soil pH & compost

[John Lakey]

Gil, The vineyard in question is on acid basalt derived soils with pH  around 5.5 under normal treatment and has skipped to 6.1 under compost.Interesting to note that most soil cations have also gone up and their substition for hydrogen may be the reason for the pH in crease.  The vineyard was established with 3 tonne per hectare lime application and experienced very little soil pH increase.  The compost  cost AUS $15 per cubic metre and is  much cheaper than lime. I am trolling through petiole analysis from samples taken at the same time to see if any of the increased soil nutrients are also showing highs in the vine. I have followed the cation balancing discussion, Albrecht etc, with tremendous interest and wonder if any one else has come up with why compost should effect soil pH?  At Uni I was told that the addition of organic material would lead to an increase in acids used by fungi to digest material and decrease soil pH leading to peat bog idea of high OM soils being acidic by nature.  But what is high?  The soils under compost have  only 2 - 3 % OM, what outcome would you get as OM approaches 5 -10%?  Cheers JL