Soil stays wet for days after H2O2 drench - root zone still not recovering

Why though? If it was for bacteria you are mich better drting her out. The amounts to be used for such things are very specific and susceptible to overdose. The entire premise behind a medium is its pH balance, potential hydrogen. Not something you should be messing with without full hindsight and expectation of result. When you add diluted H2O2 to a medium, it will initially change the pH of that medium. The final pH will depend on the initial concentration of h2o2 and the buffering capacity of the medium. Adding water to a buffer generally does not change the pH, as the dilution of the buffer components is proportional. However h2o2 is not a buffer, so its addition will change the overall pH of the medium temporarily or otherwise. Gluck.