Dear Sir. Concerning your issue about the relation between soil organic matter and electrical conductivity or pH. Soil organic matter is the combination of plant and animal residues at various stages of decomposition and cells and tissues of soil organisms. The consistent benefit of Soil organic matter (SOM) is that it buffers soil pH change. Soil organic matter offers many negatively charged sites to bind H+ in an acidic soil, or from which to release H+ in a basic soil, in both cases pushing soil solution towards neutral. Whether SOM changes soil pH in the long term depends on many factors. When organic matter first begins to decay, it releases anions and cations. Plant foliage and stems generally contain more anions, so the initial decay over the first few weeks causes a soil pH increase. This initial increase in soil pH, especially from high nitrogen plant residue, could be used to reduce H+ , aluminum or manganese toxicity in the seedling rooting zone long enough for seedling establishment. Soil microbes further break down the plant material to ammonium (mineralization) which temporarily increases pH. The ammonium gets converted to nitrate (nitrification) which causes pH to instead go down. If the nitrate is lost to leaching, pH drops even more. In the very long term, microbial decomposition decreases pH. The net effect of organic matter addition on soil pH depends on the rate at which all these processes occur and what happens with the nitrogen produced (e.g., nitrate plant uptake vs. leaching loss), the quality and quantity of plant material, and initial soil pH. Soil pH will likely increase with decomposition of plants growing on basic soils, and manure derived from such plants, deep rooted plants that draw anions from deep soil layers to the soil surface, and, plant residue high in nitrogen. Higher residue amounts increase soil pH. For more details, I think the following below link may help you in your analysis:

http://landresources.montana.edu/nm/documents/NM8.pdf

Thanks

Hello,

A low soil pH would would likely result to low organic C and vise versa.

For detailed information, please read go to this link.

http://landresources.montana.edu/nm/documents/NM8.pdf

Thank you.

Highly weathered ferruginous soils under tropical environments ( like Ultisols and acidic Alfisols) do have high OC (>> 1.0%), very less EC (1:2 soil: water ratio) and pH

I'm very pleased to read all this expertises and I would like to thank you for your explanations about my question. it's very difficulte to linking organic matter and pH but generally the pH of a soil depends on the salt concentration in the soil solution and organic matter typically have higher cation exchange capacity (CEC). the most likely hypothesis is that organic matter can have greater buffering capacity as suggested by @Isam Eldin Hussein Elgailani. and that is sufficiently to increase pH value of soil.