Assessment of Saturated Soil Paste Salinity from 1:2.5 and 1:5 Soil-Water Extracts for Coarse Textured Soils

Abstract

It is important to determine soil salinity with an accurate and simple method. Electrical conductivity (EC) of soil-water extracts is commonly used to assess soil salinity because it is an easier method than the standard saturated paste extract (ECe). However, it is essential to convert EC of soil-water extracts to ECe because plant response and salinity remediation are based mainly on ECe values. Our objectives were to develop and validate models to predict ECe from EC of 1:2.5 and 1:5 soil-water extracts (EC1:2.5, EC1:5). One hundred thirty-six coarse textured soil samples were collected from El Beheira Governorate, Egypt, of which 115 were used to develop models and 21 were used to validate these models. Electrical conductivity was determined using 1:2.5 and 1:5 soil-water extracts and saturated paste extracts (ECe). Linear regression models were established for the two methods. The results showed that ECe was highly significant correlated (R 2 = 0.96 to 0.97, P < 0.001) with EC1:2.5 and EC1:5 for ECe values ranging between 0.3 and 18.3 dS m-1. An independent validation set of 21 soil samples showed that the R 2 and slopes of the regressions between predicted ECe from both EC1:2.5 and EC1:5 values and direct ECe values were very close to 1.0. Additionally, these new models reduced ECe prediction errors by 2.4 to 7 times when compare with 8 predictive models reported in the literature. Confirming that the regressions developed can reliably assess soil salinity instead of the more timeconsuming and expensive saturated paste extraction.

Evaluation and analysis of different regression models for estimation of ECe from EC1:5—With a case study from Buin‐Zahra, Iran*

“…The type of the second layer regression model is linear, which can be attributed to fine sand texture (Table II). The linear model for the ECe and EC 1:5 relationship has been reported in almost all previous studies (Ozcan et al, 2006;Khorsandi & Yazdi, 2007;Sonmez et al, 2008;Chi & Wang, 2010;Aboukila & Abdelaty, 2017). Aboukila & Norton (2017) proposed a correlation equation ECe = f (EC 1:5 ) for ECe values up to 10.3 dS.…”

“…Aboukila & Norton (2017) proposed a correlation equation ECe = f (EC 1:5 ) for ECe values up to 10.3 dS. m −1 for the clay agricultural soils of north Egypt, while Aboukila & Abdelaty (2017) presented the respective equation for coarse soils. It was observed from these two equations that the lines slope was higher for coarse soils.…”

Soil Salinity Assessment Using Saturated Paste and Mass Soil:Water 1:1 and 1:5 Ratios Extracts

“…Ozkan et al [14] EC e = 1.93 (EC 1:1 ) − 0.57 f EC e = 5.97 (EC 1:5 ) − 1.17 f Aboukila and Abdelaty [15] Hong and Henry [16] Zhang et al [17] Visconti et al [18] EC e = 7.46 (EC 1:5 ) + 0.43 a EC e = 1. The indices a,b,c refer to coarse, medium and fine soils respectively.…”

“…The possibility for the EC e prediction from EC 1:5 measurements has been investigated in a number of regions worldwide [4,8,9,[11][12][13][14]. In these studies, soil texture, specific salts presence, and organic matter content effects were taken into consideration [8,11,12,14,15]. Less examined is the subject of EC 1:5 measurement in relation to the methodology, followed for the acquisition of the soil over water mass ratio extract [7].…”

“…Moreover, when the EC e data were separated at EC e = 4 dS m −1 , very good results were obtained for EC e < 4 dS m −1 from the quadratic curvilinear model. Aboukila and Norton [11] proposed a correlation equation EC e = f (EC 1:5 ) for EC e values up to 10.3 dS m −1 for the clay agricultural soils of north Egypt, while Aboukila and Abdelaty [15] presented the respective equation for coarse soils. It was observed from these two equations that the slope of the lines was higher for the coarse soils.…”