I really dont want to get into the higher realms of pH, some would like to attribute soil pH to covalent double electron bonds but little consideration is given to the formations of non reversible compounds at different pH's their effects on soil and combined net effect on pH and root absorbtion.
We can futher complicate this subject with soil microbes, drainage properties and soil funghi where it is noted that plant roots wouldnt work without these many many species of funghi which colonize the plants roots and eneable nutrient synthesis and uptake/exchange.
It is noted that under dense canopies such as rainforests that plants with next to no light manage to grow into very big strong trees even when in competition with much stronger neighbours and trees. Surely the soil funghi is providind nutrients from other trees to this small sapling under the low light otherwise it wouldnt be able to grow up to the canopy and gain acess to sunlight, species grow well next to their own kind for this reason.
I certainly write a lot for this site and threads, i rarely like to give advice more considerations for others to decide whats best. Should we really get into pH this much in soil grows, hydro growers simply pH their water and ferts in which the plant grows and dont have long discussions on pH. Know your media and adjust depending on pH of water and ferts rather than trying to keep it sweet by adjusting water and ferts! I have soil i know will hold pH for a few months and long enough to harvest in no matter what pH i throw at it, others dont but i think the difference would be the levels of lime in the soil and futher added buy the grower.
Water - Water is made up of hydrogen and oxygen hence the H and O in H2O! Now futher break this down and we get two Hydrogen molocules and one Oxygen molocule, simples.
Each molocule has a charge across its length, a dipole or net charge ,which we would refer to atomic bonding to understand fully, which translates to the fact that the positive Hydrogen molocule is attracted to the negative Oxygen molocule.
The Oxygen molocule forms loose bonds with the Hydrogen molocules proton whilst holding onto the electron enabling many Hydrogen molocules to swap their protons with suitably arranged Oxygen molocules creating a mixture of H30 and 0H which would be a simplified result of the meeting of two H20 molocules or that the proton from one H20 molocule was attracted to the Oxygen molocule of the next H20 meaning one H20 lost a proton and one H20 gained a proton or H20 + H20 = H30 + OH
Simply put the H30 we call Hydronium and the Oh we call Hydroxide (ions) and at any given time water contains a certain percentage of these which contribute to pH whereby the more Hydrogen the more acidic and the less H30 the more alkaline, balance them out and we get neutral. Because of the proton exchange the H30 becomes positive and the OH negative.
So we could say that an acidic substance is one that donates Hydrogen molocules and an alkaline one would be one that absorbs Hydrogen molocules by recombining them with OH to form H2O or water.
Water itself can react with itself to form H30 and OH but the reaction is quickly over and has a knock on effect so to say and is irrelevant to our field of study (ionization of water). Incedentally this is how ionized water is made.
Pure water has a concentration of 1 molocule per billion and can be writte as 1x10-7.
Salt fertilizers Contrary to popular belief we actually feed our plants salts, salts of various compounds that contain the word Nitrogen or Potassium or Calcium. Now fertilizers have a pH and just the same as water it is dependant on the prescence of good old Hydrogen molocules as in previous posts. We add more and generally the pH of our water/fertilizer solution goes down etc etc.
Now not to screw with the norm but this really dosent correlate to the type of, for example, Nitrogen that might be held in the fertilizer of which there are three main varieties used-
Ammoniacal Nitrogen, written as NH4-N
Nitrate Nitrogen, written as NO3-N
Urea which we would consider a form of Amonical Nitrogen or NH4 and again split into NO3 and 2H+
So plant nutrient absorbtion is another three degrees at Oxford or Harvard and involves the ionic transfers within cells and metobolic utilization rates blah blah blah but basically put the plant roots spit out compounds to counter balance the compounds they want to or have to uptake (the plant didnt want to uptake all that nitrogen on purpose)
In the case of ammoniacal nitrogen it spits out positively (lets forget the positive and negative charge bit for ease of understanding) Hydrogen ions which as we saw with pH increase the acidity! Nitrate nitrogen uptake causes the plant to spit out OH and HCO3 bases which actually increase the soils alkalinity.
Simply put the type of nitrogen far out weighs the pH of the fertilizer solution but ontop of this due to the nitrogen cycle some types of bacteria actually cause the Amonical nitrogen to change to Nitrate nitrogen through nitrification and also involves Hydrogen ions being released into the soil. The result of the Amonical nitrogen being converted to Nitrate nitrogen through nitrification can release a lot more Hydrogen ions into the soil mixture than a solution of pH5 fertilizer.
Now the Amonical nitrogen charge has to be worked out since it has no correlation with pH but more with the amount of Hydrogen ions it will release. Most if not all fertilizers are a combination of the two different types of nitrogen. Take if you will some common fertilizer salts -
Potassium Nitrate
Calcium Nirate
Ammonium Sulphate
We notice that we are acumulating some different nitrogen forms and percentages. Over time these will release Hydrogen ions into the soil or visa versa as said before in the last post. So we could try and cancel the Hydrogen ions out with the bases in our water making H2O from H and OH but we would have to calculate the nitrogen charge first in our Ammoniacal nitrogen.
Another way would be to use lime or Calcium Carbonate written as CaCO3. The Hydrogen (acidity) reacts with the CO3 or the carbonate part of the calcium carbonate to form CO2 and H2O.
