Abstract
Soil salinization and sodification are types of degradation due to salt
accumulation in the soil. They develop in all climatic zones but are
prevalent in arid and semi-arid areas. Assessment of their true
occurrence is challenging owing to inadequate consideration of their
evolution, lack of harmonization steps, and omission of diagnostic soil
properties in the assessment. This paper developed a new assessment
protocol using combined application of time-series diagnostic soil
indicators, remote sensing, and environmental variables related to the
occurrence of soil salts. The protocol focuses on standardization of the
soil indicators, digital soil mapping, and application of classification
schemes to identify levels of salt accumulation in the soil. It was
tested in Lesotho, Afghanistan, and Sudan using measured soil electrical
conductivity, pH, and exchangeable sodium percent, and covariates such
as relief, remote sensing indicators of soil salinity, climate,
hydrogeology, and land cover between 2001 and 2018. It was able to
identify different types of salt-affected soils and levels of salt
accumulation with over 80% accuracy on holdout samples. It identified
emerging subsoil (30-100 cm) salt problems in agricultural areas in
Lesotho, advancing topsoil (0-30 cm) salinization and subsoil
sodification in agricultural areas in Sudan, and salinization of saline
topsoils in Afghanistan. It also established important environmental
covariates which can be used in periodic monitoring of salt accumulation
in the soil. We recommend its wide application in different temporal and
spatial scales to improve its performance in identifying salt
accumulation in agricultural areas