Editing Soil pH (section)

==Effects of soil biota on soil pH==
Soil biota affect soil pH directly through [[excretion]], and indirectly by acting on the physical environment. Many soil fungi, although not all of them, acidify the soil by excreting [[oxalic acid]], a product of their [[Respiratory system|respiratory]] metabolism. Oxalic acid [[Precipitation (chemistry)|precipitates]] calcium, forming insoluble [[Crystal|crystals]] of [[calcium oxalate]] and thus depriving the soil solution from this necessary element.<ref>{{cite journal |last1=Casarin |first1=Valter |last2=Plassard |first2=Claude |last3=Souche |first3=Gérard |last4=Arvieu |first4=Jean-Claude |title=Quantification of oxalate ions and protons released by ectomycorrhizal fungi in rhizosphere soil |journal=Agronomie |date=July 2003 |volume=23 |issue=5–6 |pages=461–69 |doi=10.1051/agro:2003020 |bibcode=2003AgSD...23..461C |s2cid=84663116 |url=https://www.researchgate.net/publication/41706199 |access-date=20 August 2023}}</ref> On the opposite side, earthworms exert a [[buffer solution|buffering effect]] on soil pH through their excretion of [[mucus]], endowed with [[Amphoterism|amphoteric]] properties.<ref>{{cite journal |last=Schrader |first=Stefan |title=Influence of earthworms on the pH conditions of their environment by cutaneous mucus secretion |journal=[[Zoologischer Anzeiger]] |date=1994 |volume=233 |issue=5–6 |pages=211–19}}</ref>

By mixing organic matter with mineral matter, in particular [[clay]] particles, and by adding mucus as a glue for some of them, burrowing soil animals, e.g. [[fossorial]] [[Rodent|rodents]], [[Mole (animal)|mole]]s, [[Earthworm|earthworms]], [[Termite|termites]], some [[Millipede|millipedes]] and [[fly]] larvae, contribute to decrease the natural acidity of raw organic matter, as observed in mull [[Humus form|humus forms]].<ref>{{cite journal |last1=Guhra |first1=Tom |last2=Stolze |first2=Katharina |last3=Schweizer |first3=Steffen |last4=Totsche |first4=Kai Uwe |title=Earthworm mucus contributes to the formation of organo-mineral associations in soil |journal=[[Soil Biology and Biochemistry]] |date=June 2020 |volume=145 |issue=107785 |pages=1–10 |doi=10.1016/j.soilbio.2020.107785 |url=https://www.researchgate.net/publication/339991303 |access-date=27 August 2023|doi-access=free |hdl=21.11116/0000-0006-600A-3 |hdl-access=free }}</ref><ref>{{cite journal |last1=Zanella |first1=Augusto |last2=Ponge |first2=Jean-François |last3=Briones |first3=Maria J. I. |title=Humusica 1, article 8: Terrestrial humus systems and forms – Biologicalactivity and soil aggregates, space-time dynamics
 |journal=Applied Soil Ecology |date=January 2018 |volume=122 |issue=1 |pages=103–37 |doi=10.1016/j.apsoil.2017.07.020 |bibcode=2018AppSE.122..103Z |url=https://www.academia.edu/95860148 |access-date=27 August 2023}}</ref>