surface albedo and energy partitioning. We assessed the biogeophysical impacts of CA in maize fields during two successive seasons (2021/22-2022/23) at two long-term experimental sites in Zimbabwe with contrasting soil properties: Domboshawa Training Center (DTC) with a light abruptic Lixisol (sandy soil) and the University of Zimbabwe Farm (UZF) with a dark xanthic Ferralsol (clayey soil). We monitored surface albedo, longwave radiation, leaf area index (LAI), and soil moisture/temperature under three treatments: conventional tillage (CT), notillage (NT), and no-tillage with mulch (NTM). Our findings reveal that, across all treatments during the two monitored seasons, the average surface albedo of the xanthic Ferralsol at UZF was consistently lower than that of the abruptic Lixisol at DTC. It results a cooling effect in both NT and NTM treatments compared to CT in the clayey soil at UZF. During the 2021/22 season, the mean annual radiative forcing (RF) of NT and NTM were -0.83 W.m-² and -0.43 W.m-2 respectively, while during the second season (2022/23) the annual mean RF was -1.43 W.m-2 for NT and -1.03 W.m-2 for NTM.On the sandy soil at DTC, a warming effect was observed due to soil darkening induced by mulching. The mean annual RF of NT in this site was -3.34 W.m-2 during the first season and -2.78 W.m-2 during the second. In contrast, NTM showed a warming effect with an RF of 1.2 W.m-2 in 2021/22, and 2.77 W.m-2 during the 2022/23 season. The RF induced by albedo change were converted into CO2-equivalents in order to compare it with biogeochemical effects of CA through changes in soil N2O emissions and SOC storage. The results demonstrated an opposite effect on RF and o

Introduction - Climate impacts of agricultural management practices such as mulching and no-tillage are usually evaluated with regard to soil organic carbon stock changes or greenhouse emissions. However, albedo effects of these practices that have been found to be of similar importance for climate change mitigation are usually ignored in this kind of assessment. This is even true for agricultural systems in Africa, which are less studied than temperate systems. In this study, we aim to assess the effect of land management on albedo dynamics and Radiative Forcing (i.e. climatic impact) in two long-term experiments established in Zimbabwe in 2013 with contrasting soil types. The Radiative Forcing (RF), is a metric used to quantify the change in Earth energy budget (radiation absorbed and emitted by the Earth) relative to an assumed default state (Betts 2000; Forster et al. 2007). The albedo of a cropland depends on soil properties, surface rugosity, soil moisture and coverage by plant litter, but also on plant density, phenology, architecture and spectral properties. Note that the latter may change for instance with phenology. The RFs resulting from land management changes are determined by their effects on the surface albedo dynamics but also by the solar radiation and atmospheric transmittance dynamics. Using a soil-crop model such as STICS coupled with a spatialization method that allows to represent changes in vegetation and soil properties is a promising solution to upscale RF related to albedo effects associated to land management changes at regional to global scales. 1. Modelling albedo using STICS Surface albedo is the fraction of solar radiation reflected by Earth surface back to the space. Currently, STICS estimates surface albedo as a function of soil and vegetation albedo (Brisson et al., 2008). Soil albedo is a function of soil colour and moisture and also depends on the presence of mulch at the surface. Current formalism considers total leaf area index