preliminary soil salinity assessment - Mid Western Regional Council

3 SITE INVESTIGATION RESULTS AND DISCUSSION3.1 Results of Laboratory AnalysisA summary of the results of the top (A horizon), upper subsoil (B horizon) and lower subsoil (Chorizon) soil sample analysis for each site is provided in Table 16: Summary of Laboratory AnalysisResults. The laboratory Certificate of Analysis with details of the soil analysis is contained inAppendix C: Laboratory Certificate of Analysis of Soil Samples.The EC 1:5 recordings within the study area were low ranging from 28 to 292 µS/cm. The topsoils wereloam and light clay type soils and the subsoils (B and C horizons) ranged from loams to heavy claysoils. Based on the soil textures for each site and corresponding conversion multiplication factors(see Table 11: Factors for Converting EC1 :5 to ECe), the EC e across the site ranged from 0.21 to 1.99dS/m. Therefore, the soils sampled at each of the four sites are considered Non-Saline based on theelectrical conductivity results and taking into account the soil texture multiplication factors. Notethat the EC e of the topsoil at Site 1 and lower subsoil at Site 4 are slightly elevated (1.99 dS/m and1.75 dS/m respectively) and close to the threshold for soils considered Slightly Saline (2-4 dS/m).Exchangeable sodium percentage (ESP %) varied across the site. The topsoils (A horizons) and uppersubsoils (B Horizons) were all found to be non-sodic. However, the lower subsoils (C horizons) at Site1 and Site 4 were highly sodic measuring 23.7 and 16.2 ESP% respectively. The lower subsoil (CHorizon) at Site 6 was also found to be slightly sodic with an ESP% of 6.3.Chloride levels in most of the soils sampled were found to be low, consistent with the EC findings.However, chlorides were slightly elevated at Site 6 measuring 320mg/kg in the topsoil (A Horizon)and 360mg/kg in the lower subsoil (C Horizon). Although this level of chloride in clay soil wouldgenerally be considered slightly elevated for agricultural production and may cause chloride toxicityon some garden plants, these chlorides did not result in elevated EC levels and according to theAustralian Standard 2159: 1995 Piling – Design and Installation, this level of chlorides would beconsidered non-aggressive for steel piles in soil. Chloride levels were also slightly elevated at Site 4(290 mg/kg) and in conjunction with the high sodium levels and slightly elevated EC e calculated forthis site, indicate that the main type of salt contributing to the slightly elevated EC e is sodiumchloride. This chloride level would also be considered non-aggressive according to AustralianStandard 2159: 1995 Piling – Design and Installation.The pH varied across the subject land with the pH of the 17 soil samples ranging from slightly acid(6.2) to slightly alkaline (8.6). According to AS 2159: 1995 Piling – Design and Installation this pHrange is considered non-aggressive.PRELIMINARY SOIL SALINITY ASSESSMENT20