I want to mesure ECe for field soil so my question is the read obtained from EC meter for 1:1 saturated paste represent the real value ,or this read must multiplied with correcting factor.
thanks
The EC of soil to water suspension is not real one, it must be multiplied by some correction factor to find EC. This conversion factor is not 10 (handbook 60), it will be different for different soils. You must first calibrate and determine the factor for yours soils.
Hi Ali
A 1:1 soil to water suspension is not the same as saturated paste EC (ECse). If you measure ECse (done according to standard methods), the result you obtain can be used to compare directly with salinity threshold data in such publications at the FAO Water in Agriculture paper (see http://www.fao.org/docrep/003/t0234e/T0234E03.htm). If you use a 1:1 soil to water suspension, you cannot do a direct comparison of the result with ECse thresholds and as Abdul suggests you need a conversion factor which is soil texture dependent. An example of this conversion developed for Australian soils (conversion of 1:5 soil water EC to ECse) can be found at https://publications.qld.gov.au/dataset/salinity-management-handbook/resource/529b12b0-8e23-4cd3-a1cd-7659d0b9b3b4 - look at Table 27 Chapter 9.
Hope this helps.
Andrew
Saturation paste EC(ECe) is considered best , instead of any dilution factor to be used unrealistically as endorsed by our colleagues earlier, but again saturation paste will be highly dependent on the particle size distribution ( You can refer USDA Salinity handbook , most authentic and widely referered information ) .
Anoop is correct that the saturated paste method is the best measurement, but it is cumbersome and time consuming and thus expensive in many counties, It is therefore not done as a routine analysis for large scale sampling programs or screening of large numbers of samples or rapid site characterisation. In many cases, a standardised suspension extract is sufficient to identify critical salinity issues and assist land management decisions but the results must be used with caution if important decisions need to be made. If you are doing research then you would probably only use saturated paste extract. If dilute extract results are borderline - you would always get back up with saturated paste extract. Also for soils that contain gypsum, dilute extracts overestimate EC and saturated extract is the only way to go for these soils. The method you choose really depends on the situation you are in and how critical the result is - as always.
Dr.Ali and other colleagues,If the EC values have to be used for interpretation of salinity problem in saline and sodic soils, one can opt for the saturation paste extraction for EC estimation.1:1 soil water extraction is the next best alternative. The Australian study Dr.Andrew referred followed 1:5 soil water ratio, much dilute than 1:1.Even for salinity appraisal in in saline and sodic soils, one can develop such relation between saturation paste extract ECe and 1:1 extraction EC for soils of different textures.I agree with Andrews that for routine soil salinity interpretation in predominantly normal or near normal soils ,1:1 soil water extraction EC can safely be used.Even 1:2 soil water extraction is more convenient than 1:1 extraction in many soils.If sufficient data is generated,even 1:1 EC data can be directly used for developing crop tolerance criteria and soil reclamation/amelioration procedures for country level using appropriate statistical procedures.
Dear Andrew and other colleagues , how would you decide which ratio is correct to precisely measure the EC of a given soil ?. Is it the amount water available in given soil between field capacity and permanent wilting point , popularly called available water content ?.
Hi Anoop.
The Saturation extract already takes the soils water holding capacity into account. In simple terms it is the lowest practical soil:water ratio that is reproducible. Rhoades in Methods of Soil Analysis states that it is often related in a predictable manner to field water contents. If you care to measure the water content of the saturated paste you will see it varies with texture - just like moisture content at field capacity.
Dear colleagues .In order to interpretation the effect of salinity on growth parameter is the determination of ECe enough ,or i need to determined specific ion toxicity when i use drainage water in my experiment.
regards
Ali Alhayany
Apart from determination of ECe, determination of common cations and anion in drainage water may help to interpret the composition of crop plants including excess, toxicity or imbalance if any of some ions.
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