Add POXC, a common soil health indicator/soil property

[pvgenuchten]

Permanganate oxidizable carbon (POXC) or reactive carbon is a popular soil health test developed to measure “labile” C via the reduction of permanganate, dependent on several stoichiometric reduction oxidation assumptions.

Unfortunately POXC is not much described in some of the common vocabularies (agrovoc, gemet)

Would be good to introduce the property and procedures to estimate it in Glosis-ld

[Montanaz0r]

@pvgenuchten We are happy to extend the Procedure module as long as we can connect those with properties through either new or existing observations. I guess we could discuss details during the next meeting. You are welcome to join us!