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Soil nutrients form an important part of agro-ecosystems in various landscapes, including mountainous areas. Most foothills in tropical mountains are heterogeneous in terms of the accumulation of soil nutrients due climatic location and ecological endowments. Since most mountain foothills have potential for the provision of environmental services, it is imperative to assess the salient soil nutrients including carbon in order to determine the amount. This study assessed the accumulation of soil organic carbon (SOC) in the relatively undisturbed foothills of Uluguru Mountains whose geology indicates that they were formed during cretaceous age (i.e. ≈50 million years ago). The study also determined the trends of rainfall and temperature because these elements of climate have important influence on carbon accumulation. In conducting this study, we sampled Kiroka Village (in Kiroka Ward) because it is found at the foothills of the Uluguru Mountain and most of its parts are relatively undisturbed. In this place, sixteen soil sampling points were established within one hectare and these points involved two soil depths (i.e. 0-20 cm and 20-40 cm) and two locations (i.e. lowland and upland). The Walkley–Black Method was used for SOC analysis while Mann–Kendall Test was employed for climate data analysis. The results exhibit that there have been significant variations in SOC accumulation under the two soil depths and locations. In the lowland areas, SOC was 1.1 and 0.43 MgC ha−1 for the depths 0–20 cm and 20–40, respectively. Besides, in upland areas, SOC was 0.38 and 0.31 MgC ha−1 for the depths 0–20 cm and 20–40, respectively. Most cereal crops require a considerable amount of SOC in the soil that ranges between 0.5 and 2 MgC ha−1. Additionally, the mean annual rainfall and temperature patterns from 1980 to 2020 declined and intensified at R2 = 0.15 and 0.19, respectively. Therefore, these results inform environmental experts, climate practitioners and other relevant stakeholders to endorse suitable and sustainable environmental management methods in the mountainous areas. [ABSTRACT FROM AUTHOR]

Unsustainable agricultural practices deplete soil organic carbon (SOC), affecting ecosystem services, land productivity, soil health, and water quality. This study evaluated the long‐term effects of row crop (RC), agroforestry buffers (AB), grass buffers (GB), and grassed waterways (GWW) on SOC. Agroforestry buffers (grass and tree) and grass buffer treatments were established in 1997 on a corn (Zea Mays L.)–soybean (Glycine Max [L]. Merr.) rotation. Grid soil samples from 86 locations were collected in 10 transects to determine SOC at 0–10 and 10–20 cm depths. The general linear model and the generalized linear mixed model were conducted to evaluate treatment, landscape, soil depth, and series effects on SOC. Kriging interpolation was used to visualize the temporal and spatial change of SOC in the watersheds, comparing samples collected in 2000 and 1994 with samples collected in 2020. The mean SOC percentage (SOC%) in the top 10 cm depth for the RC, AB, GB, and GWW areas was 1.94, 2.19, 2.41, and 2.51%, respectively (ρ <.001). The soil depth was significant (ρ <.001) between samples from 0–10 cm and 10–20 cm. The mean SOC% among soil series showed no significant differences at the studied depths. The mean SOC% of 0–10 cm for RC, AB, and GWW were 1.85, 1.88, and 2.30% in 2000 and 1.94, 2.19, and 2.51% in 2020. The foot‐slope position had the highest (2.41%) and the summit position had the lowest SOC (2.02%) percentages. The SOC% in the RC treatment from 0–10 cm at the summit, backslope, and foot slope positions were ranked 1.83 < 2.22 < 2.31%, respectively. Perennial vegetation and undisturbed land management practices increased SOC compared with the RC areas. Core Ideas: Sequestration of carbon in soils under grass and agroforestry buffers was evaluated after 23 yr of implementation.Agroforestry and grass buffers increased the soil organic carbon among watersheds and treatments.This study indicates the importance of agroforestry buffers on carbon sequestration, leading to healthier soils and mitigate climate change.Soil depth and landscape positions are important factors affecting C distribution in soils. [ABSTRACT FROM AUTHOR]