How to lower the PH of Compost tea? It's very alkaline. I use lots & get mineral deficiency

Hi, all,  I percolate water through a compost pile and I get a lot of compost tea.  It's probably great plant food but it is too alkaline. If I could lower the PH to between 6.5 and 7,  I could use it directly in hydroponics.   I used it last year to grow tomato plants in sand,  it did work but there were issues with yellowing veins etc. so there was definitely deficiencies due to it being too alkaline.   I know peat is acidic, but we are not supposed to use much because it comes from bogs.  Is there some other naturally acidic medium that I can use?  I started up the Tomatoes in sand again last week.   It's automatically watered with the compost tea.    Any suggestions for what to use as a buffer to avoid the deficiencies?  Thanks,  Brian in Victoria BC

I'm interested to hear about your composting process.

Does it get turned? If so how frequently?

I imagine that you are seeing high alkalinity due to potentially a high amount of 'green' material being in the pile not being balanced by enough carbon.

I'm curious how this will shake out.

I live where the soil is very alkaline so my suggestion would be to change the pH with baking soda or vinegar.

May make several test experiments to see how each effects the compost teas pH.

Brian, do you have access to pine or other evergreen needles? That's what I use to mulch my acid loving plants like blueberries.

My acid-loving plants get the used coffee grounds, so that could work. If you're not a coffee drinker, a local cafe might be willing to recycle via your compost.   Also rhubarb leaves - I use them directly around the rhubarb plant as a mulch - they have oxalic acid in them which is why we are warned against eating them or feeding them to animals, although that doesn't seem to deter the kangaroos which eat the leaves through the fence.  There are other things that are used, particularly for camellias, but most are chemicals, like alum or sulphur.

Coffee grounds (used) are surprisingly in the low 6’s for pH in my testing and reading, with the acidity coming out in the brew. As are most conifer needles, with the acidity of conifer forest coming mostly from root exudates and fungal dominant soil processes. Still, again counter intuitively, I have seen creeks in old growth conifer forests run in the upper 7s for pH.

As mentioned above, I would suspect the compost being used is alkaline and bacterially dominant due to hyper-aerobic conditions from frequent turning. I would let it age at least a month, and if that did not suffice I would mix in up to an equal amount of wood chips and let it age unturned and with chimneys (Johnson Su/BEAM style) up to a year. It will then be in the slightly acidic range and extremely diverse, with fungal dominance. If this seems too time consuming, I’d try intermediate amounts of woodchips or shredded leaves until you find your sweet spot.

How high is the pH? Finished compost would have a pH of 6-8. Is used diluted, every 10x dilution will change pH by 1 unit. I am not sure about hydroponics,  but in soil with good biology, the pH around the root hairs is lowered to facilitate nutrients uptake even though the soil solution is alkaline.  Besides pH, another possibility for deficiency is phosphorus being too high. It is common in compost made from manure as cations are tied up by high level of phosphorus and less available to plants.

Hi. Some questions - What is the pH of your compost tea? Have you tested your compost tea to see how much nitrogen it has in it? And what percentage of your compost is green vs brown?