Abstract
The present study investigates the effect of three different methods of obtaining 1:1 and 1:5 soil-over-water mass ratios (soil:water) extracts for soil electrical conductivity (EC) measurements (EC1:1, EC1:5). On the same soil samples, also the electrical conductivity of the saturated paste extract (ECe) was determined and the relationships between ECe and each of the three of EC1:1 and EC1:5 values were examined. The soil samples used were collected from three areas over Greece (Laconia, Argolida and Kos) and had ECe values ranging from 0.611 to 25.9 dS m−1. From the results, it was shown that for soils with ECe < 3 dS m−1 the higher EC values were obtained by the method where the suspension remained at rest for 23 hours and then shaken mechanically for 1 h. On the contrary, no differences were observed among the three methods for soils with ECe > 3 dS m−1. Also, in the case of EC1:5, the optimal times for equilibration were much longer when ECe < 3 dS m−1. Across all soils, the relationships between ECe and each of three methods of obtaining EC1:1 and EC1:5 were strongly linear (0.953 < R2 < 0.991 and 0.63 < RMSE < 1.27 dS m−1). Taking into account the threshold of ECe = 3 dS m−1, different ECe = f(EC1:5) linear relationships were obtained. Although the linear model gave high values of R2 and RMSE for ECe < 3 dS m−1, the quadratic model resulted in better R2 and RMSE values for all methods examined. Correspondingly, in the 1:1 method, two of the three methods used exhibited similar slope values of the linear relationships independent of ECe value (ECe < 3 or ECe > 3 dS m−1), while one method (23 h rest and then shaken mechanically for 1 hour) showed significant differences in the slopes of the linear relationships between the two ranges of ECe.
Highlights
Soil salinity is one of the basic limiting factors in food production especially in arid and semi-arid regions since most crops are sensitive to increased salt concentration in the soil solution [1].Soil salinization is acute in arid and semi-arid areas with shallow groundwater as well irrigation water of poor quality.Soil salinity assessment is based on measurement of the electrical conductivity of soil saturated paste extract (ECe ); this has been established as the standard method [2,3]
In Argolida, 12 samples were collected from various irrigated crops at the end of the irrigation period, while in Kos, 27 samples were collected from a horticultural greenhouse
In the case of soils with ECe > 3 dS m−1 there is no significant differences between agitation methods since all methods gave almost the same results and the slope of the linear relationship is almost 1 (Tables 2 and 3)
Summary
Soil salinity is one of the basic limiting factors in food production especially in arid and semi-arid regions since most crops are sensitive to increased salt concentration in the soil solution [1].Soil salinization is acute in arid and semi-arid areas with shallow groundwater as well irrigation water of poor quality.Soil salinity assessment is based on measurement of the electrical conductivity of soil saturated paste extract (ECe ); this has been established as the standard method [2,3]. Soil salinity is one of the basic limiting factors in food production especially in arid and semi-arid regions since most crops are sensitive to increased salt concentration in the soil solution [1]. Soil salinization is acute in arid and semi-arid areas with shallow groundwater as well irrigation water of poor quality. Saline soils are considered to be the soils where the saturated paste extract has ECe values greater than 4 dS m−1. This method is laborious and time consuming especially in the case of ECe determination for a large number of soil samples. The method appears to be more difficult and requires skills and expertise to obtain saturation point for clay soils
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