Analysis of the relationship between the soil index (SI) and vegetation cover index (NDVI) in Al-Mishkhab district using GIS technology for two different seasons

Abstract

Studying the relationship between soil characteristics and vegetation cover using satellite imagery and spatial mapping with Geographic Information Systems (GIS) in the Al-Mishkhab district of Najaf Governorate is an important study addressing the agricultural situation in the region. The study employed a scientific comparison of two distinct years, 1990 and 2024, and two different seasons: the hot season (July) and the cold season (December). It also utilized two spectral indices, SI and NDVI, due to their close correlation in agricultural climatic aspects. The results showed an increase in SI values ​​for the moderately saline category (1990) at 45.4%, followed by the highly saline category at 30.6%. Conversely, salinity values ​​decreased for the latter category (2024) to 25.2%, corresponding to a decrease in NDVI values ​​for the same season, indicating a decline in dense vegetation cover. For the third category, the salinity decreased from 25.9% in 1990 to 13.3% in 2024 due to climate change, rising temperatures, and increased evaporation rates. During the cold season of the 1990 SI index, the highly saline category saw a decrease from 19% in 1990 to 14.6% in 2024. This can be explained by the fluctuations in rainfall and its varying intensity in the last year, which contributed to the leaching of soil salinity and the expansion of dense vegetation cover in the same category from 9.9% in 1990 to 28.4% in 2024. The study also showed a correlation between low-salinity soils and moderate or dense vegetation cover, while the opposite was observed in high-salinity areas with moderate vegetation cover. This correlation is attributed to factors related to the natural and human environment in the district, or to variations in the timing of satellite imagery.