- Mar 4, 2011
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Raz, thanks for linking that, it was really interesting. I like to understand things. This:
"While two studies on coffee ground composting reported mildly acidic pHs of 4.6 and 5.26, others have measured neutral (7.7)
to somewhat alkaline (8.4) pH levels. One researcher found that the pH of soil treated with coffee compost increased after 14 to
21 days of incubation, gradually decreasing thereafter."
seems to correlate with another article I'd just been reading yesterday that said this:
"...we were sent some test results that showed grounds to be neutral on the pH scale! To find out what gives, I called Will Brinton,
founder and Director of the Wood’s End Research Laboratory in Maine, the definitive testers of soils, composts, and raw ingredients
used in large-scale composting. Will solved the mystery instantly. Woods End, it turned out, was the source of that neutral test!
Ah, but some follow-up investigation later revealed that it hadn’t been coffee grounds alone, as the person submitting the material
for testing had stated, but grounds mixed with raw yard waste, the classic ‘dry brown’ material that is the heart of a good compost pile."
It also went on to say,
"“Coffee grounds alone are highly acidic,” says Will, who saved all the grounds from his Lab’s break room for a week recently just to test for us (“Eight o’ Clock” coffee, which I remember fondly from our old A & P neighborhood supermarket). They came out at 5.1, a perfect low-end pH for plants like blueberries that thrive in very acidic soil. “But that’s the most gentle result we’ve ever found,” Will quickly added, explaining that the other 31 samples of raw coffee grounds they’ve tested over the years all had a pH below 5, too acidic for even some of the so-called acid loving plants."
So I am sure my best bet is really just to test my soils, as you always say, and maybe I will get around to making that PH tester from violet flowers I have considered trying a few times, although it's probably a bit vague for you tastes.
