Abstract
Soil salinization is the widespread problem seriously affecting the agricultural sustainability and causing income losses in arid regions. The major objective of the study was to quantify and map the spatial variability of soil salinity and sodicity. Determining salinity and sodicity variability in different soil layers was the second objective. Finally, proposing an approach for delineating different salinity and sodicity zones was the third objective. The study was carried out in 871.1 ha farmland in Southeast of Dushak town of Ahal Province, Turkmenistan. Soil properties, including electrical conductivity (EC), soil reaction (pH), sodium adsorption ratio (SAR), calcium carbonate and particle size distribution (clay, silt and sand fractions) in 0–30, 30–60, 60–90 and 90–120 cm soil layers were recorded. The EC values in different soil layers indicated serious soil salinization problem in the study area. The mean EC values in 0–90 cm depth were high (8 dS m-1), classifying the soils as moderate to strongly saline. Spatial dependence calculated by the nugget to sill ratio indicated a strong spatial autocorrelation. The elevation was the primary factor affecting spatial variation of soil salinity in the study area. The reclamation of the field can be planned based on three distinct areas, i.e., high (≥12 dS m-1), moderate (12–8 dS m-1) and low (<8 dS m-1) EC values. The spatial trend analyses of SAR values revealed similar patterns for EC and pH; both of which gradually decreased from north to the south-west. The amount of water needed to leach down the salts from 60 cm of soil profile is between 56.4–150.0 ton ha-1 and the average leaching water was 89.8 tons ha-1. The application of leaching water based on the amount of average leaching water will result in higher or lower leaching water application to most locations and the efficiency of the reclamation efforts will be low. Similar results were recorded for sulfur, sulfuric acid and gypsum requirements to remediate sodicity. The results concluded that the best management strategy in planning land development and reclamation schemes for saline and sodic soils require accurate information about the spatial distribution of salinity and sodicity across the target area.
Highlights
Soil salinity is the most widespread soil degradation processes mainly in the arid and semiarid regions of the world
The descriptive statistics for some of soil properties in all soil layers are given in Tables 2 and 3
Soil salinity and sodicity indicated by electrical conductivity (EC) and sodium adsorption ratio (SAR) values indicated high salinity and sodicity with strong variability in each soil layer (Table 3)
Summary
Soil salinity is the most widespread soil degradation processes mainly in the arid and semiarid regions of the world. Reclamation of saline-sodic soils rates compared to precipitation, characteristics of soil and topography that impede water drainage and cause salt accumulation in the soil profile [1]. Salinity restricts production of arable lands, causing degradation globally of 0.3–1.5 million hectare year−1 [2] and >50% of arable lands of the world may be affected by the salt accumulation until 2050 [3,4]. Salt and sodium-affected lands should be used in agricultural production to meet the demands of increasing global population for food and fiber [5]. Productivity function of salt and sodium-affected soils should be improved to extend the coverage area of arable lands. Assessing salinity and sodicity distribution is a prerequisite to identify the problem areas and develop appropriate management practices [9]
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