Assessing soil organic carbon responses to tillage and extreme weather in pakistan using the CQESTR model

Authors: ZAHID, ADNAN - University Of The Punjab; Gollany, Hero; ALI, SAJID - University Of The Punjab; IQBAL, NADEEM - Rice Research Institute

Submitted to: Soil and Tillage Research
Publication Type: Review Article
Publication Acceptance Date: 12/28/2025
Publication Date: 1/24/2026
Citation: Zahid, A., Gollany, H.T., Ali, S., Iqbql, N. 2026. Assessing soil organic carbon responses to tillage and extreme weather in pakistan using the CQESTR model. Soil and Tillage Research. 259. Article 107047. https://doi.org/10.1016/j.still.2025.107047.
DOI: https://doi.org/10.1016/j.still.2025.107047

Interpretive Summary: Intensive tillage has depleted organic carbon soil (SOC) and threatened the sustainability of the rice-wheat cropping system of South Asia. This study assessed SOC dynamics using the CQESTR model, a process-based model, to identify the best management option under five tillage and extreme weather scenarios: (i) conventional tillage (S-1), (ii) residue incorporation (S-2), (iii) direct seeding with straws removed (S-3), (iv) direct seeding with rice straw returned while wheat straw removed (S-4), and (v) conservation tillage with both rice and wheat residues retained (S-5). Five yield scenarios (i.e., current yield, 5 or 10 % decrease/increase) were simulated with three extreme weather scenarios. The CQESTR-simulated and the measured values were strongly correlated (r = 0.99) across different tillage scenarios. Nash–Sutcliffe efficiency of 0.99 confirmed simulated and measured values were well correlated. Among the tillage scenarios, the highest SOC gain was recorded under the continuous conservation tillage with total residue returned (S-5 scenario), followed by S-4, S-3, and S-2, respectively. In contrast, conventional tillage (S-1) was predicted to lose under predictive periods of 2019-2038. The conservation tillage with residues retained (S-5) sequestered SOC, while S-1 depleted SOC across all scenarios. The S-5 had a maximum SOC increase at 110% yield with baseline weather during 20 predictive years. Therefore, continuous conservation tillage with total residue returned) can potentially reduce the effects of extreme weather while increasing SOC and enhancing the region's sustainability.

Technical Abstract: Intensive tillage has depleted organic carbon soil (SOC) and threatened the sustainability of the rice-wheat cropping system of South Asia. This study assessed SOC dynamics using the CQESTR model, a process-based model, to identify the best management option under five tillage and extreme weather scenarios:(i) conventional tillage (S-1), (ii) residue incorporation (S-2), (iii) direct seeding with straws removed (S-3), (iv) direct seeding with rice straw returned while wheat straw removed (S-4), and (v) conservation tillage with both rice and wheat residues retained (S-5). Five yield scenarios (i.e., current yield, 5 or 10 % decrease/increase) were simulated with three extreme weather scenarios. The CQESTR-simulated and the measured values were strongly correlated (r = 0.991, p < 0.001) for the 0–45 cm soil depth across different tillage scenarios. Nash–Sutcliffe efficiency (NSE) of 0.99, a root means square error (RMSE) of 0.36, and a mean square deviation (MSD) of 0.13 confirmed simulated and measured values were well correlated. Among the tillage scenarios, the highest SOC gain of 1.84 Mg/ha/year was recorded under the S-5 scenario, followed by 0.24, 0.21, and 0.21 Mg/ha/year under S-4, S-3, and S-2, respectively. In contrast, conventional tillage (S-1) was predicted to lose 0.49 Mg/ha under predictive periods of 2019-2038. The conservation tillage with residues retained (S-5) sequestered SOC, while S-1 depleted SOC across all scenarios. The S-5 had a maximum SOC increase of 3.0 Mg/ha at 110% yield and 2.6 Mg/ha with baseline weather under RCP 4.5 during 20 predictive years. Therefore, continuous conservation tillage with total residue returned (S-5) can potentially reduce the effects of extreme weather while increasing SOC and enhancing the region's sustainability.