please state that what was the soil type, Any particular soil Xray, Edax, or results from the SEM, anything that can help understanding such a high ratio of the sodium involved. tq.

If the EC =150 dS.m-1 it means amount of total cations Na,Ca,Mg and K approximately =1500 meq per liter ,for this reason 2500 times dilution is too much,

after saturation the soil with NH4 as mentioned from procedure ,then calculate exchangeable Na by the following formula:

Exchangeable Na= total Na -Soluble sodium

the soil profile is in Playa of Urmia Lake, south eastern shore of Urmia Lake, next to Bonab Plain

We need to determine soluble sodium in saturation paste extract  and exchangeable sodium , either directly by saturating with ammonium acetate or by estimating the total sodium , and finally subtracting the water soluble sodium from total sodium . You can refer standard literature Richards 1954 , Hesse 1970 ...

My further interest is to see , how such high soil  EC affects the SAR values..?

Ms.Nikou,is there salt incrustation on the site of sampling? Is the site supporting any vegetation?

yes, the soil profiles are developed in remnant sediments of Urmia Lake (salt Lake). with salt resistant vegetation cover.

In highly saline soils ,before going for estimating exchangeable Na or CEC it is desired to remove the soluble salts by leaching with alcohol. After removing the salts,exchangeable Na can be estimated by replacing the Na with NH4 using  1 M ammonium acetate.Detailed procedure can be obtained from standard laboratory manuals.

Please state the units of EC measurements. Sea water has EC of about 55-60 dS/m, FYI.

EC= 80-100 dS/m. in soil profile. in the lake bed, EC= 178 dS/m

I agree to the suggestions of Dr. A. Subbarao. After scrapping the surface accumulation of deposited salts, you may take 2-5 g air dry soil and load that on a nylon filter paper fitted in a funnel. Leach the soil with 60% alcohol till the leachate test negative for chloride ions, make up the volume of leachate to 100 or 250 mL and estimate Na in the same as measure of soluble Na in soil. The remaining soil on the filter paper may now be leached by 1M ammonium acetate to collect sufficient volume of leachate and the leachate may be estimated for Na as a measure of exchangeable Na. Since the soil is highly saline, therefore, it is likely to be very hygroscopic, therefore it would be advisable to use oven dry weight of soil in place of air dry weight in your final calculation.  

Dr.Srivastava, good description /elaboration  of the procedure to remove soluble salts and estimate exchangeable sodium.

Dear Ms. Hamzehpour,

This means you are dealing with some Salic horizon.

In such cases, take 10 gram of representative sample and give multiple washings with distilled water. Filter entire sample using membrane filter under suction. This would remove entire amount of soluble Na. Dry this soil residue in a hot-air oven at 105 degree C.

Say, the soil residue obtained = X g

Note: Be careful not to lose any amount of clay fraction form the soil sample.

Dissolve 1 g soil residue in 250 ml of 1 N neutral ammonium acetate and equilibrate overnight. In this process Na+ will be displaced by NH4+. The extractant solution now will contain the exch. Na+ of the soil.

Read Na+ in the extractant using a Flamephotometer. The calculations will be as follows.

Dilution factor = 1 g soil residue -----> 250 ml = 250 times

Exch. Na+ in the extractant (meter reading) = Y micg/ml of extractant

The exch. Na+ in the soil residue = 250Y micg/g soil residue

The exch. Na+ in the original soil sample = 250 * Y * X micg/g soil sample

Regards,

MKD

 Mr.Manojkumar, what you are getting is water soluble Na not exchangeable Na.Please note.

Yes, Dr. Subba Rao, I just noted that. Here, I have corrected my statement made above.

thank u for the comments. I tried something:

first, we centrifuged 5 gr of soil with 33 ml of water and gathered the solution. we did it three times. after that, I assumed that I have removed soluble Na from the soil.

then, we added 33 ml of ammonium acetate on the remaining soil (5 gr of the soil which is already had been washed) and then shake and centrifuged it three times. we gathered the solution and assumed that is only exchangeable Na. to make sure, I summed up soluble and exchange Na  and compared it with previous results with routine method of Na-ex measurement. they are close to each other.

now, Na-ex from the second method, is matching our CEC results.

I appreciate any comments on this method.

Mr.Manoj Kumar, now the procedure appears o.k.But one problem remains.If one makes number extractions with distilled water,initial extractions remove only water soluble Na, but subsequent extractions may possibly remove some exchangeable Na.So  it is better to extract with water,say a few extractions and later 3-4 extractions with 60% alcohol. Then combine all the extractions(water plus alcohol) and make up to desired volume and estimate water soluble Na.Rest of the procedure is o.k.