Soil physical quality and organic carbon in agricultural systems of the Dry Chaco: influence of land use intensity and predictive models

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Context The expansion of the agricultural frontier in northwestern Argentina occurred at the expense of deforestation of native forests, particularly in the Dry Chaco. This land-use change alters soil physical properties and soil organic carbon (SOC), compromising sustainability. Aims This study evaluated the impact of land-use change and management on soil physical properties and SOC and developed predictive models for agricultural expansion areas in the Dry Chaco. Methods A total of 113 sites across 14 farms were surveyed. At each site, SOC and soil physical properties [bulk density (BD), macroporosity, and particle size distribution] were measured at 0–10 and 10–20 cm depths, while infiltration was determined at the soil surface. The SOC at equivalent soil mass and a land use intensity index (percentage time with vegetation cover) were calculated. Principal component analysis and linear models explored relationships among variables. Key results The BD increased and SOC decreased after deforestation, at rates of 0.0089 Mg m−3 year−1 and 0.20 g kg−1 year−1, respectively, with stronger trends in soils low in clay and silt. Higher land use intensity was associated with lower compaction and greater SOC. Infiltration declined with increasing BD, with a threshold at 1.40 Mg m−3. Models explained 53–60% of variability in soil properties, using years since deforestation, land use intensity, and texture as predictors. Conclusions This study underscores the value of considering soil texture and land-use history to guide management strategies. Implications The predictive models represent a useful tool to anticipate soil quality evolution in transformed Dry Chaco landscapes.

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