Aims: Rice straw burning is a common practice in northern Iran. Therefore, examining its short-term effects on the physical and chemical properties of paddy soils in northern Iran is critical. The purpose of this study lies in its immediate pre–post fire sampling design, the use of PCA-based minimum data set (MDS) for SQI determination, and the development of a predictive SQI model tailored for paddy soils exposed to residue burning.
Materials & Methods: Soil samples were collected from the top 0–5 cm of burned and unburned paddy fields, after harvest. Several physicochemical indicators were analyzed, including organic Carbon (OC), soil moisture (SM), pH, electrical conductivity (EC), bulk density (BD), cation exchange capacity (CEC), and soil texture. The Soil Quality Index (SQI) was calculated from PCA-selected soil properties.
Findings: Soil properties showed significant changes following rice straw burning. OC and SM decreased sharply by approximately 33% and 34%, respectively, whereas pH and EC increased significantly by 13% and 56% (p < 0.01). These outcomes demonstrate that dynamic soil properties are more sensitive to burning than stable ones.
Conclusion: Burning rice straw impacts the topsoil of paddy fields by decreasing organic Carbon and soil moisture, while increasing pH and electrical conductivity. These changes cause a notable decline in the Soil Quality Index. Sustainable practices such as residue incorporation, composting, mulching, and soil moisture management are recommended to preserve soil health. These findings provide field-based quantitative evidence of the immediate degradation of soil quality caused by rice straw burning.