In the pore water of a long-cultivated paddy soil with high CEC (smectitic clay dominance), high organic matter and a clay pan (physical constraint) below 15 cm depth, can the total anion equivalent be greater than the total cation equivalent? The soil has been fertilized with KCl (twice a year) and ZnSO4.7H2O (once every two years) for the last 33 years.
The dominant ions in the pore water of the given soil are Chloride>bicarbonate>sulphate>calcium>magnesium>other cations
and
the total anion equivalent>>total cation equivalent.
I am hypothesising that:
1. The clay pan is inhibiting the easily migrating chloride and sulphate ions from getting leached out of the surface soil.
2. The high CEC is causing negative adsorption of anions and, at the same time, keeping the cations from going to the soil solution to maintain charge balance.
Do my hypotheses make sense? Is there any study to substantiate my findings?
Once you have extracted the pore water from the soil, the total equivalent of anions must be equal to total equivalent of cations in that extracted pore water, irrespective of the properties of the soil from which you have extracted it, period. If the pH of the extracted water is not equal to 7, then one should consider H+ along with other cations and OH- along with other anions.
