Geospatial mapping of soil salinity and sodicity: Insights for crop suitability and management in Thanjavur District, Tamil Nadu

Soil characteristics significantly influence the sustainability of agriculture. Physico-chemical characteristics such as pH, electrical conductivity (EC), and exchangeable cations (calcium, magnesium, sodium, and potassium) significantly influence soil salinity. Understanding the spatial distribution of salinity and sodicity is crucial for planning site-specific management strategies, especially in degraded lands. Thanjavur, often called the "Rice Bowl of Tamil Nadu," encounters challenges sustaining agriculture due to its varied soil characteristics. This study examines the spatial distribution of pH, EC and exchangeable cations across various blocks of Thanjavur district to understand their agricultural implications. Analysis reveals significant variability: The mean soil pH varied from slightly acidic (6.63 in Thanjavur) to alkaline (8.01 in Peravurani) and the mean EC ranged from 0.71 dS m-1 in Thanjavur to 8.26 dS m-1 in Sethubavachatram, indicating stark differences in salinity. The mean exchangeable calcium ranged from 6.49 Cmol (p+) kg-1 (Papanasam) to 14.2 Cmol (p+) kg-1 (Sethubavachatram), and mean exchangeable magnesium from 3.91 Cmol (p+) kg-1 (Orathanadu) to 7.67 Cmol (p+) kg-1 (Sethubavachatram). The mean exchangeable sodium levels span from 1.48 Cmol (p+) kg-1 (Thanjavur) to 3.68 Cmol (p+) kg-1 (Sethubavachatram) and mean exchangeable potassium from 0.12 Cmol (p+) kg-1 (Thanjavur) to 0.37 Cmol (p+) kg-1 (Sethubavachatram), Blocks like Sethubavachatram. Peravurani exhibits higher salinity, challenging salt-sensitive crops, while Thanjavur, Thiruppanandal, and Thiruvidaimarudur are better suited for diverse crops. Using geospatial mapping, these findings offer a valuable resource for farmers, agronomists, and policymakers, facilitating targeted interventions for sustainable agricultural development in Thanjavur district.