High pH in lasagna bed - advice?

15 years ago

Hi all,

I have a home pH meter and last year my beds tested between 7-8, looked like right in the middle. This year they are way above 8.

Some background:

These are 3 year old lasagna beds that are about 4 x 12.

The first couple years, I used coir, compost, leaves, straw and alfalfa topped with worm castings and potting soil. That is about the first 12 inches of soil now.

Last year we built 2 foot tall raised bed frames. I had a free source of horse manure well aged (6 months to 9 months) from horses with woodchip bedding. In an effort to cheaply fill up the last 12 inches of my beds, last fall I used this compost horse manure-woodchips in alternating layers with alfalfa, straw, leaves and worm castings. During this layering I mixed in rock phosphate and green sand. This ended up being about another 8 inches on top of the 12 already there.

This spring I topped them off with a bit more manure-woodchips, leaves, alfalfa, coir, some compost, castings and potting soil on top. The worms are absolutely huge and plentiful in there.

I should have checked before doing anything in the spring, but I forgot, and now that I checked my pH, it seems off the charts high. My meter only goes up to 8 but the pointer is on the extreme left, indicating it might be higher that 8.

Now I don't know what to do. I feel like I keep finding conflicting info. I wondered if the woodchips might be the problem (they are pretty broken down) but then I read most wood products are acidic.

Any ideas on what to do?

I know a soil test would be best, but those take a month to get back, plus I worry that with my lasagna bed "composting" as it sits there, the results might be off anyway by the time I get them back. I have a home kit for pH, N, P, and K that I could use to double check my meter results.

Seems like adding sulfur will take too long to help this growing season (just planted tomatoes). Should I do that for the long run?

Should I add peat moss and sulfur to the top few inches and water heavily and hope for the best? I usually water through soaker hoses but I could try the vinegar approach for a while.

All the recommendations seem to be "add compost" but my lasagna beds are already mostly compost. When I've called my county extension, they mostly weren't familiar with lasagna style gardening anyway so I'm not sure that will help.

Help! I don't want tasteless tomatoes!

Thanks for advice!

Amy

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Comments (6)

User
15 years ago
How are the plants doing?

If your plants are doing well, forget the test results.
chervena_chuska
Original Author
15 years ago
Hi lazygardens!

I don't know yet - just planted the tomatoes yesterday and I haven't planted anything else yet in those beds. It's been very cold this entire month - hovering around 20 degrees lower than normal.

Wondering if I should try some amendments before planting anything else - if it did drop the pH a bit eventually, it'd still be within the target range.

Any suggestions? I'm a bit of a worrier though - maybe I just need to relax and see what happens.

Amy
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Kimmsr
15 years ago
Those inexpensive home pH meters are very unreliable, but if you have some distilled water you could test that and see what the meter reads, which should be 7.0.
garystpaul
15 years ago
Amy, it sounds like you've already made some great amendments. One can't know for sure without a professional soil test, but this wouldn't be the first time a home ph meter gave skewed results. In your place I wouldn't hesitate to plant in what seems from your description like terrific soil. Good luck. Gary
mackel_in_dfw
15 years ago
You might stop using manure. The salts in manure would push up pH. In an acidic soil, manure is good, in alkaline soil, use with caution. You can get the same benefit over time using straw as a mulch and alfalfa pellets, for example, as fertilizer.
chervena_chuska
Original Author
15 years ago
Gary,
I think you hit the nail on the head - I decided to test my meter (a garden store purchase) in vinegar and it read 7.0! So I think your guess about the results being skewed must be on track. So I will run another test with the pH testing tablets to see what they give me.

Mackel,
I did use lots of straw and alalfa meal/pellets in the beds when layering to build up the height of the beds, as well as the coir, leaves and castings, so while it was a lot of manure, it was balanced out by plenty of organic matter too. My hope was to avoid the "too much manure" problem I've heard about. I do use straw mulch every year as well and then pile on over top in fall so it gets incorporated. Thanks for the suggestions though, reassures me I'm on the right track.

Thanks for the helpful comments, everyone! Just wanted to run my situation by some knowledgeable soil people before panicking and it seems there's no reason to panic. I'm a bit obsessive when it comes to my garden, I have to admit.

Amy