Assessment of agricultural soil sustainability using selected spectral indices: an applied study in Al-Saqi Farm – Western Desert of Karbala Governorate, Iraq

Abstract

This study aimed to evaluate agricultural soil sustainability in arid environments using a set of advanced spectral indices, namely the Normalized Difference Vegetation Index (NDVI), Green Normalized Difference Vegetation Index (GNDVI), and Optimized Soil-Adjusted Vegetation Index (OSAVI), based on Sentinel-2 satellite data processed within the Google Earth Engine platform. The study was conducted at Al-Saqi Farm located in the western desert of Karbala Governorate, using (50) field observation points. The results showed that NDVI values ranged from (-0.041 to 0.135), GNDVI values ranged from (-0.114 to 0.269), and OSAVI values ranged from (-0.036 to 0.113), reflecting the dominance of sparse vegetation cover and bare soil conditions. Spatial analysis revealed that bare lands constituted (63.95%) according to NDVI, (80.52%) under severe stress conditions according to GNDVI, and (83.50%) as barren lands based on OSAVI. Statistical analysis indicated a very strong correlation among the indices (r = 0.86–0.89, p < 0.01), demonstrating their integrative capability in characterizing environmental conditions. Furthermore, the composite sustainability index (SI) results showed that more than (80%) of the study area falls within the low sustainability category. The findings confirm that spectral indices represent an effective tool for assessing soil sustainability in arid environments and can be reliably utilized to support sustainable agricultural management decisions.