barnhardt9999
Full Member
Posts: 50
Joined: Mon Jul 18, 2011 4:23 pm
Location: Charlotte, NC

Very Acidic Soil

A few days ago a bought a soil ph and moisture meter to check around my figs and blueberries. First I checked my blueberries and the ph was about 5.5. That's pretty good but not as low as I had hoped. Then I checked my figs. Around 7.5 which is perfect. I was feeling pretty good that I had achieved good ph levels without ever measuring. I was also confident that my raised beds would be a perfect 6.5 considering the earlier results (I lime the figs and sulfur the blueberries seasonally).

I thought what the heck and measured the raised beds. It was about 7 a few inches below the surface but much to my surprise when I put the sensor the full 8 inches deep the PH moved below 3.5 (the lowest level on the sensor). Unfortunately, my tomatoes are already planted (and thriving) so I can't just till it up and mix in a bunch of lime. I think I believe the ph sensor too. The past few years my tomatoes do very well until it gets hot (at which time it relies on the deep roots that I doubt function at 3.5ph) Two questions:

(1) How in the world did my soil get so acidic?
(2) What can I do to fix the ph without disturbing the tomatoes already there? I'm afraid that adding enough lime to the surface would fry the roots of the tomatoes there.

Mr green
Green Thumb
Posts: 372
Joined: Sat Mar 14, 2015 6:08 pm
Location: Sweden

Tomatoes love wood ash, that would be my recomended amendment if its something you have at hand or can come by. You ever limed the garden plot? If your watering with rainwaetr it can become more acidic, also certain industries in the area can make your soil acidic (like in my neighbouring town were they have a paperfactory wich release tons of sulphites in the river and the air.) But 3,5 is very low tho and sounds like could be even lower according to your meter?

Its hard to make a really good quick fix to this problem.

barnhardt9999
Full Member
Posts: 50
Joined: Mon Jul 18, 2011 4:23 pm
Location: Charlotte, NC

Thanks for the suggestion. I have plenty of wood and a fire pit. I've added charcoal to the garden before but never ashes or lime (I was worried that it would be to basic). Do you think there is any risk of burning the roots by adding too much ash?

I use about 50/50 rain barrel water and city water. I think maybe my compost is part of the problem - its probably 50% oak leaves and 25% Starbucks grounds and 25% other stuff.

imafan26
Mod
Posts: 13947
Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

Oak leaves are acidic, but most composts are worked into the top of the bed and that part is actually fine. Wood ashes will work and so will dolomite lime, but unless they are mixed in, they will only affect the pH in the top few inches where you don't really need it. It will also take 1.5 -6 months to make a difference. I would wait and mix up the bed very well after the tomatoes are gone. To have such a variance in pH you have to have very different soil or not have incorporated the compost very deep. Compost itself is neutral to alkaline but it has the ability to buffer the soil pH so it behaves more neutrally. My soil is acidic but it has a pH of 6.4 which is really perfect for most plants. I do not lime and I use acid fertilizers. All I add is compost which in my case has a pH of 7.8 so it keeps the pH in a good range.

User avatar
Gary350
Super Green Thumb
Posts: 7392
Joined: Mon Mar 23, 2009 1:59 pm
Location: TN. 50 years of gardening experience.

If you bought a battery power ph tester from Lowes or Home Depot they don't work. I bought one it gave me crazy readings. I then bought some ph paper to do testing to compare to the battery ph tester. The battery tester never matched the ph paper.



Return to “TOMATO FORUM”