Re: soil pH & compost
Composts do increase soil pH. Organic matter and manure can , on the other hand decrease pH by increasing its acidity. Compost is stable organic matter and has lots of organic compounds that do have a buffer effect in soil pH ( they resist to sudden changes in soil pH). Compost contributes with some Calcium, Magnesium, Potassium and also Sodium. All those cations can influence soil pH with Sodium and Potassium being the ones that would influnce pH the most. I believe that the effect on soil pH is also an indirect one by the increased microbial activity leading to the release of blocked minerals specially calcium from tricalcium phosphates. Jose 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
Re: soil pH & compost
Hi! John, I think the big difference is that Lime is in the line of chemical thinking, where compost is much more complex and has to do with stimulating soil biota and providing food for it. On other than you volcanic soil, I would be suggesting the addition of some rock dust, but you soil should provide all the necessary. Do you do the green manure bit to help the soil carbon levels? I envy you with 2-3% OM. Near where I live we have large areas of very mean lime soil with pH as high as 9.8 and on one soil analysis 0.01% soil carbon. Now that is one mean paddock. He is a chemical farmer and in 45 to 60 days all his applied fertiliser is locked up. I am in some good granite country, some of the best in the district. I wish I could but a good compost at that price ours is $A25 or more. Gil John Lakey wrote: 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
soil pH & compost
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
