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The potential of the soil to hold plant nutrients is governed by the cation-exchange capacity (CEC) of any soil. Estimating soil CEC aids in conventional soil management practices to replenish the soil solution that supports plant growth. In this study, a multiple model integration scheme supervised with a hybrid genetic algorithm-neural network (MM-GANN) was developed and employed to predict the accuracy of soil CEC in Tabriz plain, an arid region of Iran. The standalone models (i.e., artificial neural network (ANN) and extreme learning machine (ELM)) were implemented for incorporation into the MM-GANN. In addition, it was tested to enhance the prediction accuracy of the standalone models. The soil parameters such as clay, silt, pH, carbonate calcium equivalent (CCE), and soil organic matter (OM) were used as model inputs to predict soil CEC. With the use of several evaluation criteria, the results showed that the MM-GANN model involving the predictions of ELM and ANN models calibrated by considering all the soil parameters (e.g., Clay, OM, pH, silt, and CCE) as inputs provided superior soil CEC estimates with a Nash Sutcliffe Efficiency (NSE) = 0.87, Root Mean Square Error (RMSE) = 2.885, Mean Absolute Error (MAE) = 2.249, Mean Absolute Percentage Error (MAPE) = 12.072, and coefficient of determination (R2) = 0.884. The proposed MM-GANN model is a reliable intelligence-based approach for the assessment of soil quality parameters intended for sustainability and management prospects. [ABSTRACT FROM AUTHOR]

• Using in-situ measurements, size fractionation from soil to sediment was investigated for numerous calcareous soils. • The 0.2 mm was suggested as the boundary between high and low erodible fractions of calcareous soils. • Size range of 0.063–0.2 mm was found as the most susceptible fraction to wind erosion. • Soil fraction of 0.063–0.1 mm intensified calcareous soil potential for suspension-size sediment generation. • Critical values of various soil PSD criteria for wind erosion rate of calcareous soils were suggested. Soil texture and soil surface aggregate size distribution (ASD) are key factors to study soil erodibility by wind and sediment size distribution (SSD) in arid and semi-arid areas. However, less research has studied the effect of soil fractions on soil erodibility and wind-blown sediment size of calcareous soils. In the present study, we focused on the size fractionation and particle size distribution (PSD) of 60 calcareous soil samples collected from 20 semi-arid and arid areas in Fars province, southern Iran. Extensive in-situ wind tunnel experiments were conducted under controlled high wind speed to measure wind erosion rate (WER) and SSD. The results showed that the calcareous soils had different erodibility based on their PSD. Generally, the most erodible soils to the wind force were those with less than 10 % of clay and higher frequency of the 0.1–0.2 mm size class. However, when the soil clay content exceeds 20 %, ASD got dominated with the fraction of 0.4–0.8 mm and WER of the calcareous soils got limited. Besides, size range of 0.063–0.2 mm was suggested as the most wind erodible fraction of the calcareous soils. Furthermore, the mean weight diameter (MWD) of sediment particles averagely reduced 1.3 times as compared to that of the soil samples and WER got inhibited for regions in which the difference of soil and sediment MWD exceeded 0.05 mm. The SSD was significantly controlled by soil PSD and suspension-size sediments < 0.1 mm (SSS) were negatively proportional to soil clay, MWD, geometric mean diameter of soil particles (GMD), dry stable aggregates > 0.25 mm (DSA), and organic carbon as logarithmic equations. Moreover, the presence of the size fractions > 0.2 mm restricted the potential of calcareous soils to generate SSS, which would be quite beneficial for wind erosion combat and dust control of calcareous soils. [ABSTRACT FROM AUTHOR]

Understanding spatial variations of soil properties is necessary for the management of rangelands vegetation ecosystem. The present study aimed to assess the spatial variations of soil properties in the hillslope of the Taftan semi-active volcanic mountain, Sistan and Baluchestan Province, south-eastern Iran. The locations of 30 sampling points were determined using random - systematic method and soil samples were taken from two depths: 0–30 and 30–60 cm. Spatial distribution of soil properties and relationships between soil properties and covariates were investigated using Random forest method. Model validation was done through 10-fold cross-validation approach. Based on results elevation, channel network base level and vertical distance to channel network, were the most importance environmental variables in predicting of the some soil characteristics such as soil clay, silt, sand, SOC, and EC in two studied depths. The maps produced indicated higher clay at 30–60 depth in the higher elevations. EC amounts were increased in the lower parts of the mountain because of leaching. Furthermore, the highest map accuracy was related to EC map at both depths and clay at 30–60 depth. The prediction maps of other properties of soil had low accuracy. [ABSTRACT FROM AUTHOR]

• Invasion of the test soil clogged the space between the inner and outer pipes of the Hydroluis drainpipe in two weeks. • High flow velocity at the soil-envelope interface and low retention capacity caused poor function of the Hydroluis. • Based on Stokes' Law, the design of Hydroluis drainpipe is unsuitable for filtering fine silt particles (0.002 < D < 0.02 mm). • PP450 drainpipe showed good hydraulic and filter functions under the same laboratory conditions. Subsurface drains, when installed in non-cohesive soil, are typically covered with an envelope to tackle problems of clogging and siltation. Selecting a suitable envelope material, however, is complicated and depends primarily on soil characteristics in the area where the drains are to be installed. A new promising drainpipe-envelope concept, Hydroluis, has been developed which the designers claim works in a wide range of soils. The Hydroluis drainpipe consists of a corrugated inner pipe with three rows of perforations at the top and an unperforated outer pipe that covers the top two thirds of the inner pipe. We analysed the hydraulic and filter functions of this new drainpipe in a soil tank laboratory model with a saline-sodic problem soil from south-western Iran and compared Hydroluis performance with that of a locally-manufactured synthetic envelope material (PP450). The silty clay soil used in this study was 40 % clay, with a plasticity index (I P) of 16.9 and an exchangeable sodium percentage (ESP) of 60.4 %. The Hydroluis drainpipe clogged during the first two weeks of the test due to invasion of the test soil into the space between the inner and outer pipes. Of the substantial volume of sediment that entered the Hydroluis inner pipe, 38 % removed from the pipe in the first day. In contrast, the PP450 drainpipe showed good hydraulic and filter functions, entering very little sediment to drainpipe during the entire test period and stabilizing at drainage rate of 28 mm/day and entrance resistance of 55 days/m, at around day 50. Our analyses suggest that the clogging and poor drainage function of the Hydroluis drainpipe was caused by the higher flow velocity (21.5 times higher) at the soil-envelope interface of the drainpipe, in addition to the lower Hydroluis drainpipe's soil retention capacity (18 times lower) compared to the PP450 drainpipe. Assuming Stokes' Law governs filter function, the results of Hydroluis design evaluation also suggest that in stable soils, very fine sand or coarser soil particles (D > 0.05 mm) place no serious limitations for Hydroluis drainpipe application, whereas the current design is unsuitable for filtering fine silt particles (0.002 < D < 0.02 mm). In conclusion, we suppose the Hydroluis drainpipe does not perform well in silty saline-sodic soils, such as those found in south-western Khuzestan Province, Iran. [ABSTRACT FROM AUTHOR]