Soil organic carbon and nitrogen stocks and isotopic signatures under contrasting integrated crop-ivestock systems in sub-humid Zimbabwe
Abstract
Soil organic carbon (SOC) and soil total nitrogen (STN) are critical indicators of soil health and vital sinks in agroecosystems. However, knowledge gaps remain regarding how long-term crop-livestock integration impacts coupled SOC and STN stocks on commercial versus communal smallholder farms in Africa. This study quantified whole profile SOC and STN stocks under two land-use types (croplands and grazing lands) and two livestock management facilities (congregation points and corrals), across two adjacent, distinct mixed crop-livestock farming systems, while evaluating how these land uses influence δ13C and δ15N isotopic signatures. A commercial farm and an adjacent communal smallholder farm with similar soil types were selected. Soil samples were collected from six depth increments (0–5, 5–10, 10–20, 20–40, 40–70, 70–100 cm) to determine profile-wide SOC and STN stocks alongside their δ13C and δ15N signatures. Land-use and management type impacted SOC and STN stocks more significantly in the communal system (p < 0.001) than on the commercial farm (p < 0.05). On the commercial farm, whole-profile SOC (Mg C ha−1 ± SE) and STN (Mg N ha−1 ± SE) stocks peaked in grazing lands (129.7 ± 12.8; 10.32 ± 1.14) and reached minimums at livestock congregation points (68.1 ± 2.7; 7.04 ± 1.16). Conversely, in the communal smallholder system, both stocks peaked sharply at livestock congregation points (150.0 ± 4.6; 12.26 ± 0.27) and were lowest in croplands (56.5 ± 1.5; 5.20 ± 0.20). Deep subsoil layers (40–100 cm) stored a greater relative proportion of total stocks on the commercial farm (36%–43% SOC; 39%–45% STN) than on the smallholder farm (28%–39% SOC; 29%–39% STN). Soil δ15N values increased with depth across all land-use and management types. Lower δ15N values in commercial croplands compared with smallholder croplands likely reflect higher synthetic fertilizer use, while the highest δ15N values occurred in cattle corrals. Contrary to typical microbial fractionation—where preferential loss of 12C during respiration enriches δ13C at depth—no consistent vertical increase in δ13C was observed; all land-use types were enriched, averaging −17‰. Our results demonstrate that, within the narrow range of soil textures evaluated, land-use and management serve as the primary determinants of SOC and STN stocks and their isotopic signatures. While livestock congregation points create intense, localized nutrient hotspots, their small spatial extent limits their landscape-scale sequestration. Consequently, adopting conservation practices in commercial croplands as a proactive intervention, and optimizing the management of extensive communal grazing lands and croplands are collectively essential for enhancing regional biogeochemical storage and ecosystem resilience.
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BibTeX
@article{masunungure2026soil,
title = {{Soil organic carbon and nitrogen stocks and isotopic signatures under contrasting integrated crop-ivestock systems in sub-humid Zimbabwe}},
author = {Premrose Masunungure and Armwell Shumba and Rémi Cardinael and Marc Corbeels and Vimbayi Grace Petrova Chimonyo and Santiago Lopez Ridaura and Gatien Falconnier and Tesfaye Shiferaw Sida and François Affholder and Sieglinde S. Snapp and Régis Chikowo},
journal = {Soil Use and Management},
year = {2026},
month = oct,
doi = {10.1111/sum.70315},
url = {https://hal.science/hal-05840286v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Soil organic carbon and nitrogen stocks and isotopic signatures under contrasting integrated crop-ivestock systems in sub-humid Zimbabwe
AU - Premrose Masunungure
AU - Armwell Shumba
AU - Rémi Cardinael
AU - Marc Corbeels
AU - Vimbayi Grace Petrova Chimonyo
AU - Santiago Lopez Ridaura
AU - Gatien Falconnier
AU - Tesfaye Shiferaw Sida
AU - François Affholder
AU - Sieglinde S. Snapp
AU - Régis Chikowo
PY - 2026
DA - 2026/10/16
JO - Soil Use and Management
DO - 10.1111/sum.70315
UR - https://hal.science/hal-05840286v1
AB - Soil organic carbon (SOC) and soil total nitrogen (STN) are critical indicators of soil health and vital sinks in agroecosystems. However, knowledge gaps remain regarding how long-term crop-livestock integration impacts coupled SOC and STN stocks on commercial versus communal smallholder farms in Africa. This study quantified whole profile SOC and STN stocks under two land-use types (croplands and grazing lands) and two livestock management facilities (congregation points and corrals), across two adjacent, distinct mixed crop-livestock farming systems, while evaluating how these land uses influence δ13C and δ15N isotopic signatures. A commercial farm and an adjacent communal smallholder farm with similar soil types were selected. Soil samples were collected from six depth increments (0–5, 5–10, 10–20, 20–40, 40–70, 70–100 cm) to determine profile-wide SOC and STN stocks alongside their δ13C and δ15N signatures. Land-use and management type impacted SOC and STN stocks more significantly in the communal system (p < 0.001) than on the commercial farm (p < 0.05). On the commercial farm, whole-profile SOC (Mg C ha−1 ± SE) and STN (Mg N ha−1 ± SE) stocks peaked in grazing lands (129.7 ± 12.8; 10.32 ± 1.14) and reached minimums at livestock congregation points (68.1 ± 2.7; 7.04 ± 1.16). Conversely, in the communal smallholder system, both stocks peaked sharply at livestock congregation points (150.0 ± 4.6; 12.26 ± 0.27) and were lowest in croplands (56.5 ± 1.5; 5.20 ± 0.20). Deep subsoil layers (40–100 cm) stored a greater relative proportion of total stocks on the commercial farm (36%–43% SOC; 39%–45% STN) than on the smallholder farm (28%–39% SOC; 29%–39% STN). Soil δ15N values increased with depth across all land-use and management types. Lower δ15N values in commercial croplands compared with smallholder croplands likely reflect higher synthetic fertilizer use, while the highest δ15N values occurred in cattle corrals. Contrary to typical microbial fractionation—where preferential loss of 12C during respiration enriches δ13C at depth—no consistent vertical increase in δ13C was observed; all land-use types were enriched, averaging −17‰. Our results demonstrate that, within the narrow range of soil textures evaluated, land-use and management serve as the primary determinants of SOC and STN stocks and their isotopic signatures. While livestock congregation points create intense, localized nutrient hotspots, their small spatial extent limits their landscape-scale sequestration. Consequently, adopting conservation practices in commercial croplands as a proactive intervention, and optimizing the management of extensive communal grazing lands and croplands are collectively essential for enhancing regional biogeochemical storage and ecosystem resilience.
SN - 0266-0032
SN - 1475-2743
ER -