I guess such data may not be available. In case you are interested please get such data for soils where water KCl pH is greater than water pH.

Bindu's question and Pal Sir's answer are both in right direction. Anion exchange capacity will be of great importance in acid saline and acid sulphate soils of Kerala where marine sediments with fossil materials are playing an important role getting influenced by sea water inundation and flushing of fresh water after heavy rains and some times with dissolved salts. These areas have potentials for making bumber crops of rice if harnessed well

Years ago I used a method by Chao et al. (1962) (see citation below) that was essentially an estimate of anion exchange capacity of soils.  This used the sorption of sulfate ions by the soil followed by desorption by phosphate.  This capitalizes on the preferential sorption of anions by soils as follows NO3-  =  Cl-

thank you Dr Larry Sir good piece of information thank you for sharing

anil

Thankyou sirs for the guidance

Regards

Bhindhu 

Greetings Bhindu, I am in full agreement with Dilip. In my experience, soils with a net positive charge are not common in southern Africa, but do occur under extremely acidic conditions, such as those found in subsoils of the highlands of central Madagascar. There, it is not uncommon to find soils where the water pH is as much as a unit lower than the KCl pH.. In the unlimed state K leaches rapidly, while NO3 is adsorbed.. Here in KwaZulu-Natal, many soils have considerable positive charge --- the differential between water pH and that in KCl is, on average, closer to 0.5 of a unit than the widely accepted differential of one --- but we do no more than use delta pH as an indication of the likelihood of positive responses to gypsum. Regards, Mart.

Soils in which the predominant colloids are sesquioxides (oxides of Fe and Al) may have a net positive charge. This creates opportunities for anion adsorption and exchange.

A clay-size particle of hydrous aluminium oxide has a positive charge under acid conditions, as indicated in the following reaction and therefore contributes to the soil’s anion exchange capacity (AEC).  Materials like sesquioxides may acquire a pH-dependent charge.

                           Al(OH)3 + H+ ↔ Al(OH)2+ + H2O

 At sufficiently high pH, sesquioxides can contribute to cation exchange capacity by acquiring extra hydroxyl groups.  However, most soils abundant in sesquioxides are naturally acidic and as such contribute to AEC.  

Anion exchange capacity is the ability of soil to retain anions against leaching.

Positive charge develop on oxide surfaces and clay lattice edges at acidic pH's

Anions attracted to positive charge, adsorbed.

Bond may change to a stronger covalent bond (chemisorptions).

Strength of Retention- HPO42- , H2PO4-  >    SO42-  >>  Cl- or NO3-

Monovalent anions not adsorbed (conservative).

Phosphate adsorption - prevents Lake Eutrophication.

Sulfate adsorption - prevents Lake Acidification in Ultisols (high oxide)

Dear Bhindhu, I agree with everything that has been said in this regard, but question the real world significance. in this regard. Certainly, P fixation is higher in soils with positive charge, but so too is the chance that the soils are  excessively acidic --- something more readily determined by lime requirements based on acid saturation. In my experience, if the acidity is reduced to acceptable levels, the effects are not meaningful -- at least from a practical perspective.. A very interesting "theoretical" effect, but not one which is significant from a practical perspective. I suspect in KwaZulu -Natal,at any rate, it is a chemical phenomenon of little consequence.. Perhaps a nice and impressive Ph.D. topic, but of little real world consequence. Sorry for sounding so negative, but our task is in the real world. My best regards to you, and all the best for your studies and research, Yours Mart.

I suggest electrodialysis method will work. I have done thousands of soil samples using this method and works well for extracting both cations and anions. You need two Pt electrodes about a cm square. The rest is just beakers, filter paper, transformer and a 30 watt light bulb. One cm3 soil placed in a folded filter paper / in a beaker with about 20mls weak boric acid solution / two pt electrodes with filter paper between / Transfor current to DC with 30 w bulb in line and run for ten minutes. The current will pull both cations and anions from the soil into solution. Eyedropper wash electrodes with weak acetic acid (5%) and bring solution to 30 mls. with water Boric acid is to keep the pH from moving to extreams. The solution then measured for nutrients.  

Thankyou sir, can you please cite any reference for the procedure, it would be very helpful.

If you search electrodialysis on soils there was a lot of work around the 50's. I worked in the lab 40+ years and now retired. Modified the set-up to do 8 samples at a time. Also used it on Biochar. Nice to pull the ions off without chemicals into a clear solution for testing. Not sure I can find the original (before modification) but will look.

looks good! protocols for biochar use for this purpose?

Ms.Bhindhu,I have seen a method for determination of anion exchange capacity of soil  by Mehlich(1953) described in 'A Text Book of Soil Chemical Analysis 'by P.R.Hesse(1971) p.105 John Murray(Publishers)Ltd ,London.Probably the method is also available in Mehlich,A. (1953) J.Ass.Off.agric.Chem.,36,445.

I used electrodialysis on soils for my first ten years at the lab then 'forced' to change to more approved chemical procedures. When getting in to testing biochar for cleaning water I dusted the equipment to see how well it would work. Passing chemical treated water through the char then testing the char Before & After to see the difference. Having use a lot of testing procedures for soil I think the electrodialysis was the best. And will work nicely for biochar. I think Universities should backtrack and do more research on this procedure.

Sir, I had estimated AEC of soil samples,  adopting the method by Mehlich(1953) described in 'A Text Book of Soil Chemical Analysis 'by P.R.Hesse(1971). I wanted to find any other works done on similar soils and / or by any other method.

Regards

I think both Electrodialysis and Mehlichs method are good to estimate AEC. Attached reference you may find the other method people are trying for the degraded soil, which also I find good to use.

Gillham (1979). A proposed method for the measurement of exchange properties of highly weathered soils. Australian Journal of Soil Research 17,129-139.

Thanks a lot sir for the updates and methodology shared

anil

Thank you sir for the guidance

Regards

Bhindhu