Investigation of parameters affecting soil quality under saline and semi-saline conditions (case study of south and southwest of Khuzestan province)

Low rainfall, lack of irrigation water of good quality, high water level and high annual evaporation in the southwestern region of Khuzestan, has led to the emergence of saline soils. Various environmental factors, such as low production of soil organic matter, high salt content, high concentration of sodium ions, high pH and quality and depth of groundwater, have significant effects on the qualitative indicators of saline soils in arid and semi-arid regions. Soil quality indicates the ability of the soil to provide biological services to living organisms. These services include food production, water treatment, pollution absorption, carbon dioxide absorption, and the production of a variety of medicinal and industrial plants. Soil quality is an important indicator of agricultural and environmental sustainability and is used to assess soil quality. Each soil quality index must have biological characteristics, be sensitive to environmental and managerial changes, and be effective in measuring measurable and quantitative processing. The present study was conducted to determine the soil quality index in a part of the southwestern lands of Khuzestan province with three land use of agriculture and industry, traditional agriculture and barren lands in a part of the southwestern region of Khuzestan province. In this study, using systematic networking method as well as the characteristics of the study area, a total of 180 soil samples were selected and 22 physical, chemical and biological parameters were determined in each sample. The parameters studied in this study were: electrical conductivity, pH, ions such as sodium, calcium, magnesium, chlorine, bicarbonate, sulfate, SAR, CEC, exchangeable potassium, ozone-absorbable phosphorus, percentage of organic matter, activated carbon, Percentage of clay, silt and sand, average soil diameter, water permeability coefficient in saturated state, specific apparent weight and surface soil hardness. After the laboratory results were determined, using statistical method of factor analysis (FA) and principal component analysis (PCA) in SPSS statistical software, among all the characteristics affecting soil quality (TDS), five characteristics of electrical conductivity, sodium concentration, Chlorine, sulfate, and SAR were identified as the most important characteristics affecting soil quality (MDS). The selection of these factors as MDS indicates the high impact of soluble salts and the low depth of ground water on soil quality indicators of the study area, so that the accumulation of salts on the surface and depth of soil, mainly affects soil quality. To evaluate the lands, two models of cumulative soil quality index (IQI) and Nemro quality index (NQI) were used in two sets of MDS and TDS. Then, in order to compare the performance of soil quality index methods, common methods of secondary root and maximum limitation were used. The results showed that in general, the lands of the region were at different levels in terms of soil quality indicators and land suitability assessment methods, so that the lands of cultivation and industry showed maximum quality, lands under traditional cultivation with medium quality and barren lands showed minimum quality. The Kappa coefficient calculated between the Cumulative Soil Quality Index (IQITDS) and the second and maximum rootstock methods was 0.83 and 0.37, respectively, indicating a high and moderate level of coordination between the data obtained from the various methods tested. The calculated correlation between the results obtained from IQITDS and IQIMDS is equal to 88.43% and also between the results of NQITDS and NQIMDS is equal to 80.59%, which are statistically significant. This suggests that a well-prepared MDS set can be used to represent the TDS set. Therefore, MDS can be used instead of TDS to reduce the time and cost of implementing similar research projects. The results of this study show that soil leaching and leaching of salts from the surface and depth of soil profiles, especially in barren lands and under traditional agriculture has been observed and this is the main cause of differences between these lands and lands under agricultural management and industry. In cultivation and industrial lands, due to leveling, drainage and leaching, additional salts have been washed from the soil profile as much as possible and the conditions for plant growth have been provided. It seems continuity of agricultural and industrial land management, especially in the field of adding low-consumption elements, organic matter and improving physical properties, should be done in such a way that soil quality indicators are closer to the optimal range.