Silvia , that's very interesting . I think , addition of Sulphur along with inoculation with some Thiobacillus could bring down the pH of the composted material . But , it needs to be seen , how much time does it take to notice such distinctive reduction in pH. Such reduction in pH,  perhaps  will be largely governed by the C:N ratio of the final product . On the other side , if this is the pH , it will be doubly effective as an amendment on acid soils .

Silvia,

Mature compost pH ranges from 6-8. During decomposition organic acids accumulate; you can aerate composting material for reduction of pH values.

Finished compost may be incubated with cultures of Azotobacter, Azospirillum, phosphate solubilizing bacteria cultures singly or in consortia for 7 to 15 days.

natural composting method reduces pH value at a slower rate

if you simply opt for vermicomposting using earthworms it will reduce pH

Silvia , I would suggest to  you to please first ensure that your compost is having pH 8-9  along with EC to know the salt index of the compost. Is it poultry manure ?.  Did you prepare the compost or you purchased  it from outside source . If you have prepared the compost , try to see what kind of composting materials , you subjected to composting . Once you are confirmed with pH, then you can add sulphur along with fresh dung as a microbial inoculants. Try to evaluate pH and EC periodically to see , how much time does it take to throw out the manageable pH , preferably on the acidic side. I agree with Prakash , natural compost will not so easily undergo reduction in pH, unless C:N ratio of the compost is on the higher side .  

Thanks everyone for their answers. I will consider your recommendations.

Dr. Anoop Kumar Srivastava, I'm preparing composts using the poultry litter as a raw material (mixture of rice husks used as bedding material, poultry manure, and a little amount of feathers and food that falls during the chicken life). The compost pH we get usually is between 8-9, and the EC is between 18-22 (Ds/m). 

Silvia , that's very interesting . I think , addition of Sulphur along with inoculation with some Thiobacillus could bring down the pH of the composted material . But , it needs to be seen , how much time does it take to notice such distinctive reduction in pH. Such reduction in pH,  perhaps  will be largely governed by the C:N ratio of the final product . On the other side , if this is the pH , it will be doubly effective as an amendment on acid soils .

Hi Silvia,

my experience has been that reducing the pH of a mature compost is very difficult as the tannic and humic acids strongly buffer the pH. Trying to compost material under acidic conditions causes odour problems and may lose some of the nitrogen content. I too have been involved in composting chicken wastes and to control odour and ammonia production it was important to use woody materials with a good lignin content to prevent acidification and odour problems and nitrogen losses.

best wishes,

Richard

Dear Silvia

To start with the pH of compost depends very much on the materials you put into the compost. If you use wood products like saw dust they will make the finished compost more acidic. If you use more manure or add in some ashes from the fireplace it will be more alkaline. So the pH of any particular compost depends on the material being composted.

most peat based composts start off at pH4 and are limed to bring them up to ph6/7 and this is common for mushroom compost. in order to reverse the process of liming you have to neutralise the lime added before acidification occurs. it can be difficult to do this without adding other ions to the compost but you can use sulphuric acid and this adds sulphur to the compost. or you can add hydrochloric acid but this adds chloride.

If anaerobic conditions develop during composting, organic acids may accumulate rather than break down. Aerating or mixing the system should reduce this acidity. Adding lime (calcium carbonate) generally is not recommended because it causes ammonium nitrogen to be lost to the atmosphere as ammonia gas. Not only does this cause odors, it also depletes nitrogen that is better kept in the compost for future use by plants.

Regards,

Ata

Silvia, your compost has pH and EC both really high . Poultry manures do have such issues to be addressed. Adjusting pH with addition of elemental sulphur or pyrite ( An amendment used for reclamation  of soils)  would help a great deal to bring down pH...

Addition of sulphur are some thiobacillus is the only option to reduce pH and EC of poultry manure.