Temporal dynamics of soil organic carbon and salinity in irrigated wheat croplands of southwest Iran (2011-2021)

Document Type : Original Article

Authors

1 Associate Professor, Soil and Water Research Department, Khuzestan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Ahvaz, Iran

2 Assistant Professor, Soil and Water Research Department, Khuzestan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Ahvaz, Iran

Abstract

Soil degradation poses a major threat to global food security, particularly in arid and semi-arid regions where intensive agriculture, climate variability, and unsustainable land management practices accelerate the loss of soil health. Among the most pressing challenges are the decline in soil organic carbon (SOC)—a key indicator of soil fertility—and the accumulation of salinity, which together compromise agricultural productivity and ecosystem resilience. This comprehensive study examined decadal changes (2011-2022) in key soil quality indicators across wheat-cultivated lands of Khuzestan Province, Iran's primary wheat belt. Utilizing a systematic sampling approach, we analyzed 254 and 718 representative soil samples respectively collected during 2011 and 2022, assessing electrical conductivity (EC), SOC content through standardized laboratory protocols. Our findings reveal alarming degradation trends: mean SOC levels declined significantly from 0.76 to 0.67% (p < 0.01), accompanied by a 13% expansion of carbon-deficient areas (SOC < 1%). Concurrently, salinity levels showed more dramatic increases, with mean EC rising from 4.59 to 7.76 dS m-1 (p < 0.01), representing a 69% surge in soil salinity and 23% expansion of salt-affected lands (EC > 4 dS m-1). The relationship between SOC and EC exhibited a threshold-dependent pattern: positive correlations (r = 0.173 for EC < 4 dS m-1; r = 0.045 for 4–8 dS m-1) reversed under higher salinity (r = -0.122 for 8–12 dS m-1; r = -0.148 for EC > 12 dS m-1). Therfore, The overall weak positive trend between EC and SOC (r = 0.106) is likely driven by the predominance of low-salinity samples (76% of the dataset, EC < 8 dS m⁻¹). These trends reflect the cumulative impacts of intensive cropping, inadequate organic amendments, and improper irrigation management over the study period. The documented 11.8% SOC decline and near doubling of salinity levels have substantially degraded the soil resource in this vital food production region, with direct implications for wheat yield potential and long-term agricultural sustainability. Our results underscore the urgent need for adopting threshold-specific management strategies to reverse these damaging trends.

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References

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Dryland Soil Research (DLSR)
Volume 1, Issue 2
December 2024
Pages 67-75

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